not sure what it is but the engine sounds OK when idling or when coasting down the road but once i get on the throttle it starts to knock a little. also gets worse as the biek warms up, not so soticable when it is cold. i have not had a rod bearing or main bearing go in an engine so i am not sure if that is the problem or not.
any info would be great as i just got this dam thing back together and now this i am not a happy camper.
If you threw a bearing it's going to knock and carry on at all the rpm's in the range. From idle to redline. It would be more so of a violent vibration in the bars. Have you changed the oil? See if little metal bits come out when you tap into the drain plug...Hopefully not.
Did you pull the plugs? What color are they? [make sure you run the bike for a bit get it real warm. Come back to the garage wait for the engine to cool off then pull the plugs and note the color.] I would go ahead and put new plugs in anyways since their cheap.
I think you just need a valve job IMHO. Sounds like one of the exhaust lobes is a little out of spec. There is a FAQ about how to do a valve check.
define valve job? if you mean check their clearances they are at .005" or .002" over spec.
I will check the oil and change spark plugs just did not think that would be the issue.
if there is anything else that comes to mind let me know
mike
Hard to tell about a noise without hearing it, but if it is heard on acceleration and is worse as the engine warms up it could be gasoline knock/pinging. Can be bad on a GS as carbon builds up with many miles on bike.
What grade of gasoline are you using? If regular 87 octane, try a tank of premium 91/92 octane and see if it's better. If you are using heavier than 10-40 or 15-40 oil, that could make it much worse. Change to the lighter oil if it's the 15-50 or 20-50 and see if that helps.
It's much worse on 2000 and earlier GS500s than on the 2001 and later GSs that have the 3 circuit carbs rather than the old 2 circuit. If it's one of the older type and it pings badly when you open the throttle a small amount try opening it more. That usually stopped the pinging on my 97.
Running 15-50 Mobil 1 synthetic in my 97 GS I went from reg grade gas to mid range and then to premium grade gasoline over a couple years as milage added up at 15-20k miles/year to reduce gasoline knock. After changing from the 15-50 oil to 15-40 Delvac 1300 oil I could run it on regular gas again. Heavier oil makes the air cooled engine run hotter. Good oil flow is necessary for cooling the head.
jack would the timing advancer do that as well? i am running 10-40 oil just put a tank of 93 in and running a advancer. i am playing with the carbs as well i am currently 140 main with 2 washers. 3 turns out with pilots. definately runing rich i can head it popping in the exhaust can. will cut back fuel and see if that helps at all. just really hope it is not the rods.
If it were possibly a mechanical knock, it would be more likely a main bearing rather than a rod bearing. Main bearings knock under heavy load while rod bearings generally knock when backing off the load. I doubt if it is either in this case.
Advancing the ignition timing in a gasoline engine definetly makes gasoline knock worse, one of the things generally done in past years was to retard the timing to reduce the knock. A little light pinging under acceleration is harmless but heavy gasoline knock can do serious engine damage. Can you put the standard ignition setting back on to try to see the effect? Both of my GSs are stock engine wise and will probably remain so although I've considered rejetting the 97 to make it more suitable for winter use. Someone like Srinath could give you better advice on your carb mods but it sounds to me like you bike is much too rich if it's popping back in the exhaust. Ignition missfiring will also cause backfiring, are your plugs good?
Quote from: russomfjack would the timing advancer do that as well? i am running 10-40 oil just put a tank of 93 in and running a advancer. i am playing with the carbs as well i am currently 140 main with 2 washers. 3 turns out with pilots. definately runing rich i can head it popping in the exhaust can. will cut back fuel and see if that helps at all. just really hope it is not the rods.
Advancer makes it knock easier yea. But 140's are too rich with stock air box, and too lean with K&N pods. 3 turns out with pilots - you mean air screws ... Popping in the exhaust does not mean rich, it could very well be lean, or even normal. Misfire could also be lean. Not just rich. Rich misfires are sorta wet sneeze like, lean misfires are much more louder and sharper pitched.
