My M750 has a new trick! A headshake at high speed turns! - Ducati Monster Forums: Ducati Monster Motorcycle Forum
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post #1 of 21 (permalink) Old 01-18-2019, 05:29 PM Thread Starter
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My M750 has a new trick! A headshake at high speed turns!

2001 M750 has been running perfectly since the idle issue was solved. (Thank you Ronski. You were right, I didn't replace the battery. ) I took it out yesterday and did about 50 miles. The first half of the trip was smooth. Parked it for about 2 hours and then heading home, I noticed the front end felt wobbly when I'd take it hard into corners or when I'd go higher than 70mph. I thought maybe I had low air pressure and stopped at a gas station but psi was fine.



Bit of history... The handlebars were replaced because they were bent from when I went down last year but I don't think that would be related now. Then again it sat for a long time since the drop and handlebar replacement. When kept at lower speeds I feel no wobble at all. High speeds and hard turns, I get the feeling me and the asphalt are going to meet, again. So my question is what would cause a wobble?

Last edited by MotoGirl; 01-19-2019 at 03:53 PM.
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post #2 of 21 (permalink) Old 01-18-2019, 07:32 PM
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You checked the rear tire too, right?
A low rear can make the front wobble and feel weird.
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post #3 of 21 (permalink) Old 01-19-2019, 03:19 PM Thread Starter
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Quote:
Originally Posted by Monster4Lee View Post
You checked the rear tire too, right?
A low rear can make the front wobble and feel weird.

Quote:
Originally Posted by Monster4Lee View Post
You checked the rear tire too, right?
A low rear can make the front wobble and feel weird.
Thanks for the reply, Monster4Lee. I did not know that the rear pressure could be the culprit. I need to check both. I had them at about 32 front/34 rear. That night when I checked the pressure on the front it was hot so I need to check them again cold. I cycle so I know how much tire pressure can effect the ride. I was told once that if I don't ride a motorcycle too hard, and I'd like a little more life out of my tires, try 40 front/40 rear. I haven't done that because, well, 1.) the manufacturer puts a max psi for a reason. I'm not comfortable going rouge on these matters just yet. 2.) the source does not own a motorcycle and never has. He heard it from Click and Clack on Car Talk, in reference to tires on a car. Lol.

I just started back riding my Monster in November after a long gun-shy hiatus from dropping it. Since Nov I've dropped 37lbs and I've read that could cause a difference in ride feel and bike performance. But would it go so far as cause a wobble?

Maybe I'll set them at 36/38 or so and see how that works out. But I will definitely check that back tire and hopefully that will sort it out.



Thank you again!

Last edited by MotoGirl; 01-19-2019 at 03:42 PM. Reason: To clarify
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post #4 of 21 (permalink) Old 01-20-2019, 09:45 AM
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Also maybe go by the shop and have them see if your steering head bearings are worn or damaged, or if you may have bent the forks any in your crash.

PhilB
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post #5 of 21 (permalink) Old 01-20-2019, 05:40 PM
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Originally Posted by philb View Post
Also maybe go by the shop and have them see if your steering head bearings are worn or damaged, or if you may have bent the forks any in your crash.

PhilB
If you get help you can check this at home. Maybe not quite as close inspection as a pro, but...
There should not be any click or "detente" feel when turning bars side to side.
Should not be front to rear play in the front end, but you may need the front wheel off the ground to check that.
Also make sure tires are not worn out or worn funny.

I learned about the low rear effecting the from when I had a rear flat on my Tuono about a year ago.
Cruising along the back road and the front felt vague, started to wobble a little.
Then it got worse and turned into a tank slapper while I wondered what was going on. I was able to get it stopped OK, and the back tire was destroyed. If in doubt, pull over and check things out NOW, not later.

Good luck fixing the issue.
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post #6 of 21 (permalink) Old 01-22-2019, 06:59 PM
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I will just add a few things to what the other guys said.

Firstly, be careful over inflating bike tires, yes, car tires have less rolling resistance when hard, but bikes are meant to roll/lean around corners. Very hard tires bounce easier, something I wouldn't want hard over in a corner.

