V-Twin Forum banner

Front end knock?

17K views 11 replies 11 participants last post by  SaigonBill  
#1 ·
I need some help, I'm out of things to consider.

Quick summary...85 FXRS...Had the stock 35mm front end, worked ok, but blew a seal on the FDR in Manhattan so I decided to upgrade to a 39mm front end. Got the one off my buddy's 92 FXR when he upgraded to a 1200s so I got the entire set up.

In the process, I decided to get 2" over tubes to get a little more clearance in the front so I bought some from BK Rider, they had the EZ fill caps, came with progressive rate springs, spacers, dampers, basically came pre-assembled to drop right in. Sounds easy. It was easy. Went together no issues. Preload is set to about 20-25mm and thought I should be good. Trees were set up properly, neck bearing looked fine so I used the existing set and felt smooth tightened down to spec. Assembled the rest of the front end, all snug and in place.

This is where I cant figure out the rest and wtf is happening. I double check all is secured once its off the lift and on the ground. Take it for a ride around the block and the sidewalk has a chunk missing before you get to the street so I always go over that and instantly there is a thud or a knock coming from the front end somewhere. Ride is around more, keep hearing it. It sounds like its making a noise on the rebound. Its only on larger square edge bumps. Over small stuff, it feels normal and pretty standard and makes no noise, no movement in the front end, besides the compression and rebound. I roll it forward and get at the brakes to see if there is play in the bearings. Nothing. Check the tank (have had a knock before from this being loose), its tight and no movement. I wonder somehow if I didnt snug the damper rod bolt but thought that I'd see fluid if this was somehow loose. I decided to take the front end apart to make sure everything was assembled correctly. From top down is was as follows..Cap>Spacer>Main Spring>Damper Rod>Top out Spring. checks out fine. I call BK rider and they suggest adding a little bit more oil to each fork as it sounds like it might be on rebound. Try that, seems to be less but still there and now its suuuuper stiff.

I wanted to do a suspension upgrade and thought this was a good time to do it, maybe it was the **** I bought in the forks that was causing this somehow. Bought race tech springs and emulators, installed those today as per their guidance on settings. Went in perfect. Did the same thing, checked all the fasteners and took it around the block. Went down the same piece of sidewalk to test it out before I got on the street. THE ****ING KNOCK IS BACK. Sounds about the same as before. I am so confused and stumped because it has a completely new internal set up from a proven suspension company (which, besides the knock feels ****ing fantastic), everything is tight and feels great at a static position. Its just over the same roads that it does virtually the same thing. So I wonder if its the forks or something else?

Anyone have any thoughts? I am stumped. Many thanks in advance and pardon any grumpy tone in this.
 
#4 ·
suggestion; it seems that you can get it to "clunk" right there in your driveway.
get someone positioned there. As you hit that hole to make the clunk, see if they can isolate the noise from the front end. Possibly, if you have someone you trust to ride the bike past you could be the one listening. You will of course, have a better knowledge of what you are listening for and trying to locate. Good luck
 
#6 ·
If it is topping out it might be easier to check the sag. The forks should sink 25% to 30% of their travel from fully extended, or no load, to where they sit with you on and the bike. If the sag is less you may want to reduce your preload. I personally don't think it would top out in your driveway.

The steering stem being loose is common culprit, but you've checked this. I read about a guy in another forum who's brake pads were making the clunking sound. He discovered it by hitting a bump that always creates the clunk, but hit it with his front brakes lightly depressed and no clunk. I've heard other people discovering their gas tank being loose.
 
#7 ·
I'm betting on calipers/pads. Hit that same bump with the brakes slightly dragging and see it it stops.
 
#8 ·
change the neck bearings and races, do, all 4 pieces.. I've seen quite a few make a similar noise. neck bearings get worn in flat spots. You used the bearings from the new to you front end with your old cups. A recipe for a noise.
Or a very good suggestion on the pads and calipers, many people get the parts together wrong it causes noises as well.
 
#10 · (Edited)
Well I got to the bottom of it I think. The old 35mm set up had a chrome hub cover on the right side as it was a single disc set up. I re-used the cover on this 39mm and I noticed the axle didnt fit through it the same way but the design of the axle was different as well. The step up on the end of the 39mm axle that goes through the entire right side bottom slider pushed up against the chrome cover which sat up against the wheel and seemed to set the wheel in the forks perfectly with the speedo/spacer so I proceeded. Everything seemed good, didn't feel weird so I never thought it would be the culprit.
Here's the cover as described..
Image


Turns out that cover wasn't allowing the wheel to sit properly and even though the wheel looked center, brake caliper and all, it was sitting on the axle a tad loose. Took the cover off (granted this is maybe 18 ga. steel so not super thick but prevented from sitting properly), the spacing was now off but the wheel sat tight in between the forks with just very neglidgible play and had a few others give me their opinion and thought it all looked fine, just needed to be spaced over about 3/32" or so. Happened to have a thick washer on hand that matched, spaced it out spot on, same tight feel from side to side. Put it all back together again, rode it around the block. Nailed it. Still a very small tiny clunk, but now I can clearly tell that the loud hard clunk was in the wheel, which probably amplified in the brake caliper. The small tiny sound is has got to be the neck bearing, even though they are tight and feel smooth, something has to be be up with those too but this diagnoses them and I fixed the major issue today.

I am going to heed the advice about those and replace the races and bearings. Makes total sense about mismatched old/older stuff and no reason not to. 30 year old bike needs a little extra lovin sometimes.

Thanks a ton for the guidance. Brakes on over bumps got me pointed in the right direction and was able to troubleshoot from there.

P.S. - Race tech emulators and springs......worth it. Now I just need better brakes, rear shocks and this is like a whole new bike.