I’m working on an old 1940 ULH with about 2200 miles, post rebuild. The cycle was properly broken in for the first 1500 miles W/O the sidecar. It was about 95 degrees that day when I was running in traffic at about 65mph. I have a generally stock looking ULH, except for the Velorex side car, and VM 36mm Mikuni carb. I had stopped for fuel, retarded the spark to start the motor, and neglected to re-advance it before pulling away to rejoin traffic. After riding about 12 more miles, I felt a power loss. That nauseous feeling came over me as I pulled to the shoulder. That’s when I noticed the distributor was still retarded. The engine was too tight to restart.
When I pulled the top end, I discovered the rear piston had stuck on the rear (exhaust) side. My plugs were a dark grayish brown in both cylinders. I checked for air leaks prior to disassembly and found none. I had experienced no problems with idle or popping or performance. No damage to the front cylinder. My rear Cyl. is o.80 over. I am aware that there are .090 pistons available. The front is .040 over. I have a spare .020 oversize 13 fin front cylinder, but no extra rear cylinder. My plan is to send my rear cylinder to LA Sleeve, and sleeve back to stock. I want to send along a new piston and specify exact clearance
Does piston clearance need to be different if I use pistons without the strut. What’s best? The stuck piston had the steel strut. I honed the clearance to .0025 with a Sunnen hone. Where is a good source of Pistons? Must I buy them as a set? Steel strut or no?
I wonder if anyone has ever tried using the really late model flat top pistons in a old side valve engine.
I guess things like pin hole offset, would need to be considered too. Do you suppose the piston would reach high enough in the cylinder if it did fit on a rod?
I believe that I’ve relearned a hard lesson about timing. Much too costly. I look forward to your shared experience and recommendations.
Thanks a Bunch,