Have you Decked the cylinder

My JE stock bore had oil galleys to the wrist pin and no dome, flat top. However, does anyone know how many cc's the valve reliefs are? I'm guessing around 6cc's. Didn't measure,don't know, just kind of looks like like about 6cc's.
Seems to me that the valve reliefs could be important when figuring true comp. ratio especially when the combustion chamber only measures around 38cc's ( at least that's what I've read). Even if it is only 4cc's it would make difference.

OK-- sorry. Upon retrospect, I think my stock bore JE had a slight dome to it. ( I'm cind a retarted, no life, single parent, and women hate me).

Matt Fisher- I recall where some pro engine builders have found the Ross piston ( among others) to not have the piston pin alignment be exactly square with the bore and/or rod bearing. As much as .001 off. I know it's not a big deal but like all precision equipment it wouldn't hurt to check. BTW- I too like the semi-custom pistons from Ross, they are a work of art.

[MIKE400EX]

Wiseco 440 piston differences? Mine has the same pin height as stock, w/in .0005"!

Took the bike back apart last night to check the head nuts. You definetly need to go back and retorque the composite head gaskets! The GTT cam and un-hardfaced rockers had no scuff marks or signs of failure at all. Will check after some time is on it.

What did the piston,pin,rings & clips weigh together Matt? I found the stock to be 383 gms. & the Wiseco 440 402 gms.

2slow, the Wiseco 440 and stock reliefs both are close enough to 1 cc total (all 4 combined).

[Ononewheel]

Just thought I would throw in a reply to move this up a little. This thread turned out to be the best thread I personally have ever read. Thank you all for all the input and questions that this brought. Is there somewhere this can be saved for future engine builders? It contains alot of very important information. Later for now.

Thanks MIKE400EX!
Guess I just expected them to be larger. Shouldn't make much difference If it's just 1cc total.

[powerslider]

Yes I agree this maybe the best information I have read, thanks to all who contributed this valuable information for us future engine builders.
The moral of the story is, question everything and prove it to be what it is meant to be. It makes you wonder how many sub-par engines are out there that aren't running up to their intended potential. Those builders that use this information to correctly assemble their own motors will be many quad lengths ahead of those who don't know the real story.

Thanks again!!!!!!
Jim.

Guys this thread is without a doubt one of the most imformative I have seen yet and thanks.

I had an interesting talk with J&E the other day and it led to a few good talk with some tech people etc.

After calling J&E and speaking with their tech guy who was very easy to deal with I found out the following. First they claim to only manufacturer pistons for the EX400 (89mm 440) up to 10:1 under the J&E name. He had said that they do go up to 13:1 for IMS, and that he had little if any info on these and gave me IMS's #. I had imformed him of our discussion here and he had asked that I update him of my findings on the actuall compression numbers on any of their products.

After speaking with IMS they were not familiar with the actual installed compression of their product and had no info or suggestions in reference to deck heights or installed piston measurements, they did claim that there have been no negative feedback info on the compression issue.

IMS also had asked to update them on this issue as well. They did tell me that the 10 1/2:1 on up were dome top pistons with valve reliefs. IMS does offer a few interesting pistons for this application. the one that had stood out to me was a 13-1/2:1 89.5mm piston that was accompanied with the disclaimer that it could only be rebored once.

When I asked the tough questions about the decking and actual compression numbers thay had refered me to white Bro's as they not only sell their product but also have some experience with the set up through their race sponsorship.

I am still awaiting a call back from White Bro's and will update all with the info when they call back.


I guess what I am trying to do is see if I use a certain piston I can get away with just using the thinner gaskets and still get an acceptable compression ratio.

Still no reply from White Bro's yet.

Will be doing std comp test and removing head thur night.

Will post all measurements that I get.

[86atc250r]

First they claim to only manufacturer pistons for the EX400 (89mm 440) up to 10:1 under the J&E name.

That's odd, the JE catalog I have states otherwise....

Well, maybe he's technically right - my catalog only lists pistons for the XR400...

[Matt Fisher]

Things may have changed now, but when JE's 89mm piston was developed, IMS had the exclusive.