New motor troubles


New Member
Jan 24, 2017
Austin Texas USA
Hello all, this is my first install and I obviously did not do the "necessary" homework before hand....I've watched many vidoes and read lots of forums since my open box,read instruction here's my problem, FYI have only just finished my first 16:1 mixture(half gallon)....I didn't check before initial start but realized immediately after startup that head bolts where not tight, so I tightened them and off I went....put in a couple miles ,no real throttle, parked and inspected ...i noticed a small knock at the time but had lots of issues to deal with after inital ride thus the homework ....jumping to the end of story, ive taken off a cracked head, noticed that the piston is/was hitting the head on one side (thus thus knocking and fracture)...I can tell the top of piston has small crescent indention/wear mark but the cylinder walls look good.....
obviously need new head and plug (any suggestions?), read I can double gasket for more clearance, but what of the piston? Is it ok, will i need to dig deeper? Want to add boost bottle as well , figured while I'm waiting I would port intake and exhaust too


Feb 10, 2013
Southeastern GA
The piston is easy to replace, and you can usually get the whole top end as a kit. That will come with a new piston, rings, jug, and head. It's unfortunate that you have to deal with this though. Maybe try contacting the seller?

The culprit may not be so apparent, but is it missing anything obvious? Is there a gasket between the jug and case? Head gasket? Does the wrist pin wiggle around in the piston?

Also, don't bother with the boost bottle. They're worthless. Port work, expansion chamber, and high compression head are about the best performance modifications you can do.


Well-Known Member
Sep 30, 2012
agree that first thing is to contact seller - never saw this in any new motor over all the years I've been repairing these

may have been a mix up at seller's warehouse