I am interested in any differences between TLR250 engines and RTL 250 engines ( the one with the side exhaust port which fits a single front down tube frame ). In particular any differences in

gear ratios

camshaft timing, valve events

clutch plates or springs

If there are differences the RTL part numbers would be great.

Thanks

Well, in respect of the production motors, don't have any part numbers to confirm anything but my mate has stipped a few TLR250 and RTL motors and components such as valves, pistons, rings, cam, head etc are the same on both. The RTL does have a different ignition. From riding both the gear ratios appear the same, no noticeable difference. (we have a couple of TLR250 and a Seeley with RTL motors fitted)

The clutch on the later RTL, '87 on I think, is a bigger item than the earlier RTL which is the same as the TLR. It has 1 more spring in the pressure plate than the early one. Whether it works any better than the earlier woeful clutch I can't confirm....

The exhaust port position on the production RTL/TLR head is the same and it will fit in either the twin downtube RTL or the single downtube TLR/Seeley with no problem.

The RTL with the single front downtube was the works bike, you don't mean that do you as there is no documented info on those anywhere, they were complete one-offs. To get to 270cc was a major exercise even for HRC, stud pattern widened, oil feed relocated, piston was offset on the gudgeon pin.

I used to own a TLR250 when bikes were still current, and it seemed to run totally different to a mates RTL..............is this just down to the digital ignition and HRC exhaust fitted to the RTL?