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Post by scooternub on Jul 14, 2015 19:16:29 GMT -5
Got a 72cc bbk installed. Here is the story. While back with all stock, I briefly took out the air restricter cone thing out of the airbox, it stuttered and putted. So I put it back on, back to normal now.
Now, with the bbk, I just took a trip and it spattered and sputtered, only top out at 25mph. Instantly I thought of the restricter. I took it out but now it only tops out at 33mph and the sputtering spattering is gone.
Previously I could hit 35-40mph.
Used a #85 jet.
Would anyone know why it is topping out at 30-33mph?
Should I try a #90 jet, will that help me go faster?
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Post by frank50e on Jul 14, 2015 19:49:29 GMT -5
Logic tells us you need to go leaner.What size was your stock jet?
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Post by scooternub on Jul 14, 2015 20:07:40 GMT -5
Logic tells us you need to go leaner.What size was your stock jet? not sure.
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Post by frank50e on Jul 14, 2015 20:28:36 GMT -5
Well if you have run it long enough to get the rings to seat,I'd put the stocker and restrictor in and do a plug chop.New plug, run it up to max rpm,shut it off and coast to a stop, and change plug, show us the result.Don't wring it's neck for 5 mins just real quick to max and shutdown.Jetting a carb is a process,there is really no such thing as a prejetted carb.
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Post by dude on Jul 14, 2015 20:47:43 GMT -5
The easiest is to tape off the air box intake some. See if it's better or worse. If better up jet. If not down jet. My guess up jet. If the timing chain is right.
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Post by spaz12 on Jul 14, 2015 21:13:56 GMT -5
Yes, 1 tooth off it'll run, but crappy.
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Post by frank50e on Jul 14, 2015 21:27:50 GMT -5
He already did that by removing the restrictor ,more air, ran better,too rich, down jet.Can't hurt to check valve timing.
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Post by Availien on Jul 14, 2015 22:49:48 GMT -5
I never check valve timing. I just put some loose nuts, a few spoons and butter-knives, and a handful of sand in the valve cover. 75mph boost. Runs great.
Just kidding. Don't do this......
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Post by scooternub on Jul 15, 2015 5:29:31 GMT -5
Edit:removed.
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Post by encephalon on Jul 15, 2015 5:40:31 GMT -5
I'm pretty new to the scooter scene but from my experiences thus far, If you've taken OUT the airbox restrictions you should upjet. Try that #90. More air=less fuel. So you have to compensate. If the airbox restrictions are IN #90 is too much. Just like ALL the other guys said, check your timing chain. Top dead center flywheel, top dead center cam gear. ALSO like everyone else said, check valve clearance. Just my 2 cents.
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Post by scooternub on Jul 15, 2015 6:05:13 GMT -5
I'm pretty new to the scooter scene but from my experiences thus far, If you've taken OUT the airbox restrictions you should upjet. Try that #90. More air=less fuel. So you have to compensate. If the airbox restrictions are IN #90 is too much. Just like ALL the other guys said, check your timing chain. Top dead center flywheel, top dead center cam gear. ALSO like everyone else said, check valve clearance. Just my 2 cents. i paid some guy to do it. should i take it back to him?
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Post by 90GTVert on Jul 15, 2015 7:06:49 GMT -5
i paid some guy to do it. should i take it back to him? If it's a reputable mechanic, yes. If you literally just found some guy willing to do it... maybe not. From what's happened so far, he may not know what he's doing. Not saying he doesn't, but there's always that possibility.
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Post by scooternub on Jul 15, 2015 7:20:57 GMT -5
i paid some guy to do it. should i take it back to him? If it's a reputable mechanic, yes. If you literally just found some guy willing to do it... maybe not. From what's happened so far, he may not know what he's doing. Not saying he doesn't, but there's always that possibility. he is very reputable. motorcycle, small engines and big engine mechanic. he upped the size of the jet by a percentage. odd isnt it? i thought its feel drive tune it, hear it and test the spark plug "jetting the carb". 33mph is unsafe.
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Post by scooternub on Jul 15, 2015 7:41:48 GMT -5
I will take it back. and explain to him, whats going on. As far as what I know, from reading here.
What was odd was is that, when he took the valve cover off, I watched him during this process, he turned the crank shaft till valves were both free from contact from the arms. Which took the cam shaft holes three lined up. I asked him to check the fly wheel, see if it was on the T mark "TDC". It was off. Turned the fly wheel to the T mark, now the cam shaft holes were diagonal. So he went with his expertise not going by the fly wheel TDC, but by lifters being free of contact of the arms and I seen the 3 holes on the cam line up when he did this process. Oh yea, he used a special marker and marked the timing chain and cam.
For this I have no idea whats really going on.
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Post by 90GTVert on Jul 15, 2015 8:59:58 GMT -5
I would ask to check if where the flywheel lines up to TDC is indeed TDC. If it is, reinstall the cam so it's marks line up when the flywheel is at the T mark for TDC.
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