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C10 handling anomaly

mbsevans2722

Member
Member
Got my rebuilt 1999 back on road yesterday, took her for a shakedown ride this evening. Had fluid puking from final drive, so I have ordered 2 O Rings and the main seal. Beyond that, I found the straight line handling of this machine THE MOST disconcerting of any bike I have ever ridden. I have roadraced and done much in the area of 2 wheeled handling, however having just rebuilt this machine with completely rebuilt front end, Racetech springs, bushings, seals, oil and a C14 rear shock in the rear plus new wheel bearings I am quite disappointed this evening with what I can only describe as a hinge in the middle feeling. Ideas?
 
My 95 had Avons when I bought it. At low speeds it would rock side-to-side as if constantly correcting itself. Merely annoying, but that went away with the Shinko Verge 011s. Still wagged a bunch at 70-80, particularly in the wake of a truck. Mounted a Michelin Commander on the rear after the Shinko wore out. Now it's oddly stable at slab speeds, though requires very deliberate countersteer to tip in.. Not as solid as my Road King, but close enough.

Hinge in the middle sounds like something really wrong though. Obviously go back and re-check everything you touched. With all the parts changes, what is the ride height and sag now?
 
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Most probably, it's the rear tire.
Next how much air is in the rear shock?
Slack in swingarm?
Or, check for a click as you turn the bars left to right. May possibly be a notch worn/fretted in the front bearings.

Ride safe, Ted
 
My 95 had Avons when I bought it. At low speeds it would rock side-to-side as if constantly correcting itself. Merely annoying, but that went away with the Shinko Verge 011s. Still wagged a bunch at 70-80, particularly in the wake of a truck. Mounted a Michelin Commander on the rear after the Shinko wore out. Now it's oddly stable at slab speeds, though requires very deliberate countersteer to tip in.. Not as solid as my Road King, but close enough.

Hinge in the middle sounds like something really wrong though. Obviously go back and re-check everything you touched. With all the parts changes, what is the ride height and sag now?
No idea on height or sag.
 
+1 on the engine mount bolts . The top bolt is prone to break on some bikes . Some have needed a shim in one side to prevent that . Because our engine is a stressed member (no frame) it can really mess with handling if broken .Other then that are you certain the head bearing is tightened correctly ?
 
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+1 on the engine mount bolts . The top bolt is prone to break on some bikes . Some have needed a shim in one side to prevent that . Because our engine is a stressed member (no frame) it can really mess with handling if broken .Other then that are you certain the head bearing is tightened correctly ?
I checked all bolts when she was apart, nothing seemed amiss. I am suspecting the head bearings I installed, I may need to tweak them.
 
Steering head bearings that are too tight will cause handling problems.

C14 shock .
OOPs. I missed that.

Did you also install a Lowering Rocker? If not, the rear is 1-2" higher than stock.
If not, Did you raise the front forks in the tripple trees to counter the tall back?
Guessing that the imbalance could cause handling issues.

Also Sag should be looked at. The C-10 has a very soft front suspension (If stock, I suggest adjusting the front to maximum pre load), and the C-14 rear needs about 14 clicks adjustment to get the rear sag near correct.

On my buddies bike: He installed a new set of radial tires. The rear of the bike would wobble very easily.
NOTE: I rode behind him and watched when he got near a truck. Was un-nerving.
He solved the problem by installing a belted tire on the rear.
We later realized that he had a huge windshield on the bike that added to the movement.
At the time, many thought that the issue was the radial tire didn't have enough side wall strength.

Do a Test; Before you change tires or other, try adding air pressure to the front and rear tire to a minimum of 40 PSI.
Also ride without the bags, and/or the windshield.
See if that improves things.. If so, I suspect rear tire is the issue.

