Honda CB750 Sandcast

General Category => General Discussion => Topic started by: mrores on March 31, 2023, 04:19:38 pm

Title: 70 cb750 oil leak
Post by: mrores on March 31, 2023, 04:19:38 pm

Has anybody heard of the early 750's sumping?

Title: Re: 70 cb750 oil leak
Post by: mrores on March 31, 2023, 07:07:51 pm

I need to clarify the oil leak issue on my bike. Since I got it running a while back I noticed it was leaking oil above the #1 and #4 cylinder thinking it was the valve cover gasket I replaced it, the leak stopped over #4 but was still leaking over #1. Upon closer inspection it's not leaking from the valve cover.
Just got it back from the shop and the mechanic said it hadn't leaked the several times he ran it and rode it. He delivered to me yesterday and said it started leaking when he rode it the day before. He told me the early 750's sometimes suffered from sumping which I never heard of, he said it was common in Nortons. He also said if it's run every few days the leak would eventually stop as the upper end gets broken in as the new rings and  valves get seated.
Anyone ever hear of this?

Title: Re: 70 cb750 oil leak
Post by: Sam on April 10, 2023, 01:51:36 pm

I have not. More likely is the pucks under the can towers are leaking. Thats pretty common. Can you post of a photo of the leak source?

Title: Re: 70 cb750 oil leak
Post by: mrores on April 10, 2023, 04:32:38 pm

Here are a couple of photos.

Title: Re: 70 cb750 oil leak
Post by: mrores on April 10, 2023, 04:35:05 pm

OOPS! Here's the other.