Hitchcocks Forum

The last Week we had finally ended our vision of a 750cc engine for the usual RE 500 PreUnit. After spending a lot of time in thinking and getting special parts.... we now finished the project.
The engine should look like a normal PreUnit Bullet from the outside, but should have 750cc inside. As far as we know, nobody did that before having success.... And since yesterday in the evening:
RUNNING: https://www.youtube.com/watch?v=dVjR6yUKEUA

Neat

The largest oversize Bullet engine I have heard of until now was the Tollgate Classics 720 engine. What size bore and stroke is this engine?

It will be interesting to know what the vibration is like, or how well the standard size main bearings cope - unless you have uprated these.

A.

This looks very much like the Hitchcocks long stroke crank which will take the capacity to 570 cc - and even with the 87 mm piston this will only be 612 cc - I cannot see the room to go much bigger on the sleeve and crankcase mouth - please tell us all how you got this to 750 cc - love to know ...

Nice job but the liner looks very thin

Just watched video ???
I was thinking that has gone way over the Sweet spot for a single now I know it has
Sorry not for me

Hi, with a 87mm bore the stroke will be 126 mm. Or 90x117 or 97x100. I'm interested what compression this is running on! Vince2

It'll be interesting once it's in a bike.

A close friend did similar with an AMC single.

Yes, it would be nice to see and hear it doing its job... in a bike.

.... this engine has a stroke of 121mm. and we realized a bore of 88mm
which makes exactly 736cc ...... we thought, we can call it 750 already.....

The thickness of the liner is now 2.7mm. But since you may go down to a liner thickness of at least 2mm and there are pistons with 88.5 an and least 89mm easy available, you may have a real maximum of 753 cc.
As you may see on the video, the vibs of the engine are not heavier (even less) as they are an on a standard engine. We had the engine running for about 15 minutes and smooth run it hot to check the complete oilsystem is working properly. Plus we wanted to retighten the crankhead nuts after the first run. The engine had a smooth idle gas and a good throttle responsiveness. Even better than we expected ....
Since i don't have a Bullet with a broken engine.... and i don`t have time to just change a engine for testing purpose... or i don't want to build up a Bullet with sidecar (where such an engine would be useful) for myself..... this engine will stay good visible in my garage just to proof that it is possible to bulid a running Bullet engine with 750cc....!

Hi, rather a lot of work for a garage ornament! Vince.