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Post by troj4nm4n on Jan 8, 2009 17:47:52 GMT -5
i just installed a 72cc kit on my beamer ... all went well until i got it on the road , it still goes 45-48 like before .. also fixed the exhaust up a little , now my ? is could there be another restriction im not seeing im thinking its electrical as a matter of fact it has to be .. when it gets to the above mentioned speed it just cuts out and wont go any faster ,, its no where near wound out ... any1 know anything about the newer beamers? its a 07 50cc thanks
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Post by cruiser66 on Jan 8, 2009 18:08:49 GMT -5
To take full advantage of the 72cc kit, usually requires increasing the size of the main jet. The larger displacement means more air flow through the carb which is already too lean coming from the factory. A quick search of the forum will give a ball park figure for the most successful starting point. I have a 4 stroke so I don't really know what size would be good.
66
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Post by 90GTVert on Jan 8, 2009 19:32:20 GMT -5
Everyone thinks upjetting is a must with a big bore kit. That's not always the case though. My 70cc actually ran more rich than when it was a 50cc with the same carburetor and jetting. I believe it is due to the additional vacuum created by a larger bore pulling more fuel in. Others have reported using the same size carburetor on different engines the larger engines tend to need the smaller jets. Experiences seem to vary, but do some plug checks before deciding it needs rejetting.
I would look further into your theory of an electronic rev limiter. I don't know anything about your scoot though, sorry. I do know some scooters have an additional wire on the CDI that can be cut to remove the limiter. Others have a limit programmed into the CDI itself. If it runs great and shows no other symptoms, I think you're on the right track.
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Post by rallyrrr on Jan 8, 2009 23:08:10 GMT -5
Expecting to get more top speed from a mere displacement increase is false reasoning. One can install a larger motor in a car and if that motor does not rev any higher than the one it replaced top speed will remain the same. Acceleration will be quicker due to increased torque but top speed will be unaffected.
You will either need to upgear your rear drive gears and/or allow your engine to rev higher. High speed air flow is improved by less restriction in the intake path (filter, carb, reeds). An expansion chamber can help pull more air through your engine too. You did not say what exhaust mods you did. Reducing exhaust back pressure does not result in power and rpm gains with a two stroke the way it generally does with a four stroke.
A low restriction air filter is a good cheap start, necessitating up-sizing of your main jet. Carbon-fiber reeds allow more efficient air flow at speeds around 9000+ rpm. This is another inexpensive and easy upgrade. Going the next step with an expansion chamber usually necessitates dropping roller weight mass and stiffening up the contra spring pressure to compensate for torque losses in the lower rpm band caused by expansion chamber characteristics.
A tachometer is invaluable in letting you know what is going on rpm/speed wise. $40.00+.
And that's why they call it scooter tuning. Ya gotta fiddle with it til you like what ya got. Usually you're never satisfied, knowing that you can always make it a little faster and/or quicker.
Are you sure you want to be one of us junkies? If you have deep pockets you can attain some pretty lofty highs... even tracks on your arms, etc. But fortunately that's just road rash... no collapsed veins.
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Post by 90GTVert on Jan 9, 2009 0:12:11 GMT -5
A lot of good info, as usual, from rally, but more power often equals more speed in scoots. It just depends if the scoot is limited by power or by gearing/rpm prior to modding. My scoot could go faster with it's stock gearing, but just didn't have the power to do it. You usually can't see big gains, but it's not unreasonable to expect a speed increase with big bore kits when you're dealing with 49cc scoots. Even with the 70cc kit, my scoot had room on the top end. I never saw my max potential unless I was on a decline or had a strong tailwind.
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Post by troj4nm4n on Jan 10, 2009 22:15:25 GMT -5
thanks guys for all the info ... ever since i had this thing even going down hill at full throttle it refuses to go any faster than 45-48 .. once it hits that speed it sorta cuts out and thats what made me think about the cdi ... it has 2 plugs on it and a green wire on the back .. it was cut when i brought it home from the dealer .. even after modding the muffler and adding the 72cc kit it still does the same thing .. in other words i feel like it was a waste lol .. FYI i already took out all the other standard restrictions ... aka variator washer and plug in the air box and also cut off the extra tube on the exhaust .. no 1 seems to know about the electric part lol .. i shall keep screwing with it thanks again
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Post by 90GTVert on Jan 10, 2009 22:33:49 GMT -5
even after modding the muffler and adding the 72cc kit it still does the same thing .. in other words i feel like it was a waste lol It doesn't even accelerate faster than stock? |
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Post by rallyrrr on Jan 10, 2009 23:03:35 GMT -5
Could you explain exactly the cutting out process? Level running? Downhill? A dead pause and then catch? Sputtering and stuttering? If its like a dead cut then catch it is probably a fuel flow problem. The gap on your plug is not too wide either I assume. Otherwise you need to sub a known good CDI in and see what happens. If its a fuel flow prob start with eliminating the vacuum controlled fuel release valve under the tank. I merely cut the bottom off of mine and removed the spring leaving the diaphragm. You can add a manual shutoff then if you wish.
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Post by troj4nm4n on Jan 15, 2009 17:31:41 GMT -5
when it cuts out it sounds like sputtering and popping sounds .. fuels ok it gets to top speed in a 1/4 mile or less dont miss or anything ... seems still restricted somehow
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Post by troj4nm4n on Jan 15, 2009 17:31:50 GMT -5
It doesn't even accelerate faster than stock?
[/quote]
it sure dont feel like it ... i know 22cc's arent a lot to add but i should feel something , feels the same to me
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Post by rallyrrr on Jan 15, 2009 20:56:00 GMT -5
Sounds like your spark may be breaking up. Try another CDI. Be sure you get a good ground.
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