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.

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 - 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


Right


Right again


Needle wise...


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.