Ride safe, Ted

PS:
On my C-10 (In an effort to have stiffer radial sidewall) I installed a 180/60-16" rear tire. I think stock size is 150/80-16.
I have no wobble, but the different profile (because of the big tire on the narrow rim) really corners aggressively.
Mine also has stiffer front spring (done by removing 4" from the stock spring), a fork damper (Emulators) (Cost approx. $50/EZ to install), C-14 rear shock, and lowering rocker (very hard to find anymore).
Suspension (loaded) sag is set at (I think) 35mm.
{I'll try to find the fork spring/emulator installation instructions for you in the Forum}.

See Post #14
 
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OOPs. I missed that.

Did you also install a Lowering Rocker? If not, the rear is 1-2" higher than stock.
If not, Did you raise the front forks in the tripple trees to counter the tall back?
Guessing that the imbalance could cause handling issues.

Also Sag should be looked at. The C-10 has a very soft front suspension (If stock, I suggest adjusting the front to maximum pre load), and the C-14 rear needs about 14 clicks adjustment to get the rear sag near correct.

On my buddies bike: He installed a new set of radial tires. The rear of the bike would wobble very easily.
NOTE: I rode behind him and watched when he got near a truck. Was un-nerving.
He solved the problem by installing a belted tire on the rear.
We later realized that he had a huge windshield on the bike that added to the movement.
At the time, many thought that the issue was the radial tire didn't have enough side wall strength.

Do a Test; Before you change tires or other, try adding air pressure to the front and rear tire to a minimum of 40 PSI.
Also ride without the bags, and/or the windshield.
See if that improves things.. If so, I suspect rear tire is the issue.

Ride safe, Ted

PS:
On my C-10 (In an effort to have stiffer radial sidewall) I installed a 180/60-16" rear tire. I think stock size is 150/80-16.
I have no wobble, but the different profile (because of the big tire on the narrow rim) really corners aggressively.
Mine also has stiffer front spring (done by removing 4" from the stock spring), a fork damper (Emulators) (Cost approx. $50/EZ to install), C-14 rear shock, and lowering rocker (very hard to find anymore).
Suspension (loaded) sag is set at (I think) 35mm.
{I'll try to find the fork spring/emulator installation instructions for you in the Forum}.

See Post #14
Gotta read my post mate! LOL I rebuilt the front end with new bushings new race tech springs .9 kg/mm² and 10W Motul, pre-load spacers as per race tech specifications which would stiffen up the front end to match the C 14 shock in the rear. Tires are brand-new Avon‘s 35 front 32 rear.
 
ARghhh.. Another OOPs on my part.

I think the rear (without Lowering rocker) is still too high.
ie; The C-14 shock is (approx. 1") longer than the C-10 shock.
So, the original C-10 suspension geometry is changed.
Additionally, (Unless I missed it) you didn't add an Emulator or Gold valve to improve the damping?
So the combination of stiffer front springs, lighter oil, stock damping, different geometry may be an issue.

I am not a suspension expert by far. (Just guessing and trying to assist)

Buddies tires were also new Avon's.
At the time; Several members had wobble issues after installing them.
And, 35 / 32 is too low due to bike weight.
Try C-10 specified pressure of 40.

Ride safe, Ted
 
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Appreciate the feedback folks! She’s up in lift with final drive exposed waiting for parts.
One thing to mention - if you happened to overfill the final drive it would cause it to puke fluid, even with good o-rings and seals. This could happen if you turned the wheel during filling. I always drain completely, pour in 220ml (at the most) or until it comes back out the fill hole and then replace the cap. Never turn the wheel while filling.

I know you ordered parts already, just wanted to throw this out there in case you didn't know.
 
One thing to mention - if you happened to overfill the final drive it would cause it to puke fluid, even with good o-rings and seals. This could happen if you turned the wheel during filling. I always drain completely, pour in 220ml (at the most) or until it comes back out the fill hole and then replace the cap. Never turn the wheel while filling.

I know you ordered parts already, just wanted to throw this out there in case you didn't know.
Thanks. Drive was drained, flushed and exactly 220cc out in. Seal is definitley leaking and possibly large O ring as well.
 
