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Well i decided to check the valves at 18.5k this winter and check compression and what not. When i went to do a compression test cylinder 1 wont quite get to 150psi and cylinder 2 will get there after 9-10 cranks. Cylinders 3 and 4 will get to 175 (recomended by honda) in 3-5 cranks.

So i did a leak down test on cylinders 1 and 2 to find 30 % leakage. So i go ahead and check the valves to see if maybe one was tight and possibly holding a valve open. Nope. All valves where in spec ( usually are on these bikes). So i think i must have some bent valves. I can hear leakage on the intakes of 1 and 2 when i do leak down on them so i know its the intake valves.

Now what. I know the idiot before me must have beat the crap out of the bike. It still runs hard. I made 141hp when it was 60F and 137 hp when it was 85f outside. So i know it makes good power.

I also have a black smoke problem only under hard acceleration so theres a fuel enrichment problem with the map as well. It needs its own custom dyno tune for sure.


Any thoughts?
 

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Have you done a wet compression test (small amount of oil in each cylinder) before condemning the valves? The only reason I say this is you may have ring issues not valve problems.
 

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Well when you do a leak down you can tell because it will suck air threw the bottom end and number 4 did have a small amount. But it also had the best compression.

I know its the intake valves because you can hear it comming up the intake runner. Its either bent or has carbon built up
 

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Ah a very valid point I must have missed that somewhere. Anyhow I hope you find what out what is causing the issue for you. Happy cycling:cool:
 

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When i went to do a compression test cylinder 1 wont quite get to 150psi and cylinder 2 will get there after 9-10 cranks. Cylinders 3 and 4 will get to 175 (recomended by honda) in 3-5 cranks.
A compression test is a comparison of the pressure in each cylinder _at the same number of revolutions_ not how high you can get the gauge.
You need to compare the numbers after the same number of revolutions to know how worn each cylinder is compared to the other three.
If a valve were bent, staying open or miss-timed I'd expect a lot less compression than that. My guess is carbon on the valve seats if they're leaking air pressure when they should be closed.
Do all the plugs look similar?
 
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