My bike makes a loud rattling noise when above 3500 RPM

[andrewclaycomb]

You shift at 3500 RPM?

Whhaaaattttttttttttttttt?

I just got this thing running really well, and I'm afraid of braking something new.

I've also never gone WOT with it.

I have no idea where the sound is coming from. Tomorrow I'm going to ride around and try to figure it out. The other thing is it may only be happening under load. Not in neutral.

[andrewclaycomb]

Alright I located the buzz. It's coming from the the locking cover that goes over the fuel cap. When I press down on it the buzzing stops. Any ideas on a way to stop it? Temporarily I'm thinking about putting a small hand towel/ shop rag underneath it.

This is starting to get really exciting because after a year and half of replacing parts on this thing, I'm starting to run out of problems with it.

[earlfor]

Stick a small piece of foam backed insulation to the underside of the gas cap cover. Had the same thing on my old 79 750. :-)

Earl

Alright I located the buzz. It's coming from the the locking cover that goes over the fuel cap. When I press down on it the buzzing stops. Any ideas on a way to stop it? Temporarily I'm thinking about putting a small hand towel/ shop rag underneath it.

This is starting to get really exciting because after a year and half of replacing parts on this thing, I'm starting to run out of problems with it.

[andrewclaycomb]

Stick a small piece of foam backed insulation to the underside of the gas cap cover. Had the same thing on my old 79 750. :-)

Earl

That's a great idea, thanks.

[tkent02]

+1 on the piece of foam, then go out and open up the throttle and run it up to red line a few times, preventive maintenance.

[earlfor]

All bikes will, to some degree or another, "piston rattle" if you have too low an rpm, too heavy a load and try to add throttle in too high a gear. If you try to (for example) go up a hill at 20 mph with it wide open in 5th gear, its gonna rattle. That is a BAD thing to do. It puts excessive loads on internal engine parts. Try selecting a gear that will always keep the rpm above 3500 or so as a starting point if you want to accelerate. If you're cruising down the road, putting along in 5th at 2500 rpm and you want to go to full throttle, downshift to 3rd or possibly 2nd, then twist the throttle. These engines need some rpm. They aint V twin cruisers that top out a 4k rpm. They are just starting to run and breathe at 4k rpm.

Earl

My bike makes a loud rattling noise when above 3500 RPM. What do you think it is? It's done this for as long as I've owned it. It's clearly audible above my Vance & Hines 4-1.

EDIT: It's actually more of a buzzing sound.

[andrewclaycomb]

Stick a small piece of foam backed insulation to the underside of the gas cap cover. Had the same thing on my old 79 750. :-)

Earl

Was this the type of stuff you used?

[earlfor]

NO, I used the soft, black or grey plain foam stuff you get for weatherstripping on screen doors etc. Its an adhesive backed, peel and stick on.

E.

Was this the type of stuff you used?