Popping through carbs

[Thom]

Right i've managed to temporarily fit my float valve seats firmly into the carb with the help of some glue to stop them leaking until i get a new set.

Problem is since i completely had the carbs appart (i mean both of them seperated and everything) the bike has began popping when at low revs, won't idle by itself and if i hold the throttle fixed at any point the revs drop until it stalls.

I thought it could be the valve timing out but it would appear this isnt the case (Checked it), and there is once again smoke coming out of the exhaust but unlike last time when it was oil this smells of unburnt fuel and appears to be white-ish/blue.

Could it be i've got the mixture screws simply set wrong? The plugs don't appear to be too far off the wrong colour to be fair. and theyre not fouling now.

Its probably really obvious but i cant get my head around it.
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Current Bike: 1996 Yamaha TRX850 (The Japanese-Ducati One).
Previous Bikes: 1990 Honda NSR125 'Rothmans' (The smoking one), 1990 Suzuki GS500e 'Caf? fighter' (The loud one), 1987 Kawasaki GPX400r (The quick one), 1997 XJ600s Diversion (The reliable one), 2000 Kawasaki ER-5 (The spontaneously combustive one)

[Ichy]

Did you sync the carbs when you put them back together? Did you remove the mixture screws and how did you adjust them when refitted?
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https://www.metacafe.com/watch/1972097/how_to_behave_on_a_forum/

[Thom]

I've synced them by eye but not using the vacuum guages as of yet because i cant get it to run long enough to do so.

the mixture screws were removed and set at 2.25turns out as per the manual

The carbs are synced in the same way i did it last time so i dont think thats the problem (although by no means am i an expert) but could there be an air leak between carb an engine causing the problem?
____________________
Current Bike: 1996 Yamaha TRX850 (The Japanese-Ducati One).
Previous Bikes: 1990 Honda NSR125 'Rothmans' (The smoking one), 1990 Suzuki GS500e 'Caf? fighter' (The loud one), 1987 Kawasaki GPX400r (The quick one), 1997 XJ600s Diversion (The reliable one), 2000 Kawasaki ER-5 (The spontaneously combustive one)

[Ichy]

Seems like there could be an air leak, either through the manifold joints or maybe one of the vacuum connectors or pipes. Usual trick is to spray stuff (I use easi start, others, I believe use WD40) around all the joints to see if the engine note changes.

Just another thought, did you check the float height after patching them up?

Have you tried adjusting the mixture screw?
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https://www.metacafe.com/watch/1972097/how_to_behave_on_a_forum/

[Thom]

yeah the float heights are fine and ive left the mixture screw where its supposed to be.

ill try checking for air leaks monday, working tomorrow
____________________
Current Bike: 1996 Yamaha TRX850 (The Japanese-Ducati One).
Previous Bikes: 1990 Honda NSR125 'Rothmans' (The smoking one), 1990 Suzuki GS500e 'Caf? fighter' (The loud one), 1987 Kawasaki GPX400r (The quick one), 1997 XJ600s Diversion (The reliable one), 2000 Kawasaki ER-5 (The spontaneously combustive one)

[Thom]

Right i've just been playing with the bike and im stumped.

Had it running albeit poorly. I've tried dousing everything that is pressurised in WD40 but it doesnt seem to change a thing and therefore im saying it can't be an air leak.

The popping appears to be from both carbs also as apposed to just one.

I'm not sure what to do really as the timing appears correct after checking it.

If its any help, when removing the carbs from the engine white smoke comes out of each inlet, this to me says the exhaust valves arn't doing their jobs properly, and i also noticed my cam chain feels a bit slack.

Could the cam chain being slack cause the valve timing to go enough to cause this popping problem?
____________________
Current Bike: 1996 Yamaha TRX850 (The Japanese-Ducati One).
Previous Bikes: 1990 Honda NSR125 'Rothmans' (The smoking one), 1990 Suzuki GS500e 'Caf? fighter' (The loud one), 1987 Kawasaki GPX400r (The quick one), 1997 XJ600s Diversion (The reliable one), 2000 Kawasaki ER-5 (The spontaneously combustive one)

[bandit_nate]

Hi,
What bike do you have?
I don't know the whole background story but i thought i'd say that it sounds to me like poor valve clearances, if you've definitely ruled out air leaks that is (make sure all the vacuum bungs are in place and all jubilee clips are secured).
A loose cam chain shouldn't have an effect on the timing as the tensioner will take up the slack unless the tensioner has failed, they're simple to replace/ service

[Thom]

it's a gs500e from 90 mate.

and how do i go about checking valve clearances, by checking the shims?
____________________
Current Bike: 1996 Yamaha TRX850 (The Japanese-Ducati One).
Previous Bikes: 1990 Honda NSR125 'Rothmans' (The smoking one), 1990 Suzuki GS500e 'Caf? fighter' (The loud one), 1987 Kawasaki GPX400r (The quick one), 1997 XJ600s Diversion (The reliable one), 2000 Kawasaki ER-5 (The spontaneously combustive one)

[bandit_nate]

gs500's a pretty easy bikes to work on, i've never done valve clearances on a gs5 before but i'd guess it's similar to a gpz5.
You have to remove covers on the engine casing, one for attaching your socket driver to the shaft nut and the rocker cover to access the valves, then rotate the engine to whatever marking (Remove right "suzuki" cover and locate the R and R-T marks).

