Here's a basic one, On the across since I've had it running (6000km) its been flawless, in the last month its started picking up this problem where it will sometimes foul cylinder 4 (the farthest right cylinder if your sitting on the bike) with no real pattern on a cold start sometimes within the space of one night. It starts on all 4 but after about 5 seconds it'll surge and puff out the exhaust like an attempted backfire and drop to 3 cyls. Warming the engine to max temp and hammering it to the redline won't bring it back to life either. Plug has to be taken out and cleaned before it runs again. Its sooty and dry. I've swapped the plugs around and it still does it so its definitely particular to that cylinder. Once it is going though it won't happen again all day no matter how many starts. Sometimes it won't happen for another month and sometimes the next day. Once it is running however it goes perfect as always. So i don't see if being something ignition related. The spark is really strong once the plug is clean. Oh and using no choke at all or full choke has no bearing. It's done it using either method. SOOO i'd like some input on the situation. My thoughts are that either: 1) Stuffed piston ring oil fouling the plug cause the bike is using a decent amount of oil. But the plug isn't wet. 2) Issue caused by valve clearances. I checked them 6000km ago and they were tight but within range. But defo need doing again cause its hard to start and runs a bit crap in the lower ranges. Possibly caused by tight clearances?? Im sort of thinking this might be it atm. 3) Stuck needle valve in that carb. I don't see how it could though given the tank is below the float level and its pumped up. the only fuel left in the system would be from the short downhill run from the airbox to the carby itself. Surely that's not enough to flood it? Unless the fuel still flows like a siphon, cause i do leave the fuel tap on all the time (under the though the fuel cant flow from tank to carb without the pump going). 4) overly rich idle mixture. Doubt that too because the revs hang if i even adjust it out 1/8th. And the economy is great. Pulling the carbs apart for another clean tommorow anyway as a measure of course, so if that doesn't sort it what do you reckon? Thanks heaps
Hey Desmo If it was rings, it would consistiently fouling the plug, an easy way to verify it would be to use a set of compression gauges to see if the compression is down on that cylinder. Carby's are a good place to start, in particular a blokced main jet ( dont forget to clean the emulsion tubes), do you have a set of balancing gauges, would be interesting to see what's happening on number 4. As always, valves can cause all sorts of erratic behavior, maybe a trip to your lcoal bike shop for an adjustment is in order. Let us know how you fare Chris
Valves are easy done myself just have to ride it out for another 500k till its time for the service and ill do it all at once! Cleaned the carbies. There's a wierd looking sediment in the bowls, which is very odd because the fuel filter is clean and i know the tank is clean inside from when i had it out not so long ago. Looks like northern territory red dust or something. how odd! Maybe its just dirt from the 91 fuel im using? ??? Polished the valve seats as a matter of course but it all looked good in there. However this looks like the symptom. Number 4 carbs dropped its slide. Derp. should have known to check those first >.> Only replaced the damn holders a few thousand k ago! how lame. Time to cook up a better solution for those stupid holders i thinks. The way its done on the gsxr400 carbs which are similar is far better. so perhaps replicating those holders to fit the smaller carbs will be the way foward. Fixed it up anyway, so i'll see how it goes. fingers crossed. A bit baffled by how its managed to run so well considering :-\ lol
