Finally got my bike back together (will update my ancient project post at some point) replacing much along the way but it has an issue with idling.
From cold (high single figure Celsius, ambient) it won't start without choke but only needs maybe a third to a half to get it to 2000rpm and after about 30 seconds will run at 1500 rpm without any choke. I don't think this is right.
What it has:
valves in spec
new rings in honed bores, valves lightly ground back in (original valves in original guides on original seats) (first time at a top-end rebuild)
new head and base gaskets, no obvious leaks.
new exhaust, think stock.
125 mains (formerly 115s), 40 pilots, new gaskets carb cleaned up. 2 or 3 turns (tried both) from closed on the air mix screws. all jets are new. needle jets are the notched type and are (i think) on 3 (i don't know how you count this, which end is one?). i don't know how this relates to 'washers'. emulsion tubes clean.
no obvious air leaks, an unlit blow torch around the boots didn't seem to effect it at all. the boots aren't A+ but aren't horrible.
float height should be right, using the 'pipe on the carb drain test' the levels were approx steady with the gasket.
revs without hestiation, possibly a smidge slow at returning, but maybe my imagination.
turning the bars either way doesn't change the revs, i am certain there is free play in the throttle cable, if anything very slightly too much.
i don't think the choke is stuck part on
not mammamamamoeteredededed the carbs, need to sort this issue.
fuel flows on prime, only flows on on/res with the engine. fuel filter new. fuel lines new.
Suspicious things
vacuum tube carb->petcock has a little fuel in it, like a smidge you can see jumping around with the pulses not a lot. more than i expected.
plugs are black but not wet (its mostly just idled, its out of MOT so i can't ride on the road, i'll need to fix this before MOT, so thats a problem with getting it hot)
slight white exhaust smoke on first few strokes of revs but its cold so i expect some residual moisture condensed in the exhaust.
no throttle screw, backed off completely, turning it up increases the idle.
I think its running way too rich but I can't tell from what? I've not run a compression test ( no tester ) but i'd expect low compression to be a worse idle not one that is very steady and regular. The exhaust doesn't smell of petrol but the bike does have a slight smell. the new oil doesn't smell of fuel.
The fuel in the breather hose is a bit odd, not sure where that is from. its definately fuel, tipped it out and its petrol.
everything else seems alright, the RR lunched itself so got replaced and there is 14.5v over the battery and all the electrics work. on the stand it'll go into gear and spin the back wheel. I'm expecting that the bike should need choke for a good five minutes and then be able to idle at 1200 rpm, probably needing a little throttle screw to get it there. I'm reluctant to take it for a test, fail on emissions and then lose the free retest since getting time to sort this is sometimes problematic ( new job, weather, time-of-year, money ).
any ideas folks?
no choke needed points too, too rich on startup. Pilot jet is too rich, or there is too may shims on the needle.
switch to old pilot jet, see if it goes away.
It's most likely that the o-rings on the pilot needle (what you are calling "air screw", which is not only incorrect but misleading because it controls fuel, not air, and it's not really a screw...) are shot and leaking. This leads to fuel leaking past those needles regardless of their setting so mixture adjustment at idle has no effect, it's always too rich. I cover this pretty thoroughly in my blog post on fixing these carbs. (https://joshkarnes.blogspot.com/2017/09/fixing-common-gs500-carburetor-issues.html)
Other things to check:
1. Maybe the e-clip setting on the needles is too low. Move it so that the needles are "longer", that is, they will seat deeper into the jet. You want the main jet basically totally closed when the bike is idling.
2. if #1 is true, then ensure when your throttle stop screw is backed all the way that the throttle plate is actually closing. Could be a nick on the edge or carbon buildup in the carb throat causing it to not close.
It could also be the choke sticking open. Worth checking while you're in there.
My money's on it being the pilot needle o-rings. Everyone overlooks those. Once you start turning them it breaks the factory seal and a hard/flat o-ring no longer holds fuel.
J_Walker: The old pilot jets were wrecked, i had to drill small hole into them to knock an allen key in to turn them out... they probably weren't duff just had to be destroyed to be checked. they were also 40s. Would the needle jets be doing anything at this point? I'd sort of thought they got going somewhere after a quarter turn?
mr72: cheers for the blog post, I read it last night after I posted. Seems to be exhibiting those symptoms, didn't even realise there was an o-ring in there. I'll pull the carb and check the state of those O-rings. The adjusters don't have a great effect and one adjuster is a bit crunchy so might be this for the winning diagnosis!
