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Odd Handling

10K views 73 replies 15 participants last post by  Glenno 
#1 ·
G'day All,
Some may have read here about the quirk in handling that I have with my 2000 F4 750 Through corners it wants to fall into the corner. That is when you go into a left hand corner then I have to push quite hard on the left hand bar to keep it from wanting to steer in on its self. When going through a right hand corner then I have to push hard on the right hand bar. A concerted effort has to be made to keep it steered out of the corner. My son has a 99-2000 F4 750 as well and his is perfect through corners. Mine has had new tyers, suspension settings returned to factory specs then variations tried. Forks have been up and down through the triple clamps, spring ride heights moved about but it still does the same, nothing changes.

I have oft read in magazines etc. that F4s have adjustable rake but have not seen any where how it is ajusted.. Can some one point me in the direction to where and how this is done

I have been riding 50s, 60s and 70s British bikes for 48 years as daily transport. My sons Ducati and MV also all go very easily around corners, the bars can be held between fingers and thumbs and they just waft around. Why won't my MV?
 
#2 ·
Have you checked your ride height with the Link Rod Screw? It might be set too high -- too far turned out. What about having your suspension configured to your weight? Also, tire pressure to 33?
 
#3 · (Edited)
Idea... pick a common visual marker on each bike towards the furthest point near each brake light. Drop a measurement from that point to the ground while holding each bike straight up. Try this without sitting on each bike. If your bike measurement is greater than your son's bike then your ride height is set too high, too great -- given you said his bike rides well for you and it's the same model.

UPDATE:
Check this image posted by Alex on his store. It's an easy reference to help visualize the ride height linkage. (Suspension Link Rod)
https://mygpracing.com/product/suspension-link-rod-f4-pre-2010/
 
#4 ·
This "potentially" sounds like a frame geometry issue. Do you know the history of the bike? - Was it involved in a small crash?

New tyres and updating the suspension will highlight a problem that may be masked earlier.
 
#6 ·
Thanks for the replies guys. I have set the bike back to factory suspension settings and started from there. The ride height has been varied incrementally up and down including with me aboard. I don't know the history of the bike but the fact that it is the same both left and right, not biased one way or the other, tends to say all is straight with it. My previous experience with steering head bearings is that they become notchy, balls or rollers dropping into divots, but there is no eveidence of this even with the front end suspended. Oh, I forgot to mention that the book says 33 PSI tyre pressure front and back but I have incrementally gone up to 42 PSI front and back and variations of.
Googling this problem shows that I am not alone with this with others having the same problem with different bikes.

Ken.
 
#7 ·
Check your ride height again.
42psi in your tyres is way too high for a MV.
Stick to 33 as the manual suggests.
I don't understand part of your comment
You say when you tip the bike into a L/H corner and push on the L/H bar (countersteer)
that will make the bike tip over further.
Well that's what countersteering does on any bike.
You are making the bike lean over further.
So I don't get your problem.
 
#9 ·
G'day Mitchy. Whilst going through a LH corner I have to maintain heavy pushing preasure on the LH bar, its pushing back against me If I relax that pressure then the bike will rapidly and increasingly run in towards the inside of the corner. If I want to take a wider line through the corner it takes a fair bit of pressure (push) to make it run wider. It takes concerntration and a fair bit of effort to keep it from running right into the inside of the corner, into the dirt. Same thing on RH corners. Now, on my Norvin, Vincents, BSA R3, Ducati Monster 659, my sons MV, Ducati S4R, Ducati 600 Monster, once they are in the corner, I can hold the bars between thumb and fore finger and they just waft around. If I was game enough I am quite sure that I could go around with my hands right off the handle bars.



Ken.
 
#10 ·
Not braking into turns Edward, just riding around open road corners. It will do it on small slow in town corners as well. The only difference I have noticed with the braking between the two is that my sons MV seems to have a more solid lever, mine a softer lever. Under similar braking my front brake lever comes further back and is a touch softer, his lever is further out and a touch harder.


Ken.
 
#11 ·
Recheck your brakes are working evenly. Bleed them, it's simple.

Next... triple clamps/head. Have you removed the clamps to have them inspected? Like @cruiser wrote a crash may have occurred sometime during the bike's history. Suspicion is your front wheel is out of alignment.

(Mind this is for a dragster but full of info)
1.
https://www.mvagusta.net/forum/56-s...-tech/142114-wheel-alignment.html#post1526650

2.
https://www.mvagusta.net/forum/56-s...-tech/142114-wheel-alignment.html#post1527610

3.
https://www.mvagusta.net/forum/56-s...-tech/142114-wheel-alignment.html#post1551794
 
#12 ·
How about your Steering damper?

