[voodoochild]

Hey Guys,

Well, I took a little road trip to see my family down the shore, a trip I make pretty regularly on the bike. (Only 90 miles one way, but I take the long way so it's 2 hours) Here's my point.....I developed a vibration between 62-70mph. The only thing I did before I left was adjust my tire pressure, check oil, add some tools to my seat bag. The vibration seems to be either on or off the gas, I rode the brake to see if it was in the front wheel or anything but couldn't tell. I was on a section of newly paved interstate for a few miles and that's when I noticed it. I checked my wheel weights and they are still there. When I go slow I can hear my front rotor rubbing on and off but when I hit the front brake I have no pulsation or anything like that. Should I check a motor mount? Remember I ride a Dyna and the motor trans and rear fork are all bolted together? There is no wobbling going on in the front end, it fells up and down. Would a front fork do this? Man, I am baffled. I'm working today, but I will get a chance to look at her tomorrow so any advice provided would be a great start for me.

TIA, (thanks in advance)

Chris

[stevenh]

Hey Voodoo,
I'm still somewhat new to the M/C world but there's a highway up here that was just paved a year ago and I get the same thing on my Softail. Come to find out there is a definite problem with the paving job that was done.
Just a thought. I'm sure you'll get some better answers soon.

[voodoochild]

Thanks, I appreciate any advice/suggestions.

[chucktx]

my o'lady says "dont change a thing, she will be right over for a ride!!!!"

actually, steve makes a good point about the roads. some here are like that. try it on a known smooth road, if ya can find one.....ya got a tach on the bike?? if so drop a gear and run at the same rpm and see if ya get the vibration, if so it is in the engine, if not then check the drive train....let us know what ya find!!

[voodoochild]

Damn Chuck, I got no tach! Any way to hook one up temporarily? I didn't think of that when I was riding, I was a little nervous of that vibration turning into a wobble or something and both times on that highway I was surrounded by 18 wheelers. (although I didn't tell the wife that!) I just held on with a death grip and got the hell off that road. Could it be in the motor really?? If it was, what could cause a vibration like that? Thanks for the info.....by the way....what's your wife look like anyway? Does she like short balding men? (no disrespect intended chuck, just F-in with ya)

[Sleepy]

not being sure if you've changed the gearing in your bike or how the the 240 tyre will affect your speedo accuracy but i think @ 70-75 miles per hour should be around 32 RPM in fifth..[bear with me I'm trying to convert from klicks to miles] forth gear should be around 50-55? so find a nice quiet place and play around. 62 miles per hour in top gear is not a happy place for a Dyna..or FL for that matter, especially when you load the motor up. If you get the same vibes in fourth @ 50 as you do in top gear @62, something is out with your power train..rubber mounts or something......if it stays @ 62 mph..in fourth....[around 3600?? or so your vibration isnot motor related. sometimes you can get a crummy tire..just had one..the bike didn't like it one bit....good luck

[CD]

I would first determine the type of vibration.
Rubber mounts almost always have a characteristic harmonic vibration even new. The mounts isolate the harmonic but as they age, the vibration will increase. The harmonics tend to be highest at certain RPM when the mass seems to be just a little out of kilter. Every bagger, FXR I owned and even my custom FXR exhibited the same harmonics. If you want to see the rubbers at work, observe your drive trains motion at idle on the kick stand then have some one hold it up and look again. The stabilizers, engine mount and tranny pivot mounts all wear overtime. Most seem to have the harmonic at about 2200 and again at 4400 etc.

Wheel vibration is actually easy to trouble shoot. Find the speed that gives a consistent vibration and then slowly increase speed until it stops and then slowly decrease speed until it stops. Then, do it again in different gears so that the RPM is different. Do you have spokes? Have they been trued each tire change? If not, get them done. Wheel bearings tend to be a constant vibration / noise at a give wheel speed so engine RPM is not a factor....

The thing that I would try to do is determine the type of vibration. Is it RPM related? Engine RPM only? Does the vibration stay when you pull the clutch in at the speed it vibrates at? Does it only happen in 5th gear or???

[voodoochild]

Thanks guys, I will definitely try some stuff tomorrow morning when I do some checking.

CD, I have custom wheels, 5 spoke from Hogpro in Cali. I was thinking tonight at dinner, on the first leg of my ride, I took an off ramp, changing highways, and hit a bump in the road, hard enough to knock off one of my rear turn signal covers. (there was no way to avoid it.) Do you think that could have dented my rear wheel somehow? I wouldn't think so but I guess you never know. I'll post back tomorrow after I get some checking done.

