I have a 2 part question. Any input on either would be appreciated. I'm back on a bike I haven't rode in over 20 years. No riding between then and now so I don't know if what I'm experiencing is typical. 87 FLST. Engine is stroked but I don't know any of the specifics off hand.

Vibration:
Bike runs great. No odd sounds, hesitation, or inconsistencies. I get a substantial increase in vibration at a specific RPM. It's RPM specific and not related to speed. Occurs It's kind of hard to describe but it's like the level of vibration doubles in intensity and frequency. It goes from a consistent rumbling to a very intense buzzing. I don't have a tac and don't know the specific RPM this occurs at. It's does it just above the point I would typically shift if I'm just cruising. It does it when I get on it or hold a lower gear on a long incline. I tend to stay out of this range for the most part but do hit it just about every time I ride.

Fender:
This might need to go in the paint section but since I'm already here.. The rear fender had a long tear when I got it. Previous owner claimed vibration was the cause. I assumed it was more likely a late night curb hopping but it appears he could be correct. I got a new fender and paint. New fender probably has less than 150 miles on it and is starting to tear again. This time on the other side. I had the body shop fill holes and recesses to match the existing fender. This was done with some sort of filler. Would welding the holes be a better route?

 

I have a "barn find" 87 FXRC. Last season while riding, I noticed, what I thought were excessive vibrations through the chassis. When the bike idled, it looked like the engine wasn't moving around. This winter, I've replaced the front motor mount with an OEM Harley one. Feels smoother now. The original one wasn't cracked but it was dry. Might look at that.

Greg

 

Setting for 20 years, Id check the engine mounts, the rubber does give up after awhile

 

Bike hasn't been sitting for 20 years I just haven't rode it for 20. **** 25 now that I think about it.. It was my dads bike. I rode it when I was younger. He sold it to a friend at one point years ago and I now I have it.

The engine is rigid mount to the frame. No rubber mounts.

 

Vibration issue could be the comp sprocket. Springs go south in it.

 

FLST from the EVO era have the motor solid mounted and as it is a EVO there is no balance axel to assist as in the Twin Cam B

They do shake a fair bit, and yours beeing a stroker could alter things.

I assume You have checked ignition timing and that the carb is running correct.
Easy to check and rule out as a contribution to the vibrations.

Soon some more EVO guys will chip in with their vast knowledge.

 

Yes the bike is a solid mount engine.. Could be when the motor was stroked it was never balanced (different heavier pistons).. But to answer your question yes the vibration if severe enough will do that to the rear fender.. Hell, one of the wheels could've shifted.. What crank is in it? if you open the timing inspection plug on the left side case you might be able to see some type of serial number of the wheels.. Post up a pic if You can... I think you should take it to a reputable Indy and have them take a look at it...

 

They all vibrate, but if yours is vibrating to the point that its breaking the tins, that's a whole other ballgame.

 

Thank you for all the input!

I watched a couple of videos. This is something I could tackle. I really should open up the primary for inspection and fluid change anyway.

It has a Dyna digital ignition. I'm not to familiar with it and not sure about adjustments. I need to look into this. I believe carbs are dialed in. The bike runs better than it did when I had my first go at it way back when. Idle, acceleration, and downshifting are all better than I remember.

It was stroked in the late 80's or early 90's. I can't confirm but I believe everything was done correctly. My dad put a lot of miles on it after that. I did one 2,000 mile and two 1,000 mile trips on it. I will open the inspection plug and see if I can get any numbers.

​​​​I'll inspect the compensator sprocket and if that doesn't appear to be the issue I'll probably have to bight the bullet and take it to someone.

Thanks again!!

 

The only time I get vibration issues like that is in the 5000 to 6500 rpm range.. I actually have a video on a dyno of my bike where you can see the fender dancing around.. You ain't going to get away from it on a solid mount motor especially if it's built.. it's the nature of the beast.. balancing everything is critical on a solid mount motor if you're looking to go into the 90 to 100 horsepower range on an EVO... Take it from me, I have a lot of experience in that..