02 Yz 250 Sub Fram Lowering

[JOHNNI]

Can anybody help me with the right way to lower my sub frame?

just from looking it looks like i would have to shorten the air boot were it meets the carb? just wanted some advice befor i started, thanx....

ps mud in seattle, bubba first almost laped rc who got a very bad start, points tied, i think see you in vages................

[xt600stocker]

I would also like to know how to do this?

[Wideopen24_7]

I shortened the subframe on my 2003 250f just by ovaling out the lower subframe mounting holes by 5mm with a file. This is the easiest way if the welds around the box tubing don't get in the way. Wasn't an issue on that bike. I am thinking about doing my 05 yz167 but the welds may be an issue. I'm not too short for the bike I just think lower is better and Yamaha has about an inch of extra clearance under the back fender. The hard way would be to cut the box tubing, remove a few mm's, and reweld. I know some ktm guys that did this. Remember geometry comes into play so don't just go and cut out an inch of box tubing. The proper way to get it perfect would be to remove the shock spring, reinstall the shock, and push it down and see how much it actually takes by marking the mounting holes or if your cutting just take out a little at a time. That won't be easy.

[JOHNNI]

IV heard of the technique you used, but what about the air box conection to the carb, my air box is conected to my sub frame and is looks like i would have to do somthing were the carb meets the box

[Wideopen24_7]

That boot is flexible enough to move in a few mm with no problems.. It only takes a few down there to make up an inch at the seat. Honestly the carb boot should not be an issue at all. I couldn't tell a bit of difference on my 03 250f.

[JOHNNI]

Are The Lower Sub Frame Bolts On Your Bike Threaded?

[Wideopen24_7]

The threaded part is in the actual frame, don't mess with that. You need to modify the holes in the subframe by elongating them or by drilling new ones if possible. I just looked at my 05 and I think I can drill a new set of holes right next to the stock ones. I will position the holes as close to the old ones as possible and this will offer two settings. Once I get the holes done and if I think I can go lower I will file the new holes out some. If the new holes make the fender too low then I will have to file back towards the old hole and make one long oval hole.

[Wideopen24_7]

Are The Lower Sub Frame Bolts On Your Bike Threaded?

Yes the bolts are threaded but they don't screw into the subframe, they go through the subframe and screw into the frame.

[JOHNNI]

im sorry that is what i ment to say, the holes in the frame are they threded.

i got you make the holes in the sub frame longer, copy

thanx for the help

[DigilubeJay]

Like Wideopen has explained, you are simply elongating the holes of the sub-frame mounting.

You will know what the longest you can go is from when the welds of the sub-frame tubes bottom out on the frame mounting tabs. Many stop here, but I actually machined the welds a bit flat to get just a taste more. Be certain not to comprimise the welds. And this doesn't have to be done, and won't gain you too much final seat lowering, but you may find that one sides welds bottom out before the other side does. Flattening the welds out can provide them the same height to sit on top of the tabs.

I think cutting and re-welding the sub-frame tubes will work, but I think the 5mm that KTM takes is a bit much for the geometry of the yz's.

I would stick with simply elongating the sub-frame mounting holes.

[Wideopen24_7]

I repositioned my subframe holes 5 mm and never once rubbed the back fender. With my 05 I am going to remove the rear shock spring, push the back wheel all the way forward, and push down the backend and drill a new set of holes with the fender touching the wheel.