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Old 03-21-2019, 03:37 AM
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Exclamation Here we go... 1982 yz80j problems.

     

Hello everyone , I've recently bought an old yz80j. When I first got it and tried to get it started it ran but ran like poop (bogging hard) I then I put a new spark plug in and it ran a bit better but still would bog out at 1/4 - full throttle . So naturally I guessed carb clean and cleaned everything in carb completely. Jets looked like they'd been taken in and out a hundred times but didn't think much of it. Put it back together and slammed her back in the bike and tried it out. This time it ran a lot better and would sometimes hit powerband after cutting and bogging . So I thought surely it's the age of the carb so I got a new one.. now it idles and revs high with 1/4 throttle but still farts and coughs when full throttle is applied or bike is under load. I've messed around with air screw and idle screw but can't seem to find the sweet spot . I've moved the needle clip down 1 (3rd from top) and it helped a little but still bogs down if I apply full throttle and sometimes backfires back through Carby.. I've taken the reeds out and flipped them over and they seem like they are fine.. has a strong spark when I check it by hand so really not sure where to go from here... Can anyone shed some light . Cheers -Shae
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Old 03-21-2019, 06:11 AM
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Put a timing light on it and make sure the timing is correct, consistant and not jumping around. At least eliminate that, but I do think it is carb related.
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Old 03-21-2019, 07:49 AM
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Low compression will cause these issues.

Paw Paw
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Old 03-21-2019, 12:44 PM
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Quote:
Originally Posted by Brett Campbell View Post
Put a timing light on it and make sure the timing is correct, consistant and not jumping around. At least eliminate that, but I do think it is carb related.
It's just had a new carb tho.. it's been cleaned etc too..

I'll have a look at timing after work but don't think it's that because it revs high and idles good when standing
I'll take a video after work of what it's doing

---------- Post added at 07:44 AM ---------- Previous post was at 07:43 AM ----------

Quote:
Originally Posted by PawPaw View Post
Low compression will cause these issues.

Paw Paw
It has good compression.
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Old 03-21-2019, 04:03 PM
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What is the compression reading?

Paw Paw
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Old 03-21-2019, 04:07 PM
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Originally Posted by PawPaw View Post
What is the compression reading?

Paw Paw
I don't currently have a compression guage (I'll try find one to borrow ) but feels ok to me .. I've been able to kick start it once warm also . .
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Old 03-22-2019, 08:49 AM
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Originally Posted by Rickoshae View Post
I don't currently have a compression guage (I'll try find one to borrow ) but feels ok to me .. I've been able to kick start it once warm also . .
Compression can "feel" ok even when the motor is on the low end of spec and on the verge of not being able to run at all. Judging compression by feel works as a basic diagnosis often times but when you're trying to sort out an issue like this knowing the actual compression value can be helpful. Or, at the very least it could help point you in the direction you need to go.
A couple other things to check- is the air filter clean and in good shape? Condition of the airboot between air filter and carb? Condition of boot between carb and reed block?
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