81 kz305

Ive done some work on my bike over the last year or two. rebuilt the top end, new seals, lapped vavles etc. also put in a new air filter, had a piece of foam glued in when i bought it. replaced both slides with diagrams.

last year i noticed that the engine seemed to be struggling at full throttle, if i closed the choke half way it seemed to run smooth through the higher rpm, when cruising it would buck unless i opened the choke .

to me it sounds like the main jet is too small and not giving enough fuel at full throttle but the secondary and the idle is great. so i was just looking for a second opinion to see if im right about the main jet or not. i believe the valve clearance is good but dont remember, would that even be able to cause this issue?

Are you running completely stock? I would be more inclined to think vacume leak,dirty carb, stuck advancer, ect than the main jet size (if your running the stock setup). Stock my 305 will do 80+ at WOT

New carb boots. Checked advancer a couple times, it's not stuck. I've cleaned the carbs a couple times last year. Just took it out yesterday for the first time since last year and it's the same issue.

Reason I wonder about the main jet size is because the air box was cut and the foam glued in I though it could be possible someone switched the jet to compensate possibly.

This started after I rebuilt the head , cleaned and fixed carbs and put a proper air filter in. Reason I think it's jet size is because it runs fine in all other ranges but full throttle.

Last year I put new sliders in and it ran great but when I took the head off after the valves were full of carbon build up.
I plan on taking the carbs out tonight and checking the jet size though.

You say this was the first ride since last year. Were the carbs drained before it sat? Around here, fuel begins to fossilize in as little as 3 or 4 weeks.

Carbs were drained. Like I said. Same condition as last year before it was put away I just didn't care enough to try and fix the issue as I just finished a rebuild and just wanted to ride. Dirty carbs isn't the issue.

What are spark plug readings after high speed throttle chop procedure?

Are valve clearances within specs?

Good Fortune!

Has to be ruled out. Out of the last 10 people with a 305 that had issues 11 of them had dirty carbs or leaky boots. :laugh: it always starts with the same questions, don't mean to insult your intelligence.

havent done a plug chop. havent checked valve clearance, can that cause this?

i didnt take it as an insult. im pretty easy going on the internet.

ive spent more on this bike than its worth and i cant stop now.

Rule out the valves first.
Steve

here are the plugs

took the carbs out, mains are 65 and secondary are 82. from what i can find on partzilla.com the factory sizes are 62 and 85.
i'll be doing the valves this weekend.

Finally got a chance tonight to do the valve clearance. All of them were out. The intake was about 0. Haha.

After that I decided to redo the point gap and timing. I find the instructions in the manual to be difficult to understand. I set the left side all good then go to the right and the gap opens a little early so I adjust the point gap to get it and then the gap is too small. Next it says to adjust gap to .35 then move the whole plate to get the right side timing.
Check left gap and timing readjust if necessary. But to check the left timing I have to move the plate again. It just seems like I'll just mess up the right and I'll be in an endless loop.

Any tricks for this?

You set the plate for #1 then move the little plate for #2 when you turn the crank to the right position.
Steve