starfire T40 keeps blowing head

leezy_1

leezy_1

New Member
i got a new starfire t40 only the other day, but every time i go out on it say a mile it keeps blowing a gasket.

i am constantly tighting the head bolts down, just leaving it ticking over for awhile and i find that i have to tighten them again and again.

when it first starts and goes it goes well, but then it loses power slowly but surely until it stops running, then its hard to start again.(gasket)

and now i have snapped a stud..:(

any idea's would be most welcome.

thanks

alan..

:-||
 
Yeah, check the flatness.

You need to locktite the long studs on the engine case side. If you have acorn nuts throw them in the trash and get regular ones. Order should be head, flat washer, split lockwasher and regular nut.
 
i did use locktite but seemed to still do it. and yes it has acorn nuts, and they are going in the bin. ill have another go today

thanks
 
better hardware.? you mean nuts.???

not sure if the head is flat as not check as yet but on it today...
 
A recent 49cc I bought didn't even have the jug machined at all :p 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.usflg
 
By hardware I meen hardened studs and nuts. You could get bolts instead of studs. Then you only have one set of threads to worry about backing off.
 
thanks for the info but im in the uk, if you have any links you can give me to get some of the stuff you say that would be great.
to be honest it wasnt getting very far before it blue. say half a mile. :/

ill do the glass theory ive herd of that one just recently on here when looking about.

its half stripped for now just waiting for new nuts and gasket to arrive.

thanks...
 
I'm a believer in RED locktite on ALL studs. You can't use it with bolts, just studs. Should I ever need to remove a stud, I'd pull the head and jug and heat it up so the locktite will free the stud. I make (cut to size) all the studs out of all thread. Cylinder, exhaust, intake and engine mount. I use locking nuts that are all metal (self locking) on the head and nylock nuts for the rest, I've gone as far as to use double nuts on other applications excluding the head. I don't believe in lock washers for the head nuts, but do use flat washers. How many aluminum heads on cars use lock washers. Those that do, well that's fine. I don't put a head on that "I" haven't milled, one of my number 1 rules. Hardware is a number 1 rule. I also tap to the bottom case threads. With this you have to remove the cylinder. Just my .02...do as you think, but do it right. All good recommendations.
 
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.
 
DaveC said:
A recent 49cc I bought didn't even have the jug machined at all :p 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.usflg
Click to expand...

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.
 
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