My 919 recently started wobbling the handlebars at 40-45mph. It only happens when I take my hands off the bars. When I put my hands back on, it stops. It happens very consistently at this speed.
The bike is mostly stock, except for sprockets/chain, heavier springs in forks and Wilbers shock in back.
Here's what I did so far:
- asked bike shop to check wheel balance front and back (was ok)
- changed tires front and rear (Dunlop Roadsmart 3)
- checked tire pressure
- visually inspected rims by turning and holding tool next to it, seems ok but could be more subtle
I haven't run over any hard bumps or curbs. It was ok until a couple of months ago.
1. Steering stem bearings, check both loose and worn.
2. Fork alignment - I'm dealing with this myself as I'm just finishing rebuilding my front end (forks, new tire, brake pads, fluids...)
3. Wheel alignment, both tires pointing the same direction. You can use the "string trick" to check, I think a laser will check as well.
4. Suspension adjustment, yet another thing I'm dealing with right now. I screwed up my rebound adjustment because I had it too low and have to take the top of the forks off to adjust the nut under the fork cap.
5. General inspection for loose or worn things, fork clamps, rear tire axle bolt (might as well adjust the chain while there).
This assumes that they inspected the tire.
How old is the fork oil and what weight did you use?
Steering stem bearings, 95% chance. If they're not totally worn, the congealed original grease can cause stiction and problems at this point in time. These bikes aren't new any more.
My 919 recently started wobbling the handlebars at 40-45mph. It only happens when I take my hands off the bars. When I put my hands back on, it stops. It happens very consistently at this speed.
There is a natural tendency for this to be able to occur.
Typically, it is not a precursor to highway speed tank slappers.
Typically, it's nothing to be scared of.
BUT, that is not to say it should be ignored.
IF everything has been checked and found to be OK, and I do mean everything, then I'd suggest revisiting the steering head bearings again as they are a likely suspect, as CB700S pointed out.
Steering head bearings in anything less than perfect condition should be binned.
Steering head bearings are as problematic when they are set too stiff, as when set too loose.
The factory manual setting is too stiff for my liking, but it can take many tries to get them set looser with no detectable clearance.
Never set them with detectable clearance.
Aged grease can be a problem, but it very depends on the grease.
I've seen grease a few years old losing its oil, as well as decades old grease that is just as fresh behaving as when it was new.
I have replaced fork oil about 6 months ago. It might have started aster that.
I will check fork alignment first and if that doesnt help will check stem bearings.
There is another thing I noticed today. There are 4 weights for balancing on the front tire that the shop put on where Ibhad the tire installed. I believe they are .5oz each or something like that.
However they put all the 4 weights on one side of the rim. I would think its better to put half on one and half on the other side. I may give that a shot before doing anything else.
The weights are supposed to be split on each side. They should also be towards the center if you can, but still on a somewhat flat surface.
One shop did that to my rear tire, kinda lazy if you ask me.
Someone did a write up on setting the forks, but one thing you do is loosen everything that touches the forks except the top of the clamps. Then force the bike up and down on the forks to get the tubes to line things up... then tighten things back up.
The front/rear is basically using a string (or laser) to form a straight line to see if they are both pointing the same direction. You have 4 edges to line up, two rear tire edges that are wider and two front tire edges where you measure them to see if all for touch the line at the same point.
Note that this should be done AFTER you line up your rear tire. You can measure the distance inside the adjusters or count the threads or look down the length chain.
Interesting that you mentioned that it might have started after the new fork oil. I'd go thru the adjustments. The manual left out how to set the center rod with the nut inside. Personally, I'd go thru the whole process of setting the forks and adjusting all the settings.
My bikes steering bearings are worn. Also loose maybe Idk. Bike does the same thing urs does if the top case is on. I just keep my hands on the bars and it works fine
Tire non-uniformity is almost always the culprit in front end "wobble" on motorcycles. Just because you put on a new tire on the front doesn't mean that it is uniform for vertical and lateral force variation. 2oz of weight is a lot of weight to be added to bring a front tire into balance and that would immediately cause me to wonder about the tire. I put a new Continental tire on the front of my 919 a couple of years ago and ended up with a front wobble. Dealer re-balanced the tire 3 times and each time it ended up with a different distribution of balance weights and the wobble continued. I finally got disgusted with the situation and pulled the front tire off and looked at it very carefully from the inside. There was an obvious "wrinkle" in the carcass which to me said the tire had a construction flaw and would never operate correctly. The place where I bought it agreed and refunded the purchase price....but not 3 mount and balance charges. I think you'd be time and money ahead to get a different tire for the front. Not necessarily a different brand or model but just a different tire.
