Topic: 71 CB750 ID/tampering question

[chin765up]

Hey there - I just recently bought what was listed as a 1970 CB750, but the title says 71 so I started looking at VIN #s and it would be a 71, Frame # - 1045776.

The problem that I ran into is that the Engine has no numbers on it.  I am pretty sure the engine ID would be directly under the air filters, on the left hand side, correct?  that area has been definitely tampered with a long time ago, which seems really sketchy to me.  So, this sort of puts me in a weird position, as I am not exactly sure how I should proceed...any suggestions?

Thanks.

[754]

 Sounds like a made after mid 70  model.. should be an early K1.

 If cases were replaced they could be blank, but there should be a number pad.
 When you look at the cylinder head from the side how many bars do you see between the fins? (trying to see if you have right engine)

[chin765up]

There are 3 bars between the fins...Not sure if it would help at all, but there is a little tab on the front stamped 736cc

[srook]

Do you have a title or transferable registration?  Either way look at the VIN on the title/registration.  If it matches your frame number you are fine.  You are looking at the number actually stamped into the frame on the drive side head stock for the frame number right?  The tag on the other side should match the number stamped into the frame and the title/registration VIN.  If the tag doesn't match its ok as they can be removed and replaced quite easily.  If the number stamped into the frame doesn't match your title/registration VIN then you have a problem. 

Lots of things happen over 40 years.  Engines blow up or get damaged and are replaced by a shop or swapped by the home mechanic.  There were also a rash of replacement cases for the CB750 becuase the chain would come off the engine sprocket and punch a hole in the crankcase.  Many of those bikes had new cases installed from the dealer.  Some stamped new numbers some didn't.  Take some pics of the motor and post them.  Many can tell you in an instant from your pictures what the deal is.

Scott

[chin765up]

I do have the title and the number stamped on the frame do match.  I appreciate your guys' help, I will work on getting some decent pictures up here in a minute just for some further peace of mind...before the super bowl starts!  Go GB!

[754]

if you have 3 bars, its a 73 or later engine, or at least cylinder head.

[chin765up]

ok, here are a few pictures of my bike/engine:

[chin765up]

and a few more

[MCRider]

Its like its been said, the frame should match the title. That should be enough. The engine doesn't matter ( there may be a state or two where it does.)

The dealers were supposed to stamp the old number into new cases when they were replaced. I would bet money that the vast majority were left plain. The dealers I worked for would never pop for a number stamping kit. Even if you had engine numbers, on Hondas they never matched the frame numbers, that was standard. They should be in the range for that model, as defined by the frame number, but that could be several hundred or thousands off.

[chin765up]

Awesome, thank you guys a lot.  when i started checking the numbers and couldn't find any on the engine, I started getting that horrible feeling in the pit of my stomach.  But - i have a matching frame and title, so now i am back to being super excited about getting this bike started.  Cheers!

[Don R]

As they took engines off the line to be sold as replacement engines the numbers got further and further off. Some manufacturers did match the engine and frame no's but Honda never did. another question is some have a build date on the frame which is not always the year of title.

[faux fiddy]

As terry in australia would say;

I once had a friend who became a cop- so you should pull the engine and send it to me- I'll see if we can put it into evidence until we get a determination.

[splitt]

This will help you on the time line question.

http://www.hondachopper.com/engine/engine_timeline/timeline.html

[AshimotoK0]

Its like its been said, the frame should match the title. That should be enough. The engine doesn't matter ( there may be a state or two where it does.)

The dealers were supposed to stamp the old number into new cases when they were replaced. I would bet money that the vast majority were left plain. The dealers I worked for would never pop for a number stamping kit. Even if you had engine numbers, on Hondas they never matched the frame numbers, that was standard. They should be in the range for that model, as defined by the frame number, but that could be several hundred or thousands off.

Did the dealers have stamps to exactly match the Honda lettering or did they use any old available stamp?

Cheers!

AshD

[MCRider]

Its like its been said, the frame should match the title. That should be enough. The engine doesn't matter ( there may be a state or two where it does.)

The dealers were supposed to stamp the old number into new cases when they were replaced. I would bet money that the vast majority were left plain. The dealers I worked for would never pop for a number stamping kit. Even if you had engine numbers, on Hondas they never matched the frame numbers, that was standard. They should be in the range for that model, as defined by the frame number, but that could be several hundred or thousands off.

Did the dealers have stamps to exactly match the Honda lettering or did they use any old available stamp?

Cheers!

AshD

I worked for 5 dealerships and 1 After market dragrace/chopper shop in 3 states between 1970 and 1976. None of them had stamps. I think Honda would sell them, but the dealers wouldn't buy. We replaced a lot of cases under warranty, no numbers, customers didn't care. If you didn't have a reason to have it, it was a worthless tool. I'm sure the dealers figured they never needed it before and soon wouldn't need it again. After Honda got the problem fixed.

