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Warped fuel bowls. #713276
10/31/17 12:21 am
10/31/17 12:21 am
Joined: Dec 2006
Posts: 3,878
Massachusetts, U.S.A.
B
btour Online content OP
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btour  Online Content OP
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B
Joined: Dec 2006
Posts: 3,878
Massachusetts, U.S.A.
T120R 71

This goes along with the hard to kick start thread.

Stock carbs.

What causes the fuel bowl to warp? Is it over tightening?

How do you fix it? Lap it on glass surface and emory paper? What if has been lapped to the limit already? Does lapping effect the fuel level? In other words is there a limit to lapping?

Short of seeing a leak, is there anyway to determine if the carb is sucking air through the carb fuel bowl gasket interface?

Last edited by btour; 10/31/17 12:22 am.

Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
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Re: Warped fuel bowls. [Re: btour] #713285
10/31/17 12:41 am
10/31/17 12:41 am
Joined: Nov 2012
Posts: 291
Isle of Wight, UK
K
koan58 Online content
BritBike Forum member
koan58  Online Content
BritBike Forum member
K
Joined: Nov 2012
Posts: 291
Isle of Wight, UK
Yes, overtightening, akin to the flange warpage situation, and I reckon a fix along the lines of JohnH's flange straightening would be better than the cheap rub with emery, which only makes the tangs weaker.
This often happens when the bits of the gasket start to break up around the screw holes, the reduced support then makes it easy to warp the cheese metal.
Once that has happened, apart from the obvious petrol leak from the gasket, the pilot fuel take up from the bowl will not work properly.
Can't think of an easy way to actually witness the air leak fault, just rectify surfaces and new gasket to be sure it is as it should be.

Re: Warped fuel bowls. [Re: btour] #713286
10/31/17 12:48 am
10/31/17 12:48 am
Joined: Nov 2008
Posts: 2,712
Bishop, Calif.
D
desco Online content
BritBike Forum member
desco  Online Content
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D
Joined: Nov 2008
Posts: 2,712
Bishop, Calif.
Stick two gaskets on it and adjust the float as/if needed.


1968 T120R
1972 T120RV
Any advice given is without a warranty expressed or implied.
Re: Warped fuel bowls. [Re: btour] #713290
10/31/17 1:23 am
10/31/17 1:23 am
Joined: Nov 2012
Posts: 291
Isle of Wight, UK
K
koan58 Online content
BritBike Forum member
koan58  Online Content
BritBike Forum member
K
Joined: Nov 2012
Posts: 291
Isle of Wight, UK
Love the elegant simplicity, shall retire for the night on that satisfying thought

Re: Warped fuel bowls. [Re: btour] #713297
10/31/17 2:28 am
10/31/17 2:28 am
Joined: Aug 2001
Posts: 4,125
Santa Barbara, California
KC in S.B. Online content

BritBike Forum member
KC in S.B.  Online Content

BritBike Forum member
Joined: Aug 2001
Posts: 4,125
Santa Barbara, California
Some of us,....... Me included here, have had good luck with a flange fix....... Slamming the thing down hard on a flat surface! Not kidding. At least you'll feel better if it still leaks.


Down to 1 BSA, 2 Triumphs, 2 '56 Chevys
Re: Warped fuel bowls. [Re: btour] #713311
10/31/17 6:40 am
10/31/17 6:40 am
Joined: Aug 2001
Posts: 7,026
scotland
triton thrasher Online content
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triton thrasher  Online Content
BritBike Forum member
Joined: Aug 2001
Posts: 7,026
scotland
Flimsy design is the culprit.


Amateur Loctite enthusiast.
Re: Warped fuel bowls. [Re: btour] #713331
10/31/17 11:56 am
10/31/17 11:56 am
Joined: Aug 2001
Posts: 1,513
Jordan, NY
Al Eckstadt Online content
BritBike Forum member
Al Eckstadt  Online Content
BritBike Forum member
Joined: Aug 2001
Posts: 1,513
Jordan, NY
I have used this method to straighten the tangs. I use a metal ring I found that has an ID that will clear the float bowl but will press only on the tangs. I hold the ring in position on the bowl and use a small vise to press the tangs back. (Place a wood block on the bowl drain to protect it from being marked by the vise jaw).
To reduce the stress on the tangs always use a new float bowl gasket.
Al

Last edited by Al Eckstadt; 10/31/17 11:58 am.

Al Eckstadt
Re: Warped fuel bowls. [Re: btour] #713337
10/31/17 12:40 pm
10/31/17 12:40 pm
Joined: Sep 2008
Posts: 593
Skudeneshavn Norway
S
Stein Roger Online content
BritBike Forum member
Stein Roger  Online Content
BritBike Forum member
S
Joined: Sep 2008
Posts: 593
Skudeneshavn Norway
When you learn how to treat them, they are good instruments. Use an air filter. Do not tighten anything very hard. Change the needle jet after 10-20K miles. Always use quality cables. Learn how to clean the idle jet. Learn how to check the float level and don't aim for the often quoted.080" below the edge, it's too low. Don't use the brass float needle, I've changed all mine back to nylon. Use good or new gaskets. Learn how to drain the bowls, they can collect water in a downpour or when washing the bike.
Most important: Keep the bike serviced and adjusted at all times, it'll make it easier to determine whether "it's the electrics or the carbs"...


Moderated by  John Healy 


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