DT125X front fork speed wobble
This is my second Yamaha DT125X, the previous one I sold was because it had slightly bent fork stanchions, I upgraded to a DRZ400 but I didn't like it's cruising speed so I bought another DTX which is really in good shape.
This DT had original exhaust on it so at first there wasn't any wobble as the accelereation was much slower and top speed also.
Now I have full giannelli, snorkel removed, upjetted, everything set up and as I shift to 6. gear I have the wobble again, so from 110 km/h and up.
What I did so far:
-Rebuilt front forks (this time not replacing bushings, on the previus DT I did but it was like even worse) with 10W oil, new fork and dust seal.
-Disassembled steering bearing and regreasing it, set it up so it is not loose and not binding.
Fork yokes are straight, fork stanchions are moving evenly free in yokes and wheel axle is free moving across the two fork legs.
-After installing front wheel, bouncing the bike a few times before tightening the two fork leg screws.
-Moving up forks like 1cm in the yokes.
-New Michelin Pilot Street Radial, static balanced it, and before installing the new tyre, I got the wheel balanced (by the spokes I mean, no runout at all)
-Tried increasing front spring preload by adding 9mm machined spacer on top of the stock 3mm one. (Between the spring and the top fork "screw")
-Setting rear sag (1/3 of the travel, I don't remember exact numbers now but it is set properly)
I am 160 CM and 55 KG if it means anything. I found the front forks too soft at first but now with the spacer I feel it is enough.
The wobble goes away as I step off the gas, and it is almost totally fine on good road surface and no wind. If I have cross wind and pretty big bumps, it is pretty scary.
I don't have any other ideas what could I try, perhaps I should install later a DRZ front complete or so?
Thanks in advance.
declan last edited by
@lorant2 can you post a picture of the bike
How much speed and acceleration have you gotten from a new pipe? Surely it can’t be enough to cause problems that weren’t there before. Are you reaching previously unreachable speeds now?
Previously it was 110 kmh top speed by speedo (115 by gps). Now it is 125 by speedo and 131 by gps. That is what my previous dt could do too, but that dt was indicating more on the speedo than actual. Strange but I can live with it
The acceleration howewer is much better. I'm only thinking I am too lightweight and the front forks expand that much that free play in the forks is too much? I will upload a photo later when I'm on computer. Bike has 26.000 kms on it.
Oh and I also tried going lower and higher tyre pressures than recommended. That also didn't change much. Stock is 1.8 bar in front and 2.0 bar rear as i recall. Tried 1.6/1.8 and going even for 2.2/2.4
Calum last edited by
@lorant2 I mean, by bike is a bastardisation of several bikes all put together in a shed, and mine doesn't wobble.
I'd raise the front end back up. Lowering the forks through the yokes, will make it more nimble but will make it less stable in a straight line.
NINJA last edited by NINJA
declan last edited by
@lorant2 try a ride without the front mudhuard fitted and see if the wobble stops
Nottsbiker last edited by
@declan yes I was thinking it could be caused by wind / drag etc
Thank you guys for the replies
About that pie part, well im like eating too much but it just wont grab on me or idk
I will try basic setting in the front and removing mudguard.
Also one other thing, above 100 kmh if i just grab the clutch or push the handlebar the wobble starts. So I can like simulate the bad road or crosswind with this.
Is the rear end raised?
No, I just decreased the spring preload a little to get 1/3 of the travel as sag. Didn't have to do much adjustment tho. No aftermarket dog bones or any other sht installed. So it is actually lower than stock. (it was 620mm between the two measurement points and now it is 600 if I recall correctly.)
Was that after the wobble started?