top speed loss Magneto issues 66cc

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SpAsTicJaX

New Member
May 27, 2013
39
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Adelaide, Australia
ok, so after nearly a month of working on my motor, trying to figure out why it was maxxing out at 41kms an hour, and would cough and splutter at top end, i swapped heads, exhausts, rejetted carby, new manifolds and then found out by chance thoughts,

IT WAS THE DAMN MAGNETO!

these things annoy me so much, i always seal the magneto cover with a copper gasket maker, but it just happened that from brand new, the magneto winding must of been dodgy.
just thought id post this for other people who have the same speed issue. :p.bf.auflg
 
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SpAsTicJaX

New Member
May 27, 2013
39
0
0
Adelaide, Australia
since replacing the magneto with a spare one i had lying around, it now reaches a max of 50.3 kms an hour, running on a 44 tooth sprocket, as soon as i have finished running te motor in,im upgradin to my spare 36 tooth sprocket

dance1
 
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SpAsTicJaX

New Member
May 27, 2013
39
0
0
Adelaide, Australia
well, i thought i had found the problem, but took it out last night fora test ride, and boom, lost top end again, going down hill it will pick up speed and try to rev out, but its just like its not getting full throttle. i have checked the carby slide, and upon action with throttle, it opens all the way up, i really am stumped as to why i cant get full revs. its really making me come to my wits end
 
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SpAsTicJaX

New Member
May 27, 2013
39
0
0
Adelaide, Australia
i dont have the tools required, but it does have quite a bit of compression, hard to pedal when starting lol. im wondering if maybe i should drill the jet out a tad? or run it wot and pull choke on a bit, that will let me know whether its jet size issues,.
it gets to a bout three quarter throttle then bogs down and fourstrokes
 
2door

2door

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Staff member
Sep 15, 2008
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Littleton, Colorado
How many miles does the engine have on it? Less that 300? If so don't expect the engine to perform perfectly. It needs to break in then you'll see better power.
What fuel to oil ratio are you using? 16:1 is too much oil. Drop your ratio to at least 24:1, 32:1 is even better.

Tom
 
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2door

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
These little engines are as unpredictable as people. Some run strong, some not so. They are all different in how they perform. Break in time is also not the same from engine to engine.

I'd give it a few more miles to assure the rings are seated and things have loosened up a little. As for making or adding modifications; I'd suggest you do only one at a time then you'll have some basis for comparison. Swapping parts, changing jets and making other alterations only confuses the issue.

I'd go back to the basic configuration and start fresh from there. Put a few miles on it then see where you're at. You might be surprised at how well the engine runs after 200 to 300 miles. Then you can start with the go-fast modifications if still needed.

Tom
 
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SpAsTicJaX

New Member
May 27, 2013
39
0
0
Adelaide, Australia
ok cool, so for now ill just put around at 40 kms an hour, with my home made dog trailer, fishing trailer conversion, and go fishing :p but what would explain the other night of it accelerating to 50.3 kms an hour or 31 miles an hour? just curious, but yeah ill go easy on it, and let it settle in through variations of high and low throttle :p cheers for helping me understand, unfortunately only being 15 i am limited to resources
 
2door

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
A temporary lean condition such as a partially clogged jet or fuel line could have given you a short burst of power/speed but that's not a condition you'd want to be in permanently. Running lean can damage things.

Take a look at the electrode end of your spark plug. Is the porcelain dark and wet/oily, or very light colored? Preferably you'll want it somewhere in between; maybe a nice chocolate brown color. But there again you need to run that engine for a while to get a good plug reading.

Good luck. Keep us informed. Good to see more younger members taking an interest in mechanical things. Congratulations.

Tom
 
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SpAsTicJaX

New Member
May 27, 2013
39
0
0
Adelaide, Australia
thank you very much, i have always loved these, been riding since i was 12. ut got into a major car accident on one when brakes failed and a car pulled out in front of me, i hit the trailer while going 50kms an hour and ended up getting rushed to the hospital in an ambo, so its been a few years since i rode one, then got my parents to let me get another one, i absolutely llove these little engines, very fun to tinker with, but can be such a ***** to me aswell lol. will keep updating here when i gain more power :p cheers for the help tom
 
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SpAsTicJaX

New Member
May 27, 2013
39
0
0
Adelaide, Australia
by the way, im running an ngk b6 hs i think, and after blowing through a few dodgy plugs, i am using one thats been cut back to the tip of the centre electrode, and wow, gives way faster takeoff an accel. running cinnamon brown
 
crassius

crassius

Well-Known Member
Sep 30, 2012
4,032
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USA
a good indicator of how close to being done with the run in is to take off the muffler and look at the edges of the rings - new rings have a black coating that will rub off when the rings start to get a good seat - when the rings are shiny, you're about there
 
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SpAsTicJaX

New Member
May 27, 2013
39
0
0
Adelaide, Australia
BREAKING NEWS!! UPDATE!!! UPDATE!!

since i got overwhelmed with problems i was having i went to try another magneto, opened up the case to find my crankshaft seal had blown, or wasnt in correctly at all. the magneto aand all inside of the cover was drenched with oil, so i got to it, removed the magnet (yes i marked which way it must go back :p) and pushed the seal in a bit, but i am having major problems trying to get the magnet back on with the key, as soon as i push the magnet down, the key flys out and sticks to one of the magnets, so i have put this motor aside for now.

i have since has my previous engine's chain sprocket welded back on (ate trough the key way and shredded everything in its path) and am now reaching 46kms/h so atm i am pretty happy !dance1.we.
 
crassius

crassius

Well-Known Member
Sep 30, 2012
4,032
158
63
USA
I keep a bobby pin with end filed really thin to reach into the slot of the rotor to hold down the key while sliding it on - a long sewing needle will work too. I do the same when taking them off.
 
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SpAsTicJaX

New Member
May 27, 2013
39
0
0
Adelaide, Australia
just a quick update, i have since removed the crank seal, and replaced it. and motor is currently sitting in a toolbox in my shed until i get a hd free wheel for my shift kit from sbp.

may i say i was extremely happy with my purchase, excellent communication, and help throughout. very good people to deal with and from now on i will be forking out the extra money for postage and will do the majority of my purchases through them. was very happy!!.shft.
 
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