I saw one once that a mechanic owned, I think for impure purposes. It was a wooden box filled with 3-4 inch long punch like tools that had numbers and letters on the end of each one. I don't think it was an official Honda kit. Maybe it was.  He implied it was expensive. He charged a lot, under the table, for its use.  

[Hinomaru]

These CB750 replacement cases have been stamped by someone. I wonder what the significance is of the extra 6 punch marks? Bike had a frame data tag dated 11/69.

(click on photo for a larger view)

[bryanj]

Number/letter stamps are a common tool and not expensive(http://cgi.ebay.co.uk/ROLSON-38-PC-AUTOMATIC-NUMBER-LETTER-STAMP-PUNCH-SET-/170379461567?pt=UK_Hand_Tools_Equipment&hash=item27ab6843bf) BUT they never match the original Honda type.

I didn't think Honda sold replacement engines complete and the explanantion of the gap in number that i was given was that the missing ones failed test on the test rig before they got anywhere near a frame.

Gets even better if you replace a frame with a new part (accident at less than 12 months old usually) as they dont come with numbers either and have to be stamped!!

[Spanner 1]

Your frame # 104xxxxx is exactly correct for the build date on the steering neck of 7/70... I agree that the motor cases were replaced ( busted chain made a hole in the original cases, common in the '70's ) and just not stamped by the dealer....... it's a K1 for sure  

[chin765up]

You guys are champs, thanks....now lets see about getting parts for this bike 

[Old Scrambler]

You need to be more careful when reading some of this advice...........We still do not know the REAL frame ID on the left of the neck.........754 advised correctly that you have a mid-K3 or later head............the stamped numbers on the motor cases are BOGUS........The E is missing!

Now, if the stamped frame numebr and the ID plate number match the title.......your still good to go. You just have to be careful when you look for any motor parts to stay with the later motors.

[MCRider]

Number/letter stamps are a common tool and not expensive(http://cgi.ebay.co.uk/ROLSON-38-PC-AUTOMATIC-NUMBER-LETTER-STAMP-PUNCH-SET-/170379461567?pt=UK_Hand_Tools_Equipment&hash=item27ab6843bf) BUT they never match the original Honda type.

I didn't think Honda sold replacement engines complete and the explanantion of the gap in number that i was given was that the missing ones failed test on the test rig before they got anywhere near a frame.

Gets even better if you replace a frame with a new part (accident at less than 12 months old usually) as they dont come with numbers either and have to be stamped!!

It was the "original Honda type" that I was referring to with my "expensive" comment. But I could be off there as I'm truly just guessing, maybe a whiff of a distant memory.  It would be interesting to know. Would close the circle on my speculation about why dealers looked the other way on the issue of restamping replacement cases.

I think it hard to match the font Honda used. I've seen some replacement cases stamped with numbers and they always look a little off.

[chin765up]

You need to be more careful when reading some of this advice...........We still do not know the REAL frame ID on the left of the neck.........754 advised correctly that you have a mid-K3 or later head............the stamped numbers on the motor cases are BOGUS........The E is missing!

Now, if the stamped frame numebr and the ID plate number match the title.......your still good to go. You just have to be careful when you look for any motor parts to stay with the later motors.

Yea - the number stamped on the left of the neck matches the tag on the right, and the title that I have.

Is there any way to get a better idea of what engine I actually have?  or is it just safer to stay within a certain year range as far as parts go?

[MCRider]

You need to be more careful when reading some of this advice...........We still do not know the REAL frame ID on the left of the neck.........754 advised correctly that you have a mid-K3 or later head............the stamped numbers on the motor cases are BOGUS........The E is missing!

Now, if the stamped frame numebr and the ID plate number match the title.......your still good to go. You just have to be careful when you look for any motor parts to stay with the later motors.

Yea - the number stamped on the left of the neck matches the tag on the right, and the title that I have.

Is there any way to get a better idea of what engine I actually have?  or is it just safer to stay within a certain year range as far as parts go?

I've lost track of what engine its thought that you have. In my experience there are only a few parts that are different, amongst the various "K" motors. If you check the microfishies at places like motogrid.com, etc. you can identify if the part you are looking for has ever been changed or upgraded. Parts shouldn't be a problem.

If you were to disassemble the engine, you'll better tell as between K1 and K2 Honda added a slathering of ORings to the head/cylinder interface, as opposed to just 2 on the earlier engines. That will be a big tell.

[chadwick70]

Here’s a weird one, I just picked this motor up today and it has this funky Vin number ending with the Honda wing logo. I have never seen this on an engine case.

[bryanj]

What motor is it you picked up?
That stamping is not original Honds but done on replacement cases