QuestionQUESTION: Mr. Samel,
I have a 1985 V65 Magna. When I tach between 4000 and 5500 RPM I get a rather significant vibration throughout the bike. I have gone through all of the usual suspects (i.e. new tires and balancing, etc.), but nothing has helped. The best way to describe the vibration is like riding at 55 MPH on blacktop on knobby tires. I know it's in the engine. When I pull in the clutch, the vibration completely stops. Speed doesn't matter. . . 20 MPH or 65 MPH. When the tach is at 4000 the vibration is there.
Thanks for your generous insight Wayne. Any input will help!
ANSWER: Marc,
sounds like the engine is causing
the vibration. Have you tried loosening
the motor mounts, revving up the engine
a bit and retightening them?
-Some vibration may be normal around that
speed, sometimes it helps to have the carbs
synchronized. It may be something that only
an engine teardown can find, like a loose
bearing or wear on camshaft system or engine
parts. Have you tried different oil weights
to see if it changes the vibe?
Look online for magna/sabre forums,
sometimes they have some info.
---------- FOLLOW-UP ----------
QUESTION: First of all, thanks a ton for this good advice. I loosened the motor mounts, revved the engine up a bit, and then took the bike for a test ride. Unfortunately, no change. So I re-loosened the mounts and took the bike for a slow and easy cruise. I tightened them back up and went on test ride number two. Again, the vibration was still there.
Like you, I thought that the problem could be due to a worn bearing or camshaft (or some other damaged internal part). Since I couldn't figure out the vibration problem, my initial plan was simply to ride the bike until the vibration got bad enought to easily pinpoint (i.e. the bearing would get seized or badly torn up enough to easily detect during a teardown). However, that was over 3000 miles ago and the vibration is still exactly the same.
Also, I manually synchronized the carbs while the engine was on the bench (i.e. spent time to really eyeball them close). I can't imagine that they could be out of synch enough to create such a problem. . . do you? In addition, I have tried different oil weights in the past (not necessarily to fix the vibration problem though) and the vibration was the same.
I have recently posted my question on several Magna forums. I have my fingers crossed. Any additional suggestions that you could provide would be greatly appreciated. At this point, I'll try anything to fix this vibration problem. Thanks again for your help Wayne.
AnswerMarc,
it seems few people with Magnas have experienced the levels
of vibration you have. Some mention a characteristic
V-engine vibe but nothing really bad.
Vibrations while driving are usually caused
by bad wheels, tires, steering head or wheel bearing
problems. Other causes could be bent frames or
driveline trouble.
-Your vibrations seem to indicate an imbalance in the engine which is
usually caused by an engine where the cylinders
are fighting due to a tuning issue.
It can be a difference in compression,
or one cylinder running lean or rich,
or a timing advance issue.
Also as I mentioned the carb sync being out.
Last but not least is an internal imbalance
caused by faulty engine parts or incorrectly
installed parts or badly timed cams.
A bad engine bearing could run a long time but
cause a crankshaft shake.
Have you checked compression and read the plug
colors to determine the fuel mixture?
At this point you may have to double check
things to narrow it down. As you say
it may be difficult if nothing changes with
added miles. If I have any lightbulbs go on
I will let you know.