Thanks again for the tips,

C

[chucktx]

voodoo....cd gave the good answer....i have nothing to add to it.....good luck!

[voodoochild]

Headin out right now to give her a look.......

[voodoochild]

Ok, I made a few test passes. At the speed in question, no real vibration today. I know, WTF right? I did however determine that there is NO vibration at that speed when the clutch is pulled in and the bike is just rolling along. (It is not near as windy today as it was on Friday. Friday was by far the windiest day I have ever ridden in.) I noticed a slight vibration at that speed but not constant, and usually when I was on the throttle, not off. It didn't seem to change when I was in fourth gear at that speed. I dunno. I did what CD said and looked at the motor idling on the stand and then idling off the stand. No change in the amount of movement on or off the stand while idling. How do I go about checking out the motor mounts? It's not like this bike has alot of miles on it, (6500), cripes, I barely got to ride it this year so far. Do I just ride it and say F it?? At least I know it's not a tire vibration or anything....

Thanks again in advance,

C

[chucktx]

you didnt have the vibration before ya went to 240, correct?? it may be that this new swingarm and tire config. is causing your vibration. it may be common with this conversion. tire pressures, tread type on certain type roads may be causing it. use a bar of some type to check the mounts...be careful not to damage any thing else....wood would be good. see if anything move abnormally. because you havent ridden much with the new converson, it may be normal.....

[voodoochild]

No vibration before the 240 chuck. I will check the mounts and stuff this week sometime, I'm loaded with work again so I'll get to it asap.

Thanks,

[voodoochild]

Well, another little update.....I took the same route to the shore over the past week and noticed this time that the vibration came in at about 73-75 mph, and only appears to be when rolling on the throttle. It also happens at the lower speed mentioned before and at higher speeds as well. Again, only when rolling on the throttle. WTF, am I missing something somewhere? Anybody got any ideas? I don't think it was the newly paved road because it only happens when I roll on the throttle. I also seemed to feel it when my leg was touching the horn on the left side, it seemed that the motor was vibrating. (duh, I know it's supposed to but it was noticeably more than normal) Could it be a loose motor adjuster? I haven't checked that yet, and I had adjusted it when I did the 240 kit. Damn, this is annoying that I can't figure it out. Any help?

[chucktx]

i dont remember, do ya have spokes on that rear??? if so, check em....might be a loose one or two in there. i would double check everything i did to do the 240 kit....hope ya find the problem....

[voodoochild]

No spokes Chuck, it's a custom wheel (5 spoke design, like the old style Cregars) I just don't get it. Why only when I roll on the throttle, ya know??

[mwelych]

Motor mount or some sorta mount???

[kenfuzed]

If it only happens when you roll-on I think it would be motor mounts. However there is also the slight possibility that theres something with the rear suspension. When you roll on the throttle the rear naturally compresses. I saw this several years ago on someone's FXR. He replaced the mounts but still had a high speed vibration under acceleration. Later he replaced his shocks and it turned out that one was weaker. Perhaps this caused the rear to twist slightly under acceleration and the rear tire wasn't tracking straight, which might have only been felt under speed.

[voodoochild]

Originally Posted by kenfuzed

If it only happens when you roll-on I think it would be motor mounts. However there is also the slight possibility that theres something with the rear suspension. When you roll on the throttle the rear naturally compresses. I saw this several years ago on someone's FXR. He replaced the mounts but still had a high speed vibration under acceleration. Later he replaced his shocks and it turned out that one was weaker. Perhaps this caused the rear to twist slightly under acceleration and the rear tire wasn't tracking straight, which might have only been felt under speed.

I appreciate the tip Ken. The shocks are still stock, and I didn't do anything to them since they were brand new. I never had this problem when the bike was totally stock, and have only recently noticed this. The reason I adjusted that top motor adjuster was that the motor wasn't perfectly aligned within the frame. I found that out while setting up for my 240 kit. How do you check shocks for equal strength? I've got to check the motor mounts and rule out that possibility first, then I guess I will start messin with the shocks. Hell, I'll rip that whole stinkin bike apart again if I have to, that vibration is pissin me off! Thanks again for the tips guys, and any others are welcomed as well.

[fxdxriderleo]

Hey, In the repair manual for my 03 FXDX under vehichle alignment. It say's that if you adjust the stabilizer link more than 5 turns, the vibration my be unacceptable, if so loosen the , not remove, all the mounting bolts on the egine isolators start engine, run 5 seconds this will center the mounts on the frame and power train assembly. tighten mont bolts to 25 ft-lbs. the book says this will fix the vibration. Hope this helps fxdxriderleo