Hi!


I had exactly the same experience when I first got my SR .. It would want to "Drop into corners" at slow to moderate speeds = al lot of countersteer. It turned out to be a combination of geometry (too high ride-height and too hard suspension setup for my weight and height) -- But most of the problem was that the steering damper was set way too hard ..
 
#15 ·
Hi!


I had exactly the same experience when I first got my SR .. It would want to "Drop into corners" at slow to moderate speeds = al lot of countersteer. It turned out to be a combination of geometry (too high ride-height and too hard suspension setup for my weight and height) -- But most of the problem was that the steering damper was set way too hard ..
G'day DK. The ride height on mine is quite low but I have had it set high as well trying different settings. I can't see how thew steering damper would be a cause. A damper is there to prevent severe oscilations of the forks so the slow movement as it is tipped into a corner wouldn't be a problem. Also given the time a bike spends in a corner is quite long compared to the micro seconds that a damper has to damp.


Ken.
 
#16 ·
Steering Damper

Hi! I'm inclined to agree with you completely, The steering damper should not have any real influence on turning in to slow or medium speed corners, but I assure you that was the case with mine .. My theory is that you actually unconciously do a lot of minute movements with the handlebars as you "negotiate" a corner. (Just like you can not ride a bicycle in a narrow track that just allows the width of the tyres, and go a.. over t..s when you try to ride a tram-line track) If the damper is way too tight, you can not do these small movements, and the bike feels out of control and wants to drop you against your natural counter-steer --- Mind you its just a theory... :grin2: I may have changed other settings or things on top of finding out that the damper was maxed out.
 
#17 ·
Hi! I'm inclined to agree with you completely, The steering damper should not have any real influence on turning in to slow or medium speed corners, but I assure you that was the case with mine .. My theory is that you actually unconciously do a lot of minute movements with the handlebars as you "negotiate" a corner. (Just like you can not ride a bicycle in a narrow track that just allows the width of the tyres, and go a.. over t..s when you try to ride a tram-line track) If the damper is way too tight, you can not do these small movements, and the bike feels out of control and wants to drop you against your natural counter-steer --- Mind you its just a theory... :grin2: I may have changed other settings or things on top of finding out that the damper was maxed out.
I will give it a go DK, its easy to do.
 
#19 ·
Hey,not sure if you have rechecked the wheel balance in your endeavours because it sounds similar to the effect I was getting when the front wheel on my 1090 RR lost one of its balance weights. My bike was dropping into turns quite scarily and I can only guess it was the gyroscopic force of the unbalanced wheel. Not sure if there is anything else that could upset the gyroscopic force of the front wheel but checking the wheel balance is fairly easy, I couldn't believe how much it was affected by the wheel weight being missing.
 
#20 ·
Just to add to the speculation and tips.
No F4 has adjustable steering head unit.
Front brakes are connected to one solid axle, mounted rigidly to the forks, one brake being more efficient than the other can not affect steering.

Increase front suspension pre-load, see if this makes a difference mate, change one thing at a time and do so in big amounts. Don't just increase pre-load by one turn, do a few but keep note of what you're doing.

Good luck
 
#24 ·
Thanks Mitchy and Donsy, yes, I agree with you. Thanks Donsy for clearing up the adjustable steering head, I could find no clear evidence that the F4 steering head was adjustable or indeed could not figure out how it would be adjustable. I can stop trying to figure that out now and its one more thing off the worry list. What you say about the brakes is true too. Oft I have heard people say about one brake pulling one way or the other. How do they explain single discs. Yes, I agree, make large adjustments, and then I return to standard before trying some thing else. I have ridden bikes with twisted forks and yes it is like bent bars.

Phelps.
 
#25 ·
Hi Ken, Have you set your bike the same as your sons?

Fork Height, ride height etc.

When you are hitting corners on your sons bike are you doing it at the same speed as yours?

When were the suspension components last serviced?

I must say I have the same problem as Mitchy understanding your problem? If you are pressing hard on the inside bar it should continue to fall in more not steer out. BUT this pressure can also cause you to lose the front because it is stopping the wheel from "castoring" back into line after your initial steering inputs.
 
