Ugh!!! Weird results changing jets and other mysteries.

yuckfoo

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First time builder here. I have a PK-80. It comes stock with 70 or 72 jet. (I've been told both.) Needle clip was at 2nd from top on a 5 position needle. I put a 68 in and had better results trying to get it started, but it was not quite right. I put 65 jet in thinking I was on my way in the right direction but it got worse. With the original jet it would start and run for a few seconds only with the choke closed. With the 68 jet it would run better and longer with the choke open. With the 65 jet it would not run with the choke open but only with it closed just like the 70 jet. This makes no sense in my book. Why would the 70 and the 65 run with the choke closed and the 68 with the choke open? I could see the 70 and the 68, or the 68 and the 65 running the same way, but why would the one in the middle run differently than the other two? I then changed the clip to the center and I got a really good run out of it (comparatively ... were talking like...12 seconds instead of 3) but then I couldn't get it to run anymore. Also I have another problem which may or may not be related ...


I have a sickbikeparts shiftkit. I don't know if that matters but I'm letting you know. Sometimes I can't get the cranks to go more than halfway around. It seems to bind up and I don't have enough strength to push past the pedals being one up and one down. I've noticed that I could nudge the bike backwards with the clutch lever out and when I did this it would free up whatever was stuck and then I could pedal normally again. But after awhile this was not working very well anymore. What could be causing this?
 

Chainlube

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First time builder here. I have a PK-80. It comes stock with 70 or 72 jet. (I've been told both.) Needle clip was at 2nd from top on a 5 position needle. I put a 68 in and had better results trying to get it started, but it was not quite right. I put 65 jet in thinking I was on my way in the right direction but it got worse. With the original jet it would start and run for a few seconds only with the choke closed. With the 68 jet it would run better and longer with the choke open. With the 65 jet it would not run with the choke open but only with it closed just like the 70 jet. This makes no sense in my book. Why would the 70 and the 65 run with the choke closed and the 68 with the choke open? I could see the 70 and the 68, or the 68 and the 65 running the same way, but why would the one in the middle run differently than the other two? I then changed the clip to the center and I got a really good run out of it (comparatively ... were talking like...12 seconds instead of 3) but then I couldn't get it to run anymore. Also I have another problem which may or may not be related ...


I have a sickbikeparts shiftkit. I don't know if that matters but I'm letting you know. Sometimes I can't get the cranks to go more than halfway around. It seems to bind up and I don't have enough strength to push past the pedals being one up and one down. I've noticed that I could nudge the bike backwards with the clutch lever out and when I did this it would free up whatever was stuck and then I could pedal normally again. But after awhile this was not working very well anymore. What could be causing this?
Check the chain from the motor to the jackshaft. Sounds like it's binding, try to get it as tight as possible.
 

yuckfoo

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Check the chain from the motor to the jackshaft. Sounds like it's binding, try to get it as tight as possible.
I have a left side chain tensioner. But I'll take that off tomorrow and investigate, see if I can see any evidence of that. Thanks!
 

yuckfoo

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Check the chain from the motor to the jackshaft. Sounds like it's binding, try to get it as tight as possible.
You're right! I can see that the chain links have flat spots on them. The chain is perfectly tight with the tensioner. I guess I'll have to see about grinding a bit more clearance. Good call!
 

Chainlube

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I have a left side chain tensioner. But I'll take that off tomorrow and investigate, see if I can see any evidence of that. Thanks!
When you said you backed up the bike it would work again, that sounds like th chain is riding up on the gear and binding. Check that while you have the cover off.
 

yuckfoo

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Check the chain from the motor to the jackshaft. Sounds like it's binding, try to get it as tight as possible.
Solve my no-start problem now will ya! 😅 I'll have a new video up tomorrow showing what's going on. Hopefully you'll get a chance to watch it.
 

Chainlube

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Solve my no-start problem now will ya! 😅 I'll have a new video up tomorrow showing what's going on. Hopefully you'll get a chance to watch it.
Just put the clip on the bottom of the needle and try it like that. Go with the 65 jet, and work your way up with the clip to find the happy spot.
 

yuckfoo

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When you said you backed up the bike it would work again, that sounds like th chain is riding up on the gear and binding. Check that while you have the cover off.
I wonder if it's binding on the left side tensioner sprocket. I can see the chain has flat spots on it. I'll give it a good look tomorrow. I bought the chain tensioner because I could see that the chain was going to bind between the case and the underside of the engine gear.
 

yuckfoo

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Just put the clip on the bottom of the needle and try it like that. Go with the 65 jet, and work your way up with the clip to find the happy spot.
With the original jet I had the clip in every position (four out of five) except all the way down. I'll have a new video up tomorrow. Meantime, did you see this one when I had the original jet? It's very short. Maybe you could give it a watch. But clip all the way down ...? At that point wouldn't it be better to use a larger jet?

 
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