YZ80 overheating and no powerband

[snakeyes3602001]

Ok, well I have a 93 YZ80 that had no powerband working. it would just bog out. so we cleaned the carb and had a mechanic look at the reeds. they said they were fine. so we checked the engine and put new gaskets in. we cleaned the engine out and now when we turn it on it overheats. but it seems like the radiator is pushing coolant through but is there a trick to putting the radiator back on yz80s? because it just overheats right away. we took the air bubbles out and it still does. also any help with the powerband. This Fu##ing bike drives me crazy. it been running like this for a while and everything we try does not work. i just hope someone else can help me figure out how to get the powerband work and how to stop overheating without a bunch of confusing terms or tools to use like all mechanics do. Thanks if you can help.

 

[Dirtbikehunter7]

theres alot of reasons why you arent able to get your powerband. Do you have a pipe on the bike? the pipe helps shape the bikes powerband and if you dont have a pipe, it can lead to unburned air/fuel mixture going right out the exaust thus losing some of your power. another thing that it could possibly be is that you have alot of carbon buildup inside the cylinder head where the scavenging takes place. All a powerband is basically is the correct RPM where the most air fuel mixture is caught in the top of your cylinder for compression and combustion. Since you said you replaced the gaskets then it should not be a Ignition crank seal leak so thats why its not overheating... (if it was done correctly) One thing I would like to know is what ratio are you mixing your oil and gas at? If you are mixing it too thick then it actually makes your engine run lean and hot because too much oil prevents the mix from atomizing in the carb as well and that keeps the engine from getting as much lubricant. So one thing you could possibly try if you are running a thick oil ratio is to take the ratio down a little. I run 44:1 on my YZ 250. but I think if you mixed less oil your bike would be able to atomize more air/fuel/oil which would keep the bike cooler AND help your powerband... anybody else agree? I will try to think of some other things but in the meantime try mixing your gas a ratio or 2 lower. Make sure you go through a proper startup drill (let the bike temp warm up) and give it a shot. oh one last thing.... who put the new gaskets on the bike?

Hunter

 

[bikepilot]

Do a compression test and report back please. Also a leak down test would be good.
How are you determining that it is over-heating? If you fill the rad all the way up it should spew a little coolant out when the bike warms up to a normal temp (coolant expands when it gets warm, and unlike your car your YZ has no resivor to catch the fluid that is pushed out.) If the bike is pushing a lot of coolant out very shortly after starting it is highly unlikly that it is actually overheating, but is probably the result of a bad head gasket or warped head. A compression test will help spot this. Also, with a cold eninge you could start the bike with the rad cap off and watch for bubles. When you say you replaced the gaskets, which did you replace and did you lap the mating surfaces first?

good luck