classic motorcycle forum

Motorcycle Discussions => British Bikes => Topic started by: ramwing7 on August 09, 2022, 08:36:41 PM

Title: Carb leak
Post by: ramwing7 on August 09, 2022, 08:36:41 PM

Trying to put the finishing touches on a 1973 Triumph Bonneville refurbishment.
It's all together, carbs synched as good as I'm gonna get 'em.   Bike runs pretty well.

Problem is on cold start.
But when I push down on ticklers and let up, the gas keeps coming out unless I give each carb a gentle tap. 

Says to me the floats are wanting to stick, but it does seem odd that it's both and consistent.

 I've done a thorough clean on the carbs, replaced the float needles, cleaned jets, etc.

Any ideas, suggestions, etc.

I'm thinking a belt sheath for a small hammer might work.   :P

Title: Re: Carb leak
Post by: L.A.B. on August 10, 2022, 12:00:24 AM

Are they original hollow 'white' (or brownish) plastic floats or the later black and metal StayUp type?

Have you fitted the later 'waterproof' extended ticklers?
https://www.classicbritishspares.com/products/amal-concentric-long-extended-tickler-conversion-kit-622-172-triumph-bsa-norton

If the hollow plastic floats, shake them or hold them up to the light to check fuel hasn't got inside. 
If the StayUp type then check the float needle slot for rough edges and if there are then carefully file or sand them off.
Polishing the float pins if they aren't new could help to stop them from sticking also check the floats aren't catching on the float bowl gasket in the area shown below if so then trim the gaskets but only the minimum amount necessary for them to clear the float.

(https://i.postimg.cc/C5DCRXN2/Screenshot-from-2022-08-09-23-23-45.png) (https://postimages.org/)


 
 

Title: Re: Carb leak
Post by: Oggers on August 10, 2022, 08:19:40 AM

All the above is good advice. I would add

Obviously check float height. It is not necessarily quite as per the book as shut off point is dependent on a number of variables.
Are the ticklers themselves sticking?
Are the needle valves OK - no scoring etc. Viton tipped needle valves tend to perform better.
Needle valve housings can also be damaged. It doesn't take much for gas to pass between housing and valve.
 

Title: Re: Carb leak
Post by: Rex on August 11, 2022, 08:47:03 AM

The ticklers can be set at different heights. Is the OP pushing them down to their fullest extent or just enough to get the required slight overflow?

Title: Re: Carb leak
Post by: ramwing7 on August 11, 2022, 09:08:13 PM

Pushing it down just enough to get the overflow.

Title: Re: Carb leak
Post by: Rex on August 12, 2022, 07:30:27 PM

Then I would say the gasket-trimming would be a good place to start. I've had the same problem with pattern gaskets from Ebay.

Title: Re: Carb leak
Post by: ramwing7 on August 20, 2022, 10:05:43 PM

Yep.  Trimming seemed to do it.  I did put in the extended tickler while I was at it.

Thanks. to all.