If you got stock air box and UNI or stock paper - you need 125 mians and 1 washer along with 40 pilots.
With K&N pods you need 150 mains in place of the 125.
Cool.
Srinath.
I'm saying main bearing, but I'm a glass is pretty much empty kind of guy.
srinth
i have uni pod filters, full system 2 into 1 yosh exhaust, advancer, 3 turns out with air screws, jet needles are probably equal to 3 washers, and 140 main jets. also milled heads .020", web cams, and the engine does not have more than 300 miles on it since the rebuild.
did not make this noise at first (122.5 main jets) but since i richened the air/fuel it started to make this noise. i will do new plugs soon and any suggestions for air screw and main jets?
OK a stock motor will need 150's ... milled and modded cams = :? :? :? ... but 140 still sounds wrong ... 122.5 was better ... ??? I doubt it ... but no real Idea, if you make the heads flow better you'd need to jet up I think ... but hey no real definite idea.
Cool.
Srinath.
i know. i bought the bike from a friend who did not have the time to put it together. he was setting it up for a track bike so i have a lot of different things on it to help improve performance. i will start with plugs and 150's and go from there.
dump a whole bottle of octane boost in there and it should fix the problem for now. with the intake and exaust you are running about lindsay lohan lean, on 140 mains, you need atleast the 150's. and if you want to run 87 gas with the advancer get a stock head, and if you want to run the milled head, retard the timing from stock. if you want to run both, atleast 92 octane. btw i got a set of pistons so when you blow a hole in one of yours let me know and I'll sell them for a good price.
davipu
appreciate the info even with the sarcasm. i will jet to 150's and run 93 octane. i removed the advancer but now it stumbles pretty bad off the line, what pilots should i be running? how do i set them up once i get them in.
again info is much appreciated.
With stock motor 40's ... the one guy I knew from way back when, that ran a pumped motor (dont remember the details really ...) with stock carbs I believe used 45 pilots and 155 mains ... 40/150/1/3 is a starting point for a modded motor ... yea and run it too lean and you'll have to take up davipu's offer ... I'd actually start with ~160/45's and get leaner ... going lean to rich is the risky way to jet. Besides, 1 jet size too rich and you'll know right away. 1 size lean and you may never find out. I'd jet leaner from 160/45, and see what change gave you the best bump in performance and go back 1 step. say it ran much better with 155's than 157.5's ... you'd go back to 157.5. You also need to jet it in the dead of winter, not in summer. But that back 1 step will work just fine.
Cool.
Srinath.
if you want to get it right the first thing to do is find a shop that has a dyno with a exaust sniffer. and they will tell you aprox what to go to then do the trial and error. Srinath's suggestions 99% of the time are right on the money, if you didn't want to spend the money on the dyno run I'd follow his suggestions.
160/45/1/3 OK i know the 165/45 but what is the 1 and 3? is 3 the number os turns? what is 1 then.
thanks
one shim on the needle.
ok so i went 155/45 3 turns and no change to the washers. now it hardly idles. i sounds like it is firing on 1 cylinder and gets a huge puff of black smoke every time it fires. i can hardly get it to 5k then it starts to sound normal and take off. do i need to go back to a 40 pilot? i even tried turning in the air screw to 2 turns and it got better but not perfect. this is really starting to wear on my nerves i work on the f-ing thing more than i get to ride it anymore and that is starting to upset me. little help please i just want to go riding and not have to work on this thing.
i have a fuel injected bike and never had these kind of problems.
OK back down to 40 or 42.5 pilots, and over 5K it runs fine ?? then try 160 mains ... you need to jet it down from "crappy rich" ... not up from "fine but lean" Yea you mod the motor ... you're in un charted waters buddy, I worked on my jetting for almost a year ... you start on this 2-3 days ago and expect it to all be peachy ... yea ... FI is good, but over bore it, over size the valves, flow it and mill it and see how much harder it is ...
Cool.
