Smaller jets?

Skyler

New Member
Jul 14, 2019
18
8
3
34
Colorado Springs
I am at high altitude, about 6k ft.

I am running bikeberrys stage 4 racing engine with high compression head and expansion chamber. I am running the stock carb. My needle is dropped the clip is as high on the needle as it can be. I have it jetted with the .61 jet from bikeberry.

I’ve included pictures.

This bike runs well. I don’t have a chain on it to pedal it. It does 30. But it’s 4 stroking often. Always after 3/4 throttle, also when cruising or maintaining any consistent speed. if I shut off the fuel at the petcock the bike takes off. I’ve recorded an increase of 5 mph after shutting off fuel. This is constant and repeatable. I can maintain the higher speed by keeping my fuel off and turning it on long enough to to let a little more fuel in but shutting it right back off. I tried adjusting the float level to keep less fuel in the bowl but it didn’t change anything. It seems like it likes the vacuum created when the fuel line is closed. I think I just need smaller jets. Does anyone know where to get them? I’ve read a little about soldering and drilling and I know that’s an option but not one I want to choose first.
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Greg58

Well-Known Member
May 1, 2011
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Newnan,Georgia U.S.A.
Some of the replacement jets are not the same as the original, I ran into that when jetting a carb a few years ago. I solder and drill mine, it's not hard to do. I have a pen type drill set that is by hand, it's similar to a ink pen with a chuck on the end. I solder jets with a high watt iron, I've never had a problem.
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
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Los Angeles, CA.
There are several companies that advertise here that sell smaller jets for those carbs...

My advice for jetting is not to go too small!!! Running your engine too lean will feel like more power but will blow up your engine in just a few miles of riding.
I jet my carbs by 'feel'... I get it down to where you can still feel a tiny bit of that sputtery 4-stroking feel but it mainly feels crisp.

Another thing you can do for your bike is remove that cheap expansion chamber... You'll get better performance from simply cutting the end off your stock pipe... (then do the jet)
 
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Skyler

New Member
Jul 14, 2019
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34
Colorado Springs
Motor was a little loose.....‍♀....stock exhaust without a cap is just too loud for me. It runs smoother though for sure. But she purrs now. Are these things suppose to get hot? I feel like there is never any heat coming off this thing. Although my trips are rarely more than a few miles.
 

Greg58

Well-Known Member
May 1, 2011
4,142
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Newnan,Georgia U.S.A.
When the engine doesn't heat up it's a sign of a rich condition, like Norm said take your time going smaller on the jet till you get it right. I like mine where it 4-strokes a little for about a mile then clears up when the engine warm to temperature.
 

Skyler

New Member
Jul 14, 2019
18
8
3
34
Colorado Springs
And the engine gets hot to the touch but if I’m sitting at a stop light and put my hand right next to it it feels like there is no heat coming off of it. Hold my hand above it and I can feel a little heat. I just figured they would produce more than that. And Greg that’s exactly what it does, now, it 4 strokes till it’s warmed up but then smooths out, it still 4 strokes sometimes on the top end but nothing like before. I maxed out at 38, which is plenty fast. I can cruise at 30. And I don’t feel like I’m on a rocket built from left over toys hahaha.

However, the manufacturer said it can do 45, granted it’s at sea level, I feel like if I can get it to do that speed I will have learned a significant amount more than I already know.