SOHC.co.uk Forums > CB750

Head Bolts

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Martin6:
Hi, would welcome some further advice, please.

I had a minor blow from the head gasket, which became a small drip whenever I stopped and popped it on the side-stand. I investigated the nuts visible next to the spark plugs. One of them (next to cyl  no.3) was so loose I could turn it with my fingers. Cyls 2 and 4 were also not very tight. When the previous owner bought my bike, he found a handwritten note stating the piston rings had been replaced. The bike has done 650 miles since then. I'm guessing it has settled and requires a re-torque. That's my experience with old British twins, don't know if that happens on the CB750?

I've tightened them up and I think it is much improved. I would also like to check the rest. Is it possible to check and tighten the remaining head nuts, without removing the engine?

Thanks,

Martin

Nurse Julie:
The CB750 rocker cover will not come off with the engine in the frame. And the bolts ( not bolts as they have studs with a washer and nut on ) must be tightened in a pattern and should never come loose .

Bryanj:
As Julie said Honda specified a pattern and torque for the head nuts and did not specify a re torque.
Having said that some of our US cousins like to leave the engine for 24 hours and re torque anyway as, also as Julie says the rocker cover can not be removed with engine in standard frame

Martin6:
Thankyou both.  :-\ Yes, that's what I understood, was just hoping for a miracle!

Also, I know about the tightening sequence, but my feeling was, on balance, leaving the nuts loose was more likely to warp the head, than tightening them, especially as the nut close to cylinder 1's spark plug was fully tight.

Further investigation, I was cleaning up the front fins using compressed air to blow out engine degreaser. In the corner of my eye, I saw something vibrate. It was the top of a bolt I'd not previously noticed. It is completely free. I think it has sheared. Initially I was puzzled, as I can't see the bolt mentioned in the factory service manual, but I found a brief mention in the Haynes book and to a similar one at the rear of the head: "Do not overlook the two small bolts in the centre (front and rear) of the cylinder head." I am now feeling a bit dejected! What do they say, "buy in haste..."

I am desperately trying to avoid engine out. I don't think I have the skill to tackle something as complicated as this motor. I've done a lot on my Norton, but not full engine surgery. I've only done that on a small 2-stroke, which is a much easier proposition. Once the engine's out, given some of the things I've found and the mileage (40,000), it would deserve a thorough inspection and a fair bit of preventative work. Probably the cost of sending it to someone trustworthy, if I can find someone, is likely to be beyond me at the moment. I was hoping for 1 or 2 seasons of riding, before getting to major jobs... Not sure what to do.

As the weep is fairly minor, at the moment, I'm tempted to just ride it and save up for work to be done over the winter, either later this year, or next.

Bryanj:
If you can work on a norton you can do a honda.
Download the honda manual, get a 3/8 drive six sided socket set, cirlip pliers and torque wrench plus a mate to help lift the engine out.

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