Tank Drumming

Chris Launders

Chris Launders

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VOC Member
Hi everybody
The tank on my twin I got a couple of years ago starts "drumming" above 3000 rpm and gets really loud.I cannot see anything substantial touching the UFM or motor to cause this,above 4000 it is a real knock and I really hate it. Does anyone else get this or is it just me and what can I do about it, I seem to remember the Rapide I had 40 years ago had some sort of felt pad between the tank and UFM. Would something small,say a cable adjuster trapped between them cause this ??
Chris Launders
 
J

Jim Richardson

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My Rap did something similar, I had the tank off for some reason and noticed a mark on the crashbar, the tank was clear when stationary but touched as it vibrated. the cause was perished front tank rubbers, I also lifted the back of the tank slightly and silence ( or as near as it ever gets) returned.

JimR
 
P

Peter Holmes

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chrislaun said:
Hi everybody
The tank on my twin I got a couple of years ago starts "drumming" above 3000 rpm and gets really loud.I cannot see anything substantial touching the UFM or motor to cause this,above 4000 it is a real knock and I really hate it. Does anyone else get this or is it just me and what can I do about it, I seem to remember the Rapide I had 40 years ago had some sort of felt pad between the tank and UFM. Would something small,say a cable adjuster trapped between them cause this ??
Chris Launders
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If you using the standard chain oiler, check that your rear chain is not a little loose and clipping the chain oiler pipe, the sound seems to get amplified.
 
ossie

ossie

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is the rear tie on the tank resting on the valve cover due to the rubbers under the rear tank fixing being to thin.
OSSIE
 
Chris Launders

Chris Launders

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Had a quick look, the tank is close to the crash bars but there is no mark in the paint. The tie bar is in place as are the rear tank rubbers but it looks as though the tie bar may be hitting the rear valve spring cap when it vibrates, as it is the corner of the hexagon it would catch I will try to turn it a bit, if not I will try packing up the tank a little.
Chris.
 
Chris Launders

Chris Launders

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Just took off tank tie bolt spacer, this definately hitting rear spring cap, made up new slimmer spacer and refitted, now plenty of clearance. Will take it out tomorrow if I have time.
Chris.
 
vibrac

vibrac

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Tank bolt spacer & tie rod
I always use a piece of alloy bar (round or hex) just wide enough to take a 1/4 BSF tapped hole both ends then add a short 1/4 BSF hex set screw & washer each end lighter and narrower especially if you have jacked the rear up one rubber FT172/1
 
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