Any idea what the dimensions of the o-ring is? Looks a bit like 1mm CS x 3mm ID?
After much hunting, looks like 1x3 is about right. the bmw f650 uses the same/similar bst33 mikuni guide here (http://faq.f650.com/FAQs/Carb_Clean.htm) - might grab a 1x3 and a 1x25 and maybe an intermediate one and see which fits best. Suzuki want at least £10 for two which is taking the piss. of course, if i lived in the states this would be easy...
13295-29900-000 looks to be the Suzuki part number but they are asking more for 1 before shipping than 5 nitrile 70 ones from a seal merchant including shipping.
The O-rings are a bit flat and a bit crusty. the LHS mixture needle head isn't great either but the needles look ok and the orifice isn't blocked on either. O-rings looks to be approx. 5mm diameter and a shade under 3mm ID. once upon a time i hazard they were 1mm c/s but today they are not. Replacements on order, will update once its back together.
Left
(https://s17.postimg.org/7kaoohva3/lhs.jpg) (https://postimg.org/image/7kaoohva3/)
Right
(https://s17.postimg.org/f09yaayez/rhs.jpg) (https://postimg.org/image/f09yaayez/)
Right again
(https://s17.postimg.org/hud3nqsvf/rhs_two.jpg) (https://postimg.org/image/hud3nqsvf/)
Needle wise...
(https://s17.postimg.org/qqnvrkwbf/needle.jpg) (https://postimg.org/image/qqnvrkwbf/)
Which position is that? I pulled the brown donut washer thing back to expose the other 4 slots. the loose whitish bit sits on the E-clip and the spring from the diaphragm acts on this. But is the E-clip on position 2 or 3? And would it benefit being a position higher ( or lower) for 125 mains and a stock exhaust given this bike is going to work as a commuter hack rather than a toy?
Choke seems fine, unless its broken internally, which i doubt. one buttlerfly was very slightly open compared to the other so i'll set those to be the same then sync them when its running ok.
125 mains and 40 pilots with needle in the middle slot and air screw set @ 3 out is a good starting point.
Cool.
Buddha.
Oh you may have high float. Check that, should be set to the top of the bowl, no more than 1mm off for good behavior @ start up as well as crisp throttle response.
Cool.
Buddha.
I think the float is ok although I'll check, one side was out a bit when I put them back before the no-choke condition and was adjusted a smidge.
I sort of hoped 40s + 125s would be a good starting point.
I'll leave the needle position where it is, I'm assuming thats position 2 (out of 4) and is 'slightly lean' of middle. I suspect my needle jet isn't original, clip positions seem a little less hacky than washers?
3mm ID x 1mm cross-section looks a smidge on the thin side, 2.6mm ID by 1.2mm cross-section looks quite close though. Adjusted them to 2.75 turns.
Fitted them but will have to reassemble the bike tomorrow to find out if they are winners.
That's the stock non US spec 89-00 needle.
Cool.
Buddha.
mr72, you were indeed right. cheers for the lead, wouldn't have even looked in there :) The bike now needs the choke to start and stay alive.
The mixture isn't right and the idle isn't great but some fiddling with the throttle adjustment, getting it up to temperature and syncing the carbs should help that.
I noted the exhaust-to-can join leaks.
Still its headed in the right direction.
Quote from: tobyd on April 11, 2018, 12:33:35 PM
mr72, you were indeed right. cheers for the lead, wouldn't have even looked in there :) The bike now needs the choke to start and stay alive.
The mixture isn't right and the idle isn't great but some fiddling with the throttle adjustment, getting it up to temperature and syncing the carbs should help that.
That's good news! Not a super easy fix because sometimes that o-ring gets jammed in the carb and it's hard to "pick" out of there but it sounds like in your case it was not hard.
Regarding the carb/idle adjustment, again you can look at my blog post linked previously and it'll walk you through this.
The key things are:
1. DO NOT ATTEMPT TO FINE TUNE UNTIL IT IS FULLY WARMED UP. You have to ride it like 15-20 minutes ON THE ROAD going through gears and with load to get it correctly warmed up. You can make adjustments when it's not warmed up but invariably you will wind up with the pilot too rich and the throttle stop too open and you'll get hanging idle and someone will convince you that it's too lean, which is wrong, and you'll chase your tail. Don't do that.