Srinath.
i bought the engine form a friend i thought he had all this sorted out before he gave it to me, that is why am upset i did not choose to have the engine work done. just frustrated is all i seem to be in the bike more than i am not. why go to 160 mains if i am getting black smoke? should i just go to 40 pilots and see from there? think i am changing too much each time to get a base line. also what does the air screw do and how is it supposed to work on our carbs?
You are way over jetted on the mains and running very rich. I was running 145 and 147.5 with the 555. I kept playing with which one I liked the best. With 150's it would run flat. I know the new owner changed the jetting slightly but that have to do with location/elevation.
Are you running stock pistons?
stock pistons yes, decked heads, web cams. help please
I will need to look at my notes on the jetting I was using prior to boring for the 79mm pistons. Other than overbore and your milled head, our setups are the same.
dgyver thanks a lot i look forward to your input. thanks to everyone else who has helped.
can anyone still tell me what who the air screw works?
OK dgyver you made a larger chamber ... and needed slightly smaller jets, he's got a larger (well what did you do ... dude I dont remember) ... but larger Chamber with same carbs = smaller jets ... remember in the old days suzuki used to fit similar carbs to 750's and 1100 and they'd jet the 750's with larger jets and smaller in the 1100. Bigger chamber = more velocity = smaller jets, now larger valves and milled head dont actually result in an increase in velocity like the larger chamber does (who knows my instinct tells me its not) ... so you'd have to jet up.
Now black smoke under 5K is cos pilots circuit is too rich ... whihc may be wholly different from the main. You drop to 40 pilots, you lean out the mains further (pilots affect the mains and Vice versa) ... so I'd rather you dont start with a jet size that give you max power ... start with somehting that is so over rich it runs like sheite ... and drop into the right jet sizes.
I dunno, I'd try 40/160's instead of 40/150's. A tweaked motor is more likely to blow a hole in the thing even if its slightly lean ...
Cool.
Srinath.
Do not forget about the cams. High lift + longer duration = more flow
When I ran the 75mm pistons (the rest of the motor was the same as the 79's), 140 mains worked good. I tried as big as 147.5 and it had nothing on the top end. Try 140 and then you may want to go down a size or two.
Another question...are you using stock needles or DynoJet needles?
Quote from: dgyverDo not forget about the cams. High lift + longer duration = more flow
When I ran the 75mm pistons (the rest of the motor was the same as the 79's), 140 mains worked good. I tried as big as 147.5 and it had nothing on the top end. Try 140 and then you may want to go down a size or two.
Another question...are you using stock needles or DynoJet needles?
You had DJ needles in right ... huge difference ...
Cool.
Srinath.
i have 3 different needles i can use. stock and the other 2 are as follows 1) same length as stock but the end is tapered down for the last 1/2" to 1/2 the diameter. then i have a set that are about 1/8"-3/16" shorter but have ther same taper as stock. i am running the shorter set than stock right now so i do not have the washers in the system. so should which pilot jet should i go to? 40, 42.5 (if they make it)? i have to go buy some tomorrow. thanks again guys much appreciated.
Use the stock jets first, as long as they are in good shape. The shorter and tapered ones may open up too fast.
Use the 40 pilots. I tried 42.5 but it did not help but it did not hurt either.
Also, try plugging one of the holes in the bottom slides. It helped with my idle hang.
OK so go 140 mains, stock jet needles (no washers) #40 pilots and about 3 turns maybe less. thanks for the starting point. your input has been much appreciated.
I do not remember the exact number of shims I was running, it was only 1 or 2. The needle height affects the mid range so start with 0 or 1 shims. The main jet size must be within 1 size (no more than 2) before adjusting anything else. It affects all the throttle ranges.
OK i will start with 140's and see if i can get a set of #40 pilots today, then set up the rest from there. you have been a great help, how will i know if i am running lean or rich? i keep getting told to run rich then lean out but do not know when i am running rich or lean, what are the symptoms for both?
