Engine vibration in an 82 Seca 750

I have developed a vibration in my Seca 750.....first it seemed like it was coming from the faring, so I removed it......then it seemed like it was coming from the exhaust....and so on. I have went through the bike and torqued every fastner on it, and it is still there. It is rpm related when on the road, as when I let off the power and clutch it it goes away. It is not nearly as pronounced when revving in neutral in the driveway, almost not there......but on the road it is an uncomfortable tingle in the bike and loud. It starts at about 3000 and is there to the red line. I do not remember this before I woke her up this year.

After doing some searching I have seen refrence to the little rubber wedges in the fins........can anyone tell me how many there are supposed to be on a Seca 750, and where exactly they are supposed to go? I did a count and I have 7 on the right side in various places, and 2 on the left side in various places......I am leaning towards this being the source

 

Is your exhaust stock or after market? After sitting for long duration if bike was in an unheated garage the mufflers can rust internally and look fine out side. Rust particles can break off somewhat plugging up and can also cause vibration . I had a Virago dropped exhaust while doing a clean up of the bike ....could not believe the rust and dirt I dumped out of pipes ...sounded better after wards. I would have thought it would have blown out muffler but I guess not. Hey it was just a thought...noises and vibrations can be frustrating to pin point. Cheers

 

Exhaust is stock......I am really thinking it is coming from the engine. How many of the wedges do you have in yours Jetfixer??? The 2 on the left side really has me leaning towards that as according the the diagram it looks like there should be 14 total???

Wondering if I lost some when I had to hop a ditch and end up in a cornfield after I was pulled out in front of on a blind corner.....but I kept it on two wheels till I was almost stopped

 

Cylinder Head Fin Insulators:

yy5) OEM Yamaha rubber CYLINDER FIN RUBBER INSULATORS. These are the small, rubber, wedge-shaped noise absorbers that fit between adjacent levels of the cylinder head cooling fins at various places on the heads. Usually hardened or missing from original motors. Replacing these insulators with new ones really helps to quiet down an engine, and especially eliminates the fin "ringing" which can sound very much like valvetrain noise, while giving your engine that authentic, original appearance.

The HCP1840A insulators are the larger of the two types (taller/wider) and are typically used when there is a relatively larger spacing between adjacent cylinder fins (such as in the area in-between the spark plugs, on the top of the head, and on the “upper” set of fins on the sides of the head). The HCP1840B insulators are smaller (shorter/narrower), and are usually found on the lower fin sets on the sides of the head.

We’ve never seen these insulators installed within the cylinder jugs fins, but, they would also fit in there. However, most fin “ringing” occurs from the cylinder head, not from the jugs.


HCP1840A OEM cylinder head rubber LARGER FIN INSULATOR, for the right side of engine. Differs between models, but normally use 8-10 per engine on the right side. Fits all 1982-83 XS400, XJ550, 1984-85 FJ600, 1986-88 FZ600, 1986-90 YX600 Radian, XJ650, XJ700, XJ750, 1977-79 XS750, 1980-81 XS850, and all XJ900 models. Each:
$

HCP1840B OEM cylinder head rubber SMALLER FIN INSULATOR, for the left side of engine. Differs between models, but normally use 15 per engine on the left side. Fits all 1982-83 XS400, XJ550, 1984-85 FJ600, 1986-88 FZ600, 1986-90 YX600 Radian, XJ650, XJ700, XJ750, and XJ900 models. Each:

 

Is this a vibration that you feel, or just one that you hear?
If you feel it, then I would suggest that it's time for a running carburetor synch.

Given the nature of your near miss, I'd also suggest checking the tightness of the engine mounting bolts (back them off, and re-torque to spec).

The loss of fin dampeners only results in a high-pitched singing of the fins; not a felt vibration.

 

Ahh now I see Kmoe is spot on check all your engine mounts for tightness and cracks the rear mount might be harder to view but if you cracked a mount this would cause a vibration.

 

I am not 100% sure I would call it a vibration.....it sounds strange, but it is almost a "tingle".......I will re check everything again. Thanks!

 

Tingles are good

 

I do not remember this after my stuntman impersonation, and I probably put 1000 miles on it after that. I will go back over the mounting bolts again, and give it a good sync tonight....ordered the wedges from Len, so will see if that fixes the issue.

 

Also check the chrome exhaust collector covers. A cacked mounting tab can cause a tingle.

 

I wonder if this is the same noise I keep complaining about when my engine is thoroughly warmed up and pulls above 3500 rpm... same thing, gone when roll off throttle, returns when load on engine.

I keep thinking I've got it down to a small exhaust leak I can't find but never quite get rid of it. For the first 10-15 minutes of riding it's not there... then it burns a whole in my head because I can't stop listening to it. Almost sounds like faint rod knock...

 

In cylinder detonation - pinking in the uk? Then again it could be big end knock, the oil thins out and it dissappears?

 

Can you hear it at idle? From the right side of the valve cover? Ignore it. Normal.

 

Nothing at idle... Sorry didn't mean to hijack the post