Topic: CB750/RC890 Project has started Pic

[Gregorymoto]

Hi well hear is the greasy RC Motor i was telling you all about. I went and pulled it out of storage last week and hear is what I'm starting with. This is one of 4 motors i got off this guy when i was doing my UG at UW.
3 of them where 836 and this one is 890. I only have one of the 836 left. Want a good laugh, i gave this 1/2 OZ of BC Bud for all of them, at the time that worked out to be $30 USD per motor and 2 of them ran.
If you have information for regarding the mrakings on the motor let me know. I'm all about learning.
So far the motor looks ok on the inside, going to pull the bottom cases apart latter on in the week and see if the crank is RC. I suspect it is being i can see a date and initials on the side.
I'll keep you updated.
Thanks for looking.
G. Mountain

[754]

Do the rods have bronze bushings in the top?

Look to see if the crank is stamped on outer edge of the weight close to the cam and primary chain.. check both sides.

Can you measure the bored part of the case, where the sleeve fits in. looks pretty big like maybe enough for a 1000cc..
 What cam did it have?

[Jerry Rxman Griffin aka MuthaF'er]

I see stock non bronze bushed rods, HD studs, aluminum retainers, lightened crank, opened case, big pistons with thinner walled sleeves, modified combustion chambers with stock valves, plugged starter gear hole and possibly a stock cam chain (can't tell from the pix)? Damn good start! Ditch the aluminum retainers, get some titanium retainers, new springs, HD cam chain and Big Jay's new rods. Can't wait to see the ports of the head and the engine internals. Talk about the cam for us too.

[Gregorymoto]

Man the bad news is he pulled the cam out and used it in his bike before i got my hands on it. I have a few to use for core. That is something i will be thinking about latter on. The one thing that is of concern at the moment is the combustion chamber it looks a little off, like someone went at it with a die grinder it not even and smooth in the dish. I also do not see RC stamped on the head so I'm guessing that part never made it to the RC Shop. As far as parts I'm looking at the M3 Racing catalog and I'm so stoked to get this motor in my bike.

I'll measure our the sleeve tomorrow and post.
Thanks

[greenjeans]

$90 for 1/2 of BC    what year was that.....damn inflation

[MRieck]

Man the bad news is he pulled the cam out and used it in his bike before i got my hands on it. I have a few to use for core. That is something i will be thinking about latter on. The one thing that is of concern at the moment is the combustion chamber it looks a little off, like someone went at it with a die grinder it not even and smooth in the dish. I also do not see RC stamped on the head so I'm guessing that part never made it to the RC Shop. As far as parts I'm looking at the M3 Racing catalog and I'm so stoked to get this motor in my bike.

I'll measure our the sleeve tomorrow and post.
Thanks

Some of RC's porting/chamber work left a lot to be desired. This was especially true towards the end of their run. Can you take a pic of the intake ports?

[voxonda]

Hi MRieck,

It's a shame that sending a cylinder head over to the states is so costly. Would like you to have a look at one for me.

Like the look of your avatar very much.

Cheers, Rob

[strangedaze39]

$90 for 1/2 of BC    what year was that.....damn inflation

 It would actually be $120 for 4 engines. Which is even better, the more RC engines I could have bought at $30 a piece the better!!

You lucky, lucky sob   

I have no idea how much RC engines are worth, but wouldn't these engines sell for something like a grand each? 

[Gregorymoto]

Hi Guys.
I have pics but my wife has the patch cord at work. I'll post more tonight.
The Bore is 67mm
and at the case it is 78mm.
Got all the valves pulled they look good. I'm going to need to send the head off to be boiled there is so much oil that has turned into blob or hard.

I got this motor in 95, yes Bud was much cheaper before 9/11.

Have not split the lower yet might try and do that today.
I'll post the pics of the ports latter on to night. I'm starting to get a happy feeling in my head about this motor.
Thanks for your information .

[CrisPDuk]

Hi MRieck,

It's a shame that sending a cylinder head over to the states is so costly. Would like you to have a look at one for me.

Like the look of your avatar very much.

Cheers, Rob

A more cost effective way of doing it is to;

1/  Buy a s/h head from somebody in the States
2/  have them ship it to Mike where he can work his magic, then,
3/  Let Mike ship it to you marked up as used engine parts

That's how I got this one anyway

[Gregorymoto]

First what is a S/H Head and Second Daaaammmmmm. Looks good.
I'll be in Ireland in the fall this might work.

I looked at the Bushings and get this only 2 of them are bronze.

How much did the head work cost.
Thanks
G. Mountain

[CrisPDuk]

Sorry Greg, by S/H I meant second hand

It's a 550 head and cost me $40, from a guy in New Jersey if I remember rightly.

The head work cost slightly more (like 20 times), which, besides removing a skipload of aluminium, included new guides, springs, dismantling, cleaning and re-assembly.

It was well worth every cent

Or it will be when I actually get it assembled onto the motor   It's still occupying pride of place in our lounge at the moment