You can look at the plugs for their color. Black = rich, white = lean. Good is a medium/light tan. This can be misleading since they only show the running condition throttle position when the bike is shut off. Which is usually at idle. Without doing a plug chop at WOT, you will not know if the main is correct. Also, looking at the exhaust tip will show light carbon dusting if you are running rich.
thanks ill have to do all that to make sure i am not runnning rich or lean. better safe than sorry. so i have to be moving when i do this right? that must be interesting to pull off, let me guess, full throttle, left hand on clutch, right hand kill switch and coast to a stop. great as if riding were not hard enough as it is.
Yeah they are kind of tough to do. Then you have to wait a little bit for the motor to cool off to pull a plug.
These articles might help you to understand carb tuning / jetting better; jetting will always be a bit of a black art. Since you're starting with a milled head, you're dealing with higher compression, and the carbs will be more sensitive to the changes you make. Be sure you're tuning from rich to just-slightly-lean to just right, unless you like seeing daylight through pistons. Better to deal with fouled plugs / too rich rather than holed pistons / too lean.
http://justkdx.dirtrider.net/carbtuning.html
http://www.factorypro.com/tech/carbtune,CV,high_rpm_engines.html
Let us know if you need anything clarified or explained...
EDIT: Neglected to mention that the first link refers to the Kawasaki KDX (dirt-bike) two-stroke engine (don't worry about reed-valves etc.), but the animation and illustrations are good. IOW, ignore the two-stroke details, and focus on the specifics about carburetion, and you won't get confused.
Thanks for posting the FactoryPro link. I did not have it handy. I keep several printed copies in my log books.
btw....if you think tuning a carb on a 4-stoke is a tough, try tuning a 2-stroke GP bike. The jets have to be changed as the temp and humidity change. A friggin pain! They are a blast to ride though. If it was not for the maintenance, I would get another one.
off to get my #40 pilots and 142.5, 137.5 and 145 mains. will post up what i find as i go through this. with the pilots set i do not mind changing the mains it is not bad and i can do them hot now. just takes a rag top keep the hands from getting burned.
OK Let me know what works. I just have a feeling that milling the head, flowing it and higher lift cams dont actually significantly incread the velocity through the carb ... Higher velocity = smaller jets due to hiugher vacuum, and over boring it does accomplish that ...
Higher compression will need the same mix composition as normal compression, and its not a big step up to flow, taller cams will fill the chamber better at low revs, but sorta choke it up at higher revs duration and dont do much for velocity increase, higher duration cams will probably raise the velocity in the carbs to an extent ... and mix loss in over lap will make your motor lean ... and you'd run into limits in the carbs ... you'd need bigger ones. Now flowing ... OK that will make the flow through the carbs faster, but it will move more vacuum into the carbs and hence not actually make much of a diff in jet size ... See jet changes are needed when you alter vacuum in the carb for the same flow ... Take off the air box and paper filter and instantly your carb has a lot less vacuum, that lower vacuum will have to suck out the fuel needed ... so you;d have to drop in larger jets. You dont have anything that has increased the velocity ... a whole lot ... Anyway let me know what works.
Cool.
Srinath.
The longer the valves are opened with the high lift cams will increase the amount of fuel supplied.
I wish I still had access to CFD software.
Quote from: dgyverThe longer the valves are opened with the high lift cams will increase the amount of fuel supplied.
I wish I still had access to CFD software.
That will mean higher lift and higher curation. Duration is to make the thing run well at higher rpm inspite of fuel loss due to over lap. High lift fills the chamber better by effectively not letting the valve itself obstruct flow. Just high lift will not significantly alter vacuum or velocity in the carb throat ... I think ... honestly you can only fill a certain volume of chamber with so much material ... the duration the thing is open if it goes up with an increase in the overlap ends up losing mix into the exhaust ... there by it is like filling a larger chamber ... so if he got high duration cams it may need a smaller main jet ... I think ... also there is that element of having the re-atomisation thing ... you want to sorta compensate for it too ...
