Hi All,

I'm hoping to gain some insight on suspension/ride/powertrain issues I'm experiencing on a softail I recently picked up. After riding a '92 882 Sporty for a few years, I bought a '99 FXSTC that was somewhat of an incomplete mystery build which I intended to finish. The previous owner supposedly bought the bike off a mechanic friend who passed away shortly after building it. Unfortunately, the guy I bought the bike from wasn't much help in the way of identifying what exactly went into the "build". Listed below is what I have identified as "non stock" on the bike, in case it helps troubleshoot the issues I am having:

- Aftermarket 2000 Ultra Softail Frame
- BDL dry clutch (with 1.5" kevlar belt)
- Ultima adjustable Softail shocks
- 18" rear wheel (running 180 width tire which had some rub damage on the chain side from improper axle spacers/adjustments)
- Previous owner claimed the motor was "built" out. Without opening the motor, I can only confirm that there is a Screamin Eagle timing cover.

Now onto the issue I'm hoping for some help with. While riding the bike home (the day I bought her) I broke down on the side of the freeway (stripped out the clutch hub basket). Once home, I started pulling her apart and ordering parts. New BDL clutch hub basket, new primary belt, new shocks and new rear tire were all ordered and installed. About a week later (while still waiting delivery of shop manual and a few additional parts), I took her out on a series of test rides. Having never ridden a softail (or anything with a big twin, for that matter), I wasn't quite sure what to expect. The bike had substantially more power than my Sporty, but it seemed there was a strange push-pull going on while accelerating down the road. I had a few buddies go out with me to provide an extra few sets of eyes. What seemed to be happening I can only describe as follows: As the motor accelerates, power is transferred through the bike to the rear sprocket and wheel. As I'm accelerating down the road, it feels like the shocks are traveling in-and-out so much that power is not being evenly distributed to the rear axle (I would imagine the suspension is compressing as the motor torques, then decompressing for a moment before compressing again, over and over...). When I am not accelerating, she rides fairly smooth (no push-pull if I'm not on the throttle). If I shift into a higher gear and keep low on the RPMs, I don't notice the push-pull much. As the motor revs into the powerband, the push-pull becomes more extreme until I'm cruising in 5th at 50-90MPH.

I have adjusted the preload on the suspension twice now per KumaRide's post here: https://www.hdforums.com/forum/softa...djustment.html. I have now set my suspension to 238-293 lbs, which has lessened the push-pull somewhat. The problem is, I only weigh 140lbs. After looking over the shop manual, I also noticed that my shocks are installed backwards (I replaced the original shocks with new ones prior to having the shop manual, so I installed exactly as I had removed them (backwards, meaning the end with the adjustable threads/adjustable canister face the rear of the bike). Its hard for me to imagine that the shocks facing the wrong direction would cause such a drastic issue with the ride/transfer of power, but I'll gladly consider any opinions on this. Moreso, I suspect that my motor torques too hard on the rear sprocket/wheel for the suspension I have. I don't mind tightening up the preload more, but I just can't wrap my head around how my mere 140lb body needs to set my suspension to handle more than double my body weight.

Am I going crazy here? Any thoughts/advice/suggestions are greatly appreciated. Many thanks in advance, Cheers!

 

Well, the shocks are the only thing that moves, unless its the swingarm bushings. Or belt slippage but you said you have a chain. How about gears slipping?

 

Thanks for the response Ranger73. At this point I'm willing to look over any option in trying to diagnose this issue. The swingarm bushings appeared to be in good shape when I inspected them (had the bike up on the lift and back down several times while installing the new shocks/adjusting the ride height). Here is a bit more info that might help:

The BDL clutch I have uses a 1.5" kevlar primary belt, and a chain for final drive. After adjusting the preload last week, I wanted to see if there was a difference in the push-pull by adding some rider weight. I had my gal jump on back with me and we took a 10 minute ride. With a combined passenger weight of approximately 270lbs, the push-pull felt less severe than when I was riding solo. About 10 minutes into the ride, I hammered the throttle after shifting into 2nd and ripped through the kevlar primary belt. I had already ordered a replacement after noticing a bit of freying on the original belt, so I wasn't too heartbroken. All the same, I'm not sure if this was just an old belt giving way...or if this is a sign of the motor being a beast capable of tearing through kevlar belts (a feat I had previously thought quite difficult to do)?

I suppose it is possible that the tranny gears might be slipping. Unfortunately, I'm not too experienced in troubleshooting transmissions and wouldn't know where to start looking (or what I'm looking for).

Gorgeous ride btw...Cheers!

 

The shocks on the 99 do face the rear with the adjustment to the rear. I do not think it makes much difference though. What kind of motor mount do you have? Is it rubber mounted or solid like the 99? It could also be that the motor is to lean and cycling off and on. Mine kind of did that before I put in bigger jets after some mods.

