My Magna's a vibratin'

Len Averyt · April 10, 2011, 06:47:43 PM

My magna has a very irritating engine vibration going on.
You can feel it at idle and its fairly bad at 4500-5000 Rpm, Cruising speed.
Still has plenty of power to push me around.
When I get off the bike I still feel like I'm vibrating.
Its not as bad as when I ride my wife's Vtwin but close!
When I first got the bike it had 12K on it and i could sometimes not tell if it was idling or running.
Now at 43K its quite obvious.
The engine is still factory other than new plugs and normal radiator fluid and oil changes.
Valve adjustment?
Just want to get it fixed.

roboto65 · April 10, 2011, 06:56:48 PM

How old is the front tire and how is it balanced..

Chad in Michigan · April 10, 2011, 07:22:47 PM

do you have footpegs where the motor mounts screw into? my bike had them in those holes and used a different bolt and was loosened up and shook a little bit. check all engine mounting points, front tire, rear tire alignment too.

hootmon · April 10, 2011, 09:51:44 PM

When you say idle, I assume you are sitting still.. Otherwise I'd say:
check your chain for tight spots..
Carb Balancing

TLRam1 · April 10, 2011, 11:20:29 PM

Good suggestions above, I will through this one in there also. Do you hear any noise coming from the motor, could this be a chain tensioner? Never had one go out so I am unable to tell you if it adds to vibration. Check all motor mount bolts, rear wheel axle nut in case the nut came loose and for proper alignment. If only at speed look for chucks missing from your tires.

I did have my swing arm axle snap clean.

roboto65 · April 11, 2011, 08:47:12 AM

Trust me if your tensioner goes out YOU WILL KNOW

I thought someone had thrown some ballbearings in the engine

well under the carbs anyway!

dgc67 · April 11, 2011, 09:43:40 AM

QuoteTrust me if your tensioner goes out YOU WILL KNOW I thought someone had thrown some ballbearings in the engine well under the carbs anyway!

No doubt. Sounds like the motor is about to come apart until you get the rpm's up and it holds tight due to that. There is a vibrating feel at idle and low rpm, but it does smooth out. On mine I want to say over 2000 all was fine. I put like 10k miles on it like that too.

Len Averyt · April 11, 2011, 01:09:18 PM

Quote from: roboto65 on April 10, 2011, 06:56:48 PM
How old is the front tire and how is it balanced..

Less than 1K. but the vibration is at idle and at higher rev's sitting very much still.

Len Averyt · April 11, 2011, 01:31:34 PM

The engine has always had a little bit of a knock sound since Ive owned it.
Its the same sound I hear from others magnas so I'm not as concerned with that. I figure that is the timing chain tensioner.
This vibration is very different.
Its kind of what it feels like when only firing on 3 of the 4 cylinders all the time through the whole rpm range.
But i know thats not the case cause my fuel economy is dead on what it was at 12K

Its defiantly engine (RPM) speed not (MPH) speed.
It vibrates the same in first going 20 as it does going 70 in fifth.

Chad in Michigan · April 11, 2011, 02:07:57 PM

how recently did you install those plugs? i had one that i dropped and hit the electrode and i didn't regap it and it would misfire now and then. not sure.. hmm..

ToolBoxPop · April 11, 2011, 07:20:44 PM

Chad may be on to something. I had a pretty annoying vibe on my 86 magna that I just built up. I found out it was the bolt I used to mount my home-made forward controls on the right side. I installed a standard size bolt when it should have been a metric. The difference was so incredibly small that I would have bet money on it not making a difference but it really did. I replaced it with the right size and it took the vibe away. Maybe your motor mount bolt worked itself a little flat on one side and loosened up or something. Or possibly just a bad motor mount?

Len Averyt · April 11, 2011, 11:26:59 PM

Quote from: Chad in Michigan on April 11, 2011, 02:07:57 PM
how recently did you install those plugs? i had one that i dropped and hit the electrode and i didn't regap it and it would misfire now and then. not sure.. hmm..

a year, 2 tops

Greg Cothern · April 23, 2011, 10:50:13 AM

Wonder if you have a weak coil? Identify if you can, which cylinder is missing then swap the coils and see if the problem follows...

reaperkeeper · April 25, 2011, 07:03:22 PM

Len.
Your type of problem is not to hard to figure out with a little work. Lots of things could be the culprit, let talk about how to figure out what IS the culprit.
Back to basics:
1. Check all of your main electrical connections (grounds and positive on the battery and chassis grounds especially!)
2.. Pull all of the spark plugs out and check for spark at each one, its usually best to have a helper so you don't shock your self

look to see if the one you think is the problem is different from the others, if it is replace all the plugs, heck you have them out and its been over a year, replace them all anyway.
3.. Check the compression of each cylinder.
4.. If you don't find an issue with the above look for your problem to be a carb. It does not take much to mess everything up and I would look at the diaphragms first and the jets second based on your description of the problem. Do your carbs have a bowl drain like the 1st gens? if so then drain them, catch what you drain and see if there is water or junk in it.

Well thats my .002 worth and what I would do if it were my bike.
keep us posted! and good luck!

My Magna's a vibratin'

dgc67

ToolBoxPop

reaperkeeper