PLEASE HELP!!

[Jeff J10]

I purchased motor carb frame and a few other things, the kid I bought it from said it was a BBR motor... I put everything together and realized the the piston wasn't making a complete stroke. So when I took the everything apart I discovered the piston was hitting the crank shaft. So i don't know if I have the wrong piston, wrong rod or what... So if someone could please help point me in the right direction, I would really appreciate it. Thank you.

 

[Tyler6357]

The wrong piston maybe? They make different types pistons for these little engines. The ones with the shorter connecting rods require pistons with lower wrist pin locations.

 

[Greg58]

Tyler's right, the piston probably doesn't make it to the top of the cylinder either.

 

[Greg58]

Here's ba example of the type a piston.

https://www.ebay.com/itm/47mm-66-80...718409?hash=item361511be89:g:AVUAAOSwGqxbDfcI

 

[Jeff J10]

thank you guys for your input very much... I've seen some videos on youtube noting the lower wrist pin location... I just wasn't sure how many types of pistons there are and if someone could tell me which one i would need. does the marking on my connecting rod tell me what kind of piston i should get?

 

[Jeff J10]

so Greg your suggesting the piston in the link is the one i need?

 

[Jeff J10]

Here's ba example of the type a piston.

https://www.ebay.com/itm/47mm-66-80...718409?hash=item361511be89:g:AVUAAOSwGqxbDfcI

so you have a good bit of experience with these bike motors?

 

[Greg58]

Jeff put the piston back on the rod without the rings and slide the cylinder on, rotate the crank till the piston is at TDC and see if the piston reaches the top of the cylinder. It probably won't, the piston type A I posted is a low pin type, type B is the high pin type.

 

[Greg58]

I'm not a expect but have done a lot with them, I've rebuilt them and tuned several in the last 8+ years.

 

[Greg58]

If you look at the picture Tyler posted and the one I posted they are opposite, just make sure you are buying the right piston. Measure yours and find one that lists the pin height you need. I've only seen 2 types.

 

[Greg58]

The arrow on the top of the piston isn't always there, just make sure the ring end pins are to the rear on each side of the intake port.

 

[javy mcdees]

yea the piston is the wrong one you need the lower wrist pin hole piston. make sure when you get a new one and install it the ring gaps face the intake even if the arrow is opposite. alot of times the arrow is on the wrong side on new pistons.

 

[Jeff J10]

I didn't know that, thank you.

 

[Jeff J10]

Finally got the right piston and got her running, some paint next but it's getting there. Thank you everyone for your input.

 

[Tyler6357]

Finally got the right piston and got her running, some paint next but it's getting there. Thank you everyone for your input.View attachment 101775 View attachment 101775 View attachment 101776

Sweet build! I like the Spring front fork!

 

[javy mcdees]

that exhaust will give you some kinda powerband. looks kool too but I would hate to own.