YZ125G transplant

[Digga]

Q. for all the Yamaha experts/gurus out there:

Would an air cooled YZ250G/H or similar IT250 etc donk fit straight into a 1980 YZ125G roller?

The 125G has the drive on the right hand side so not sure which (if any) same period YZ/IT shared this & would/could fit into the frame with little or no mods 

[bigk]

The obvious question: WHY?
K

[Digga]

Because I'm too fat for the little thing & thought I could just swap out a bigger donk & we would all be happy 

[Digga]

But you already knew that, didn't you Loki -  LOL?

[cyclegod]

I had a YZ125G and improved it a lot by fitting an IT175H top end and pipe/carb 

[Nathan S]

IT175G/H motor will go in. Or just the top end, as cyclegod said.

If you want a 250, then just buy a 250 rather than raping the 125.

[Lozza]

Q. for all the Yamaha experts/gurus out there:

Would an air cooled YZ250G/H or similar IT250 etc donk fit straight into a 1980 YZ125G roller?

The 125G has the drive on the right hand side so not sure which (if any) same period YZ/IT shared this & would/could fit into the frame with little or no mods 

It's cheaper to tune the 125 engine for great mid range power.  Quite easy to get great mid range and still have your top end power from a 125

[Digga]

If you want a 250, then just buy a 250 rather than raping the 125.

No raping going on, was just curious to see if something bigger would drop right in. I do like the IT 175G/H idea so might look into that, thx guys 

[Nipper]

Hey Digga want to go faster, ride a Suzuki !   

[Nathan S]

I'll also recommend upgrading to a 38mm from end off a YZ or IT.
At 90kg, I can feel the 36mm forks flex over moderate bumps.

[bigk]

Or you could just go on a diet!
K

[alexbrown64]

Digga, i can understand your predicament... i rode the G brand new when i was 16 and only 60kg.  On the salt lakes, my brother over took me at high speed on his yz80.. i loved the light weight and handling but they were not that fast and at the beginning of the season, they had major problems.  Mine broke down all year and the front forks used to bend like pretzels....
Here is a pic of the most 125 G's you will see off the start line in 1980.  This one is from Southern Cross.... the only saving grace for the G on this day is that i saw a young Jeff Leisk get beaten on his Honda by Harry Banken on a G, to win the "kid of the cross".

[Digga]

Big Kev, yes you are right, I do need to go on a diet, that is the root cause of all problems 

However, this will take a while & in the meantime was just curious if there was a simple HP boost by swapping in & out a larger cc top end or full donk just for the situation where I will have to be riding the little bike in Evo open events (125 v 250/500 doesn't work for me)

In 125 Evo, it is fine & is plenty quick enough in the right hands & reasonable rider weight, so maybe the 175 upsize option is a good idea 

[OverTheHill]

Had a G brand new & thought they were great bikes--fork & all but in later years i bought a YZ125H frame just to get the forks & arm by memory for a project BUT it had-had a KX500 in it. Looked like a good stretching job too but i never saw it run as such. Was probably too fast to 'see' lol.

[evo550]

Q. for all the Yamaha experts/gurus out there:

Would an air cooled YZ250G/H or similar IT250 etc donk fit straight into a 1980 YZ125G roller?

The 125G has the drive on the right hand side so not sure which (if any) same period YZ/IT shared this & would/could fit into the frame with little or no mods 

No.