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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: harper on July 15, 2014, 03:53:09 PM

Title: Buzz at 2500 rpm
Post by: harper on July 15, 2014, 03:53:09 PM

I've had this buzz at about 2500rpm for about four years. Tired of chasing the damn thing. It also has a slight buzz when the throttle is shut off while the bike is in neutral and sitting. I'm looking for suggestions. The bike is a 1989 K100RS/35K. The buzz/vibration is coming from the engine and not the suspension. I've bumped the timing ahead and back, no difference. I'm offering a turkey for Xmas to the genius who can help me with this problem.
K100rs-r90s-r75/5-r60/6-r69s-r90/6--a couple Ducs and a dirt bike.

Title: Re: Buzz at 2500 rpm
Post by: johnny on July 15, 2014, 05:00:52 PM

greetings harper...

no corn ethyl... half 20oz bottle techron @ next 4 consecutive fill ups... throttle body sync... 

j o

Title: Re: Buzz at 2500 rpm
Post by: Scott_ on July 15, 2014, 08:30:28 PM

Check for other vacuum leaks, especially around the throttle body rubber "bushings" and hoses on the backside of the tb assy.

Might also check the valve clearances, and sparkplugs as well if it hasn't been done in a while.

Title: Re: Buzz at 2500 rpm
Post by: harper on July 17, 2014, 02:13:13 PM

Thanks for the comments. I went to the Honda Shop and borrowed their gauges to verify that my throttle body was in synch; it was at idle, at 1500, at 2500, and beyond. Needles never varied. The only thing I can come up with that would cause the buzz is the timing trying to advance at that particular rpm range. Much like the ole airheads between 2.5 and 3.0 K. I don't have that device that blinks when the timing mark has arrived at .009 btdc. I'll keep playing until I find the gremlin.............