 

Thanks for the response Jim Kraft. Good to know on the shocks. I have found some strange inconsistencies among the manual and postings online regarding the 1999 FXSTC. Some claim the motor is a 1340CC, others claim that motor was replaced with the 1450CC in 1999 (I had thought the transition took place in 2000). Learning something new every day...

As for the motor mount...it is solid (no rubber). While I was convinced the issue had to be suspension/drive train related, your cycling theory jogged something else from my memory. The bike came with a long-piped spikey air box that had a K&N hi-flow style filter in it. I couldn't live with myself so long as that air box was on the bike, so I replaced it with a less flashy air box that had a basic paper element (had planed to put a K&N hi-flow style filter in it). Acknowledging that I probably have put a damper on the air intake from what the motor was used to, I'm assuming my bike is running rich to some degree.

My question is this: Could a slight air constraint to the motor cause the it to cycle/surge in mid-high torque ranges, which in turn creates a "choking" effect on the output to the rear axle?

Thanks again for your insight guys. The only thing worse than feeling stupid, is feeling stupid and not being able to ride. Cheers!

 

I would think that if it was chocked for air it is or it isn't. I wouldn't expect a fluctuating effect. How about a sticking intake valve collapsed lifter bent rod or spring?

 

If you are stripping the belts I would look to make sure the transmission is set up right. it is loose or out of alignment???

 

A buddy of mine experienced something similar, and I remembered it when you talked about your worn out belt. His belt was actually missing several teeth on the inside and his bike would surge every time the sprocket would contact the patch of missing teeth because the pulley would basically spin inside the belt because it had no teeth to grab hold of. Once he got to freeway speeds it would stop because the belt was moving so fast it would just skip right past the blank spot so fast it didn't have time to "slip" on them. Install the new belt and then test ride it to see if the bike still does it...


Mike

 

So you replaced the clutch hub. What kind of transmission output shaft do you have(tapered our splined)? What did the transmission mainshaft look like as far as wear? If keyed what did the the key hole look like and was the shaft and key hole in good shape? If splined what did the bearing race on the mainshaft look like and did you replace the bearing race or bearing in the inner primary? Did you adjust your clutch properly as clutch slipping could result and feel like surging? Check the alinement of your pulleys between the engine and clutch hub and make sure they're spot on. Use a piece of glass layed over the top of the pulleys to make sure they're on the same plane and a straitedge for left and right. Intake air leaks, restrictive air cleaner, plugged fuel filter, loose electrics can all play in the surging thing once your mechanicals are figured out. Last summer my brothers bike had a little surging thing going but finally manifested itself as a shot bearing on the inner primary. Let us know what it was by a loud squealing. Unless you've got some weird geometry going on with the Ultima frame that's working against the suspension I would say you're shocks are crap. It's why the FXR's are so quick is the geometry of the driveline is so spot on(and then they discontinued it) good luck

 

Thanks for the replies everyone. I think after yesterday I am one step closer to figuring out this issue. I put the bike up on a lift and disassembled the rear axle for cleaning/inspection. I had just tightened up my suspension another turn (preload now set to appx 300lbs), and was at the point of adjusting the rear axle spacers when I noticed something out of the norm...With the bike in neutral and the rear wheel off the ground, I rotated the tire and noticed the slack in the chain was altering from healthy taught to overly tight. If I spun the wheel by hand with some force, the wheel would always stop spinning with the chain super tight. However, if after the wheel stops spinning I rotate the tire forward or backwards about a quarter turn, the chain loosens up to a proper amount of slack. After adjusting the rear axle to a comfortable level of slack around an entire rotation of the wheel, I set it down and rode for a bit. The push-pull is still there, though minimized slightly by the tightened suspension (just as the last time I tightened up the suspension).

My theory: I believe the chain's behavior is indicative of either A) an warped/oblong shaped rear wheel sprocket, or B) the rear sprocket is somehow mounted off-center, causing an oblong rotation (and hence the chain going from tight to loose based off rotating the rear wheel. Though I have not yet located it in the transmission diagram, there is obviously a sprocket in the transmission (final drive sprocket?) that rotates the chain through the rear wheel sprocket. I would have to assume theory A & B above could also apply to the transmission sprocket (warped/oblong shape, off-center mount, perhaps a slightly bent driveshaft?).

I studied the rear wheel sprocket, making sure it appeared in good shape, all bolts evenly tightened, rotating and watching from side profile...with the naked eye it appears to travel in a perfectly circular motion. I can't visually see the transmission sprocket without further disasembly. My question to everyone out there in the interwebs: has anyone had an experience like this? If so, how do I go about troubleshooting the culprit further?

Many thanks as always in advance, the people in this forum have been very helpful and I appreciate it. Cheers!