Has anyone put a 10:1 or 11:1 wiseco piston in their 400ex with stock bore. Was wondering if this would be a waste of money or significant improvement. BTW what is the stock compression ratio?

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THE STOCK COMPRESSION RATIO IS 9:1, I DON'T KNOW HOW MUCH POWER GAIN YOU GET. IF U GO 11:1 RATIO YOU HAVE TO RUN HIGH OCTANE RACE FEUL, 10:1 RATIO IF I RECALL YOU DON'T HAVE TO RUN RACE FEUL BUT YOU ARE SUPPOSED TO HAVE 100 OCTANE TO GET TOTAL PERFORMANCE.THAT 11:1 REQUIRES GAS LIKE CAM2 OR TURBO BLUE.

00' 400ex

 

Thanks. I've been thinking about my next mod, but always want to make an honest attempt at thorough research first.

 

I have a 85mm 10:1 Wiseco waiting to go in my 2000 400EX. At first I thought I would run it with a White Bro's trail cam that I got for a steal. However,after talking to Arlen at LRD I learned that I should really run a 11:1 or higher if I want to take advantage of that trail cam.

I also checked with XRs Only (unlike their name implies, they work on stuff other than XRs)they said I could run the 10:1 with everything else stock. As long as I have this piston I figure I might as well get some use out of it. So I think I'll put it in for a while, mainly out of curiosity, to see what it'll do.

I'll let you know how it goes. Since I don't have a speedometer or dyno, it will be a seat-of-the-pants type evaluation.

 

TrailMix,

As far as I'm concerned a "seat of the pants" evaluation is the way to go. Either get around the track faster or not. Preferrably a lot faster as opposed to a little faster. Let me know.

 

11 to 1 kicks ***!!! I put it in about 3 weeks after purchasing my bike. This made a big difference, I totally recomend it. Best hundred dollars you could spend. Guaranteeed
to leave the stock ones in the dust. I do run aviation fuel 100 octane low lead. I havent fouled a plug since I did the piston swap.. Try it you wont regret it!!!!

 

If you don't want to be married to race fuel, I'd stick with 10.5:1 or lower with a Wiseco (JE or Arias pistons, I'd trust up to 11:1 on pump fuel). Will it make that much difference? Not really, unless you also increase displacement at the same time.

You might see a tiny (read 1-5% increase) going from 9:1 to 10.5:1.

One thing about Wiseco pistons, although I use them myself in race bikes, the material they use is pretty flexible and has more of a tendency to seize than the stock pistons, or other forged pistons like JE or Arias.

One more thing -- Av gas is designed for airplane engines. Ya know, those things that run at high elevation, in cold temperatures and at really low rpms. These are exactly opposite to the conditions your quad engine sees! Av gas is higher in octane, but will run HOTTER in your engine, not COOLER -- which is what race fuel (over 100 octane) does.

If you plan on pulling the top end off the 400, why not go a little larger on the piston (2mm over?) and gain HP that way -- a 415cc kit would gain you probably 15%

Pam

 

Pam,

I read your reply a while back and forgot to say, thanks. I had a feeling the meerly swapping pistons wouldn't do a whole lot other than dig into quad budget. I'd rather stay "stock classable" than start in on boring and the such.