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Meech86

110CC cuting out at high rpm

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Hey guys,

I'm having a little problem with my bike. When I hit high rpm's my bike will start to cut out in the same way a car would be redlining (but in a much slower way of course). What I have done to try to fix this so far is play with my fuel screw, adjust my idle screw and brought the needle down a notch but the problem still persists.

I'm running a Mikuni VM22 26mm carb that I ordered on amazon and haven't made any adjustments to it internally since I thought it would be good to go since it was brand new. Am I wrong for assuming it was good to go? Should I open it up and adjust the float and jets? Are the jets inside the carb adjustable or do they just simply screw into place? I'm new to the bike world and carbs.

When I get home tonight I will clean my spark plug, drop the needle down to the last ring at the top of the needle (I'm one ring below the top at the moment) and see what kind of readings I get off the spark plug after a test run.

It's hard to tell if I'm running out of fuel or getting too much fuel or running out of spark but the bike starts with no issues and rides fine under normal load, it only cuts out like this at high rpm's.

Any guidance is greatly appreciated.

Thanks

Mitch

 

Edited by Meech86

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1 hour ago, CRF James said:

A new carb will usually have to be jetted and adjust unless you happen to get really lucky.

 

The carb you bought is most likely a Chinese clone of a Mikuni and may or may not accept genuine Mikuni jets.

 

Try this:

https://tboltusa.com/store/tech.php?pID=61/Simple+Guide+to+Jetting

 

Thank you for providing that link. So I guess there's a possibility that I need to buy some jets and swap them out?

I'll have to take a look at the float to see how it's set and go from there..  Lots to learn about these lol

 

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Try lowering the clip on the needle, doing so raises the needle and richens the mixture in the mid to upper RPM range.

Also check and see what size pilot jet and main jet you have in that carb, out of the box. The VM22 Mikuni-clone carb usually needs to be richened up on both jets to get it to work properly..

 

 

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Well i fixed that issue, i had to drop the needle all the way down. Now i just have the problem with quick full throttle in first gear. It'll choke up if i punch it from a launch.

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Try lowering the clip on the needle, doing so raises the needle and richens the mixture in the mid to upper RPM range.

Also check and see what size pilot jet and main jet you have in that carb, out of the box. The VM22 Mikuni-clone carb usually needs to be richened up on both jets to get it to work properly..

 

 

Funny you mention this, im actually running too rich. I lowered the needle all the way down (top clip) and that solved my cut out issue. My fuel needle isn't turned out all that much and I'm still running rich so i think i need to see how the float is set.

 

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So my issue with the cutting out at high revs is resolved but i now have an issue with quick full throttle on take off, if i rev it real fast right away it bogs and almost dies. If i slowly bring it up and then go fill throttle i have zero issues.

 

My float is well adjusted and my jets are clear. Would this mean i need a slightly bigger pilot jet?

 

 

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What size pilot jet do you have in the carb now?
What is the fuel screw set OUT to?
 
I have no idea what size pilot jet it has, would it be marked on it or would i have to measure it somehow?

My fuel screw at the moment is in-between 1-1/2 to 2 turns out. I'd have to drive it around some more to see if the plug is reading rich or not at that setting.

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It is usually stamped on the top or side of the jet. You will likely need to remove them to find the numbers but don’t be shocked if you don’t find #’s as I have found some generic carbs aren’t marked.

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It is usually stamped on the top or side of the jet. You will likely need to remove them to find the numbers but don’t be shocked if you don’t find #’s as I have found some generic carbs aren’t marked.
Hopefully they do have numbers. I just took it for a little rip and pulled the plug, with the way i have the fuel screw like mentioned above im still running on the verge of a little to rich

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Can you post of the plug against a white background?
Here it is20190914_135325.jpeg20190914_135342.jpeg20190914_135348.jpeg
I need help re-jetting one this weekend too. It’s one of my least favorite things to do right behind changing 10” tires.
Yeah getting it running perfect is more work than i thought lol

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Go with what dirtbkr188 tells you. He is far better at jetting than I am. I get so frustrated sometime that I will park a bike for a couple of weeks/months until I forget how frustrated I was and then start again.

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Go with what dirtbkr188 tells you. He is far better at jetting than I am. I get so frustrated sometime that I will park a bike for a couple of weeks/months until I forget how frustrated I was and then start again.

Yeah it is frustrating, you change one thing and it fixes it but then something else needs attention lol now im not sure if i need to go down a size or up

 

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