No 3 & 4 Cylinders lazy

[ookie]

just purchased a 1986 Fj1200 from  chap who has had it for over 10 years, he parked the bike up when the clutch slave cylinder failed and didnt get around to fixing it. (Approximately 16 months ago)
Anyway fixed slave cylinder, cleaned out carbs as full of red rust.
Bike starts easy enough though not firing on all 4 appears that No 3 & 4 are not pulling their weight, changed plugs and getting healthy spark, engine revs up though spits and farts about with the odd flashof sparks from the exhaust.
Previous owner said it ran well- I have no reason to disbelieve him.

Any thoughts?

Paul

[fj1289]

Fit a fuel filter.  Clean the carbs again (and probably a few more times before it's all over!).  Are #3 and #4 float bowls filling?  I've had a carb float stick in the "up" position before and wouldn't fill with fuel.

Good luck and let us know what you find!

Chris

[ookie]

Cleaned out carbs and tank again, fitted filter, reassembled, now missing on No 3 only, suspect that the needle valve is sticking as plug is dry and clean, will up date as to progress (squeezing in carbs and hoking up cables a real pain!)

[fj1289]

(squeezing in carbs and hoking up cables a real pain!)

Gets easier with practice...DAMHIK!

Chris

[fj11.5]

pod filters make carb work much easier , so does sitting a plastic tool box across the frame , and flipping the carbs over leaving cables in place, unless you prefer working on a nice steady bench 

[ookie]

Havent managed to find an adaptor for the compression tester as yet, looks as though a modification of an old plug is required unless someone can sugest another method.
Carbs off again now using a temporary fuel tank which is clean, No 3 cylinder exhaust doesnt get as hot as quick as the other 3, No 4 seems ok plug colours very similar though obviously difficult to tell condition as not running well enough to make a judgement. Still spitting back.
Engine revs barely drop when No 3 plug cap pulled off, other plug caps make a noticable difference.!

[fj11.5]

I used an old spark plug as well, couldn't find an adapter for my comp tester either

[ookie]

Compression test reveals that all 4 cylinders are between 140-145psi this is with the engine cold, going to make a connector to enable cylinders to be pumped up should show whether the valves are leaking. other than that Not sure what to look for!

[andyb]

What do the plugs say?  Almost sounds like an iffy plug cap on #3 or a gross mismatch with the amount of fuel it wants (either carb or air leak).  Plug should tell you if you ask.

Arguably, if the lash is way out, you'd have seen it on the compression check.  Possible that a ring isn't working right, but I'd have thought a comp check would have shown that too.

[fj11.5]

if your valves were way off comp shouldn't of been that high, my valves were toast, comp test didn't get past 70 psi on 3 cyl,s  0 on number 4

[ookie]

Slipped the carbs on from the x police fj onto the 86 fj- wow different machine now fairly crackles when the throttle is cracked open, need to rebuild the old carbs?