2. Set the idle SPEED using the pilot needles (mixture adjustment) when it's fully warmed up. Should idle around 1200 rpm but lower is fine as long as it doesn't stall. More fuel (richer mixture) will make it idle faster. The ordinary procedure is to get it good and warmed up and then turn the throttle stop all the way back so it idles low like 800 rpm then adjust each carb's pilot mixture needle until the revs stop increasing and then probably turn it back in 1/4 turn. Once you do that it should idle >1000 rpm if it stays warm. If it gets cold while you fiddle with it, then it may not idle as fast. The warmer the bike, the faster the idle will be.
3. Go ahead and get used to adjusting that throttle stop screw while at stop lights. After you ride a few times once you initially set it up you might need to tweak just a touch. If you find you have hanging idle then lower the idle speed (loosen the throttle stop screw). If you find that the idle dips when you stop and it wants to stall, open the throttle stop/tighten. Turning it like 1/8 turn at a time by hand is a good way to tune it as you ride. It's much easier with a glove on your right hand and to do it mid-ride after you've been riding like 30 minutes. It can take some gradual tweaking to get the idle dialed in perfectly. I actually used to carry a little stubby screwdriver around to do random idle mixture adjustments but after about a month I had it nailed down and then had to do one or two more tweaks to the idle speed mid-ride and it's perfect now and has stayed that way for many months.
4. If someone tells you "hanging idle" means "lean", stop listening to that person. There's no technical explanation that will make any sense but I can tell you precisely why hanging idle means the pilot may actually be rich but truly it's just the throttle stop set too high. This is a widely distributed internet myth as far as I can tell. I see it repeated all over all kinds of forums and it's just not correct. I guess somehow people must "fix" hanging idle by making it super rich which is why it persists. A 40 (or 20) pilot jet and 2.5 turns out on the pilot needle should be nearly right on. If you are >3 turns out then something else is wrong. I mean, my bike will idle pretty well with virtually no hanging idle with the pilot needles all the way in. It just idles at like 800 rpm.
thanks again, I read over your blog posts and its pretty comprehensive - the fun bit is getting it hot, I can't take it on the road and I live in town so I might have to start it up and leave it for half and hour at tickover, get it off choke then, and down to 1200rpm or so then get it an MOT (i hope) then sort it fully once its road legal again.
fun UK road trivia...
To be road legal you need insurance, road tax (annual rip off) and an MOT (annual check of road worthiness). You are allowed to ride/drive to an MOT without Tax but you can't road-tax your vehicle without an MOT. So if it lapses you are a bit stuck. Oddly, the penalties for no MOT are quite mild; not having Tax ( every year, "to maintain the roads" (if you say so) ) or Insurance is quite harsh.
I'll have to sort the leaky exhaust though since that's a fail. probably just not enough exhaust paste and too much adjusting it.
Exhaust may not leak once it's hot. IDK because I don't have slip-on exhaust, I have a bolt-on/flange. Oddball for a GS.
It won't ever get hot enough to properly adjust the idle mixture and speed if you run it only at idle and with no load. But you can certainly get it close enough to get it to MOT.
I'm sure you'll love this; I have to get an annual safety inspection for the state of Texas, it's $12. I just had this done last month. They literally didn't even put the key in. They didn't do anything AT ALL, just handed me a paper to sign and charged me $12, sent me on my way. Then registration yearly which is IIRC either $47 or $54. That's all the "tax" we have to pay. Automobiles and modern motorcycles with advanced emission controls have more expensive (and invasive) inspection, but it's still only like $30 or $35, I can't remember.
All of the "keeping up the road" tax we pay here is in the gas tax, which is still the majority of the cost of a gallon of gas. Fuel prices in TX are at a high for the past few years, $2.35/gal.
Oh and to rub it in even more, my motorcycle insurance is under $100 per year.
Come on to Texas. We have a lot of Brits here. Not that many GSs though.
I only noticed it was leaking because it was very damp outside, foggy and generally rank. I didn't notice it when it was running rich, but it was a lot drier then.
