fzr 1wg not firing on one

[stephen918]

ive got a fzr400 1wg genesis that ive been rebuilding from a bike that hadn't run for a while , now the problem I have is it wont run properly on cylinder 4 , ive got spark the carbs are clean but there seams to be a lack of vacuum as the carb slide doesn't move as much as the others also the header pipe on this cylinder is nowhere near as hot when running as the other 3 , now im thinking its a valve problem as it dosnt blow smoke or use oil , has anyone got maybe another idea of wot it might be that might not require removing the head , or am I about rite

[dobbslc]

It could be a tight valve clearance that you can check and re shim without taking the head off.
Or a split in the carb diaphragm losing the vacuum that lifts the slider.
Also worth checking for air leaks on the engine side of the carbs.

[Evilchicken0]

Take the air box off.
Start the engine, then spray some carb cleaner down the carb intake. If it fires then its probably the carb, if it doesn't then chances are your valves are too tight. Its usually the inlet vales they end up touching the camshaft and not closing, no compression.

[stephen918]

checked diaphragm and there was no holes , if the valve clearances were that close would the head not be scrap with the seat buried in the head , guess its cam cover of and have a look , now another question what are the valve clearances

[dobbslc]

Clearances can just close up over time so the head could be ok,
I've seen a few bikes with 0 >0.02mm valve clearance that wouldn't run properly but were ok after re shimming them. I don't know the settings off the top of my head but Boris aka evil chicken will sort that out I'm sure.
Let me have a guess though... inlet 0.18>0.25. Exhaust 0.28 >0.35mm. how'd I do?.........

[Evilchicken0]

No idea ... But go to the document library link at the the top of the page and you'll find links to the 3tj setup manual (its a big document) the clearances are in there.