I have a engine with the S/N T120 021520 which should be for a 1959 Bonneville. The engine has a alternator right side case. Did the Bonneville come with a alternator in the late 1959 model year or has this engine been changed.

That really doesn't sound right to me. It should be a generator equipped motor. Likely the case half has bee replaced at some point. Getting a case half to match would be a miracle, but your could get the cases re-machined. I've put two non matching cases together successfully but it required removing the locating dowels to do it. Both sump and cylinder surfaces needed machining for them to match. The motor came out great.....one of the smoothest I've ever done.

1960 Bonnies were alternator equipped but the numbers started with 029364, a bit later than your numbers by a fair amount.

Cheers,
Bill

What are the numbers under the cases?

Going to have to see pictures of the engine and numbers in question. Until then, it's just a guessing game.

First of all, if your serial number begins "T129..." you already HAVE a problem, as Bonnevilles are T120.
I would like to see a photo of these numbers to see if the originals have been ground off and bogus ones re-stamped in their place.

If so, that would explain the left-side case having Speed Twin or Thunderbird provisions for an alternator

I'll send you a message. Cheers

So I have a 1960 engine with 1959 numbers stamped on it. what now.http://www.britbike.com/forums/tmp/2880.jpg

What were your plans before you found out the cases are not what they say they are eg the 59 numbers.

That's too bad

I have a 1955 frame I am going to use as a bobber or flat tracker. I would like to licence it for the road.

I would have thought that as you are not doing a full 59 Bonnie restore then as long as the number shows as being clean in a check then you are ok. The 1960 number is long gone and only that would potentially cause problems.

In those years the frame and engine numbers did not necessarily correspond.
In any case-- although I am not sure of the laws in CA certainly in the North East of US the titling (the VIN#) is done on the frame number.
So the engine # is irrelevant and not even on the title.
HTH

Depends on how savvy the CHP inspector is. The engine number is listed on the title in CA and if the VIN inspector has any reason to suspect something funny is happening, they can impound the bike (the whole bike, because they won’t inspect individual parts) until the owner can convince them otherwise. VIN inspectors here are trained to identify restamps...

My B31 almost went to jail because someone may have ground off one digit from the frame number when raking the neck.

If that T120 stamp and pad doesn’t closely match what’s ‘normal’ for that era, I’d be scared to have it inspected.

Chris

Not enough in the pics dept to see clearly.
It may be genuine, did you polish up the area of the numbers? Is the metal smooth or casting-rough between and around the tamp? They are admittedly rather more neatly stamped than most, but who knows maybe Bill Bloggs had a wait before the next one came along and chose to make a masterpiece?
Is the level well below the edge of the barrel flange? Are the edges of the number area angled or smooth casting curves?

Tridentman, Glenn is working with a Triumph. BSA engine and frame numbers didn't match until 1966. but Triumph numbers certainly matched from 1950 - on.

The old adage of Triumph engine serial numbers before 1969 is:
"If they look TOO PERFECT, they are probably FAKE."

Thanks Irish---I stand corrected.

However--it is not unknown for engines to be changed out so frame and engine numbers do not always match in real life.
Also--what happens in CA if a guy buys a bike from someone in another state where the title only has the frame # as the VIN # (such as NJ where I live)?

Any vehicle brought in, even with a clear and active title will get inspected. DMV can inspect cars but all motorcycles go through CHP.

Chris

The research has shown that their is a original bike with that same number that is all together. Wish I could find that owner to confirm this. I have seen a picture of the original numbers for that bike. Numbers on my engine do not match the stamping in that picture. Calif registration of my other bike has Frame number and engine number, which is confusing, 1955 Frame, 1950 engine, registration calls it a 1950 motorcycle, on the title from 1981.