CARBON BUILD UP.. Making valves stick open?
Posted 22 April 2007 - 05:51 PM
Posted 22 April 2007 - 08:17 PM
Posted 29 May 2007 - 06:13 PM
Hi, I think I have the same problem on my RMZ 450.. it ran fine and then I parked it for a week or two and when I went to start it it was lacking compression and I couldnt find the "hard spot" to kick it - it was like an exhaust valve was stuck open.
What I am wondering is, can you take the head off and clean the valves and valve seats (as you say) without having to take the valves actually out, because I dont have a valve compressor tool to put them back in! I know I will need to get a new gasket if I do this anyway...
Thanks for any advice or tips!
Posted 29 May 2007 - 08:10 PM
The ony way to clean the carbon off the valves effectively is to disassemble them.
Posted 29 May 2007 - 08:49 PM
Posted 30 May 2007 - 04:34 AM
Posted 30 May 2007 - 04:51 AM
I can assure you that your mechanic friend is wrong about the 100k's comment. All it takes is a bike that is running a little on the rich side, which makes it build up carbon quicker than usual. All we did to fix the problem was pull the head, open each valve individually by pushing on the top of each valve (after removing the shims and buckets) with something softer than the valve itself, i.e. wood block (this is a two man job) and spray it down with a healthy dose of carb cleaner and it cleared up the carbon deposits on the valve and seat. Then we put the head back on and the motor was back to running better or at least as good as it was before. It's a cheap option when compared to unnecessarily rebuilding your head. At least check it out. I assume you have already checked to make sure that your decompressor is not causeing the problem?
Posted 30 May 2007 - 06:00 AM
Posted 30 May 2007 - 08:25 PM
I have the head off at the moment and it looks ok, its a bit dirty but thats to be expected for 100 hours. The valves move ok but there is a bit of crud around the valve seats, so I am going to do as you suggest and also do some rings because there is a small amount of wash on the piston.
I would love to check my auto decompression but I dont know how to. I dont know what to look for. I dont even really know what it is, I know its somethihng on the exhaust cam that operates on centrifugal force but the only thing I can see on there is a little spring thing and it looks ok... if someone can point me in the right direction or tell me what I need to look for I will be happy to inspect it.
Personally I think its my rings because the engine compression feels a bit mushy when the engine is code, but when it heats up (from repeated kicking or when i have had the bike started in the days previous to pulling the head off) it would feel ok. Also with the head off I can almost see down the side of the piston to the oil ring at some points!
Posted 30 May 2007 - 08:58 PM
Posted 30 May 2007 - 10:53 PM
one time i checked and i had loose valves, i had started using cheap low octane gas.
my Dealer told me to use high octane and blow the carbon out of my valves.
one tank later on high octane. the Valves were back in Spec.