Topic: 1975 cb 750 engine rebuild advice

[PPG9944]

Hello, 

I'm new to the forum.  Just picked up the cb 750.  The motor was frozen.  After a few weeks of soaking in various chemicals i decided to tear the engine out and apart.  Upon doing so i discovered cylinder 1 was pretty heavily rusted to the cylinder wall.  So I cleaned up the cylinders as best I could with a hone and wanted to know if im ok with these cylinders after clean up. 

[Jerry Rxman Griffin aka MuthaF'er]

I think those will do a number on new rings. 836 time or pick up some used cylinders. Cheap 836 kits on EBay by Cruizinimage (??) or contact member Bill Benton and he can send you some used cylinders. You can use those cylinders on the over bore 836 kit. ~ $125 + bore cost.

[PPG9944]

I'm new to this whole engine rebuilding thing.  The 836 would be bigger pistons i know that.  Then I would need to find  a machine shop that would bore out my existing cylinder walls to fit the pistons correct?  Also there should still be enough cylinder wall left after that as well right?

[bjbuchanan]

Yeah you send the whole cylinder part with your new piston set to the machine shop. They bore and set the ring gap to spec. You can specify if you want different than some normal gap.

I prefer the eBay service some guy has, he offers it for 150$ plus shipping. Super cheap compared to 85$+ per hole for my area. You can Google search the left toolbar for eBay boring services.

You are safe going to 836 it isn't a big deal

[ekpent]

Are those areas just stains in the metal or can you feel or detect depressions. How many miles were on the engine ?

[PPG9944]

On cylinder 1 you can definitely feel a few gouges cylinder 4 only feels like a stain.  The engine has 28k miles on it according to the odometer.  I have no idea if that is actually accurate or not.  I'm taking it to a machinist on saturday to talk with the guy there about the next steps.  It appears I'll be getting new pistons and the heads bored but we will see.

[Vinhead1957]

You will like it!  Fresh bore like a new engine

[Coyote13]

I just pulled the trigger on the cruzinimage eBay 836 pistons.  Received them a couple days ago and appear to be pretty good quality.  Check around to local machine or motorcycle shops.  I was quoted anywhere between $45 a hole and $100 a hole just this past week.

[CB750F2]

If you do decide to rebore ask your piston supplier and the forum what piston to bore clearance is required. If your machinist is not experienced in motorcycle rebores you may end up with too much clearance. Pat

[PPG9944]

Right now the heads are at the machine shop.  Were going to see how the cylinder clean up before ordering parts.  I'm hoping it cleans up well with minimal boring

[Don R]

Heads?

[PPG9944]

Sorry I have the cylinder Jugs and the valve head at the machinist as well

[PPG9944]

I'm doing more research and i found a head on ebay with 64 mm pistons manufactured by ART.  Has anyone heard of these pistons and where would i find a set of rings for it?

Here is the link

http://www.ebay.com/itm/131273921899?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

[PPG9944]

Also i looked and couldn't find new rings.  I would assume you could find rings as long as they're the correct diameter.  You would have to measure the grooves as well too right?

[PPG9944]

Got the new cylinders in today.  Has anyone heard of ART pistons.  These are 64mm in diameter and I'm wondering if Rings from a cb350 would work?