400ex, high compression piston and stock rod- breaking point???

[ryanh250ex]

Trying to find what is the absolute max you can go on compression on a stock OEM rod. I thought it was 12:1, but search isn't pulling up anything good.

[Bigbadfords]

I would say that the 12:1 is a bit too high for stock. I think you would be a lot safer if you stayed no higher than 11:1 or 11:5 at most. But thats just my opinion!!

[400exrider707]

It is not recommended to go any higher than 11:1 on a stock 400ex rod, although there are a few guys running much higher on here and claim to have no problems. I wouldn't do it personally but I like peace of mind

[mgraff400ex]

I've been running a 11:1 wiseco on my 416 for almost a year now and it gets run hard and have had no ill affects so i would say 11:1 is safe but i wouldn't be afraid to go a little higher. If it comes apart u know you've reached it's peak.

[250X_project]

I wouldn't worry about the rod itself, as much as the needle bearings. The higher compression the worse the wear on them. Then the crank has to be pressed apart and rebuilt.

[svahle]

I was running 11:1 on my stock bottom end. Recently had to replace the crank. Of course, it is an '01 and while it is well maintained, I do ride it pretty hard (atleast I try to).

[250X_project]

What was the actual problem with the crank? Thanks.

[svahle]

250X_project - What was the actual problem with the crank? Thanks.

The rod developed some slop at the crank and would heat up and seize to the crank periodically. Again, I do not know if this is specifically related to running an 11:1 piston on a stock rod/crank, but I suppose it is possible.

[250X_project]

Okay, I was just curious. Thanks.

[250X_project]

Okay, I was just curious. I have a 250X engine with the crank actually pushed apart because the bearings failed. That is the only one with a high compression piston, besides the stroker engine with a Vesrah rod. This case may also have no relation.