Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: Andymuck125 on March 10, 2008, 06:17:07 PM
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ok this is only my second post but its a good one.....
I have a cb750 f1 i bought it a few months back to 'tidy' up and get on the road for the summer. I was told the engine was rebuilt only 2000 miles ago with new bearings rings chains and tensioners which was nice as it started and sounded sweet as a nut with a megaphone exhaust ;D
the only problem was on the way back from the m.o.t station the engine sounded a bit rattly and snatchy. so i pulled the sump off and had a look. the primary chains and tensioner looked like new but the crank sprocket is badly worn and rounded...... typical ::)
my question is this, is it better to look for a second hand crank or is there an alternative like a cb900 longer stroke crank? i read that from satanic mechanic ;D
i was planning to pull the engine appart at the end of the summer to do the usual big bore, head work, cam, carbs etc so it looks like i might be doing it sooner than i had thought
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ok i have mabye sourced a couple of good cranks the next question is, wot sort of power and torque can a standard bottom end take? crank and primary chains?? or is there a way of upgrading it to cope with extra power. ;D
cheers folks
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The standard crank of the CB750 SOHC is well over engineered. It can take a good bit of extra power and torque. I played about with my motor back in the early eighties with some significant improvement in power and with metal removed from the crank to reduce rotating mass. I didn't use the tuned motor for long (the bendy frame and 60s brakes were far to scary at speed) but I suspect that the primary chains would have a much reduced life.
Also, if you are looking to top end mods, watch out for weaknesses in the cam drive. Expect to replace chains and tensionner parts regularly.
Steve