Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.

Messages - DuoDave

Pages: [1]

CB750 / Re: Easist way to fit engine

« on: April 16, 2009, 04:14:53 AM »

I fully agree that it is a pig of a job however you do it, but if you have a bare frame, I would get the engine on it's side and lower the frame over it. A 20 odd pound frame is easier to handle than a 170 pound engine.

CB750 / Re: STRANGE FIBRE SUBSTANCE ON CB750 OIL PUMP FILTER

« on: April 16, 2009, 04:10:28 AM »

I found the same thing when I took the sump plate off my cb750. A weird mass of fibre almost covering the filter mesh. I have no idea what it was. So what's that all about?

CB750 / Re:Smoking

« on: December 20, 2006, 08:07:45 PM »

Thanks for the replies. I had the stepped ring in the top groove, but I don't think that would be the whole problem. The smoke is blue and the oil level in the tank drops noticably after a long run. The smoking is most apparent when the motor is under heavy load, like pulling hard uphill. Piston ring/bore problems usually show up by a puff of smoke when you shut the throttle and the resultant vacuum in the bore sucks oil up from the crankcase. I don't see that with my bike, so I suspect a valve guide problem.

CB750 / Smoking

« on: December 20, 2006, 03:03:38 PM »

Hi folks, just joined the site. My early model CB750 smokes badly under load from the exhausts and engine breather. The cylinders have been rebored to +25 and has pattern pistons (ART?) and genuine honda rings. The bores look good, the pistons are a close fit and the ring gap is within tolerance. The rings were fitted with the N25 stamping facing up and spaced with the gaps at 120 degrees. I tried fitting new valve guide seals, but that did not help. The next step will be to take the valves out and check the guides. One thing I noticed is that there are two types of scraper ring in each set. One is stepped on the underside and the other is plain. There is no mention in the workshop manual of which grooves to fit them in. I don't see that it would make much difference anyway, but I would appreciate any info on this, or the smoking problem generally.