If you get front end off the ground, spin the wheel (with help of course), use flat of hand to check for shimmy or wobble of tire. Mainly, when a bike goes down, depending on the situation, the front end can 'dig in' pushing the tire sideways against asphalt. This can put a flat spot on tire which is either easy to see or not so. Your hand held against in various positions can feel this. sadly if it has a flat spot, then a new tire is the only fix.

Next, a more common cause of high speed wobble after crash is, the disk rotor(s) can get slightly bent in crash.
causing slight contact of one side of pads. Obvious effect is like intermittent braking on one side. Again, spin wheel and either use hand or plastic tool like handle of screwdriver held against forks to see if the rotors have any run out.

Check wheel alignment using string or straight edges, out of alignment can cause strange wobbles at speed.

Another check which would be least likely as the inverted forks are quite solid, get partner to stand in front and hold front wheel between legs firmly, try to turn handlebars side to side, see if any movement at triple clamps. Having ridden trail bikes with soft long forks, I was amazed how much play there was, also, do they look even at the top triple clamp. Difficult to see, maybe a shop check would be best if it gets this far.
Ducati's are much more solid but worth checking.

hope this helps,
Ron,
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Last edited by ronski; 01-22-2019 at 07:06 PM.
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post #7 of 21 (permalink) Old 01-25-2019, 11:41 PM Thread Starter
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Cheers for the replies! I finally got a chance to spend some time on this tonight. I checked the psi on the tires, cold this time. The back tire was low, 30psi. I inflated the tires back to 34 front/36 back. I took it for a ride and, though the shake isn't there anymore on the turns, it's still not tight beyond 70mph. But the rear air pressure helped greatly.


Monster4Lee, you mentioned back tire being an issue and since I'd been riding it a little too squidgy, there's a faint wear line that's formed on the tire that looks like it was made by a bulge between the rim and road. Maybe. It just seems to be the most obvious reason for the marking. I believe that's what Ronski was describing. The look of a "tire sideways against asphalt"? Overall the tires look fine aside from that rear wear line.



I took it back home and managed to take the weight off the front wheel and moved the handle bars from left to right and everything was moving smoothly. Nothing seemed to be catching anyway. I used a plastic carpenter's square and gave the front wheel a spin and I didn't notice any issues with alignment.



And Philb, I'm going to go ahead and take it to a shop so they can give it a once over, check the steering head bearings and forks. From what I've learned so far, I'd like to catch an issue before it gets really bad. The whole an ounce of preventative is worth a pound of cure.



Thanks again guys!

Last edited by MotoGirl; 01-25-2019 at 11:43 PM. Reason: Auto-misspell
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post #8 of 21 (permalink) Old 01-26-2019, 05:46 PM
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Ounce of prevention for sure.
Let the pros check it out, they do it every day and have more knowledge and a better eye for things than most of us.
Got pics of the tire treads? How many miles and years on them?
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post #9 of 21 (permalink) Old 01-29-2019, 07:00 PM Thread Starter
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Quote:
Originally Posted by Monster4Lee View Post
Ounce of prevention for sure.
Let the pros check it out, they do it every day and have more knowledge and a better eye for things than most of us.
Got pics of the tire treads? How many miles and years on them?

I'd been set on taking my bike to a shop today and getting some photos of the tires as I was supposed to be out of work early-ish. But things didn't go as planned at work and with my long commute... shops is closed. But, I'm still going to take her out for a bit. I'll get some photos of the tread and post them soon. The bike has about 12,500 miles on it now. When I purchased it the tires were new so that's 2,500 miles on them. The only thing I'm concerned about is the marks from the low psi wobbly rides. I don't know what damage I may have done but I believe I caught it early.



I'll be back with photos..
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post #10 of 21 (permalink) Old 01-29-2019, 08:35 PM Thread Starter
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Ounce of prevention for sure.
Let the pros check it out, they do it every day and have more knowledge and a better eye for things than most of us.
Got pics of the tire treads? How many miles and years on them?

Alrighty. I just made sure the psi was spot on and took out out. No wobble on turns but still a slight wobble at 80mph. I stopped and took some pictures of the tires so if there’s anything glaring I’d appreciate knowing before a shop take me for a ride. (They see me coming a mile away when it comes to cars so hoping to be armed with some knowledge before going in!)



I tried to resize these but I think they are still huge! Lol! Sorry. :/
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