"Vintage" roadrace sidecar engine

[GregT]

Just finished going through this one. Based on a CB500/4, built in the 80's for a roadrace sidecar, it's being revived to be paraded at this year's Southern Classic festival. I'd hoped to get the outfit myself - someone else is doing the chassis - but I'd promised to do the engine anyway.

It's not far short of 700cc - 750 sleeves in the 500 barrel - with oversize flat-tops of unknown origin. And a spacer under the barrel to make them fit. Cam is a local grind which I think is a copy of the old Yosh R&T profile.Carbs are I think 750 bodies in the 500 rack.

I've cleaned it thoroughly - jelly in the sump from old castor oil - deglazed the bores and unstuck rings. Lapped valves and installed new stem seals. Hardest part was removing the baked on castor - this thing has been under stress all it's working life and was incontinent...

Back in the day it was quite successful, running on big jolts of nitro - which was legal here at the time. It was never a show pony so blasting or cosmetic improvement wasn't going to happen. It's a working race unit and shows it's history and the scars it earned.

[Buffalo Bill]

Recently I was at a vintage race weekend. I saw many different sidecar racers and was surprised by all the unusual engines.
Briefly saw a triple cylinder, the cylinders were spaced apart and individual.
Have no idea what make engine that was.

[GregT]

Sidecar racers are probably the most innovative bunch of weird characters you'll ever meet. The extra space in an outfit and the removal of cornering clearance concerns have led to some very unusual engines being developed and used.
Generally the really successful sidecar racers now regard the engine as a "black box" which someone like me looks after for them - while they concentrate on making the outfit handle and perfecting their riding.
Boring compared to the old days where they did it all - including being their own fuel chemists, LOL.

This particular outfit I remember well. One local meeting I was scrutineering bikes when this one came through. I saw that there was a clear plastic tube end sticking up beside the steering head - so asked what it was for. I was told "It's a safety measure. If I see a blue flame at the end, I reach over and tap the passenger on the shoulder. He rolls off the sidecar and I abandon ship too." They'd had at least one sump explosion from nitro contaminated oil. It was the crankcase breather of course.