Originally Posted by steveloomis

I know this is unlikely but could the cam chain have jumped a cog. Exhaust every possibility. Is your spark a good strong spark or kind of spindly?

I looked back on this thread and see you got the stator re-wound and a replacement CDI. Was it a new unit or used or aftermarket CDI. Is it the CDI with all the pig tails on it or the newer TCI with the plugs built-in?

The reason I ask is my 86 would start after many kicks, the spark was not too strong. IT ran but not the best and backfired plus it had numerous oil leaks. I put it in the shed last winter and started thru it replacing seals, removing the rockerbox and resealing, setting valves, cleaning carbs. the whole gamut. When I pulled it out to start it, no spark at all, my spare 84 xt's cdi was dead too so I tested everything I could to verify my stator and trigger coils were outputting, they were and the ohm readings were pretty close. I ordered 2 replacement CDI from Hyperpak in New Zealand and forever later I finally got them, plugged one in and I had a good healthy spark. With just a few kicks it started and ran better than it did in a long time. I took the other CDI just temp plugged it in 84 bike and it had good spark too.

So I say all this to show that the CDI's can go dead or almost dead just sitting around. I think the components go bad, capacitors dry out etc.

Originally Posted by steveloomis

I am looking in my OEM Yamaha 1986 XT600 manual carb section. The fuel level should be 7mm +-1mm BELOW the float bowl mating surface. A rough measurement is carb upside down, float attached, tilt carb so float tang is just touching but not depressing the float needle valve spring. With the gasket removed it should measure 26mm +- 1mm. This gets it in the ballpark but must be checked using the fuel method.

I've found it easier to have the carb in hand, fuel supply attached, allow to fill and stop, then gently jiggle the clear tube so the fuel will settle, it tries to stick due to surface tension. If you tilt the carb and allow more fuel to flow in and raise too high, it will not flow back so you need to drain some out and allow to fill again. It is kind of a juggling act and takes a knack.

If you do the fill and jiggle a few times you will get the hang of it and if you get repeatable measurements and be assured it is correct. The level should not be a make it or break it if close.

Thanks for that Steve. is it likely that my problem will be sorted by lowering the fuel level slightly, it ran perfectly once started.

If your carbs are like mine, early 80's to 89 or so, not sure when it changed then you will also have a diaphram on the left carb on the side of the body. That is the anti-backfire control or coasting enrichner. The way it works is if you close the throttle quickly at high rpm, the high vacuum at the head where the secondary carb is attached is piped over to the primary carb and controls the diaphram. This diaphram if engaged it shuts off air to the pilot jet causing a rich mixture, this rich mixture going into the hot exhaust pipe is harder to ignite so NO backfire.

Attached is a diagram showing the pathways. If you have a plugged line to the pilot jet for the air it needs, you will be rich. Just a possibility.



To troubleshoot, notice the enrichner Air Jet. If the diaphram is NOT engaged due to high vacuum then the air is routed to the pilot jet, if engaged or line plugged no air to the pilot jet and it is rich all the time. I use brake clean or some other clear fluid from a pressurized can to check passages, you can see the fluid come out, where is hard to see air coming out. If this passage is clear, fluid should flow all the way through. You can remove the pilot jet to allow a larger flow, then check it with pilot jet installed.

I hope this helps.

Steve

Originally Posted by steveloomis

An easier way is to unplug the black wire with white stripe from the CDI, this takes all the kill functions out of the picture, bar switch and ignition both put a ground on this wire to kill the engine. Once you do this, you will have to put in gear and clutch it to kill it....

Of course you have to pull the seat and tank to do it. We are just suggesting the easy to overlook stuff. When you are in the middle of it and frustrated, it is difficult. Some time you have to walk away for a while, clear your head. I think you are close, at least it started and ran fairly well, still maybe rich.

What about the choke, is the end of it still sealing well. If it is leaking, you may be rich from that. What do you think Mezo?

Steve

Originally Posted by Jens Eskildsen

Are you familiar with kicktart bikes, they can be a real &/%%* to start without the right technique....

Originally Posted by steveloomis

I have not had mine apart so cannot speak as to how close to the marks it needs to be.

I am sure someone will be able to answer you. Glad you found something amiss. Hopefully, it will start and run better now.

Steve