Look on here...

https://www.gstwin.com/adjust_valves.htm

You don't have to remove the carbs to do this valve check btw.

Hope this helps.
Nate

[Odie]

if you have only had your carbs apart then how could it be your cam timing that is wrong?
and glue, what planet are you on?
as for not idling, try cleaning out your idle jets, you will find it helps!
If you cannot balance your carbs because you cannot get it to run long enough, take them off, find a small, and i mean small drill bit, about 2 mm, place it in the inlet side of the carb and adjust so that both carbs gently grip the drill bit in turn, the same amount, that will give you a start point.
not being funny but if you dont know, dont play, you will only cause more mess, unless you have money to pay me to fix them
____________________
You are so ugly when you were born the doctor said "I?m gonna drop it, if it falls is a rat, if it flies is a bat."

[The Shaggy D.A.]

[Thom]

[Thom]

Right, refitted the carbs to the bike and had it running again although it doesnt seem to like it.

Im going to hopefully get a small video clip of it tomorrow to post up here because im stumped!

The problem is pretty much this, i can get the bike to run although whilst on choke it barely revs up at all (less than 1.5krevs) and will soon stall (less than 10 seconds) i have to carefully give it revs.

Now i can rev the bike up fine, but it will pop every 3-5 seconds through the carb with the revs falling until the point it stalls.

Now obviously, with the throttle set at say 4k revs the revs shouldnt drop, but they do.

I can't decide whether or not the bike under or overfuelling but it feels to me as if its one of them... possibly overfuelling as it's popping through the carb, the exhaust gasses are heavy and im guessing the throttle/revs problem is because the cylinder cant burn all the fuel and so floods a little more each time?

Someone give me some instructions to tell me what to do and ill follow them!

I've just had a really stupid thought... i was running the mixture screws out at 3 turns previously, obviously this caused rich running but i didnt have this popping issue.

Since i returned the mixture to stock as per manual its been acting weird. I've missed something dead obvious?
____________________
Current Bike: 1996 Yamaha TRX850 (The Japanese-Ducati One).
Previous Bikes: 1990 Honda NSR125 'Rothmans' (The smoking one), 1990 Suzuki GS500e 'Caf? fighter' (The loud one), 1987 Kawasaki GPX400r (The quick one), 1997 XJ600s Diversion (The reliable one), 2000 Kawasaki ER-5 (The spontaneously combustive one)

[Odie]

Right then go back to the beginning and start again, putting everything back to the stock settings and checking every-thing.
That means taking your carbs off (again ) and stripping them both down to the bare bodies (f,narr, fnarr).
Check every-thing twice just to make sure, that means checking your carb diaphrams and accelerator diaphrams for pin holes / cracking, all jets including internal, internal and external air / fuel passages, making sure that you havent got your throttle slide needle clips in a different positions than stock (if adjustable)etc.

I know that this is some-thing that you have already done but you need to make sure that there isnt some-thing you have over looked.

You will also need to check the condition of your inlet manifolds, if they are cracked or have gone hard.

When you do make adjustments make only one at a time, that way it is easier to diagnos a problem than to try and figure out 2 / 3 / 4 changes at once, all it is, is common sense, run through things logically, one at a time.

Hope it helps
Odie
____________________
You are so ugly when you were born the doctor said "I?m gonna drop it, if it falls is a rat, if it flies is a bat."

[Thom]

Well i have work tonight and a very busy weekend ahead of me so it won be until monday when i get a chance to have a fiddle with the bike, ive double checked the carbs and it just needs putting back together.

After 8 months of rebuilding this bike from the ground up and encountering some stupid expenses this is a problem i cant seem to fix myself and so the garage is getting it.
____________________
Current Bike: 1996 Yamaha TRX850 (The Japanese-Ducati One).
Previous Bikes: 1990 Honda NSR125 'Rothmans' (The smoking one), 1990 Suzuki GS500e 'Caf? fighter' (The loud one), 1987 Kawasaki GPX400r (The quick one), 1997 XJ600s Diversion (The reliable one), 2000 Kawasaki ER-5 (The spontaneously combustive one)