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rmz 450 overheating with high comp

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I put a hcp in my 06 rmz 450 now it overheats. I took it apart and found nothing wrong. The plug looked pretty good light brown. I tried waterweter and no help. It keep blowing the radiator cap after about a hour of rideing. I thought of rejeting? I finally put a oem piston in to see if it is the hcp and know it runs normal.. Did I buy a bad piston or what.

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Higher compression causes more heat, also could cause detonation which causes even more heat.

Run 100 Octane with your HCP piston, and jet it a hair richer and I bet you will be good?

-Steve

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I wouldn't run high octane fuel. Everything I have ever heard and read said that it is not praticularly good for these bikes. Sticj with the stocker. Running higher comp pistons puts additional wear and teat on your crank. It is NOT the same as running one of these pistons in a 2stroke. These bikes already have a high compression ratio. Your flirting with danger down the road.

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Thanks I'll try the info... Can you explain detonation?

My understanding in a nutshell is when the fuel explodes prematurely, before it is supposed to. Octane is the fuels ability to resist this detonation. The higher the octane, the more resilliant the fuel is to detonation.

That's my understanding, anyone else care to expand?

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Are you sure it was overheating? I had the same issue and found that my head gasket was broken at the sealing ring. The break was small enough to let the cylinder pressurize the coolant but not bad enough to get water in the oil. Look at the old head gasket and see if there are any cracks.

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Are you sure it was overheating? I had the same issue and found that my head gasket was broken at the sealing ring. The break was small enough to let the cylinder pressurize the coolant but not bad enough to get water in the oil. Look at the old head gasket and see if there are any cracks.

Good point, also NEVER reuse a head gasket. Use once, then toss.

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The first time I bought cheap Aftermarket gaskets. I thought that could have caused some issues. The base gasket was paper. So I bought the oem piston and oem gaskets. Now everthing runs normal temp. Before the motor would get real hot, but the radiator seemed just warm.I would still blow the cap. I would like to run the hcp, their was a little difference after putting a oem back in the bike. It started easier and didn't have the grunt.

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You will not harm your engine by running high octane fuel. You might hurt it by running Hi octane ethanol / alcohol based fuel. But if you by something like VP racing fuel etc you should be fine. Basically though, all rubber lines, fuel hoses, O-rings etc... since about 1993 or so have been designed to handle Ethanol based fuel. So personally.... I would run 94 Octane 10% Ethanol fuel with a Tolulene additive to bring it up to 96+ and you should be fine.

Or you could leave the compression ratio the same and work letting the engine breathe better or cams etc... for more power.

If would be a very GOOD thing to understand the basics of detonation before upgrading your compression ratio.

http://www.streetrodstuff.com/Articles/Engine/Detonation/

In particular you may like page four of that article:

"Engines that are detonating will tend to overheat, because the boundary layer of gas gets interrupted against the cylinder head and heat gets transferred from the combustion chamber into the cylinder head and into the coolant. So it starts to overheat. The more it overheats, the hotter the engine, the hotter the end gas, the more it wants to detonate, the more it wants to overheat. It's a snowball effect. That's why an overheating engine wants to detonate and that's why engine detonation tends to cause overheating."

-Steve

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Great article. I knew nothing about detonation. I would like to run the hcp but, is it worth it. I try to ride alot and high octane gas is exspensive.

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I have 2 06 450's and one has an OEM piston and the other has a CP 13:1 piston in it. Everything else is stock. Both bikes run about the same on pump gas. No need to run high octane. No overheating problems either. My opinion? HCP is a waste of money, so is race gas unles you combine the HCP with porting and cams. Best money I ever spent? Tokyo Mods carb mod. Did it to both bikes and WOW, what a difference. Snappy, clean running.

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