YZ forks

[mxmaniac]

Does anyone know if forks and triple clamps from a drum brake 80's YZ 250/490 will go into a 79 YZ125f ?
Or are the standard forks decent?
Any ideas on what can work well? I am 72kg's and a medium pace rider.. (sometimes a little quicker for 1/2 a lap) 

[yzhilly]

I fitted 43mm YZ250H forks and triples straight up to my YZ400E, At 100kg the 38mm front end was struggling to stay off the stops .The bigger forks have made a huge diff to the bikes handling . But i dont know if 43mm were fitted the 125H if they werent it wuold not Evo legal to fit to your bike . With your wieght you should be able to get the 38mm forks setup to suit . Oh yeah 125H is not evo so it would be 125G stock 38mm .

[mxmaniac]

Thanks Hilly, I will have a look into it mate! I think i will get Mike Landman to have a look at what he can do to make the forks work, i will see what the benefits of the yz125g forks would be if there any different. I am new to the old Yamaha thing, thanks heaps for your help!

[DJRacing]

For what purpose do you want to go to larger diameter fork for?
Stick to the 36mm YZ125F forks, there is nothing wrong with them.
You can change the spring, the preload spacer, the weight of the oil, the amount of oil used, put air caps on and thats all before you start working on the valving.

If you feel you need to go to a bigger diameter, then dont use 43mm forks, they will look out of place and be heavier, not to mention having to balance the bike with the rear shock. The 38mm is a better bet, but you will need to pull them a long way through the triples.

[mxmaniac]

I have never ridden a yz125f, so all info is Gold to me!
 I know a guy who fitted the 43's to his and said it was sweet, but i will definately try the standards first, as it makes sense what you are saying.
With Landmans knowlege, i think he will be able to make it work for me, my standard forks condition are a bit average, so i was thinkin if there was something better i would look to them instead of toying with these.
 I will start with these and go from there, if Neil perkins rides suicide style on one.. well i think i can get one to work for me!

[DJRacing]

Neal rode my YZ125E when he was over here in NZ and He thought my fork were a little hard so he removed some oil and I think Neal had a good time racing here.

[Nathan S]

I'll second what DJ said: go for the 38s. They're quite a bit less flexy*, and usually come from a 250, so the springs are usually stiffer too.

Look at YZ250E/F forks, and they'll be closer to the correct length for a 125F, unlike the later ones which are super long.

I've got a set of 38mm IT250J forks for my 125G - but remember that the Gs have more travel than the Fs.

*Assuming that both sets of forks are made of the same material, the stiffness is D x D x D x D - so a small change makes for a big difference in stiffness. (If you want to be pedantic, its actually D^4 minus d^4 [D=outside diameter, d=inside diameter]).

[mxmaniac]

Grouse, thanks fellas.. the help is appreciated.
Now i have a honest idea of what the hell i am doing!
Them 38's off a 250 sounds the most logic i think. The guy who put 43's on his 125 said he changed them because the originals flexed to a chopper style look on a hard landing. I will ask around for anyone who has a set of 250 forks and clamps! Cheers