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Ok my question is dose anyone know what is the maximum od sleeve that can be shoehorned into a 650 block?  Thanks 

I’ve been reading and researching this site for a while now and I have an idea and I’m wondering if anyone else has tried to go down this road. I’m thinking 900/1000 oversized sleeves to get to a bore of 74mm in a 650/750 block? Is there enough room to install them with a 75.5-76mm outside diameter of the sleeve? I know it will break into the cooling fins and I would add a few thow to piston to wall clearance to stay on safe side. For pistons I think I’ve found something that’ll work with a tall blank dome that I would have to shape myself and a 15mm pin. The biggest I’ve seen anyone talk about is going to 72-73mm pistons is that because there isn’t enough room to get a bigger sleeve in there? Also I can get away with a slightly thinner sleeve if I get them nikasild I think?  Probably didn’t spell that correctly. Also if that piston doesn’t pan out I could get my hands on a few sets of rods with the correct big and little ends and do some cutting and welding to make a rod to accept the piston and be the required length (I’ve done it before with good results). Thanks for any and all input, tips and tricks.   

I have done what your asking about  - It is a lot of work and a lot of money to do it properly. For the street it is way overkill, for a race bike that is a different story.

I have a 70mm bore in a 650 block but it runs pretty hot and I would not recommend it. Those 70mm pistons are custom, piston manufactures stopped making that bore size 30 years ago, then never went bigger than that off the shelf.

You just can't stick 1000 pistons in there, they have 17mm wrist pins, the 650 has 15mm pins. The 750 turbo has the rod ends at 16mm, but I think that is the safe limit for those rods as far as the small end goes, opening them up 1mm might not sound like much but they were never designed for that. You don't want to mess with the rods, that is the weak link and for sure may spell disaster for the motor build if you mention cutting/welding its just not done.

It may be possible to go to 73mm but I don't think you could do it with the 750 block as it would be very thin. Using the 650 block it is impossible as the liner is outside the casting front and back. The only time I have heard mention of a 904cc motor it had a billet block, look over on the UK 750 Turbo forum.

Just stick with the 69mm Wiseco 810cc kit for the 750, it is much cheaper and easier to do, virtually no difference in performance from bigger bore sizes.

On these smaller engines the limiting factor is the small capacity, your not gaining much HP going up 810 to 904cc. The cost far outweighs the HP increase, more power per dollar spent can be had with a better cylinder head/cams/carbs.

A 750 block bored +3mm is the easy path as Injected mentioned.  The Cruzin Image 810cc kit actually has a good reputation, or go Weisco.  Can't go wrong with this path.

I’ve had good luck sourcing pistons from Thailand and other countries over there like these. 74mm bore 15mm pin roughly 50 bucks each. 50 bucks for each sleeve.  So if the piston is close enough to use than it’d be roughly 400 bucks plus shipping and my time to machine everything. Probably gonna order one piston and at least check it out.