A forum for owners of Yamaha TTR250 trail and enduro bikes!

leigh · Senior Member

front end twitchy at high speed.

TT-R250M · Super Guru

I think it is time to check your steering head bearings. They may need regreasing, replacing or just a ''nip up''.

I would suggest to raise the bike on a stand and check that there is no play in the steering head bearings and that that it turns smoothly with no notches or tight spots.

When retightening the steering head ring nut- first of all tighten the lower ring nut to 38 Nm (3.8 m*kg, 27ft*lb.) and loosen it one turn. Then retighten it to just past finger-tight- 5Nm (0.5 m*kg, 3.6ft*lb. ). If it is correct it should be easy to turn the steering and have no play in the steering head bearings.

I would also check the tire pressures and rims for bad buckles, loose spokes etc.

Of course, the geometry of your bike may be hindering the steering a little? confuse

Jarrah

leigh · Senior Member

thanks for that.

just checked that again and all good. had a full service 2 weeks ago and everything basically came up spot on.

rims and wheels bearings etc all fine.

Steers great, nice and tight, and seems really stable off road. much better in all respects than my crf 230 I had for the last 18mths.

such a better bike, and I rarely got up to 100 on the crf and rarely on the tarmac.

dont have much to compare it to. a mate with lots of bike experience rode it and pointed it out, hadnt really noticed till then.

mate suggested bar weights? said the wr400s had this fix as were very twitchy in the steering?

as the geometry is not standard it could be that? but like I say seems to handle really really well. not to fussed, but then again, really dont want to come off at 100 : )

maybe im worrying about nothing, not sure, just dont have the experience.

TT-R250M · Super Guru

Other than checking the engine bolts, swingarm bearings, linkages, suspension bushes/bearings, wheel bearings it seems like everything has been checked. Maybe it is just the geometry of the bike? confuse

Not to boast but my TTR250 does 130kph (140kph with nitrous oxide) with 14/50 gearing and has no wobbles whatsoever at high speed, just smooth riding. The engine has been ''tricked up'' a bit though.

Can't say that I have any trouble with my WR400 either, at top speed (180kph standard with US silencer with 14/48), it is smooth as a babies bottom. biggrin

Jarrah

leigh · Senior Member

Thanks for the feedback. Really appreciate it.

Mine has 13/48 haven't uncorked it yet etc so runs great I reckon!

New to the road so mainly do 80. 120 feels like I'm flying hahaha

Yep all that stuff is good.

Tracks well etc. like I say if just feels light in the steering like it could get the wobbles. It doesn't wobble or vibrate its really smooth
I love the thing. But feels like it could.

Steers well into corners etc.

Need to ride another one and see if it's the same.

None the less I bloody love riding it!!!!

Bugeye_bob · Veteran Member

What tyre pressures are you running on the road ?

leigh · Senior Member

14 front and 12 rear. Same as off road.

Prob should go 15 all round hey.

petenz · Super Guru

leigh wrote:
14 front and 12 rear. Same as off road.

Prob should go 15 all round hey.

And in there lies you prob....

min for the road ..... 18 front/22rear & the tyres will run cooler & last a LOT LOT longer

leigh · Senior Member

Yeah right? I thought 15-16 on road.

Shows you how much I know. Would only spend 5% or less of my time on the road. Mainly between tracks.

Will pump them up and see what they feel like.

Thanks!!

TT-R250M · Super Guru

leigh wrote:
14 front and 12 rear. Same as off road.

Prob should go 15 all round hey.

For offroad it should be 14.5 psi , anywhere from 17~22 will be good for tarmac.

Jarrah

leigh · Senior Member

Ok pumped the tyres up to 18 and 22.

No real difference on road.

I reckon it's because the steering is so tight. Feels like it will turn on a dime. Slightest move in the steering and it wants to turn.

Will try again with forks in standard position. See what it feels like.

Maybe the lowering link didn't lower it a full 50mm in the back end.

Maybe I'll end up with forks somewhere between standard and the 19mm I dropped them.

Shall experiment a bit.

Leigh.