Paraphrasing from Tony Foale's Motorcycle Handling and Chassis Design book:
Motorcycles have a Natural Wobble Frequency.
It's fairly common to have a N W F in the 40-65 kph, and most commonly manifest itself under deceleration with the hands off the bars.
A motorcycle's N W F will not manifest itself unless there is matching rhythmic forcing that is no adequately damped.
Trailing_Throttle is spot on re front tire involvement, as it's an ideal device to provide matching rhythmic forcing by a non-uniformity or non-uniformities.
Taking your hands off the bars removes damping.
Keep in mind that tires are not the only possible cause, and a tire that is involved could be acting in concert with some other factor or factors.
Suggest that "tire" be seen as being "wheel", with tire as part of it.
Especially is bad balancing is an element of the overall front wheel rotational induced forcing problem.
The first time I rode a motorcycle with considerable difference in the rim widths I found the exact shake you are describing despite having done a very careful alignment of the rear wheel to the front and replaced the steering head bearings. Subsequent rides on quite a few bikes with similar setups produced the exact same shake at the same speed range when i let go of the bars, and all it took to stop it was the lightest touch on the bars, usually just one fingertip was sufficient to stop the oscillation. From that I concluded that it is more or less normal without knowing the cause.
A couple of years later it began to come into focus, and while I have not had the opportunity to consult with anyone who had a definitive explanation it does make sense to me. For the longest time rims were close to the same width front and rear and the shake you mention never happened. Plenty of other instabilities, but not that one. As soon as the rim widths got quite a bit different the shake cropped up. Why? All motorcycles are quasi stable. I saw a video of a CHP motor officer riding on a straight uncrowned road, and it was never actually going straight, instead it was slowly weaving a small amount from side to side. This is the essence of balance: The bike is constantly trying to achieve its natural three point stable condition (laying on its side), but the physical dynamics of forward momentum try to keep the front wheel lined up with the centerline of the bike. Given that it's never completely stable on two wheels it ends up weaving to maintain stability. It all works pretty well ... until you let go of the bars. The front tire is trying to align to the center of the contact patch of the rear tire, but with a considerable difference in the width of the two contact patches the front can't find a stable position and hunts back and forth at a rate equal to the natural frequency of the vehicle, about five to ten Hz. As soon as the front line of action leaves the outer edge of the rear contact patch physics causes a counterforce which moves the front in the opposite direction, causing the oscillation. There is little force involved, explaining the ease of damping it out.
Over the years I have tried every adjustment and check possible to prevent it, without notable success. Finally I just accepted it as normal and began to play with it instead of obsessing about it.
wow so many replies and things to check.. Might have stirred up a hornet's nest :smile2:
Looking at my records the last fork oil change was actually 2 years ago, so I think I'll take the whole front-end apart, do the forks, check the bearing and so on.
It will take some time as I'll be busy with other stuff and the 919 is actually my summer bike (for lack of wind protection). Meanwhile my SV will have to take over.
- Checked rear alignment using motion pro alignment tool. Was aligned.
- Took off wheel and checked balance using a shop machine where you spin the wheel and it indicates whether it is balanced or what weight is needed where. Tire was balanced perfectly.
- Inspected rim. Had someone else with experience check it. It is perfectly straight.
- Inspected bearings. I had replaced them last year. They run smooth and there is no play.
- With wheel off, I carefully inspected steering. No play. No 'rough spots'.
- When re-installing front wheel, I loosened lower triple bolts and pumped the front prior to tightening axle- and pinch bolts.
- Torqued everything down to spec.
Still wobbles. Same thing.
But I start wondering about steering stem bearing pre-load. On page 13-32 of the service manual it specifies a procedure to measure the force it takes to move the steering (with the front jacked up) at the fork tubes. The force should be 10-15N. On my bike it takes only very little force. I don't have an accurate way of measuring it but it seems to move completely freely, apart from some friction induced by throttle and clutch cables.
Should I try to increase the steering bearing pre-load? Can I do that without taking the front-end apart? Has anyone done that?
What brand offering did you replace the bearings with? The crap Chinese ones, such as the All Balls branded units, are known to sometimes wear very quickly due to improper heat treatment, etc.
You do not have the steering bearings set correctly (or they've worn in) in that case. Per Honda, if you converted to taper roller bearings, the steering head bearing preload should be 4.0-4.85lbs for both left and right turns, measured at the ear at each side of the triple tree using a spring scale. If you stayed with OE ball bearings (why, I don't know) the number is 7.37-11.06lbs.
