Now fixing my older sons LT80. I bought this one not running, the main problem was the fuel valve was leaking into the carb and filling it with fuel.
Replaced:
Fuel valve.
Chain and sprockets. (Worn out)
Tensioner on chain. (worn and bent)
Reed valves. Had Boysen in it, but not sure how old.
Gaskets on Reed cage and carb. Had to make these as I could not see them online.
Cleaned crude out of carb.
Replaced fuel lines and added inline filter.

Now it runs good, although it sounds like it hits very high rpm when running high speed. I chose the high torque gearing when I bought the chain, this might have been a mistake.
The brakes work poorly. Rear brake is adjusted as far as possible and still seems weak. Front brake works poorly, but cables have some adjustment left.
The clutch seems to work well in general, but I think it would be better if it engaged at a higher rpm. The rider is 11 and just under 70 pounds. If I could raise the engagement rpm I think it would wheelie a little taking off, this would tickle my son to no end!
So after writing this little book:
Does somebody sell a clutch tuning kit?
Are brake shoes the only common problem?
It has a pipe that says "Fatty" and "FMF" on it. Is the packing replaceable in this as it seems very loud.

Thanks
Kurt

 

You didn't see reed cage gaskets cuz there isn't any. there is a o-ring made into the cage. There is a plastic insulator and a o-ring that goes in that.
Rear brake: Take the lever off and turn it a spline.
Front brakes: The pin that goes thru the backing plate gets froze up. Take that out and lube it. I'm guessing that's the prob there.
Clutch engagement: You need to cut the rear clutch shoes down to 180 grams each.
Silencers are usually repackable.

What gearing was this torque gearing?

 

11 tooth front sprocket, can't remember the back. I think the higher speed gearing was 12 or 13 in the front.
My son hurt the engine tonight. I put gas in it for the first time, about an hour later the engine started smelling funny. It was overheating the side rubber that directs the cooling air I think. Seems like it lost comp. Head gasket?

Kurt

 

Maybe a head gasket. maybe not.
One thing for sure, you're going to tear into it and see.
Gas for the first time..
Did it need oil? Res full?
The machine need to run on pre-mix gas?

 

soooooooo.......

whos fault was it??

 

It has oil injection, but I don't know how to tell if it's working so I mixed a gallon at 40-1 figuring to much oil should not kill it. I am watching the oil bottle level, but I can't tell if it's moving down yet.
Lots of clamps and bolts in the outer air shields loose/missing. Same owner put a new cylinder and piston on this machine, so something might be loose or installed wrong. I can hear something spitting/leaking inside the plastic and comp is down...

Kurt

 

One other thing, how can I tell what year this quad is?

Kurt

 

On the VIN there is a letter (L-M-O-etc). The letter is the year.
You'll have to look a fiche to see what letter for what year.
Remove the oil line from the carb and run the motor. Oil should drip out. It does drip slowly.
As you thought, the mixxed fuel will let you inspect the oil without damage to the motor.
It sounds like your going to take the top plastic off and check things.

 

Head gasket blew out on the left side. The bolts seemed loose, do you know what the torque is on the head studs?


Kurt

 

At least that's a easy fix.
100-115 inch pounds.