dupersunc

Chassis Building - SNT Race Engineering

Originals were T45 or reynolds 531 I believe. T45 is quite readily available still, though not cheap, or something like CFS 3BK is fine. If you are Brazing don't use 4130 cro-mo Frames are a mix of 1. 1/8" and 1" 16g Seat frames are 18g There are 100s of detailed frame pictures on google. Plenty on here too. If I get a chance I'll measure the frame tubes on my F1. There's also a facebook group for Harris F1 and XR69. Loads of info and helpful people on there including ex Harris employees.

Which type? twin shock, Mono shock? What engine? The original gs1000 motor, or the TCS oil cooled versions which has modern geometry and is smaller to suit the oil cooled motor. The you have the Harris F1 frames which are often called xr69s but frames are different, and all vary depending on the engine originally fitted. If I were building one from scratch I'd build my jig around a modern ish 750cc+ sports bike chassis, sit my engine where I want it, and join the dots using pictures as reference.

Yeah nothing wrong doing it that way if you have the parts already, I think I did my first 1100 like that, but I much rather use a male.,male Y piece when I fit a head cooler now.

all model year 750 and 1100 frames were different, though the final M models were very similar. 85 and 86 750 frames are the same, except very minor details, and more down to original market than year. 85 swing arm is shorter than the 86 85-87 1100 frames are very different. 1052 engines bolt straight into 750 frame. 1127 and 1152 engies have a larger lower rear bolt, so you need to sleeve these or drill the 750 frame to suit. Personally I think bracing the 750 slabbie frames is a waste of time. I've run 160bhp and slicks through my 85 slabbie on track and it handles just fine as long as you assemble everything carefully.

Yes, loads, samspline is used on dozens of bikes. Google JTF 520.

The part supplied in that kit is to replace the Y piece that runs down the back of the block with AN hose, not for adding a head cooler. You need a male/male, -6 -8 "T" or "Y" fitting to plumb in a head cooler.

Yes.

Email incoming.

Fantastic. Thanks Si.

Really appreciate all your help on this chaps. I'm going to persue the 3D printing route as a back up, in case Si's man in France draws a blank. Thanks, Duncan

@clivegtocould you lend me one to measure and draw up?

Some really good fillaments out there now. Carbon renforced abs would do it. It's a little pricey but still way cheaper than other options.

That would be great Si. Put me down for a pair please.

Yes. What year have you travel back from?