Wiseco High comp piston - Honda CBR250R Forum : Honda CBR 250 Forums
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post #1 of 52 Old 09-06-2011, 10:52 AM Thread Starter
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Wiseco High comp piston

I was curious if wiseco was making a high compression piston before I went to town on shaving my head. I emailed them and the reply was we are not making a piston for this bike. I asked if they were planning on it and they said possibly in the next few months. Now do I wait for a high coomp piston, or shave my head? Decisions decisions

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post #2 of 52 Old 09-06-2011, 10:59 AM
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I'm worried about the weight difference. The balance shaft in the engine was weighted to smooth the engine out against the factory piston not an aftermarket one. You may have to eliminate the shaft to do an aftermarket piston.

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post #3 of 52 Old 09-06-2011, 11:17 AM Thread Starter
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I don't see that being an issue, I run wiseco pistons in my MX bikes and my crf is basically the same engine design with balance shaft and I don't have any issues.

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post #4 of 52 Old 09-06-2011, 01:31 PM
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Wiseco will do a batch of 4 pistons to your specs if you want to go that route. Keep one, post dynos, sell the rest.

Or, if the myth is true that it's based on a CBR1000RR piston, Wiseco sells a 76mm 13.5:1 slug...
http://www.wiseco.com/ProductDetail....08&AppID=42806

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post #5 of 52 Old 09-06-2011, 02:00 PM
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or you can get a stocker off of ebay...used. 12.7:1
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post #6 of 52 Old 09-06-2011, 02:38 PM Thread Starter
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I'm i'm gunna go pull the top end off my bike i'm not going to put a used piston in it.

2011 CBR250R, Modded 84 honda spree, 2013 CBR500R 2014 Grom

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post #7 of 52 Old 09-06-2011, 02:45 PM
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Quote:
Originally Posted by BBRMotosports View Post
I'm i'm gunna go pull the top end off my bike i'm not going to put a used piston in it.
Most of the people pulling top ends apart on liter bikes are doing it to new machines for racing, stuffing in higher comp units. That 'used' piston may have only seen one quick trip to redline on the factory dyno before it was shoved in a crate to be shipped to a dealer.

Or it may be a ragged out smoker, but it should be obvious from the pics which life it's led.
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post #8 of 52 Old 09-06-2011, 03:01 PM Thread Starter
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For the price of what 2-$250.00 for a slug plus gaskets isnt bad. I would rather just throw a brand spankin new one in and be done. Either way it's gettin head work or a higher compression piston. Or even a piston and some porting. No matter what I do I will run it on the rollers and post results. It wont happen until snow flys here though.

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post #9 of 52 Old 09-06-2011, 03:20 PM Thread Starter
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Does anyone by chance know the size of the wrist pin on the 250?

2011 CBR250R, Modded 84 honda spree, 2013 CBR500R 2014 Grom

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post #10 of 52 Old 09-06-2011, 04:29 PM
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As per this post
30-32 bhp on the CBR..is it possible?

they have the same diameters, which should be 17mm.

If Wiseco are making pistons for these bikes, I want to see their skirt length, ring thicknesses and valve clearances before I'd put my money down for one. The CBR100RR might share a few things with the 250R, but with that tight of a clearance, I don't want to take chances with the valve relief angle or the weight.

From my experience, the stock 1000RR piston should be good to go. We've run it on a car engine which has perhaps a little better harmonics than a single cylinder bike engine (still an inline 4 though). As long as you have a good tune, the manufacturing quality of a OE Honda piston should be able to take the power. It is usually the connecting rod which either bends or breaks due to detonation. If someone can share a pic or two, along with various diameters and widths, I can build it in my simulator and do a FEA analysis on it to determine how strong it is. I have specifications of various forged and cast connecting rods in my database, so a comparison should be possible.
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