What is this

[justafarmer]

Hello. i recently purchased an cb750 told it was stroked out to 880. Research suggests it is not. But the real question is the serial number on the case. The pad has not been altered. The number is IDA2988another digit. In my limited research i have not found anything like this. What gives?
Yes it is definitely a cb750 motor.

 

[dirtdigger]

Gonna need some pictures.

 

[justafarmer]

Hi dirtdigger. pics of what? The numbers look hand stamped and the pad has the same pebbled look and depth as my other two cb750 motors.
Twas thinking it may be a replacement case?? i will see if i can get yous a pic of the numbers

 

[justafarmer]

pic of the pad

 

[dirtdigger]

What engine is this? sohc dohc ?????

 

[justafarmer]

it is a sohc

 

[dirtdigger]

can you send some pictures of the motor? Those numbers are not factory of any type. Had to have been some sort of a racing motor at some point. Would be interested in seeing whats inside. Have you pulled anything apart to look at it?

 

[justafarmer]

Motor looks just like my older k motor. Head is the same on the intake and exhaust as well. the old round tops fit. Runs good so no dismantling yet. Had valve cover off think it had R5 cast in cam. My 78 super sport had an R1 and the other had R5 or R3

 

[Medyo Bastos]

Replacement cases came unstamped.

 

[dirtdigger]

Cast numbers are just factory casting numbers. If the cam was reground it would have numbers stamped or engraved in it. Normally they did it on the end of the cam.

 

[dirtdigger]

Replacement cases came unstamped.

Yeah just kind of an odd stamping like it was a company or business using their own number system. Thats why I was wondering if it was a race motor at some point and the number was just an identification number.

 

[justafarmer]

The story. Dude bought motor, six years ago, off guy at swap meet. He was told it was a recent rebuild stroked to 880 done by out of province shop. Dude bought motor for a project bike he and brother were working on the brother passed away project didn't get finished. So dude never rode the bike but did have motor running once. So i bought an unfinished chopper amen frame saving grace rear suspension and a 74 cb750. pulled the rebuilt for my bike and sold the rest for 1000. So i paid a 1000 for a mystery motor.Currently working with buyer to finish the chopper

 

[Medyo Bastos]

I’m thinking that’s the number on the title

 

[justafarmer]

Cast numbers are just factory casting numbers. If the cam was reground it would have numbers stamped or engraved in it. Normally they did it on the end of the cam.

Didn't even cross that empty space between my ears to look at the end.

 

[dirtdigger]

Does the head look like it was ported or anything? I would pull the oil pan and look see if you can see any work done to the crank or different connecting rods.

 

[dirtdigger]

I’m thinking that’s the number on the title

That is a good thought

 

[justafarmer]

If i remember the shop's name right i got two choices. A Honda dealer turned Harley dealer or a shop that specialized in building drag engines mainly for cars though i was told they did a few bike motors. I guess i will have to wait till spring to find out what it can do.

 

[justafarmer]

No it doesn't look like it has been ported. What would i look for in terms of rod and crank work?

 

[justafarmer]

I’m thinking that’s the number on the title

Could be. though it is one digit short of the digits on neck tags

 

[dirtdigger]

If it was stroked there would have been welding and grinding done on the crank and the rods wouldnt be stock. Probably be some clearance grinding on the cases inside as well. Should be pretty easy to see if any work has been done