As for how to measure it? Fishing or spring scale from Walmart. Problem solved.
I'm just a punk kid who don't know nothing but I think I took a punch and a hammer to the collar and just smacked it to tighten it. There's probably more steps involved but it was something like that. It loosened up a bit again after more wheelies and hard miles. My guess is that if it's loose, it's because it's worn. My head bearings are a bit loose right now and it wobbles at the same speed yours does.
With the front end off the ground, can you move the steering with a "light finger touch"? Does it have sticking spots?
You might want to try the "string trick" where you put a string around the rear and front tires while on a center/rear stand. This string compares the 8 points.
4 points per tire, 2 front/rear for each tire.
The points on the front should be equal while the ones on the rear should be equal to each other. This shows if the front and rear are both straight at the same time compared to each other.
My 919 recently started wobbling the handlebars at 40-45mph. It only happens when I take my hands off the bars. When I put my hands back on, it stops. It happens very consistently at this speed.
This is a perfect description of classic Natural Wobble Frequency coincident with Reduced Damping by virtue of your "hands off".
Further indicative of excitation happening at N W F and due to Reduced Damping is the wobble easily stopping simply by putting your hands back on the bars.
My guess is that some factor(s?) is/are aggravating it, but remain suspicious of the head set bearings setup.
The ONLY proper way to set up head set bearings is with the front end totally stripped, I mean tubes out and fork top triple (aka crown clamp) off, just like the manual shows.
The check class of fit is done with the top triple clamp on and clamped axially to the stack per the factory torque value of the top nut.
A lightly set head set can easily have an increase in sweep drag by the addition of the top triple due to the light setting of the head set not having taken up all of the threading clearance.
Mine are set lighter than the factory calls for.
I don't even know if my bike does what yours does, seeing as I don't take the hands of the bars and make a point of never doing so anywhere in the classic N W F speed zone.
I had a '73 CB750 that I put an 18 inch wheel on with a 4.10 rear tire and it did the same thing, but was rock steady at top end.
I can't remember ever removing my hands when moving. If push comes to shove, I guess a steering damper would do the job. The 919 is one of the bikes they say never needs one, but maybe that's not the case.
Before doing that, I'd bring it into a shop and see what they say.
I used bearings by Koyo, another Honda supplier, which are available in the US from K&L. The 919 uses their extremely common part number 31-2219, shared with the 1100-1500 Goldwings and similar mid-to-large displacement Hondas of that era. You can also get the bearings separately, but unfortunately there are counterfeit bearings out there so one must be careful about suppliers.
Availability: Local US indy parts store and most dealers should be able to get them as they are distributed through Tucker-Rocky and other moto parts distributors. They are also available online through some dealers - I've dealt with these guys for years and not had problems, no connection other than as a customer: https://www.siriusconinc.com/pro_de...0_gl1200_vt1100_steering_bearings-39-1166.htm
Unfortunately not as easy to find online as they once were as all the idiots keep buying AWL BAWLS and other failtastic cheap Chinese bearings in vast quantity.
One caveat - you will need to get the 919's steering stem lower or base dust seal separately as that is not common to all the bikes this fits. 53214-371-010 is the current Honda part number. You will not use the upper dust seal as it will not fit - and the Honda mothership says not to bother anyway. I just fill the void with grease and that keeps the crud out, as I was told by several Honda factory technicians.
Something to ponder.
Tapered roller bearings are more sensitive to bearing housing accuracy.
Tapered roller bearings only exhibit their maximum life and "bearing stiffness" under preloads noticeably greater than appropriate ball type rolling element bearings.
Tapered roller bearings have greater load capacity than any comparable ball type rolling element bearing.
Auld motorcycles such as my '73 SOHC CB750 had woefully inadequate head set bearings in terms of load carrying capacity.
Putting in tapered bearings made much sense decades ago, and still does.
But they should not be preloaded for maximum load carrying capacity, otherwise the head set friction is too high.
Personally, I see no need of converting a 919 to tapered roller bearings for the head set, as I view the OEM bearing selection as being more than adequately robust for the intended application.
And I'm fiendish about using high quality bearings made and marketed by a bonafide bearing designing company.
It should be mentioned that our head set bearings are the same as used in the 1980 CB750C/K/F...
My experience is that taper roller bearings last a lot longer in the minefields of potholes around here. YMMV. It's worth noting that Honda actually made a taper roller conversion kit for the GL1500 and others before discontinuing it for lack of interest. The instruction sheet/manual addendum for that conversion is what I've been excerpting above.
I get a lot of OEM parts from Partzilla.
They are well priced and might be worth a look.
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