'88 XT600 CDI going out?

After 2 days now cleaning and double checking everything with the carb on my recent buy, I've decided the bike must have the cdi going out. I cleaned the fuel system thorough yesterday and it fired up but wouldn't idle without poping and skipping . Once throttle was rolled on it ran great. This morning went 2 miles to get gas and it didn't want to start but finally it did and it ran the same till 1/2mile from home, then suddenly bogged and popped, backfired, wouldn't rev and wanted to die, till it did. The motor sounded like it was working hard. Spark plug was really light grey and dry. Went back through the carbs and boots, triple checked for any air leak ect.. Got it back together and it started up ran smooth, idled no popping for about 2 minutes, then bog and backfire, then die. With full choke I can get it to start after five or ten minutes but won't run. Which parts are the most likely culprits on these bikes, I haven't done much with the Yamaha's in a while.

After going through pretty close to the same thing you are on my 86 xt350 i replaced the carbs because I broke them after cleaning a few times. Any way my bike ran great and it's now starting to do what I thought i fixed. I can run all day on the street but as soon as I hit the dirt and start climbing it loads up backfires and starts to die. I have to full throttle it to clear it out and it's fine unles I keep climbing. Going down hill is fine.

The only parts I havent changed yet is the gasket around the Main Nozzle. and a couple of O-Rings in the carb.


I may have my issue, or part of it, taken care of. When it first started backfiring I had just filled up with 93octane gas. I got a couple gallons of 87octane from a different gas station and drained the tank and float bowl, then refilled with the new stuff. After about 6 kicks it fired up and slowly cleared it throat. It now is running, but still has a steady stumble. When going down the road under acceleration( doesn't have to be hard acceleration either) it runs perfect. Has lots of power( quite a bit more than my Honda XL600R), just that stumble with a steady throttle or idling. No knocking or ticking at all, engine is quiet. I'm going to go through the valves and make sure they didn't go tight, I know some motors wear tight instead of loose.

I just picked up an 84 Yamaha xt600 that the previous owner said he coudnt get to run. He said it had fire and fuel and feels like great compression. We did put a. Small amount if starting fluid in and the plug looked like new but it didn't try to start. Any advice on what it Could be I would appreciate it.

Edited by Streetsmarts360

Make sure the timing is right first,(I assume you made sure it has good spark with a plug out of the cylinder and grounded against the motor). If at TDC and the marks line up, then timing is good(the key strips out on these bikes easily, so they go out of time ,or not put together right in the first place).

I have a siringe that I put gas or oil down the plug hole with, if you have spark and timing is on, compression is good, I put a tbsp. of oil first in the cylinder and kick it over a couple times to sealed up. Then I mix some 2 cycle oil (light mix 50:1) with gas and squirt a tsp in the cyclinder . I'll never use starting fluid! It'll wash down the cylinder and cause scratched walls.

The one thing I have learned with this bike is the "procedure" is rather impotant to get them fired up reliably.!! NEVER TWIST THE THROTTLE till is is physically running !!! Before turning the ignition switch on, pull the choke out fully, I kick the thing over (at a slower but crisp kicks) three or four times then push the kicker down slower till the decompression lever snaps(means you just hit TDC on the compression stroke). release the kick lever up to get a full stroke, THEN turn the ignition switch on. Then give it a kick like your trying to put your foot 2 feet into the ground!!, If it doesn't fire, kick hard again. If still nothing, it most likely isn't going to after a third kick. Take the spark plug out and see if is wet.

The other thing I have since found out with these bikes is the biggest failure ignition part that goes out is the pulse pick-up/stator, then cdi.

Edited by jjktmrider

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