TY250 76 or 77 ??? Restoration

[hcreations]

Hi all,
Ive just picked up what I believe is a 1977 TY 250. The VIN number is 493-202284 which from what Ive found on the net makes it a 77 model. I wanted to restore it in the style of the 76 which is the Dark Blue and White as opposed the 77 which is the Pale blue. It came with a 434-000655 engine in it, does anyone know if this is from the 74 model? The matching 493 motor is in bits ready to be rebuilt, there are a heap of new bits still in the packet but having never built an engine before Im not sure if everything is there so will probably take it to a professional to complete this bit. Just wondering if anyone had any tips for restoring a bike like this as this is my first attempt? Am keen to get it as nice as possible but I still want to ride and compete on it too. Cheers Adam.

[TriCub]

From the Yamaha number list that I have a 493 is a 1975 B model and the 434 is a 1974 model.

[David Lahey]

It looks exactly as you have described, a D model (1977) TY250 with an A model (1973/1974) TY250 motor fitted, and yes the motor ID number means it is from an A model.
There are no special tricks with restoring a TY250 of any model. If you have questions about particular parts of the resto I'm sure you will gets lots of help.
If I was planning to do it as you have indicated, I would want to know why someone went to the trouble and expense of buying lots of engine parts for the D model motor but not use them.
There is no problem with making a D model look like a C model. As far as I have been able to work out, they are mechanically identical, differing only in the colour scheme and ID numbers.
Yours appears to have the right carby for a C/D model which is good because parts for the A model carby are hard to source.

[David Lahey]

I thought that your A model engine number might have been close to mine and it was. They were close to being siblings on that production line in Japan. Mine is 434 000642
David

[hcreations]

Thanks David, the reason all the parts were bought buy the previous owner and not put in was that he was forced into selling a lot of his unfinished projects to finish his house so he can sell it, unlucky him, lucky me. I found a site today http://speedandsportinc.com/ which is for Yamaha Vintage Motorcycles and confirmed the numbers as a 77 and the engine as a 74 like you said. The left hand side cover on the 74 at the moment is belonging to the 77 so that will go back on when the engine is rebuilt and Ill try and source another one pref from a 74 to have that as a complete spare engine.
I noticed today the head on the 77 is actually numbered as 434 and am assuming it should be 493 to make it match the barrel. The guy I bought it off said it was definitely the head that came off that motor but who knows what happened in the 30 odd years before he had it? I found a local guy that loves these sort of bikes and is keen to help me put the engine back together so ill concentrate on removing little dings and dents and hotting up the cosmetic side of it and hopefully get to ride it soon enough.

[David Lahey]

I've just checked out two TY250D heads and one TY250B head and they all have 434-01 cast into them. I don't have a TY250A head that I can look at but I would expect that the numbering on it is 434-00.

This is not unusual because the numbering of TY250 parts is not straightforward and there is also disagreement on some parts numbers between different Yamaha parts books for the one model.

The B model is a sort of half-model that was produced at very short notice in reaction to press criticism of a few things on the original model. The A and B models were both incredibly popular. By the time the C model was released, it was obvious that the improvements over the B model only made the bike slightly more durable (swingarm strength, seat design) and slightly lighter (lighter rims). The C model was not a big seller.

[David Lahey]

I've just looked up the three Yamaha parts listings books titled:
model TY250A
model TY250A model TY250B
model TY250C
All these books list the Yamaha part number for the cylinder heads on A, B and C models as:
434-11111-00

After checking these parts books I now reckon that the A model head will have the same number cast into it as the D model head has (434-01)

[hcreations]

AWESOME, thanks heaps for that David. Its complete then, and all matching which is cool. All I need now is to source a left hand side crankcase cover for the 74 and that will be a complete spare engine. Time to get to work, thanks again.