RZ/RD 350 & Misc. 2-Stroke Tech BBS

My Harbor Freight borescope revealed a newly installed window in the LH piston....

That should reduce internal friction and allow higher RPM
Be careful decelerating as there will be less engine breaking.

sorry to see this- looks like it may have been just a skosh lean.

Sad to see, brother.

I read your other post about the last test ride.

Sucks, but I'm confident you'll get it fixed right. Keep posting. Of course, I'm curious about what went wrong.

I've seen this kind of result quite a few times with freshly built RZ engines (for a variety of causes). Scares me because I'm no RZ engine mechanic. I need to be careful and learn all I can.

Good luck, and hope you have fun on the Dragon!

Thanks for the kind words. 2024 must be the year of the blow up for me...on the last ride on Saturday at Deals Gap my other RZ seized for a yet yet to be determined problem. LH cylinder sparkplug covered in aluminum flakes. It has been together since 2015 after being resurrected from a long slumber and has many hard street miles on it. I found no obvious cause. Normal life has taken over since I got back and due to a spousal health issue no time for bikes. I did manage to get the white RZ up on the lift and drained the gas tank.
I have been wrenching on 2 strokes since the 70s and this is the first time I ever had one seize that didn't release after it cooled off. I suspect a failed LH crank seal on both but that remains to be seen. That being said Deals Gap 2024 was a great time as always.
I have been studying old posts on rebuilds and upgrades and have decided ( Depending on the damage) to turn one or both of these into 385 stroker motors retaining the YVPS cylinders and utilizing +4 MM crank and Wiseco 795 or equivalent and likely an aftermarket head properly set up for pump gas.
If the cylinder(s) are trashed since both bikes are non stock porting I would then seek guidance regarding a 392 or 421 conversion...
Can anyone who has a 385 tell me how they are in terms of reliability and service life? As always thanks in advance.

Unfortunate troubles there Tim. No personal experience with stroker cranks but I know TDR builds and races 392 engines. You may want to contact him to discuss. Charlie (RZed on here ) has a wicked 421 in service for many years. He may be helpful.

Thanks Ken!