$12! an MOT is about $60 (even with the crumbling UK economy) and they check that things work (well, they are meant to, they start it and everything), I've failed a few cars and 1 bike because a number plate light didn't work... yearly registration is £60 or i don't know, $90? a gallon (4.45l) is currently at ( 4.54 * £1.22) = £5.50 = $7.83 = ((3.7 / 4.54) * $7.83) roughly $6.30 per US Gallon. Sigh. Insurance for me is quite cheap though (circa $220). A new UK motorist, aged 18, can usually look forward to > £1.5k a year insurance for a ratbox 1 litre, 3 cylinder car. I assume you have lawnmowers in texas with more displacement?
You lot seem to insure the driver/rider rather than the vehicle? We get to insure the vehicle so whilst I can't operate two vehicles simulataneously I am required to pay for the possiblity. Great eh?
ohwaitno.
Quote from: tobyd on April 12, 2018, 03:46:04 PM
I assume you have lawnmowers in texas with more displacement?
To be fair, they have lawnmowers with more displacement in England too:
https://www.youtube.com/watch?v=bWzmdtQ-o-Q
Quote from: tobyd on April 12, 2018, 03:46:04 PM
I assume you have lawnmowers in texas with more displacement?
Nothing unique about our lawn mowers except that they don't have any kind of emission controls really besides making the carbs non-adjustable. Some 20 years ago they started putting odd throttle controls on all lawnmowers so they are either on or off with no throttle you can adjust. And of course these days everyone likes electric lawn mowers because they are easier to maintain. Every year I change the oil and the carburetor on my lawn mower.
Quote
You lot seem to insure the driver/rider rather than the vehicle? We get to insure the vehicle so whilst I can't operate two vehicles simulataneously I am required to pay for the possiblity. Great eh?
Well, sort of. We insure both the driver and optionally the vehicle. Insurance in the USA is regulated by states (10th amendment, y'all). In TX you must carry liability insurance as a driver, which essentially says you are responsible to pay for damages to injured parties in the event you are found at fault in an accident. The choice of vehicle affects the cost of this liability insurance because it indicates risk level as well as potential damages. A motorcycle can do very little damage to another vehicle so liability insurance is not expensive. If you choose, or if you have a loan on the vehicle, you can buy additional coverage which will cover repairs to your own vehicle and your own medical costs in a wreck where you are at fault. It's still much more expensive than liability insurance but far less than what you are talking about.
Most things cost far less here than there. Fuel, taxes, housing (sq. foot basis), most goods and services, etc. Only big things that may cost more are health insurance and college. On balance it's still much less expensive to live here than it is in the UK or almost any other part of Europe.
Quote from: mr72 on April 13, 2018, 07:03:39 AM
Quote from: tobyd on April 12, 2018, 03:46:04 PM
I assume you have lawnmowers in texas with more displacement?
Nothing unique about our lawn mowers except that they don't have any kind of emission controls really besides making the carbs non-adjustable. Some 20 years ago they started putting odd throttle controls on all lawnmowers so they are either on or off with no throttle you can adjust. And of course these days everyone likes electric lawn mowers because they are easier to maintain. Every year I change the oil and the carburetor on my lawn mower.
Quote
You lot seem to insure the driver/rider rather than the vehicle? We get to insure the vehicle so whilst I can't operate two vehicles simulataneously I am required to pay for the possiblity. Great eh?
Well, sort of. We insure both the driver and optionally the vehicle. Insurance in the USA is regulated by states (10th amendment, y'all). In TX you must carry liability insurance as a driver, which essentially says you are responsible to pay for damages to injured parties in the event you are found at fault in an accident. The choice of vehicle affects the cost of this liability insurance because it indicates risk level as well as potential damages. A motorcycle can do very little damage to another vehicle so liability insurance is not expensive. If you choose, or if you have a loan on the vehicle, you can buy additional coverage which will cover repairs to your own vehicle and your own medical costs in a wreck where you are at fault. It's still much more expensive than liability insurance but far less than what you are talking about.
Most things cost far less here than there. Fuel, taxes, housing (sq. foot basis), most goods and services, etc. Only big things that may cost more are health insurance and college. On balance it's still much less expensive to live here than it is in the UK or almost any other part of Europe.
The UK is overpriced even just by European standards, to be honest. A fair few of our continental neighbours pay a lot less and get a lot more! Talking motorbikes specifically: our roads are among the worst in Europe, and there is unprecedented levels of motorbike theft (and general crime issues) here. I mean seriously, you could leave a motorbike out with maybe a disk lock - if you're feeling paranoid - in 90% of European cities, but you'd better have more than a few locks handy if you want to leave your bike anywhere in this country.
