Motorized Bicycle Engine Kit Forum  


Go Back   Motorized Bicycle Engine Kit Forum > Motorized Bicycle > Motorized Bicycle General Discussion

Motorized Bicycle General Discussion All topics regarding bicycles with engines.

Thread Tools Display Modes
Old 06-18-2011, 09:23 PM
John the Chimp John the Chimp is offline
Motorized Bicycle Senior Member
Join Date: Jun 2011
Location: Simi valley ca
Posts: 81
Default Re: starfire T40 keeps blowing head

You dont need a gasket either. I use yama-bond or something similar. Any motorcycle gasket maker works. I like #8 hardened hardware myself. #5 at the least. Thats my opinion though.
Reply With Quote
Old 06-18-2011, 10:10 PM
Allen_Wrench's Avatar
Allen_Wrench Allen_Wrench is offline
Resident Mad Scientist
Join Date: Feb 2010
Location: Indianapolis
Posts: 2,754
Default Re: starfire T40 keeps blowing head

Originally Posted by DaveC View Post
A recent 49cc I bought didn't even have the jug machined at all I did the sand paper/glass thing to have a decent surface for the gasket to seal. I also use Permatex Copper Spray-a-Gasket. The jug-to-case gasket I put silicone gasket on to help it seal. The stock head gasket is made from dead soft aluminum. It's made to crush to form a seal. The after market gaskets are a bit thicker and not as soft and seem to seal better. Another thing to watch for is the Chinese sometimes don't tap the stud holes to the bottom. Not having enough thread in the block can cause the threads to pull right out of the block. I tap the holes. You can get a good Metric tap set from Harbor Freight for under $15.

Use a pattern of some kind when you torque the head down, something like an "X" or "Z" pattern so the head pulls down evenly. Go up in torque in stages like 24 inch pounds or 2 foot pounds. Believe it or not I use Moly assembly grease on the nuts for the head studs. I learned that from ARP, American Racing Products. They make bolts and studs for race cars that are considered the best you can get and they say to do it that way, so I do

Just going around the head and torquing to spec on each bolt in turn will almost guarantee a leak. Re-toruqe right after the first ride after letting it cool. Don't torque hot, readings can vary a lot from the cold torques. Check it again after every tank of gas a couple of more times and you should be good.
These guys got the good advice. Get the good hardware. Do the milling with the sandpaper on glass, and that should keep you from blowing your head off.

"There is nothing wrong with wanting a motorbike that is an extension of your personal taste and fashion sense; if you must ride somewhere, I say do it with style!"
Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

All times are GMT -5. The time now is 05:28 PM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2016, vBulletin Solutions, Inc.