TT-R250M · Super Guru

leigh wrote:

I reckon it's because the steering is so tight. Feels like it will turn on a dime. Slightest move in the steering and it wants to turn.

Leigh.

Not sure what you mean by that because if the steering was too ''tight'' it would not turn so easily. Maybe you mean that the steering is in good condition?

If it seems a little loose a notch up on the steering nut will fix it, trust me, had that problem many times after rebuilding my bikes. They all seem to need a nip up after about 1000klms.

Jarrah

leigh · Senior Member

I mean tight as in turns really well.

I understand dropping front forks through the triple clamps make it less stable but turns tighter?

I noticed off road it turns into corners much better now. But didn't notice a loss of stability.

Thinking maybe on road now it's a little too responsive in the steering?

Again I'm new to this so not 100% sure.

leigh · Senior Member

Ok round 3

Not that anyone is probably that interested : )

Put forks back to standard position. Definetly more settled at 80kph and above. Then at 10mm above the triple clamps and feels reasonably settled.

Going with 8mm and see it I'm happy offroad.

j180 · Senior Member

My OE is quite stable upto it's top speed of 112 kph so far, it does move around a bit but I put this down to the mx tyres. Definitely quicker at turning than my road bike.

leigh · Senior Member

Ok so for what's its worth thought I'd update this post.

Worn the 110/100 out and bought a 100/100. Same tyre ac10.

Much more stable on the road. Noticeable difference.

Seem to pull a bit better too. Offroad tmrw see what it feels like.

Leigh.

TTRfan · Super Guru

biggrin biggrin biggrin

Fladdem · Senior Member

I'm running a 140/80-18 on the back of mine, I think it's a six days. I didn't pay for it, I know a bloke that owns a trials bike shop, competition people always seem to swap tyres after about half use, that's where I step in and rummage through the tyre bin. I find it more stable at speed and haven't noticed a difference in performance or cornering. It seems harder wearing than the AC10's I used before, although not used it offroad yet. I run about 20 PSI in each, I find it a good compromise, knobblies seem to wear out faster with higher PSI, i.e. 30 PSI, and same when you get down into the teens, and it's so fat, my logic is, I won't need to drop the pressures off-road. smile

-- Edited by Fladdem on Saturday 12th of April 2014 04:38:09 PM

LRJ · Senior Member

I have an AC10 (100/100) on the rear of my bike, and it is a bit twitchy on tarmac, but it was way worse on the back of my Serow. Trying to go in a straight line without the bike wanting to meander was impossible on the Serow with the same AC10. It felt really unsafe. Perhaps there is a bike weight to tire size ratio that comes into play and creates an unstable ride with these tires.

TT-R250M · Super Guru

Fladdem wrote:
I run about 20 PSI in each, I find it a good compromise, knobblies seem to wear out faster with higher PSI, i.e. 30 PSI, and same when you get down into the teens, and it's so fat, my logic is, I won't need to drop the pressures off-road.

-- Edited by Fladdem on Saturday 12th of April 2014 04:38:09 PM

For offroad riding the pressure should be around 14.5 psi. Road riding the maximum is 25 psi with the recommended being 22. You should never exceed 25psi as a blow-out or excessive tire wear will be the result.

http://www.dunloptyres.com.au/tips-and-advice/motorcycle-tyres/

Jarrah

TT-R250M · Super Guru

Here is a list of things to check for unstable handling-

Handlebars

Improperly installed or bent

Tires

Uneven tire pressure

Incorrect tire pressure

Unevenly worn tyre tread

Front forks

Uneven fork oil level

Uneven spring tension (uneven dampening adjuster position)

Broken spring

Twisted front fork

Drive chain

Improper adjusted chain slack

Swingarm

Worn bearing or bush

Bent or damaged

Rear shock absorber

Fatigued spring

Improperly adjusted spring load

Oil and gas leakage

Steering

Improperly installed upper bracket

Bent steering stem

Improperly installed steering stem (improperly tightened ring nut)

Damaged bearing or bearing race

Wheels

Incorrect wheel balance

Deformed cast wheel

Loose bearing

Bent or loose wheel axle

Excessive tire wear

Frame

Twisted

Damaged head pipe/stock

Improperly installed bearing race

Enjoy!

