I know there are a million threads about Dyna vibrations, but I have two specific questions about mine... First the back story: I recently did a bunch of stuff in a short timeframe which I know makes troubleshooting challenging sometimes, but that's how my available time panned out... Before working on it, I really didn't have any bad vibration, other than the fact that my engine really doesn't like 1900 - 2100 rpm, and has always vibrated quite a bit right there. No big deal. I did get a touch of weird high speed handling, so I installed a Predator front mount which was a definite improvement. Around the same time, I installed a set of freshly powder coated stock alloy wheels, along with new rotors, pulley, chrome axles, and Avon Cobras. I had the complete wheel assemblies balanced at the dealer before installing them on the bike.

I've put several hundred miles on the bike since, and I have what feels like moderate-to-heavy engine vibration pretty much through the whole usable rev range that wasn't there in the past. It's not too bad to ride, but it really just doesn't feel right. I feel it through the seat and pegs, but not through the bars which are completely smooth. I've checked and rechecked belt tension and rear wheel alignment, and I messed with the Predator mount a bit. With the bike on a lift just enough to stand upright, I loosened the center bolt and two forward bolts on the mount and let the engine idle, blipped the throttle a little, and retightened everything while it was running, thinking that maybe the mount just hadn't really found it's own center properly. Nothing has changed the vibration.

Here are the two thoughts I would like some input on:

1. Since the stabilizer link on the predator limits left and right engine motion, is it possible that certain engine frequencies that were soaked up by the stock mount are now being transferred into the frame? I assume that if the engine wanted to move left and right with the stock mount, it still wants to now, whether it can or not...

2. I had to use a 3/8" spacer on my back wheel to position the new aftermarket pulley properly in relation to the tire. Right now there are no clearance issues anywhere with the belt or tire, but I can see that the belt used to sit a little bit further outboard on the front pulley than it does now. Looking at the front pulley, it's very obvious where the belt sat originally because there is a belt sized band on the pulley that is bright silver, and the rest of the pulley is black. The belt now sits mostly on the silver part, but the inner side of the belt overlaps with the part of the pulley that was unused. Is it possible that 15 years of grime and oxidation has caused the unused part of the front pulley to create a vibration now that the belt is sitting on it partially?

I'm just trying to think of areas that I altered, since I didn't have this vibration beforehand...

Thanks!

 

Possible that the rear wheel is not aligned correctly, and pulling/pushing the engine against the Predator lateral rod... just a thought...

I'm running a Predator as well, with a bunch of front end and rim/hub work... vibrations are less than before..

 

I understand what you're saying... I have realigned the rear wheel a couple of times now without noticeable change, but I've been thinking about this and it may be logical that the addition of the Predator makes the bike more finicky about correct alignment. I'll go over it again, and maybe check the vertical alignment via the top mount as well.

Thanks for your input.

 

F86, any word on the vibes now?

 

I really don't know what's causing the vibrations. It could be a number of things.. You can always try removing the front link on the VT system and see if it helps. I've got a 2000 FXDX with 56,000 miles on it and for me it seems to be getting slowly worse. It has a 116 high compression motor in it and I know that the crank is slowly working itself out of true (second time). I tried a VT and it really didn't make much difference. Decel vibes at about 2000 to 2500 were worse, but it might have been a little bit better above 3000. I've even swapped out the Bassani RR1 to a set of Pro Streets to see if the muffler weight was causing the issue.. Vibes got worse. I broke the bracket to the outside pipe where it mounts to the tranny in less than 100 miles. I've replaced the compensator, other mounts etc. I should pull link up front and see if it helps.. I've been thinking about replacing the primary chain as it looke to have a stretched spot when I replaced the comp. I need to look at the swingarm mounts.. If I don't find anything I plan on pulling the motor and making it a 117. At least that way it will have 1/4 inch less stroke and lighter pistons.. 4.00x4.625 vs 4.125x4.375 and 1200 grams vs 1050 g.. Good luck with your search..

 

bwoltz, these are EXACTLY my symptoms! It doesn't seem like a coincidence that we're both talking about 2000 FXDXs with above stock compression and displacement and have identical experiences after installing a VT Predator.

archergodwin, thanks for asking and checking in!

I actually messed with it a little bit last night, and rode 30 miles into work this morning (haven't headed home yet - goofing off right at this moment). Last night I checked rear wheel alignment again, and decided it wasn't perfect. I have an aftermarket chrome axle, and the brake side doesn't have a locating divit in it, so this time I measured carefully and hit it with a punch to make accuracy a little bit easier. I got it pretty much spot on. I also loosened the rear bracket bolts on my Bassani and let the engine run for a bit and then retightened them. I thought maybe the Predator installation could have marginally tweaked the relationship between the engine and tranny cases enough that exhaust system tension was contributing to the vibration?

Anyway, it did seem a bit better this morning... It still vibrates badly in the 1900-2100 range, especially on decel. I don't spend any real time there, so it isn't the biggest issue. Steady cruising in the 2500-3000 range is still kind of rough, but above 3000 is very smooth now. No issues on the highway at 80 and above.

Interesting thought about disconnecting the Predator stabilizer... I've actually been wondering about the stabilizer recently. I just took it out of the box and installed it as is. I wonder whether there is a way to determine the ideal length for the stabilizer? If it's a little bit long or short, maybe it's under some stress and is transferring excessive engine vibes into the frame?

 

Ok, I’m draggin this up ut of the basement. Did you ever figure this out? Having similar issues, and I’m running out of ideas. Also running a predator. Next step is putting the stock mount back in and going through the alignement procedure step by step I guess. See if that makes a positive change then reinstall the predator and evaluate. I too built a lot of parts on my bike at the same time, so troubleshooting like this is tough.

 

Hi Otter, F86, and Max,
I like the rest of the gang did major mods all at once, only difference in my case is I'm using a full kit Sputhe Positrac, a full heim end upper engine link, and new factory mounts and my pipe weighs in at 10 lbs.
The vibration increased at the same RPM range as everyone else's 2000~2500 going dead calm over 2800. My vibration I would not describe as severe but there is definitely is more, in my case I sort of expected that as a trade off for chassis stability. The engine moves a lot less at idle. I think the links really limit the movement of the rubber. I also believe the factory rubber is tuned for the weight of the stock exhaust system and some of the vibes may be related to the weight loss. Not a lot of help but this is my experience.

: Mike

 

A very interesting thread; I've removed the oil filter relocation and the low mount Jagg oil cooler and I'm ready to install my Predator either today or tomorrow. I'd wondered about what potential trade-offs may happen with improved chassis stability, I'll be certain to post back my results when I'm finally able to ride this spring.

I've done the alignment procedure and my Wide Glide was in correct vehicle/engine alignment but I began to detect increased vibrations on decel late last fall and knew it was time for a new front isolator again and decided to upgrade to the Predator this time...

 

I just replaced my front mount with the Predator Mount, but weather hasn't allowed me to get any good miles in. Hopefully sometime soon I will and provide feed back as well. I don't know if my running footboards as to forwards or mid controls will share the same results felt within the frame, but either way I will share. I up graded my comp sprocket and clutch pack when I did the mount, but am sure these mods won't effect the feel. I want to get some miles in to make sure all is good before I change my wheel setup over so I don't end up with the "which mod cause this" problem.