My guess then is ... high duration = smaller mains ... the rest all are insignificant ... Happy now ...
Cool.
Srinath.
Makes sense.
Still wish I had CFD to model it.
What is CFD - computational flow diagram ??? Computerised ... whatever ... I studied flu mech, and some of this crap was what stuck ... Yea ... scary ...
Cool.
Srinath.
CFD = Computational Fluid Dynamics
i now have 140, 142.5 145, 150 and 155 mains with #40 pilots i will let you know what i find. first set up the #40 and start about 145 and will take it out runn full throttle and kill the engine check the plugs and tell you what i find. if i have to go leaner i will, richer i will. will also re-read that link to see about the cold vs hot running so see if it correlates to what the plugs show. I was debating on velocity stacks for it as well as they do wonders for the tls i was hoping they would do the same here. will let you guys now what i find as i find it.
ok at what point are plugs no good anymore? i think i have 2 bad sets now and forgive me by i am going to run lean to rich. sorry but not in the mood to buy a gross of plugs for this job. i cannot even get this thing to idle correctly. i have the 40 jet with 135 mains and it is blow black moke out the rear.
I have a question because it is different from stock but is the pilot jet supposed to have small holes drilled into the body? my 37.5 stock jet did not and it ran a little lean but my 40 has holes in the body and it runs extremely rich. is this my problem for idle?
i think i am going back to 37.5 pilot with new plugs and setting up the mains, then buying #40 pilots without holes and setting up the idle. then i'll tinker with the midrange as i feel like it. should i be looking at different heat range plugs? i am lost here the bike ran OK but never this bad i am just disgusted with it right now.
The pre-2001 used "non-bleed" pilots and the 2001 and later used "bleed" type pilots. Bleed Type run much richer than non-bleed type in the GS. So, a 40 bleed type acts like a 42.5 or 45 non bleed. That is WAY too rich at idle.
That said, if you are jetting by the trial and error method, you always start with the main jet - get that right and the rest is much easier. Get that wrong, and there is nothing you can do to figure out the mid-range and off-idle.
Your list of jets is conspicuously lacking the 147.5.
Way back in the thread you mentioned that your needles were equivilent to 3 washers and you have a 122.5 main. Are you using an aftermarket kit that came with needles? If so, are the 122.5 their jets too? If so, most of the advice on jet sizes is wrong - it is based on stock needles and standard Mikuni jets. Different kettle of finny things if you have Dynojet needles the Mikuni jets will be way richer than the Dynojet jets.
thanks for the pilot jet info. all the main jets i just bought are mikuni jets not dyno jets. the pilot jets are bleed type with the holes which explains alot. i am gong back to my 37.5 stock pilots and then a 145 main. right now i cannot even get the bike to idle correctly so i might as well go back to stock and order the non-bleeder type pilots in a #40 IF it is still running rich after i go back to stock (it should be) that way i can atleast test the main jets to see if they are the correct size and work back wards a little after i get the #40's in. if anything it will run a little more rich which is not a bad thing.
I am still learning about these carbs just wish i did not spend money on what is now junk.
Yea 40 non bleeds ... Parts unlimited number is 42-7130. Need 2 in that pack of 4, sell the rest to someone else ...
Now plugs ... stock plugs - NGK - DPR8ea-9 whatever = total junk. Somehting has happened to NGK of late, and they seem to have made their plugs a lot colder in heat range ... they plugs foul out easy and just are total BS. I went to Champion 809's for a well jetted GS, so you're rich and that makes the plugs choke up and die ... please get champions ... autolites are black on black on black ... and hence un readable ... 809's baby.
Cool.
Srinath.
much appreciated. little update i had the entire stage 3 dynojet kit so i figures i would install it. The bike runs perfectly off idle, pulls well to red line but same as before it does not seem like it has power in 5th and 6th above 8k BUT tat is above 90MPH and not a concern for me right now so the bike runs well i am leaving it alone and will pull plugs after running to make sure it is OK.