I recently bought an 88 XT600 that wouldn't start easily or stay running, but sounded good when it did. It sat for 2 years so I figured clogged carbs. Well I cleaned them(twice actually) and made sure no plugged holes. I got it running and it ran great, full throttle and all.
I filled with gas(it was old gas in it), 93 super unleaded here in the states, went 2 miles toward home and it suddenly bogged like it was working real hard and kept popping/ backfiring. till it died, wouldn't restart. after a bit with full choke it did start but same thing and died. Recleaned carbs, made sure no air leaks(even put light silicone sealer on some things).

It then started up and ran perfect, idle smooth, let idle for a couple minutes then bog and popping again and it died. I belive it would be the cdi or coil( it didn't seem to have great spark, but the bike is new to me so I don't know how good it should be) the plug color looked a bit lean and even after kicking on full choke it was dry. That says fuel issues, but outside of some internal air leak or out of spec part it isn't a clogged jet or port. BUT the popping and bog when it gets warm says cdi. Any of you that have been running these bikes have some possible solutions? Thanks JJ

No I didn't , the pin wouldn't come out easily and until I had a new needle valve and pin I didn't take it out, which I have ordered because I wanted to replace it anyways. I also didn't know it had a screen like that and that would make sense. The one question on that would be, when it did quit, I opened the bowl drain screw to check for fuel and it did come out, but whether there was enough,I don't know. It wouldn't start this morning after 8 kicks on full choke. I'm going to squirt some gas and a little oil in the cyclinder tonight. If it fires up, I know it is mostly fuel related.

Thanks for the picture, it shows what is in there.

Try a simple one first - a new spark plug. I had an XTZ that did something similar thing once and it turned out, after multiple carburettor cleanings, to be that. The plug gave a fine spark when out of the cylinder but was breaking down when under load.

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Martin

finally back on the road again


http://awayonmybike.blogspot.com/

A quick update today, I put in a different plug, still nothing but backfiring( had to stop and sleep with icepack around my ankle, afraid of it being broke from one nasty pop). Now decided to kick with my motocross boot on right foot.
I decided to rollback to when it quit running, about 1.5miles AFTER filling up with 93octane GAS. Drained gas out of tank and float bowl and got 87octane from a different company. About 6 good kicks it fired up and is running, let it idle for 3-4minutes, went around the block a couple times. It does still have a skip in the firing, runs perfect under acceleration(easily hit 85mph and still going), with a steady throttle it has a stumble.

Any ideas what the steady misfire would be? Has no backfiring, plug now looks good color. Over tightened valves? Do these motors get tight or loose with wear? No knocking or ticking at all, entire motor sounds smooth and has great power. I'm going to really like this bike once it is straightened out.

Dirty fuel filter
Carb failure
Faulty ignition coil
Faulty pickup coil
Bad CDI unit

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Christian

Leaking inlet rubbers causing a weak mixture.

They are rubber bonded to steel and they deteriorate over time. Unless they have been replaced in the bikes life you almost certainly have this problem.