Pistone Bore Clearance

[FloydIN]

HI. I have CRF450r 2007.  (Sorry for my inglish. I am from Georgia. Tbilisi ) thanks .
I want to by Wiseco  or same  piston. My bike bore size is 96.03 mm (I do not know for sure. Car engine master told me). I am interesting about clearance between bore and Wiseco piston.  What clearance will be between wiseco piston and my bike bore ? What size of same piston i need tu buy for my baike bore size? What is the real size of wiseco piston for crf 450r/ or maby will i buy another brand piston. When i look to my cylynder, i see good hone and it looks like new. mayby engine master is vrong about size.

[turbo dan]

96mm is the standard bore size.  Depending on the condition of the bore I would most likely just install a standard size wiseco and run it.  Measuring to the hundredth of a millimeter can be difficult to do precisely.  It is often easier to determine bore condition by looking for the original crosshatch in the cylinder wall.  If the plating visually looks good the wear is negligible.

Wiseco finishes their pistons to the appropriate clearance for the nominal bore diameter.  As long as your bore is good the clearance will be correct.

[FloydIN]

HI again. Can i use wiseco 11.5:1 (low compression) pistone ? What will i recived if i downgrade oem compression (12:1) to (11.5x1)? Will i get more engine life ore only lose power?

[FloydIN]

HI. I have crf450r 07 Can i use wiseco 11.5:1 (low compression) pistone ? What will i get if i downgrade oem compression (12:1) to (11.5:1)? Will i get more engine life ore only lose power?

[FloydIN]

HI. I have crf450r 07 Can i use wiseco 11.5:1 (low compression) pistone ? What will i get if i downgrade oem compression (12:1) to (11.5:1)? Will i get more engine life ore only lose power?

Edited June 6, 2018 by FloydIN

[William1]

Please do not start multiple threads on the same topic. We have merged them all together this time. Thanks!

[FloydIN]

Ok )))

[FloydIN]

1 hour ago, William1 said:

Please do not start multiple threads on the same topic. We have merged them all together this time. Thanks!

Ok )) sorry

[willbilly]

You will reduce the low-end power slightly. Engine life should be longer if all else remains the same theoretically. I use the 13.5 compression ratio piston. I have 300 hours on my bottom end.

[FloydIN]

32 minutes ago, willbilly said:

You will reduce the low-end power slightly. Engine life should be longer if all else remains the same theoretically. I use the 13.5 compression ratio piston. I have 300 hours on my bottom end.

I can install the wiseco piston 11.5:1 from 02-03 crf to 07 crf  without any problems? it fits 100 %?

[Shawn_Mc]

6 hours ago, FloydIN said:

HI. I have crf450r 07 Can i use wiseco 11.5:1 (low compression) pistone ? What will i get if i downgrade oem compression (12:1) to (11.5:1)? Will i get more engine life ore only lose power?

You'll only lose power.

if the Nickasil is intact, the standard Wiseco piston will be fine. I wouldn't put the 02-03 style, 11.5:1 piston in it. Unless the bike is trail ridden, on very slow stuff, the 13.1:1 or even the 13.5:1 piston runs fantastic. If the bike is raced regularly or ridden pretty hard, the piston should be replaced about every 100 hours. If you're really fast, 50 hours. The cranks will go about 200 hours reliably with 5 hour oil change intervals.

[FloydIN]

New problem. I dont know what to do. (    

Can i change only connecting rod. Wiseco connecting rod or pro x connecting rod fits to oem crankshaft ? And fits or no  the wiseco  or prox c.rod to oem piston? (    HELP!!!

[willbilly]

I am not sure which piston you are referring to. The standard piston size 11.5:1 should work fine.

[Shawn_Mc]

On 6/7/2018 at 3:36 AM, FloydIN said:

New problem. I dont know what to do. (    

Can i change only connecting rod. Wiseco connecting rod or pro x connecting rod fits to oem crankshaft ? And fits or no  the wiseco  or prox c.rod to oem piston? (    HELP!!!

Well, you need a rod at a minimum. A HotRods crank or a Wiseco is fine. By the time you buy a rod kit and get it pressed with the new main bearings, youre into it for the same price as a new crank.

[FloydIN]

Hi. I decided to buy a prox  piston. They have several sizes (95.96, 95.97, 95.98) . what size will be better? When i look in to my bike cylinder i see good oem scratches (hon) . in my city there is no good machinist, but one machiniat says that cylinder is 96.03 mm. But I think he's wrong becouse cylinder realy is looks very good. 

[Shawn_Mc]

5 hours ago, FloydIN said:

Hi. I decided to buy a prox  piston. They have several sizes (95.96, 95.97, 95.98) . what size will be better? When i look in to my bike cylinder i see good oem scratches (hon) . in my city there is no good machinist, but one machiniat says that cylinder is 96.03 mm. But I think he's wrong becouse cylinder realy is looks very good. 

It could look very good at 96.03, which is right at the edge of the 96.000-96.015mm. If it's me, I put the 95.98 in there. If you wanted to be "safe" 95.97mm. And if you're machinist can hold that tolerance using a bore gauge, he's pretty damn good. You're talking about a difference of only about 1/2 of 1 thousandths of an inch. .0005

[FloydIN]

15 hours ago, Shawn_Mc said:

It could look very good at 96.03, which is right at the edge of the 96.000-96.015mm. If it's me, I put the 95.98 in there. If you wanted to be "safe" 95.97mm. And if you're machinist can hold that tolerance using a bore gauge, he's pretty damn good. You're talking about a difference of only about 1/2 of 1 thousandths of an inch. .0005

Today I checked the clearance between the cylinder and the old piston with a feeler gauge. the clearance was 0.023 mm. proceeding from this I think that the cylinder is in good condition. I also checked the clearance of the old compression ring. the gap was 0.5 mm, which indicates that the rings were worn out. Does this mean that I can take a new piston with a oem size without the risk that the piston will hang out?  So prox piston 95.97 will be good yes? 

[Shawn_Mc]

More than likely the piston has collapsed. The Nickasil simply isn't that thick. The Nikasil is only about .3 of a mm thick, if that. Just put the new piston in there and you'll be fine. The ring end gap should be about .35 - .45mm or .015 - .018"

[FloydIN]

Hi my friends. Today i finish rebuild. Engine is in bike and starts on a 10 kick. Big Thanks for help!!! *****

 

(Wiseco rod, prox valves, oem piston. New bearings) job done. 

Edited July 11, 2018 by FloydIN

[FloydIN]

<3

Edited July 14, 2018 by FloydIN