Yes I'd echo the recommendations of increasing tire pressure - these heavy bikes needs a bit more pressure to keep the tire from deforming/rolling under load. This is a simple (and free) thing to try.

As others have mentioned, setting the sag and rebound damping correctly will help the bike feel more planted as well, and will help stability through the corners. Definitely take the time to do this, it has made a noticeable difference on every single bike I've done this to, both my own and friends' bikes.

Keep us posted!
 
Yes I'd echo the recommendations of increasing tire pressure - these heavy bikes needs a bit more pressure to keep the tire from deforming/rolling under load. This is a simple (and free) thing to try.

As others have mentioned, setting the sag and rebound damping correctly will help the bike feel more planted as well, and will help stability through the corners. Definitely take the time to do this, it has made a noticeable difference on every single bike I've done this to, both my own and friends' bikes.

Keep us posted!
Agreed. I need to get basic drivability and leaking final drive fixed then I can tackle suspension setup.
 
I have a 02 C10 running Avon's. Experienced some highway cruising wobble plus I have replaced the OEM progressive front springs with Sonic straight springs. The front end was therefore sitting higher. I increased the front end preload over the course of a number of rides so now the wobble is gone at normal highway speeds. PSI in the tires are 36 front/ 41 in rear.
 
I have a 02 C10 running Avon's. Experienced some highway cruising wobble plus I have replaced the OEM progressive front springs with Sonic straight springs. The front end was therefore sitting higher. I increased the front end preload over the course of a number of rides so now the wobble is gone at normal highway speeds. PSI in the tires are 36 front/ 41 in rear.
Denny, was there a question in ur post, or were u just filling us in one what u did?
 
Denny, you said; "The front end was therefore sitting higher. I increased the front end preload over the course of a number of rides so now the wobble is gone at normal highway speeds".

I'm not doubting that you solved the issue. Just want to question your reasoning on the solution.
ie; Increasing the preload "Raises" the front of the bike.

"Thinkaboutit"

Ride safe, Ted


 
I have a 02 C10 running Avon's. Experienced some highway cruising wobble plus I have replaced the OEM progressive front springs with Sonic straight springs. The front end was therefore sitting higher. I increased the front end preload over the course of a number of rides so now the wobble is gone at normal highway speeds. PSI in the tires are 36 front/ 41 in rear.
What rate are the springs you used and how long are the spacers with your current setup?
 
What rate are the springs you used and how long are the spacers with your current setup?
Based on my weight and type of riding I chose 1.1kgs with 15wt fork oil. It's been a long time since I replaced the OEM progressives with the straight springs (2011) so I don't remember how I modified the spacers but it was in accordance with the installation guidelines provided by Sonic Springs. Check out this webpage for choosing their springs, http://sonicsprings.com/catalog/calculate_spring_rate.php My bike is now setup with about 1" preload sag. I plan to experiment with 42 psi in the rear. I try to change one variable at a time and then see how that one change affects handling in both calm or windy conditions. Takes a bit of experimentation but eventually I was able to eliminate the wobble at highway speeds.
 
Denny, you said; "The front end was therefore sitting higher. I increased the front end preload over the course of a number of rides so now the wobble is gone at normal highway speeds".

I'm not doubting that you solved the issue. Just want to question your reasoning on the solution.
ie; Increasing the preload "Raises" the front of the bike.

"Thinkaboutit"

Ride safe, Ted
Connie_rider,
I'm not a suspension expert but maybe we are dealing with definitions (?). What I have been doing is tightening (turning clockwise) equally the two top fork adjusters. This is compressing the springs (I assume) which is increasing the stationery preload sag. In my case, went from 3/4 inch to 1 inch measured by the zip tie method. If I should be using different terminology, I apologize but I did get the results I was looking for.
 
(For discussion; Let's assume that you're setting on the bike)

You sed;
What I have been doing is tightening (turning clockwise) equally the two top fork adjusters.
This is compressing the springs (I assume) which is increasing the stationery preload sag.


