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Im new to this forum, and haven't ridden in years, but im planning on buying an ATV. I have a very low budget though. I found a 97 blaster with low compression, and the owner believes it is due to a blown head gasket. Is it most likely from the head gasket, or what else could cause the low compression? and how are doing the head gaskets on a blaster? what do you think about buying it? I do all my own repairs on my cars and motorcycles, but have yet to work on an atv. Thanks
More likely is it needs a top end rebuild, especially if it is a '97 and who knows when the last was done. Not hard to do. Remove carb and gas tank, and detach pipe. You could then run a compression test yourself. Take head off and remove cylinder. Get a new piston and ring set and gasket set. Get cylinder bored and/or honed by someone who knows what they are doing, and my experience was that's hard to find. Put it back together. Run another compression test after you put the engine together. And make sure you have a torque wrench. A manual helps, like Clymer
You can change the head gasket just by removing the gas tank and head. Haveing bad compression in your crankcase wouldn't have anything to do with your combustion chamber compression. Do a compression test, it shouldn't be below 125psi. Better yet, look between the cylinder and head where the gasket is, and when the head gasket goes it will blow gas and oil out the space. If it looks wet then the gasket is leaking. Alot of times I have seen people doing complete top end rebuilds on their bikes because they didn't have high enough compression but never thought to check and see if all the head bolt nuts were tight, or even there. Sometimes on blasters the studs on the cylinder that the head bolts to come loose, causing the head to have no pressure holding it against the cylinder. Check each head bolt that it is at 20ft lbs before you start diving into the top end, but either way I would replace the gasket.
Cool, Thanks alot for the helpful info. Just out of curiosity how long does it take to do the top end rebuild on a blaster? and is it worth getting a new piston kit such as a wiseco, as they appear to be fairly cheap? and if it is, what bore should i get? Thanks.
A top end job on a 2-stroke, expecially a air cooled single cylinder like the blaster only takes a short time. If you know what you are doing it can be done in a hour or so. If you choose to rebuild it, you can go stock or with a wesico piston kit, their wont be much of a difference.
If you do rebuild it, get it honed out for the new piston. You can get it bored but it won't do anything for you really. Boring a couple of thow over won't give you any noticable increase so peeople tend to only do it when necessary.