Ex 250 race bike rescue

[JohnBR]

Hi all
I am in the process of rebuilding a badly abused narrow case ex race bike for road use and I am hoping to get the spec close to how it left the factory. To do this I need to know what year and model it is can this be found out from the frame number ?
DM250*80147*IGM1985-OM
Also as part of the race prep the seat loop has been hacked off. Can anybody provide a length for the loop from the center of the suspension mounting point to the rear of the loop.
Thanks in advance, John

[Geordie]

My Mototrans Elite is currently stripped down. Measuring from centre of shock mounts to aft side of loop is 320mm. There is a central tab on the loop to take a single bolt fixing for the rear guard. It measures 18mm wide X 23mm long at a tangent to the guard.

[JohnBR]

Thanks, that solves one issue

[Ventodue]

Hi all
I am in the process of rebuilding a badly abused narrow case ex race bike for road use and I am hoping to get the spec close to how it left the factory. To do this I need to know what year and model it is. Can this be found out from the frame number ?

DM250*80147* IGM1985-OM

Welcome to the Forum, John.

Gonna need a bit of detective work, not least because one of the primary sources, the register at BevelHeaven, contains mainly American bikes and these didn't get a frame number. Also the data there are uncleaned and should be treated with caution. However ...

According to Ian Falloon, the 1961-on Daytona (UK; Diana in the US) started with 80001. This number should be stamped on "the right rear tube". And somewhat comfortingly, on the register there IS a 1964 Daytona with 80735. Why this bike should appear to be so apparently 'late' as 1964, I wouldn't hazard to say. And there is also 1966 Diana with 80910.

Btw, which country are you in? That may eliminate some possibilities. And as a first 'eliminatory move', we can count out Mach 1. While these Euro-market bikes DID get a frame number, that number sequence starts at 00001 and runs thru to 01950.

P.s The IGM code is the homologation reference. It was used on most of the singles way up until 1974. So it doesn't help none ...

[JohnBR]

Hi I am UK based but the bike could have been brought in from anywhere in Europe. If as you say it is likely to be a post 61 Daytona then that gives me something to work with. Narrowing down to a year would be nice but not essential as it will never be a pristine example. The frame number is on the righthand side of the frame down tube I do have a photo but not the knowledge to attach it.
John

[Jon Pegler]

Ian Falloons reference to number 80001 is interesting.
According to the UK Glass's guide ( a trade reference book produced in the UK) the first Daytona registered in the UK had engine no. 80001 and frame number 80090, in May 1961.
There is then a bit of a gap to the next numbers, but by November 1964 frame number 82292, fitted with motor number 82475 was registered for use in the UK.
So 80147 may well be a 1961 bike.

Regarding the rear frame loop, note that a Mototrans loop is straight, whereas the Italian 250 loop kinked up slightly at the end. Worth looking at a few photos of period bikes to compare.

Jon

[Ventodue]

Hi I am UK based but the bike could have been brought in from anywhere in Europe .. <snip>

Ok. The reason for me asking was that neither the other two models of the early (4-speed) 250 - the Monza and the Scrambler - were imported to the UK. Which kinda increases the chances of it being a Daytona.

Here's something else to look for: Does the seat rail have a boss welded on, half way along? Reference picture from Tom Bailey's book attached. These only occurred on the 1961 Daytona/Diana.

Frame boss on 1961 Dianas.jpg

Also: If you have the original front forks, you'll find a date stamp on the lug that retains the brake plate - again, see attached photo for examples.

Date stamp on brake plate retainer.jpg

[Ventodue]

Regarding the rear frame loop, note that a Mototrans loop is straight, whereas the Italian 250 loop kinked up slightly at the end. Worth looking at a few photos of period bikes to compare.

Is this the idea, Jon?

Rear frame.jpg

[double diamond]

For a drawing of the rear frame loop:
viewtopic.php?f=3&t=1063&p=7214#p7214

[JohnBR]

Thanks for all the info from everybody. The seat rail does have the boss welded on between the suspension mounting point and the front of the seat rail so this narrows it down to a 1961 Daytona if I read the information correctly. The front forks are 32mm Marzzochi which are obviously not what it left the factory with. The frame loop drawing will be useful for the replacement, I think that the best I can hope is to build a bike that is a close approximation to the original as there have been so many changes made or maybe something a little more individual.