Front wheel hop/suspension damping? 1991 K75s

[KappoBrick]

Hello,

Recently when I did my front tire, I uninstalled the front wheel, kept the bike on the the center stand with a jack under the bike to keep it up, but then with my luck the jack got a leak. I had to take a trusty 4x4 wrapped in a towel to put the forks on not to damage them on the pavement. Note, my old front tire was awful, cracked, nearly bald and due for replacement.

When I installed the front wheel back per manual specs, I noticed theres alot of vibration and and hop at cruising speed or when going over what I assume to be smooth road. It’s incredibly uncomfortable.

Did I throw the forks out of alignment? There was not much I could do unfortunately, and luckily I am having a local shop replace the oil and springs in the fork (long overdue, was suggested when I got the bike due to age). How do I remedy this? Should I have them try and reinstall the wheel? Surely when they go to the springs and oil they will have to properly align the forks and set sag, thus negating the fear of misaligned forks right?

[The Mighty Gryphon]

First of all, is your new tire balanced?  It wouldn't be a bad idea to check it.  Do you have three spoke wheels on your bike?  My experience is that the heavy spot on those wheels is not at the valve stem.  The bare wheel should be checked for the heavy spot, and then the tire is installed with the dot located there.  This will make balancing easier and more accurate.

Stiffness in the forks is often the result of stiction.  You need to loosen all the fasteners on the forks including the fork brace and then tightening them in sequence starting from the top clamps working down to the axle, bouncing the front end frequently as you go.

Last, do you know how much oil was put in the tubes?  Fork oil quantity varies a lot between models and years, and it can be difficult to identify what is on a given bike.  If too much oil was put in them, the forks will be very stiff, and there is a good chance the seals will blow out.

[Laitch]

Recently when I did my front tire . . .

I am having a local shop replace the oil and springs in the fork. Should I have them try and reinstall the wheel? Surely when they go to the springs and oil they will have to properly align the forks and set sag, thus negating the fear of misaligned forks right?

Describe the method used to mount the tire to the rim. What is the tire's maker and model? Did you notice directional arrows on the tire? Did you balance the wheel, as Gryphon indicated? Some Bricks are more sensitive to wheel balance than others

Many shops don't check fork alignment during a fork oil change unless it is requested by the customer. An extra labor charge will be incurred by having reinstallation of the wheel but having them do that is ok.

Sag adjustment is not part of a shop's fork fluid/spring replacement service. Sag adjustment needs the presence of the rider wearing full riding gear seated on the moto. It could possibly start and finish with just adjustment of the rear shock absorber while the rider is mounted.

[KappoBrick]

First of all, is your new tire balanced?  It wouldn't be a bad idea to check it.  Do you have three spoke wheels on your bike?  My experience is that the heavy spot on those wheels is not at the valve stem.  The bare wheel should be checked for the heavy spot, and then the tire is installed with the dot located there.  This will make balancing easier and more accurate.

Stiffness in the forks is often the result of stiction.  You need to loosen all the fasteners on the forks including the fork brace and then tightening them in sequence starting from the top clamps working down to the axle, bouncing the front end frequently as you go.

Last, do you know how much oil was put in the tubes?  Fork oil quantity varies a lot between models and years, and it can be difficult to identify what is on a given bike.  If too much oil was put in them, the forks will be very stiff, and there is a good chance the seals will blow out.

Wheel was balanced, and I have no clue of the fork oil. I followed the manual to avoid stiction.

[KappoBrick]

Describe the method used to mount the tire to the rim. What is the tire's maker and model? Did you notice directional arrows on the tire? Did you balance the wheel, as Gryphon indicated? Some Bricks are more sensitive to wheel balance than others

Many shops don't check fork alignment during a fork oil change unless it is requested by the customer. An extra labor charge will be incurred by having reinstallation of the wheel but having them do that is ok.

Sag adjustment is not part of a shop's fork fluid/spring replacement service. Sag adjustment needs the presence of the rider wearing full riding gear seated on the moto. It could possibly start and finish with just adjustment of the rear shock absorber while the rider is mounted.

Front tire is mounted in the proper direction, and so is the wheel. Tire is balanced, and I followed the manual to avoid stiction.

[Laitch]

Front tire is mounted in the proper direction, and so is the wheel. Tire is balanced, and I followed the manual to avoid stiction.

