Topic: 970cc for street/touring

[spiritof67]

I've been giving some thought to knocking out my '70 CB750 to the usual 836cc but have also been thinking about 970cc since I want a "muscle touring" CB. the motor will be completely redone anyway so opening the crankcase iisn't much of a change. Which would be the bettter combo for two-up fast touring, the revvy 836cc or persumably more torquey 970cc?

[Jerry Rxman Griffin aka MuthaF'er]

2 things I would take into consideration at 1L would be engine heat and oil leaks during extended touring vs a 836.

The issue of rods will come up eventually here but if you're not flogging the #$%* out of a 970 then stock rods should suffice. 2 up WILL put extra stress on the rods however.

Depends on how much you want to spend but you'd be better off with a 836 and some head clean up port work.

[calj737]

836 or the infamous 915 is largest I'd go (for the very reasons Jerry indicated). An 836 with proper head work from Mike Rieck will easily and happily tote you and another merely along any roads in the world-

[gschuld]

I agree with Jerry's comments.  An 836, along with a little improvement on the head, perhaps a little bigger cam, will be getting near the practical limits of factory rods.  Going up from there starts getting more and more expensive. 

I think you would be pleased with a well put together 836, certainly compared to a worn stock motor.  Two up would be easy power wise.  The cb750 chassis doesn't seem to like to get excessively overloaded with weight, but that's another subject though they have been riden many miles technically way overweight.

If you are itching to go bigger on the motor, that's fine too.  Just more to consider.

George

[PeWe]

My bike (K6-76) was an excellent tourer during the 80's. 836, ported head + f2 34mm inlet valves + Kenny Harmon SS-1 cam. Std carbs most of the time. (one summer with VM29)
Standard carbs works fine!

Last summer another cam close to RC295 numbers, work even better! My new carbs Mikuni TMR32 help the throttle responce.

836 with higher CR, ported head + cam.
Not the cheap 836 piston kit with low CR and not deep valve pocket. This make longer duration with overlap and higher lift not possible.

[spiritof67]

Thanks to all for the testimony. I guess I have gotten lazy in the years since 736cc was a lot, riding around on 950's or 1100's. But I see the wisdom of (1) standard carbs and rods (2) 836cc and head work with a mild cam and (3) always, as I do, having a good oil cooler and clean oil. Again, thanks!