750 Big Bore Kit / BBK INSTALL

[SomervilleXS650]

EDIT: Making this into a 750 BBK installation thread.

Picked up one of the 750 kits recently and was thinking about making the changeover before Spring. If I do, I will probably take some pics and document in my build thread, but wanted to ask a couple questions in a standalone thread for posterity in case useful to others. I know lots of folks have had a good experience with this swap, so looking forward to seeing what the difference feels like.

Few questions -

• Tensioner. I have a "type C" in my 74 TX650A. This has the 6-hole mount plate, lock nut, and larger "long acorn" cap that screws into threads on the plate (doesn't screw into the tensioner itself).
  • Will my Type C tensioner screw right into the BBK cylinder? (and is the length of thread correct?)
  • Do I need to get one of the newer style acorn caps that screws right onto the threads of the tensioner? Will that work with my Type C?
  • Any other tensioner notes/advice?
• Assume the existing front cam chain guide (including threaded nuts that seat in the jug) will all just swap right in?
• Dumb question. Any need to hone a factory cylinder? Or can it pop right in?

Answers to these, and/or any other BBK related know-how/tips would be greatly appreciated. Thanks!

 

[Liftedzuki]

I am doing a 700 je kit so bored oem cylinders but here's my 2 cents

1. No help
2. Buy a new guide, I bought mine from Hoos racing, unless yours is newer, in my opinion
3. I would clean them good with brake cleaner and oil the cylinder walls, then oil the rings before putting them in the cylinder.

I staggered the rings per oem, oiled them, and put them into the cylinders. Also make sure the wrist pin retainers are on the inside retainer groove of each piston and the pistons are in right (intake valve is bigger, therefore the cutout in the piston should match this, I haven't seen a 750cc kit), then drop the cylinder onto the engine and block it up with something clean and spin the engine so the rods go up into pistons and put the wrist pins in and outside wrist pin retainers.

Note: make sure the cylinder base o rings and base gasket is on before putting wrist pins in because rework is never fun.

Apologize for the messy post but I'm on my cell.

 

[TwoManyXS1Bs]

The 750 BBK cylinders do not have recessed grooves for the cylinder sleeve o-rings. The o-rings are omitted during installation.

Be mindful of ring end-gaps.

Reference posts #46 to #56.
http://www.xs650.com/threads/white-...-end-rebuild-it-runs.55249/page-3#post-604547

 

[Beags64]

Has anyone measured on of their BBK clearances? Seems the forged pistons may require a hair more room IIRC