hi all, hope you're all good!! today I've been doing the 125 conversion on my lovely old DT. i was looking for any advice from people who have done this conversion already, i have complete gasket sets for both cylinder and head (125/175) and have discovered i need to replace the small end bearing.... does anyone know what else might need to be changed ? thanks alot. aaron

does anyone know if i need to change the jets in the carb?

Edited November 8, 201014 yr by MrAzF

hi all, hope you're all good!! today I've been doing the 125 conversion on my lovely old DT. i was looking for any advice from people who have done this conversion already, i have complete gasket sets for both cylinder and head (125/175) and have discovered i need to replace the small end bearing.... does anyone know what else might need to be changed ? thanks alot aaron

So long as you have everything 125 from the cases up you will be fine.ie

Head

Barrel

Piston

Little end

Gudgeon Pin

Gaskets

Also you will need to re jet the carb, your carb will be a VM24ss carb ID 3U500

the 125 had a 22mm and a24mm carb over the 3/4years it ran for so for safety's sake these are the specs for a 125 f which had a 24mm carb.

Carb ID (for reference purposes if you are ordering parts)2N400

Main jet 125

Main air jet .5

Jet needle 5GL8

3rd groove from the top

Needle jet N-4

throttle cutaway 2

Pilot jet 22.5

Starter jet 20

Float height 21mm

Idle speed 1350-1500

As to the oil pump, play that by ear. If she's smoking a lot adjust it if you must but i would be tempted to leave it alone if at all possible. Little bit of extra oil won't hurt, certainly better than to little.

You will find the 125 is lacking quite a bit in the 2-5000rpm range compared to the 175, but so long as you let it rev it does around the same flat out. You just have to turn down the mechanical sympathy a little.

Hope this helps.

So long as you have everything 125 from the cases up you will be fine.ie

Head

Barrel

Piston

Little end

Gudgeon Pin

Gaskets

Also you will need to re jet the carb, your carb will be a VM24ss carb ID 3U500

the 125 had a 22mm and a24mm carb over the 3/4years it ran for so for safety's sake these are the specs for a 125 f which had a 24mm carb.

Carb ID (for reference purposes if you are ordering parts)2N400

Main jet 125

Main air jet .5

Jet needle 5GL8

3rd groove from the top

Needle jet N-4

throttle cutaway 2

Pilot jet 22.5

Starter jet 20

Float height 21mm

Idle speed 1350-1500

As to the oil pump, play that by ear. If she's smoking a lot adjust it if you must but i would be tempted to leave it alone if at all possible. Little bit of extra oil won't hurt, certainly better than to little.

You will find the 125 is lacking quite a bit in the 2-5000rpm range compared to the 175, but so long as you let it rev it does around the same flat out. You just have to turn down the mechanical sympathy a little.

Hope this helps.

yeh it does thanks i have everything but the carb kit, but i will do a bit more investigating on the carb and oil settings in my haynes manual. thanks alot for your help any more info would be great! cheers

You have the bike listed on your profile as a 2k4 thats just a chassis number prefix common to DT Mx's, if its a 1981 bike its a 4J4 chassis number 2k4-020101 onwards.

If it is an early bike then it would be a 2X2 with a chassis number 2K4-010101 onwards.

You have the bike listed on your profile as a 2k4 thats just a chassis number prefix common to DT Mx's, if its a 1981 bike its a 4J4 chassis number 2k4-020101 onwards.

If it is an early bike then it would be a 2X2 with a chassis number 2K4-010101 onwards.

oh right, cheers! its so confusing

Hi, other than changing the top end all I did when I converted mine was to swop the Main Jet and the Pilot Jet for the 125 specs. Runs perfectly.