And I'm lucky to live in a young town where I take pretty well-maintained/newly-surfaced roads to work, but where I lived before some roads were literally fairground rides. Yeah, just two reasons from a massive pile for why I won't be buying my first house in this country.
That said, you
are allowed to ride untaxed to an MOT appointment. Just be prepared for hassle, on the
very rare chance that you actually see a traffic cop with ANPR fitted.
Quote from: Kookas on April 16, 2018, 03:35:25 PM
there is unprecedented levels of motorbike theft (and general crime issues) here. I mean seriously, you could leave a motorbike out with maybe a disk lock - if you're feeling paranoid - in 90% of European cities, but you'd better have more than a few locks handy if you want to leave your bike anywhere in this country.
That's nuts. In Austin (I live in a suburb...), I have NEVER seen a lock on a motorcycle. I could probably leave the keys in mine parked on the street in front of my house and have no problem at all. I mean, nobody around here even uses the helmet lock, we just hang the helmet on the handlebar or the passenger foot peg.
Of course, in TX the use of "deadly force" by citizens to prevent crime is justified in many cases where someone would be stealing a motorcycle. Most Texas homeowners have at least one gun on their property and a there's a substantial chance any citizen you encounter may be armed. If someone goes to steal a motorcycle in the nighttime, there's a reasonable probability they will be shot.
I know. I've never heard of it in any other developed country either. Like, maybe San Francisco comes close to how the whole UK is, but that's one city with gentrification problems, not a whole country.
As I've said elsewhere, there have been people who have toured the world, including through all manner of impoverished or developing countries, only to get here and lose their bike to Britain's finest scrotes.
Quote from: mr72 on April 17, 2018, 06:34:55 AM
Of course, in TX the use of "deadly force" by citizens to prevent crime is justified in many cases where someone would be stealing a motorcycle. Most Texas homeowners have at least one gun on their property and a there's a substantial chance any citizen you encounter may be armed. If someone goes to steal a motorcycle in the nighttime, there's a reasonable probability they will be shot.
Really? Texas allows use of deadly force to prevent property crime? That seems a little extreme. Most states require there be a threat of imminent bodily harm to yourself or others before you can use deadly force.
Quote from: Bluesmudge on April 17, 2018, 10:33:06 AM
Really? Texas allows use of deadly force to prevent property crime? That seems a little extreme. Most states require there be a threat of imminent bodily harm to yourself or others before you can use deadly force.
Well there are certainly conditions. Usually it's robbery, aggravated robbery, or theft in the nighttime. But there are also special circumstances regarding your domicile or your vehicle. Considering how TX law ordinary errs on the side of the initial crime victim, I think it's unlikely anyone would be successfully prosecuted when using deadly force to stop the theft of their motorcycle. IANAL and all that of course.
So after a fair bit of fiddling with this i think its sort of right ish (enough for a test) at 2.25 turns on the mixture screws @ ~1200rpm. There is a slight hesitation on blipping the throttle from tickover and the engine isn't as smooth as i expect so I'll check the carb sync (now I've drunk two big bottles of corona, stupid me made a mamometer from plastic before realising, oh yeah, they crush...) and get that closer and see if that smoothes things over. then have another check of the mixture. It comes off choke a little too soon, maybe 5 minutes tickover @ 2.75 turns and blipping the throttle gave a bit of soot in the exhaust so if anything i think once sunk (synced? synched?) i should be able to back this off to 2 turns and have a nice setup.
Booked in for an MOT and new tyres (avon road riders anyone? ), bad time of year as i have to wait until middle of May for that...
plenty of time to clean the chain and watch the grass grow and get older i suppose.
Quote from: tobyd on April 20, 2018, 12:42:42 PM
There is a slight hesitation on blipping the throttle from tickover
Likely just normal behavior of CV carbs. There is a small time delay between when you open the throttle and when enough vacuum builds to pull the slides up.
If it's excessive delay it may indicate damage to the slide diaphragms such as pin holes or a vacuum leak.
Quoteand the engine isn't as smooth as i expect so I'll check the carb sync
Dunno what's meant by "smooth" but nearly always any running issues are due to lean conditions even if transient. Just FYI. Carb sync can't hurt and I'm told (although I have no direct experience) that the low-rpm/light-throttle stutter I have is related to carb sync.
sync'd the carbs, one side was out by a fair bit, adjusted it so the water level is steady, with slightly longer fuel lines it can be done with the tank still attached. Raised the idle speed to around 1800 to do the sync as per a guide somewhere. blue-tack worked surprisingly well as a seal.