#26 ·
G'day Glenn. Yes. The first thing that I did was set the settings back to factory settings. That didn't work so then set it the same as Ryans. That didn't work. No improvement, no change. Still dropping into corners. Yes, all corners all speeds. Even a roundabout its hard work keeping it from falling over. I have put about 20,000 KM on mine and Ryan about 15,000 KM on his, we haven't touched the suspension. Not a lot.
To keep it simple I'll talk about left handers but its the same same with right handers. Going into a left hander its light counter steer to get it over into the line of the corner, no problem there, about the same as my other bikes. The problem is once on that line it wants to keep going in, badly. I have to push quite hard on the left hand bar (or pull on the right hand bar) or it will keep wanting to fall over and parabolica into the scrub on the side of the road. I have proved this, if I test it by reducing the push on the left bar it keeds reducing the curve wanting to fall on its side. Its concerntration and hard work.

Now compared to my sons MV, my Norvin, my BSA Rocket 3 and various other Vincents, They just go around a corner. Light counter steer to get them over onto line and then just relax and they go around. I was riding around the bends of south Gippsland on the weekend on the BSA, so easy, going around the bend I can go around with a very light fore finger and thumb grip. Not game enough to go around hands off but I am sure that they would do it. Want to change line mid corner, no problems, just a very light short push or pull on the left bar to make it run a bit wide or a bit tighter then relax.

Today Ryan and I took the various sag measurements of both bikes. Not a lot of variance but I will put the figures to the website mentioned above.


Phelps.
 
#27 ·
I know you said you had changed out your tires and the problem is still there. Did you ever have your wheel bearings replaced? There should be a spacer between the wheel bearings as noted by item number 3 on the Star Twin site. Can not imagine omitting the spacer and not sure if that's even possible and still have bearing work but its an area not discussed thus far. If it is possible to accidentally omit the spacer your bike may have come from the past owner that way. 20,000k is a good amount of k to be dealing with such :(

For Reference: https://shop.startwintrading.com/en/products/f4/new-folder-26/front-wheel-assembly-19
 
#28 ·
I know you said you had changed out your tires and the problem is still there. Did you ever have your wheel bearings replaced? There should be a spacer between the wheel bearings as noted by item number 3 on the Star Twin site. Can not imagine omitting the spacer and not sure if that's even possible and still have bearing work but its an area not discussed thus far. If it is possible to accidentally omit the spacer your bike may have come from the past owner that way. 20,000k is a good amount of k to be dealing with such :(

For Reference: https://shop.startwintrading.com/en/products/f4/new-folder-26/front-wheel-assembly-19
G'day Edward. Both of us being engineer mechanicsw we realise the function of that spacer tube. Not having that there and doing up the nuts would impart a heavy side load on the bearings that would in short time be quite evident by a lot of movement in the wheel assembly. The wheels are quite smooth and devoid of any movement.



Ken.
 
#29 ·
HI Ken, Chuck here... time for my $00.02:

I have just gone through the parts manual, the shop manual and the user manual for your bike. As Donsy indicated, the Steering Head Tube is not adjustable for rake.

There is, however, a locating bolt that engages into the steering head tube on the right side of the steering head and it is to be lightly torqued into position to hold the position of the Steering Head Tube. You might check that it is still there. Overtightening will directly affect the bearing race:

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It occurs to me that there are a couple of things not discussed in your technique even you have ridden two bikes the same with differing results.

When you tip in and the tire assumes its new position on the tarmac, you must open the throttle a smidge to compensate for the smaller diameter of the tire, and thus higher rotation speed, at this orientation. It is done almost unconsciously, but if not done the bike will fall into the corner as you describe.

Another thing that I'd like to see is your tire wear and the difference between you and your son's bikes. Tire wear can grossly affect a bike's handling. As you have set both bikes to the same geometry and tire pressures, and they have the same manufacturer and size tires, then tire wear differences could account for the "handling issue".

If you would take a nose on shot of your front tire and your son's front tire it might tell a tale. Post it here for us to take a look and comment. It should be interesting.

Now I am going for the standard Public Service Announcement: Please add your bike model and year to your signature line. It will help in long thread for the folks trying to help you. We won't have to wade back through what could be hundreds of posts in order to figure out we are talking about a first gen F4.:smoking:
 
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#34 ·
G'day all,
Thanks all for your input. I checked the screws you mentioned Chuck, yes still there and secure. I have taken photos of the two front tyres. My sons bike on the left, mine on the right. Glenn, mine is the 2003, my sons is a 2000. On to that Fred, the next thing to do will be to swap wheels.

Ken.
 

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#38 ·
There is also a notable difference in the "dirt shadow" contact area between the two bikes. Did you turn your bike more when rolling it? On the bike on the right, the contact area is off to the left.
 
#40 ·
Two questions:

What brand and model of tyre?

Where is your front valve stem pointing? (Left or Right side of wheel rim?)
 
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