Hello fellas, hoping you could help me out. I have a 1998 FXD with Andrews EV-46, K&N filter, Screamin Eagle pipes, rejetted carb. My bike has developed a severe vibration only at 1800-1900 rpms in all gears. I checked front and rear motor mounts (not the upper one), primary chain, drive belt, etc. I discovered yesterday that even when the bike is in neutral and parked when I rev to 1800 the vibration is present, so it seemed to be an engine/ carb issue although the exhaust could be a part of the equation (I don't know). Also, I think my bike has started running lean. The engine coughs sometimes and the exhaust note cruising in 5th is almost non-existent.

I know you check air/fuel ratio with a wide-band O2 sensor with computerized vehicles but how can I determine for sure that I'm running lean and dial in a/f on my Evo. I haven't pulled the plugs yet.

I've read tons of posts about newly developed vibration problems but there doesn't seem to a definitive solution. Motor mounts seem to be the most common answer but I think my motor mounts are fine.

I went on a long ride yesterday and decided that I can't continue riding until this vibration is solved, it sucks. Also how do I determine if I'm running too lean. The carb was rejetted years ago when the cam, pipes, and K&N were installed and the bike always ran perfectly with no vibration problem. All of a sudden I have this vibration problem and a seemingly lean condition develop out of nowhere.

Any ideas, thoughts, or information would be greatly appreciated. I'm pretty much a lost soul if I can't ride. Thanks so much.

 

Check that upper motor mount.

 

Ok Doc, I think I need to lift the tank to check it, but I really doubt that's my problem, plus my a/f situation seems messed up. Thankyou.

 

Did you ever replace the rear rubber isolator ? It's a pain in the ars but I had several dynas in the late 90's that had similar vibration and it turned out to be the rear isolator Good luck

 

No, I just did a visual inspection of the rear mount and it looks perfect. Bike only has 10k miles. In fact the motor mounts look brand new FWIW. I'm not ruling out motor mounts but I really doubt that's the problem. I checked the bolts and they're tight so I'm not sure what else to check exactly. Is the "rear isolator" the same as the rear motor mount? Thanks for your reply.

 

1800 RPM's is below the transition of your carb(it transitions at about 2,500) so you might want to check for a vacuum leak. Also a compression and leakdown test to ensure the vibration isn't being caused by a "light" cylinder. It may als be a harmonic vibration that is being picked up by something that may have moved slightly and is touching the engine, transmission, or exhaust. What if anything was done before the vibration started. Check to ensure that a wheeel weight hasn't come off. Don't forget to check your primary chain for proper adjustment. Hope this helps, be sure to keep us posted.

 

Thankyou kindly for your response. This is very helpful.

What was done before the vibration started was new front and rear tires installed at the dealership, but the bike rode perfectly for about a month after that. Also, the vibration is present when I throttle to 1800 rpms when the bike is parked and in neutral. One other observation is that the vibration goes away when I release the clutch while riding.

Also what was done was prior to the vibrations was that I noticed I was getting some oil blowby that I discovered to be coming from air filter area, in fact I removed the filter, cleaned it and wiped off a lot of excess oil inside the filter cover which solved oil spraying on the battery box and pushrod covers. I had to reinstall the vent tube after removing the plate behind the filter and I'm not sure if installed it exactly right. I remember feeling uneasy about it after I finished.

The only other thing I did prior to the vibration beginning was I installed a chrome gas tank console. I had to disconnect what I think was a vent hose from the left inside side of the frame area. Reinstalling the new chrome console I had to make sure I didn't pinch the hose under the fuel gauge. In fact there's a slot in the fuel gauge bracket to allow for the hose go through. I thought I got that all right.

Thanks again for your help. I'm hoping this additional information will help narrow down the problem.

 

That rear isolator is actually off the rear of the trany The swingarm is attached to the rear of the trany and this rear isolator rubber keeps the engine vibrations along with the front isolator from eating up the driver/ passenger That rear isolator also bolts to the frame

 

Ok, thankyou, I'll look for it.

 

Fellas, I pulled the spark plugs and the front cylinder plug looks the normal tan color but the rear plug is black and sooty looking. It seems the rear cylinder is running rich. Any idea what the cause and solution is? Thanks.