(https://s17.postimg.cc/mq4guohy7/sync.jpg) (https://postimg.cc/image/k8spney1n/) (https://postimages.org/app)
Bike then ran appallingly. :( sigh.
Pulled the plugs (black, needs some on road action to clean them up), checked the gaps (one was slightly too tight) cleaned them off and reinstalled, might throw a new set on anyway since i have no idea how old they are. they dont look too bad.
bike still ran badly.
wound in the mixture screws and once again reset to 2.5 turns, set the idle speed to about an indicated 1500rpm, adjusted below 1500 rpm the bike is not running happily. at ~1500 rpm the throttle response is instant, no obvious signs of rich running, sounds ok seems quite smooth. Does the bike need some throttle adjustment for an idle? if i unwind the throttle stop completely is this suboptimal?
i have a suspicion the tacho isn't so good, it barely moved when i first got the bike going, was very sluggish. cleaned it up but it might not be so accurate at low speeds. or at all.
might have a poke around for air leaks, the intake boots aren't great.
Anyway, cleaned and lubed the chain and check the tyre pressures and scraped some crap off the wheels as a distraction.
Yeah the idle speed is too high. Back it down below 1200 when it's fully warm to avoid the dreaded hanging idle.
Made it worse today, ran it for a while, but wouldn't run off choke, below about 2000rpm its lumpy as anything and rapidly dies.
adjusted it up and down, checked over the cable routings and positions and they seemed ok.
then it wouldn't even start, made encouraging noises but would run for a second then die.
needing choke to work is making me think very lean. So i though "maybe its those ancient intake boots, where someones wobbed up the cracks with silicone?" que, dismantle process.
(https://s17.postimg.cc/g7goerwm7/IMG_20180422_142348.jpg) (https://postimg.cc/image/opq4j434r/)
both have splits where the boot joins the metal backing plate, although one is really mangled and has been repaired*. Not entirely convinced the carb was sat in them properly either, nor were the clips doing a great job. stumped up for some replacements...
Will put some new plugs in too then at least i know they have been done.
rechecked the float heights and they seem ok, RHS is slightly below the gasket line and LHS is exactly on gasket line.
Might having 'wrong' O-rings in the idle mixture needle/screw assembly cause an overly lean condition?
I did replace them with ones that seemed about right but weren't as specified. I'm now wondering if 2 or 3 turns on the mixture isn't enough as the o-ring is thicker and isn't letting enough fuel through once off choke? I suppose letting it out to 4 or 5 turns and dialing in won't hurt?
Plugs and intake boots should be arriving tomorrow and I might be able to get it back together Wednesday evening but I'm wondering if swapping in 3.0mm ID x 1.0mm C/S orings in place of 2.6x1.2 might be closer to factory? Definitely seems to have gone from way-rich to way-lean after swapping them?
Quote from: tobyd on April 23, 2018, 04:12:28 PM
Might having 'wrong' O-rings in the idle mixture needle/screw assembly cause an overly lean condition?
Nope.
Quote
I did replace them with ones that seemed about right but weren't as specified. I'm now wondering if 2 or 3 turns on the mixture isn't enough as the o-ring is thicker and isn't letting enough fuel through once off choke? I suppose letting it out to 4 or 5 turns and dialing in won't hurt?
No, it doesn't work that way. The o-ring keeps the fuel in the passageway from leaking down the screw shaft and out of the carb. It basically isolates the fuel from the atmosphere. And turning it out more than 3 turns is useless, the needle is all the way out of the jet by then.
The big problem wth putting in the wrong o-ring is that it may not fit in the prescribed space, causing it to bunch up or fold, or rattle around (if it's too thin/small, unlikely). And then when you screw the needle in you may munch the folded o-ring and ruin it. Also this would cause the needle to not "bottom" in the right spot, so it may be too low (too far out of the jet) when you start adjusting so maybe you go 2 turns out but the needle's in the position that it would be at 4 turns out if you had the right o-ring. Then the more annoying problem is that the wrong o-ring will probably get stuck in the carb when you remove the needle to try to replace it, and you'll have to make a tool to "pick" it out of the carb which is easier said than done. BTDT. Not worth risking with the wrong o-ring. And FWIW I couldn't find ANY off-the-shelf o-ring that was exactly the right size. I could go put a micrometer on one of those original o-rings and give you approximate dimensions but why? You can get them for like 50 cents each from http://www.thisoldtractor.com/for_sale_dr350_orings.html ... 13295-29900 ... just get the right ones and stop worrying about it.
