How do you put a traxxas 15 or OS15 on a hpi rush. The flywheel fits the hpi engines, so what flywheel do you use?

The OS15 should fit without any problems. Make sure it has the "standard crank" and not the "SG" or "short" crank. If you are going to change or upgrade the engine, get the HPI aluminum flywheel and the HPI racing clutch. That combination is almost "bullet-proof". Is is much more reliable than the "stock" clutch. If you are going to upgrade the engine, I would recommend the new OS CV-R .15 pullstart. Upgrade to a 15 tooth clutch bell ( you will need the adjustable aluminum motor mounts, less than $4.00 ) and you will be able to do "wheelies on demand". The OS CV-R is a very powerful, easy starting and reliable engine.

The rush flywheel is spaced out to clear the upper support . when you use a regular flywheel the carb. hits the support. Are their any rushes out there with OS engine what part # on flywheel and clutch bell shaft. Thanks, Dave

Venture30,
The following are Tower Hobbies part numbers for the Rush Items.
LXN373 HPI Aluminum engine mounts 3.89
LXM718 HPI aluminum flywheel 7.99
LXM719 HPI brass Collet w/washer 1.90
LXM720 HPI pilot shaft 3.90
Look in the search function at Tower Hobbies for additional HPI parts and upgrades (15 tooth clutch bell). The collet washer is necessary. It goes behind the aluminum flywheel. I would also suggest the 'racing clutch' for an additional $15.00. Install it using the second or middle holes. I have two Nitro Rushes and have upgraded both of them with the preceeding parts.
Oh BTW, you're welcome.

Thanks, for the part #'s I have OS 15 cv-rx and can't wait to run it. Later, Dave