Jarrah

leigh · Senior Member

Thanks jarrah. Nice list. Will copy that.

Ok 110klms today. Half on road half off.

Damn. Can't believe how much better the bike feels. Turns better and more stable. Really really noticeable. ESP on the road at 80-100kph.

Read on a few forums some experienced people saying 110/100 is too much tyre for a 250. That they will not turn well and tend to push the front in the corners.....anyway thought I'd see what happened by changing.

Seriously positive difference for my bike is all I know.

Leigh.

TTRfan · Super Guru

I have used the 100/100 front AC10 tyre and it seemed fine both on and off road. My front tyre of choice is the Michelin Comp IV though....

I tend to run about 18lbs in both front and rear tyres to prevent pinch punctures and it's worked so far biggrin

Brian

TT-R250M · Super Guru

No problems Leigh

I forgot to mention that when fitting the rear wheel, you should measure the distance from the tire (or rim) to the swingarm either side. It should be even if correct. Don't trust the snail adjuster, even if they are at the same number either side.

Jarrah

Fladdem · Senior Member

Thanks Jarrah!

I didn't think that too much air in the tyre was safe. Could twitchiness be down to the large diameter wheel on the front or not? How about uneven air-pressure in the forks?I tried to put about 7 PSI in each leg, but I don't trust my gauge. Although mine doesn't get twitchy until about 75MPH, according to my mates speedo. But when I am going at speed somewhere, I usually sit right forward, and try to push the bars down, to counteract it.

TT-R250M · Super Guru

I have not had any dramas using the 100/110 apart from the extra tire noise. I do find that using the 100/100 is better for stability though.

The air pressure in the forks should be even or it will cause handling issues. I prefer not to use air as it puts extra pressure on the seals.

First thing I would check is that there is no play in the steering. The steering needs adjustment from time to time.

Jarrah

BM Steve · Guru

TT-R250M wrote:
I have not had any dramas using the 100/110 apart from the extra tire noise. I do find that using the 100/100 is better for stability though.
The air pressure in the forks should be even or it will cause handling issues. I prefer not to use air as it puts extra pressure on the seals.
Jarrah

I always thought that the valves in the fork caps was to let any built up air out, not to put it in wink

So I set the bike on the ground (not on a stand) remove the caps and push the valve to bleed from time to time

I could be wrong though confuse

Fladdem · Senior Member

I thought they were to adjust the preload on the fork springs? Again, I could be wrong. I should probably just get tougher springs and a service done on them. Then I wouldn't have to worry about air in the forks.

TT-R250M · Super Guru

BM Steve wrote:
TT-R250M wrote:
I have not had any dramas using the 100/110 apart from the extra tire noise. I do find that using the 100/100 is better for stability though.
The air pressure in the forks should be even or it will cause handling issues. I prefer not to use air as it puts extra pressure on the seals.
Jarrah
I always thought that the valves in the fork caps was to let any built up air out, not to put it in
I could be wrong though

From the manual-

Standard air pressure: 0 kPa (0 kg/cm2, 0 psi)

Maximum air pressure: 40 kPa (0.4 0 kg/cm2, 5.7 psi)

So as you can see, it is up to the owner whether or not to use air in the forks. As I said, I prefer not to because it puts extra pressure on the seals.

Jarrah

Fladdem · Senior Member

The lock-nut on my steering yoke keeps coming loose, I'm sure his doesn't help stability. How would I stop it from coming undone?

-- Edited by Fladdem on Thursday 24th of April 2014 10:37:28 AM

petenz · Super Guru

loctite..... must be a yamaha thing... my xt660r kept doing the same..

TT-R250M · Super Guru

Fladdem wrote:
The lock-nut on my steering yoke keeps coming loose, I'm sure his doesn't help stability. How would I stop it from coming undone?

Tighten it to the correct torque, always works for me. Does need adjustment occasionally though. Failing that, use Loctite.

Jarrah