Quote
Plugs and intake boots should be arriving tomorrow and I might be able to get it back together Wednesday evening but I'm wondering if swapping in 3.0mm ID x 1.0mm C/S orings in place of 2.6x1.2 might be closer to factory? Definitely seems to have gone from way-rich to way-lean after swapping them?
Order some of the right o-rings and while you're at it intake boot o-rings from the same place, do it right and don't worry about it any more. FWIW some sources say that o-ring is 1mm x 3.5mm so your o-rings are in fact too fat.
I re-read your last couple of posts and don't see any indication it's running lean. In fact your black plugs make me think it's rich at idle, and likely because the o-rings are too big. But if you had leaks in the intake boots it would run extremely lean above idle both because it's leaking air in behind the jet and also because it reduces vacuum a lot and therefore never lifts the slides to pull the needles out of the main jet.
Getting the o-rings wrong on the pilot needles will cause all kinds of troubles that are hard to track down, but it's 90% at idle where these problems manifest. Once you are running off idle or above like 2K rpm and with more than like 1/4 throttle you should be mostly on the main jet and then you have to suspect vacuum issues as the primary cause of what's wrong. You know the intake boots are knackered. Fix what you know is broken and don't fret about other stuff until you can rule out the obvious.
If you must go through the cycle of take-apart-put-together many times, then go ahead and ride it with suboptimal idle util you can get the right o-rings. But if you don't have new intake boot o-rings then don't bother putting it back together IMHO. Just get fresh intake boot o-rings and new/correct pilot needle o-rings and be done with it in one shot.
BTW I don't know what your float measurement was referring to but incorrect float level will look and feel like mixture problems at conditions besides idle. Check here: http://gstwins.com/gsboard/index.php?topic=26604.0 ...
The boot o-rings were replaced when I was ordering some other parts, the boots weren't concrete hard but weren't supple. The replacement boots came with replacement O-rings amd arrived today so i'll put those on and swap the plugs over. I'll try the 1x3 orings, i bought at the same time as the 1.2x2.6 ones in place if they look messy. I'll go out and pull the carb now and have an investigate since i have to move the bike for something else anyway.
Sadly, its the shipping from the US on those that will be a problem. I doubt i'll have enough time to get them ordered and the thing sorted enough for mid may. Perhaps i'll get a set later I'm the year depending on how things go.
I'm fairly happy with the float heights. Measuring them as per the diagram isn't the most accurate thing i can think of anyway since you need need to have it 'just so' and there are no convenient flat surfaces to get anything accurate in a nice position. the drain tap + hose method seems sound enough.
edit: so the 1.2x2.6mm O-rings are snug on the needle shaft, the 1x3 O-rings are loose, about the same as the washer. the RHS needle came out as a complete assembly, the LHS needed the oring removing.
Sounds good, forgot which side of the pond you are on. You'll work it out for sure. But I still don't think you're lean.
:)
right again, replacement washers and new plugs in started up. sounded bad, very sluggish. was just on the reserve level so sucking air and petrol. flipped on reserve cheered it up.
i'd set it to 2.5 turns out and 1 turn of throttle. wasn't running great on that, got it down to mostly off choke and it wasn't great still. gave it a bit more throttle and it cheered up, backed the mixture screws down at half turns and around 1.75->2 turns seems best, bought the idle down to approx. 1400, i think its a little lessthan that since my tacho isn't great. anyway, throttle is sharp and returns quickly, exhaust seems clean. engine is a bit tappety but aren't they always? might need the valves re adjusted once I've got some miles on it. i'll need to re-torque the head bolts in a few hundred miles so will check then.
i don't think its 100% but i think it'll do for the MOT and then i can get it properly warmed up and set. might see if i can find some 3.5x1 orings and try them out. the 3x1s dont appear to be leaky yet. i dont mean to do this-old-tractor out of a job but having the measurements would be great as a general resource, most ebay seals seem to arrive the next day.
thanks again mr72!