Hi all, almost every time I've Googled something related to my latest acquisition, I end up here, so I figured it was time to make an account and get stuck in.



I recently bought what was advertised as a 1972 AT1, although the VIN number suggests it's an AT2, see photo.



The ad suggested the engine had been replaced with a 97cc version, but I can seem to work out what 97cc engine! It has the cable operated oil pump that injects to the reed valve inlet.



The clutch cable goes into the clutch cover rather than operating a lever on the top. The cylinder has 97cc stamped on it so it's definitely correct. Engine number below, but I can't seem to find a match anywhere. Anyone got any ideas on what I have here? Thanks!

from near Salisbury!

Yes, you've definitely come to the right place.

If that's 465 stamped on your engine, then that's the model code for the 1974 US/Canada Yamaha RS100. Interesting (and useful info!) that it fits into the AT frame. What number is stamped on the carb? Don't tell me there isn't one Go back and check again!

If you haven't done so already, get a seat outside, open up your laptop and have a browse through the manuals in the Tech Library. As well as Service, Parts and Owner's Manuals, there are all sorts of documents that cross reference our bikes, How To's etc, etc.

Alan

Hi, thanks for the info! Just got me way further than several lockdown weeks of relentless googling. Thanks for the tip on the Tech Library. I've just got the frame etc back from blasting and coating so looking forward to getting it all back together, but I also get to focus on the engine.

I haven't had it running but seems to be in good (for year) condition, but the kick start spring has gone, so that's my next challenge now I know what parts to order.

The carb was one of the first things I looked at, as far as I can tell, it's a VM20 (main jet accessible from the bowl) but definitely needs a refurb and all new jets etc.

Have you found the carb number yet? On a flat surface, probably on the side facing the engine.

Probably teaching granny etc here (sorry!), but don't forget to rub down any earthing points, if they were not masked off when coated.

You're right about the Chassis being an AT2 . Yamaha continued to stamp frames and engine cases
with AT1 prefix , as those parts were unchanged . Causes much confusion , if you're not aware .

Yes, AT2. Some countries DID stamp AT2 into the case/frame which adds to the confusion but the majority of the Enduros made before 1974 have a "1" in the prefix of the VIN.

Carb number on the flange carb is normally stamped into the top edge of the mounting flange.

Yeah the numbers and names do get confusing!

Looks like my carb has 305 E2 on the mounting side, if that means anything to anyone!

305 is the model code for the LT2, which I think was the predecessor of the DT100. It MIGHT therefore be the correct one.

Have a look at the various jet sizes and see how they compare to those listed for the RS100 engine that you have. You'd like to think that if a previous owner went to the trouble of swapping an engine then they'd get the carb correct, but you never know! I'm thinking out loud here, but I wonder if the 100 and 125 had the same size airbox?! Some more ferretting to do!