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Ok, seems i have some leprechauns around that im not able to solve so I have to ask this out loud here. Ive gone through every thread that had to do with this matter but wasnt lucky enough...

The engine: 1127cc from a ´92 wrecked bike I bought. While changing the spark plugs, one tiny fucker (bolt) decided to go on an adventure inside one of the pistons. It was in TDC so I didnt have space to insert a magnet…solved taking off the cylinder head and removing it. New gasket and i decided to clean the piston head and chambers, check for gas leakings, some minor polish in exhaust chambers too... small and easy stuff. Everything was perfect and in great condition so I put the head back and tightened it to specs. Timing chain was in tolerances and camshafts seated and timed to specs. Valve spacing was checked too and had to buy one of those plastic cases full of valve shims. No problems at all here.

The carburetors: 36 mm from the ´89 engine I have around with transmission problems. Cleaned thoroughly and all the internals were checked and turned out to be in great shape too. Benched synchronized and synchronized again with the engine running. 122,5 main jets and pilot jets 2 turns back from seated (taken from the manual). Idle set in 1500 rpm +/-

Spark plugs, caps and coils: working great. There is spark in all 4 spark plugs.

Oil: synthetic Castrol 10w50 that I had around from previous maintenance stuff. Ill change to 10w40 after running the bike for a while. New oil filter too.

Air filter: not new, but soaked in water and cleaned with a compressor.

Silencers: those 2 heavy OEM bazookas.

I supply the bike with fresh gas from a plastic bottle not to put the tank on it yet and make working around easy.

The 4 exhaust pipes heat evenly.



All in all, no aftermarket stuff, upgrades and so on.



So, having said all this:

-the engine breathes and lives (BIG HURRAY HERE), but the problems are:

--I warm up the engine, set the idle all the best I can to manual specs and one minute later goes up to 2000 rpm. Don’t know why

--really difficult to start the bike. Choke in max position, it wont fire easily. With its OEM battery, I would exhaust it every day. Im currently using a car battery to fire it up since it has bigger capacity. I don’t accelerate it while having the choke fully in cause ill foul the plugs most probable.

--The choke works like a charm cause when it starts in max position, rpms go up to 5000. When I push it back to the second and last position, rpms go down to 3000-25000

--When warmed up, things don’t get better neither. I still have to use the choke to fire it up. It doesn’t start easily and I would exhaust a smaller battery really, really certainly

--plugs come out great when the pilot is set to 2 turns back from fully seated but, in case I was doing sthng wrong, I did some trials adjusting the 4 pilots to 1,5 turns back from seated, to 2,15 and 2,30. No results were
appreciated.




I don’t have a clue whats going on. I checked everything ten times and its really painful to hear the bike crank over and over again without firing until 4-5 tries later.

I did trials with and without the air filter. With the air filter bolted in like normal and not bolted in (slightly separated from its casing). I tried almost every combination with no results.

I am aware that the 36mm carbs are not of this model and I do have the 40mm ones around but they still have to be repaired (impossible to adjust the float height correctly. Whatever I do, it will stay the same. Ofc, I cannot put them in the bike in that shape).

Last but not least, I don’t specially like how the engine sounds. At idle, the cylinder head makes some remarkable noise (I even rechecked the timing and valve clearances again). Of course, when you rev it, the noise turns into a symphony but as said, its not really attractive at idle. (Chances are it will get better when i pour the 10w40 in...)

So, finally, wheres the leprechaun, poltergeist, troll, etc... that’s undermining my mood recently? Any hints, help, critics, slapping or whatsoever will be tremendously appreciated. Thanks as always.


Chemoto :cheers
 

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Discussion Starter #2
forgot to say that the bike revs nicely. No symptoms of going down or stalling in any fraction of throttle twist. Rpms go down when you shut the throttle. Just normal and regular stuff here...
 

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If it responds really well to applying the choke it would seem to be lean - dragging air in via intake manifold seals ? - although you say it doesn't hang when you rev it . . hmmm
did you have the bike running with these carbs before the bolt mishap ?
 

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thanks nick, i got the ´92 engine with carbs and airbox jointly to substitute the ´89 one i had with the transmission broken so no, it didnt run before with those carbs.

irregular idle can be due to wrong pilot jets or bike going too lean but if its going lean, it had to rev irregularly. And it happens the opposite. You twist the throttle and revs go up with not a single mumble. Also it does not hang when i stop "revving" (I only went up to 5k rpm) it so im totally lost. Ill use some smoke to try and see cracks or sealing issues in the intake manifolds but i should have seen that before when i first inspected that.

anyway, i cleaned the air filter again and i noticed it had too much oil inside so I took off circa 150 ml. I also removed the silencers to continue checking things out.

more theories will be appreciated ;)
 

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Intake manifold o-rings fresh? Carb to manifold boots all TIGHT? (NO leaks/air sucking through?)

It was said before, but I did not see confirmation of those things...

Idle stop adjusted "out" enough to let proper lower idle? Throttle cables "loosened" and re-tightened WITH A LITTLE SLACK to allow throttle to shut completely?

Just some thoughts...

-crisp
 

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hi mate yeh check the boots for air leaks ,spray something like wd40 ,carb clean ,brake clean or engine start on the boots while the bike is running if it revs up you have an air leak , did you set the float heights on the carbs ? wind the idle screw right out and set the idle when the engine is warm .maybe recheck the carb balance ,just some more thoughts .
 

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to remove your leprechauns use a rat trap with a gold ring as bait if there is one in the motor it will only be small one so a rat trap should be fine leprechauns love gold if it is a gremlin dont feed it after midnight & dont get it wet
 

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Discussion Starter #8
ok folks, some answers to your comments (thousand thanks btw):

-there are no air leakages in the manifolds, boots or whatever. I proved it by spraying some carb cleaner around the intake manifolds and revs didnt go up. Same goes for the cable slack which its in order. No surprising results here.

-I suspect that the dancing idle could have been due to an improper pipe routing. I managed to direct the gas hoses way vertically to the two T´s and now the idle stays fixed. Problem solved.

--------------------------------------------------------

The engine fires a bit better now. After checking and rechecking and realizing i did everything right, I settled the pilot screws to 2 turns out (nothing new here) and proceeded to do some tuning.

jumping forward a bit (trial and error proceeding...), i settled the screws to the following config:
-carbs 1 and 4: 2 and 1/4 turns out
-carbs 2 and 3: 2 and 1/2 turns out

Now the bike starts way better but it doesnt fire with energy still. I can only make her start doing the following:
-choke to the max, twist the grip like half of a turn
-choke fully closed, twist the grip almost fully opened.

I think the bike still goes lean though. Anyway, any thoughts guys?
 
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CHEMOTO
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