Sidecar race engine advice

[fast wooly]

Hi guys,
We are a small restoration company in the UK,we specialise in repairing and refurbing petrol tanks as well as complete restorations,at the moment we race a double Triumph engined road race sidecar outift which we have got about as far as we can.We are now looking for a new challenge over the winter and are thinking about building a new outfit with an XS650 engine.We we be looking to build it around an electric start version and would like to bore it out to 750cc,we need torque as well as out and out horsepower to suit the sidecar application.We have been told that the European and American are different,is this the case and if so what are the differences?and what would be the best version to build a race engine out?
Any help or advice you guys can give us will be gratefully recieved.

Andy
MTS Classics

 

[arcticXS]

There are 3 different connecting rod lengths, 533 mainly used on the European market, 447 on the us market, and 256 on the earlier models. I believe most builders agree that the 533 rods are preferrable, as they are the longest. Any type of rod can be used with any year engine, as long as the corresponding pistons and gudgeon pins are used. You should contact Heiden Tuning in Holland, as he has LOADS OF experience from building XS650 mx sidecar engines. Maybe send your heads to 650performance for cnc porting as well (through www.650central.com)

 

[Jack]

The cases themselves will be your limiting factor of Hp output,right around 75 to 78HP before they start cracking. You can go fab your own web bracing in the cases which will allow you to push the HP up to 100 HP. As for long rods ,go 477 engine route and install Honda Sr500 144mm long rods along with Ross pistons,I'll have to search for the piston #s, Megacycle 250-30 0r 250-40 but this cam has very aggressive lopes that'll require frequent valve train inspections for wear. As for the head, get it ported by Heiden. The Aussie guys have also built some wild stroked out XS sidecars in the 900 plus CCs. If your going the standard 360 firing order,you want those pistons as light as possible,then re balance the bottom assembly by removing weight.

The XS intake ports respond favorably to port volume reduction with no lose of CFM while port velocity is increased,just keep that in mind.

 

[Signal]

I don't know what size wheels you will be running but the locals running XS 650 based machines and 10 inch wheels have a few problems with gearing. The XS uses a pretty small rear sprocket, this can be somewhat helped by using High ratio primary gears.

I have found Craig Weeks engine modification guide very useful. It is available from 650 Central.
http://650central.com/

Please keep us updated with your outfit are you building from scratch or repowering?

 

[Jack]

Is that suppose to be HONDA XR500 or YAMAHA SR500. Honda didn't do the SR500.

My bad,CR500