confused

jimbobrox

New Member
Oct 22, 2008
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i got my motor back together, mounted it, it attempted to start it. After many attempts, nothing. I take the spark plug out, it gives compression foward and back, but wheel locks after it attempts to go arond. piston is apparently not making a full rotation. any ideas why?

its late, and i dont have any light in the shop, look at it tommorow and see what i find.
 

jimbobrox

New Member
Oct 22, 2008
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before, one of the carb tabs fell in and warped the piston and cylinder.
i replaced all that, and tried to start when this occured.

i dont think the chain is jamming, its really tight.
the piston attempts to make a full stroke, then the sproket locks up and so does the wheel

that was when i was peddling with the clutch on, if i peddled then popped the clutch, the motor would make one put sound, and slow me down really fast.
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
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I would take the engine back apart & find out why it's not turning... Maybe something else went in it while you were working on it?
Maybe the new piston is "taller" than the first one & is hitting the head??
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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That exactly what I was thinking...the pistons are not all the same..

Your chain should not be "tight", it should have some slack in it- 3/4"
 

Motormac

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Sep 23, 2008
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Take the chain off and take out the plug and see if the engine rotates smoothly, if not and its stilling jamming then the problem is internal.
 

jasonh

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Jun 23, 2008
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If you don't have a head gasket on there, put one on. If you have one, you can double it up. Also you can double the lower gaskets. Mine had 2 on the bottom and 0 on the top from the factory.
 

jimbobrox

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Oct 22, 2008
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would three up top be too many?
i have two up top already, i bought one more top and one more bottom
and will put them on,
just making sure it's not too any up top
 

Norman

LORD VADER Moderator
Jan 16, 2008
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adding base gaskets will change port timing and adding head gaskets will lower the comp. how far does the piston pop out of the cylinder with the head off you may be able to machine off a little to get it working or find the correct piston.
Norman
 

jimbobrox

New Member
Oct 22, 2008
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no longer confused
the piston is hitting the head
the new piston is about a quarter inch taller thanthe old one
cant work the piston down, then the rings would be way too close to the top

would two gaskets on the bottom, and two or three on top blow the gasket prematurely?
 

jasonh

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Jun 23, 2008
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I'd give it a shot and see what happens. Best bet would be to source another new piston that's the correct height.

I'm not 100% on this, but from what I gather, removing the base gaskets will give you more bottom end torque, adding base gaskets will give you more high rpm hp....to a point anyway. If it's that much of an offset, it may be beneficial to contact Creative Engineering and see if he can machine a spacer for the head so you don't need so many gaskets.
 

bumleg

New Member
Nov 8, 2008
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no longer confused
the piston is hitting the head
the new piston is about a quarter inch taller thanthe old one
cant work the piston down, then the rings would be way too close to the top

would two gaskets on the bottom, and two or three on top blow the gasket prematurely?
1/4 inch is a lot to make up..
i would get correct piston.
as was suggested your intake and exaust will be out of time and
your compression will be way too high.
 

Norman

LORD VADER Moderator
Jan 16, 2008
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if you have enough thickness in the piston head you might be able to machine the top a little or at the edges and where the plug will be so it don't hit the piston, just some ideas NOT the best but it might get it running if you can contact the seller of your engine with measurement to get the right piston I think that would be the best way to go.
Norman

A combo of base gaskets and machining on the piston help?
what size of engine 70cc? would you consider selling the piston if you can get the right piston? I might be interested in it if its 70 or the so called 80cc engine. Is it a bushed wrist pin? That would be a plus for me. I've got evil ideas floating around in my head again. PM me if you will be selling it.
 
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jimbobrox

New Member
Oct 22, 2008
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just found out there are two types of pistons for these engines, i had the wrong one
new one's in the mail
on thatsdax.com parts page 3
you can see there are two 70cc + 65cc pistons, one has the wrist pin lower,
which made it hit the head on mine