Should be;
ie; This is compressing the springs (I assume) which is increasing "de-creasing" the stationery preload loaded sag.
,,,,,This is compressing the springs which is "de-creasing" the sag.
(Sag is how far the front of the bike goes down when loaded).

Think of it this way; When you're setting on the bike, the compressed spring is supporting your weight.
** It takes XX amount of spring compression for the spring to develop enough resistance to support that amount of weight.
Here, you have not changed the Weight. You added pre-load.

NOTE: Adding preload does NOT increase spring force. It raises the front of the bike.
Hard to explain what I just said, so will do step by step.
Remember; ** It takes XX amount of spring compression for the spring to develop enough resistance to support that amount of weight.

So,
A) If you screw in (clockwise) the pre-load adjusters; "the spring does not" compress further.
,,,,,, (It doesn't compress the spring because the spring is already compressed enough to support that amount weight)
B) If you screw in (clockwise) the pre-load adjusters, "the spring does not" compress further, but "the front of the bike rises".
If you were to screw in the Pre-load adjusters 1/2", the front of the bike would rise 1/2" etc.
That 1/2" RISE means that the Loaded sag is decreased 1/2".

Hope this helps. (??)

Ride safe, Ted
 
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(For discussion; Let's assume that you're setting on the bike)

You sed;
What I have been doing is tightening (turning clockwise) equally the two top fork adjusters.
This is compressing the springs (I assume) which is increasing the stationery preload sag.


Should be;
ie; This is compressing the springs (I assume) which is increasing "de-creasing" the stationery preload loaded sag.
,,,,,This is compressing the springs which is "de-creasing" the sag.
(Sag is how far the front of the bike goes down when loaded).

Think of it this way; When you're setting on the bike, the compressed spring is supporting your weight.
** It takes XX amount of spring compression for the spring to develop enough resistance to support that amount of weight.
Here, you have not changed the Weight. You added pre-load.

NOTE: Adding preload does NOT increase spring force. It raises the front of the bike.
Hard to explain what I just said, so will do step by step.
Remember; ** It takes XX amount of spring compression for the spring to develop enough resistance to support that amount of weight.

So,
A) If you screw in (clockwise) the pre-load adjusters; "the spring does not" compress further.
,,,,,, (It doesn't compress the spring because the spring is already compressed enough to support that amount weight)
B) If you screw in (clockwise) the pre-load adjusters, "the spring does not" compress further, but "the front of the bike rises".
If you were to screw in the Pre-load adjusters 1/2", the front of the bike would rise 1/2" etc.
That 1/2" RISE means that the Loaded sag is decreased 1/2".

Hope this helps. (??)

Ride safe, Ted
Thank you Ted for the clarification. All I was interested in conveying is the final result of my efforts to alter front end sag. When I add my weight to the bike and using the zip tie method, the sag increased from 3/4 inch to 1 inch. By "sag" I'm just measuring the movement of the zip tie on the fork and not whether the bike rises or falls but I appreciate your technical explanation. Sorry if I misled any people with my terminologies.
 
Not a problem, I understand (*and I agree) that you're explaining what you did helped the wobble.
** ie; Raising the front of the bike should improve high speed stability.
But you're missing something, and "I think you're not measuring/understanding sag correctly".

ie; Increasing the preload "Raises the front of the bike".
,,,,,Raising the front of the bike is a "decrease" in sag.
,,,, It's impossible to increase sag by adding preload).
,,,,(Adding 1/4" of preload should have raised the front from 1" of sag to 3/4" of sag).

Sag Video

If you want to go deeper; here is video that explains Suspension definitions.

Ride safe, Ted (Yes, I know I'm a PITA)

PS:
Some time ago, (while trying to learn) I posted a discussion on how to "inexpensively" improve your suspension.
For another $40-$60 you can do a lot more.
 
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