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Discussion Starter · #1 ·
Hello All,
I'm hoping you guys can help me because I'm at a loss. I rebuilt my carbs this week, and changed the jets from 40/138 to 45/140. After doing the earshave I had to turn out my air/fuel mixture screw on the rear carb 5 turns. The front carb air/fuel screw was turned out 2.5 so I was hoping changing the jets might help. I was also hoping I could rectify any possible air leaks because my air/fuel screws not turned out the same amount. It was running well until two weeks ago when it lost a little power going up a hill which is why I pulled the carbs off to do the rebuild.
Today I got the carbs installed. The bike started but the idle was uneven. I waited until it got warm and tried the throttle and it died and wouldn't restart. I waited a while and tried again. Same thing, starts, chugging idle, then died when I tried the throttle. This time there was a lot of smoke coming out of the pipes. I didn't pay enough attention to the color of the smoke but I think it was whitish.
Could this be because my jets are too big now? I've rebuilt them twice before with no issues which makes me think I've done something wrong.
 

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Discussion Starter · #2 ·
so before I took the carbs off I checked the plugs and compression and they were both fine. i just pulled the plugs and they have thick deposits on them which likely answers my question about the jets being too big. Now there is pooling oil in the spark plug chamber. outside the hole. Plugs aren’t wet though. Am I pulling the engine?


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so before I took the carbs off I checked the plugs and compression and they were both fine. i just pulled the plugs and they have thick deposits on them which likely answers my question about the jets being too big. Now there is pooling oil in the spark plug chamber. outside the hole. Plugs aren’t wet though. Am I pulling the engine?


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O-ring on the spark plug well could be leaking oil. Only on the deep holes.
 

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hmm. this was on the shallow holes. I’ll check the deep ones tomorrow.


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Are you sure it's not just excess fuel instead of oil?

Also, there are weep holes on the block down low, front and rear, to show if the orings are leaking. So that's probably not the problem.
 

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Discussion Starter · #7 ·
do you think I should put the smaller jets back in before I do anything else? It’s not normal for one air/fuel screw to be turned out 6 and the other 2.5 turns is it? Doesn’t that point to an air leak somewhere?


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do you think I should put the smaller jets back in before I do anything else? It’s not normal for one air/fuel screw to be turned out 6 and the other 2.5 turns is it? Doesn’t that point to an air leak somewhere?


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The imbalance may be from the big jets.
No it's not normal, the adjustment should be close to equal.

With that much fuel and an air leak it would probably try to hang around 3000 rpm instead of idling.
 

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Discussion Starter · #11 ·


there is oil on both of these locations. is that the weep hole underneath the filter? it did have some oil hanging onto it


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Discussion Starter · #12 ·
The imbalance may be from the big jets.
No it's not normal, the adjustment should be close to equal.

With that much fuel and an air leak it would probably try to hang around 3000 rpm instead of idling.
it was idling normally before I pulled the carbs. around 1200. After I installed them this afternoon it was still idling around 1200


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It's the smaller hole just below the crankcase vent. One on the rear cylinder also.
 

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Discussion Starter · #15 ·
It's got an oil leak somewhere.

The weep hole for the front, is on the left front of the cylinder. I'll see if I can find a pic.
thanks. I’m going to have to do a deeper dive. I can’t see the source if the leak. It’s just kind of all over the area.


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Do you mean the oil in the spark plug well? I looked at the weep hole in the front and there is nothing leaking. a


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I guess I mean the oil you saw on the spark plugs.
 

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The largest I've heard someone run is 42 pilot jets. The sizes are diameters and stock is 38. Jumping up to a 45 means 40% more fuel! (45/38)^2.

What was the reason for increasing the jet size? You're probably better off with 40/140. That's 11% more on the pilot and 12.5% more on the main.

There's a sticky thread that guides you through rejecting and how to diagnose what jet needs changed.
 
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