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Post by tuttlemon on Jul 3, 2020 18:35:08 GMT -5
Upgraded from the stock 49cc to 80. I know the idle jet is far too small now, because if I come to a stop: I have to slowly let the throttle down while I hold the breaks, or it’ll die. And after I get it to barely idle without keeping on the gas, it eventually dies. Perhaps I could be getting better performance with a larger main jet too.
Is there a good general jet size to pair with an 80cc BBK? To minimize trial and error disassembling the carb over and over trying out different jet sizes?
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Post by bornwinner461 on Jul 4, 2020 12:12:24 GMT -5
Hi. I had the same problem with my 49cc after I changed my carb. Would eventually die at idle, and coming off the throttle. I also had hesitation upon take off. The only real change I had made was to remove the stock air box. How I cured it was I moved the needle valve clip down, and cut way back in the idle mixture screw to only one and a half turns out. Runs great now. Disclaimer: I'm not a professional mechanic. I'm A 56 year old carpenter who's done his own wrenching all my life.
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Petro
Scoot Enthusiast
Posts: 149
Location: Gothenburg, Sweden.
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Post by Petro on Jul 5, 2020 3:08:06 GMT -5
People seem to be unwilling to share their jetting here, her is mine with my old setup: 49ccscoot.proboards.com/thread/27001/bbk-jets-usingOn my current setup @90cc with a 24mm carb I'm on 35/98. This carb however is a dog and going to be returned back. I just mention it's jetting so You have something to go on.
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Post by Kenho21 on Jul 5, 2020 8:11:24 GMT -5
People seem to be unwilling to share their jetting here, her is mine with my old setup: 49ccscoot.proboards.com/thread/27001/bbk-jets-usingOn my current setup @90cc with a 24mm carb I'm on 35/98. This carb however is a dog and going to be returned back. I just mention it's jetting so You have something to go on. I haven't encountered anyone who is unwilling to share their jetting, but what my jetting is has little to do with what your engine may require. Without knowing any of the specifics of the author's bike, it would be a very haphazard guess to start suggesting jet sizes, at best. To the OP, what is your setup? 2 stroke or 4 stroke? We need information if you want good advice. If you put your bike specifics in your signature, like you can see my sig line, it will make things easier moving forward when asking for advice.
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Post by tuttlemon on Jul 6, 2020 9:50:23 GMT -5
People seem to be unwilling to share their jetting here, her is mine with my old setup: 49ccscoot.proboards.com/thread/27001/bbk-jets-usingOn my current setup @90cc with a 24mm carb I'm on 35/98. This carb however is a dog and going to be returned back. I just mention it's jetting so You have something to go on. I haven't encountered anyone who is unwilling to share their jetting, but what my jetting is has little to do with what your engine may require. Without knowing any of the specifics of the author's bike, it would be a very haphazard guess to start suggesting jet sizes, at best. To the OP, what is your setup? 2 stroke or 4 stroke? We need information if you want good advice. If you put your bike specifics in your signature, like you can see my sig line, it will make things easier moving forward when asking for advice. This particular bike of mine (I have 2), was a 49cc Chicago Go (4 stroke) scooter I recently BBed to 80cc. A year ago I upgraded to an after market carb with better jetting for when it was 49cc, but I don’t recall the specs exactly. Essentially the stock carb was blocked from allowing you to up-jet it and I got an equal size that allowed for jetting, and upsized jets a bit. It has a foam UNI intake, and all the other emissions stuff ripped out.
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Post by GrumpyUnk on Jul 7, 2020 12:47:40 GMT -5
Most of the 'blocked' carbs can be made accessible by using pliers on the bowl screws, or cutting a groove with a hacksaw to make use of a flat blade possible. The idle jet 'caps' can be removed with use of a drill and some pokery. The 'broken screw removal' bit sets from web sites will also remove the idle adjustment caps. I would suggest if you can to open the idle jet mixture screw a bit to fatten the idle mix if you feel it is too lean for the new 'demand' of the bbk. You can order packages of pilot and main jets from web sites, getting a 'custom' mix if desired, such as a set of five, 30,32,34,36,38 or your choice. Main jets are also available similarly. I have a package of some in my pile of 'stuff'. I decided to accept what is unless it was obnoxious, or running too hot, rather than swap jets over and over. Maybe when I have more free time.(instead of posting here...) tom
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