When you "did your front tire", what was the method you used to mount the tire to the rim and balance it; did somebody else mount and balance it?

[KappoBrick]

When you "did your front tire", what was the method you used to mount the tire to the rim and balance it; did somebody else mount and balance it?

Mounting the tire to the rim im not sure, but the shop I took it to said he used a special machine or setting since the K bike 3 spoke wheels are a bit weaker or more sensitive to bending and balancing, and he even offered to balance it again because he was confident in his work. I mounted the wheel to the bike, lining everything up, compressing the forks multiple times, tightening the axle bolt, and then the axle pinch bolts.

[motohippy]

Along with the quantity of oil added, do you know the weight used?
This is purely subjective, but I personally found that 5w left things bouncy, and 10w was overly stiff. 7.5w works well for me and my weight/riding style.   

[KappoBrick]

Along with the quantity of oil added, do you know the weight used?
This is purely subjective, but I personally found that 5w left things bouncy, and 10w was overly stiff. 7.5w works well for me and my weight/riding style.

The servicing has not been done yet, the springs are still in transit.

[KappoBrick]

Ill state that the shop told me that if anything would compromise the K75, it would be age and not mechanical wear at such low mileage at 13000. It was his suggestion to do the front forks as he could not foresee anything else at his low of mileage effecting the front ride quality. He even offered to re-balance the front tire if it came down to it. I had mentioned earlier that I wanted the forks done anyway, since the bike sat (from what the PO had said) for a while, and it showed since when I changed the AF there was a nest in it. I never trust anything lubricated to "sit" as it gums up like brake fluid and it's a pain. He suggested it was the fork oil and possibly springs, but I opted to get get both anyway so I do not have to get it done later.

[The Mighty Gryphon]

I would humbly suggest that you loosen all the clamp bolts including the fasteners for the fork brace. 

Tighten them in the following sequence:

Top clamp, bounce
lower clamp, bounce
left fork brace screws, bounce
right fork brace screws, bounce
axle nut, bounce
left axle pinch screws, bounce
right axle pinch screws

Assuming the fork tubes aren't bent, tightening the top and lower triple clamp screws should pull the fork tubes into parallel as long as the fork brace is loose.  This is an important part of removing stiction from the front end.  Then you must tighten the fork brace so it doesn't pull the tubes out of alignment or cock the lowers.  Once the axle nut is tight, the lower pinch screws need to be tightened in sequence to prevent pulling the lowers out of parallel. 

[frankenduck]

Tighten them in the following sequence:

Top clamp, bounce
lower clamp, bounce
left fork brace screws, bounce
right fork brace screws, bounce
axle nut, bounce
left axle pinch screws, bounce
right axle pinch screws

When reinstalling forks I always loosely install the axle and pinch bolts, bounce a few times and then tighten the axle and pinch bolts before tightening the fork brace bolts.  This ensures that the forks are well aligned before tightening the fork brace bolts.

[The Mighty Gryphon]

When reinstalling forks I always loosely install the axle and pinch bolts, bounce a few times and then tighten the axle and pinch bolts before tightening the fork brace bolts.  This ensures that the forks are well aligned before tightening the fork brace bolts.

Thinking about it, it makes a lot of sense.  Get the ends of the forks in alignment and then tighten the brace. 

[KappoBrick]

Thinking about it, it makes a lot of sense.  Get the ends of the forks in alignment and then tighten the brace.

This sounds a whole lot of i'm gonna have a shop do it.

[jagarra]

Going through the process of loosening the triple clamps and fork brace when only the axle was loosened seems a bit much just for pulling the axle and changing the tire.
If that set up was OK prior to changing the tire it has to be with what was done last. I have only gone through that process when I have adjusted the forks or rebuilt them.  If the balance was done on a electronic balancer has anyone checked the tire for out of roundness or a separated belt.  The issue could be within the tire itself, maybe replacing the tire under warranty will solve the problem. 

[The Mighty Gryphon]

Since it only takes 15 minutes to go through the fork fasteners I can't see any reason not to do it whenever I pull the front wheel off.  It's just part of doing the job to the highest standards. 

It's also not a bad idea to check that stuff before going back to complain that someone sold you a bad tire.  Fifteen minutes to prevent looking like an idiot and pissing off the guy who installs your tires is a good trade off in my book.  But then, I mount and balance my own tires.