The BSA A7-A10 Forum

Technical (Descriptive Topic Titles - Stay on Topic) => A7 1946-1950 => Topic started by: pdg on 11.10. 2017 12:56

Title: AMAL 275 - spacer or no spacer
Post by: pdg on 11.10. 2017 12:56

Hi everyone,

I'm doing some work on the carb side of my 1949 A7 Star Twin. It has two 275 Amals, and came without phenolic spacers/insulators fitted. I'd like some advice about whether or not to fit the spacers, please - advantages/disadvantages, problems/issues.

Many thanks, Peter.

Title: Re: AMAL 275 - spacer or no spacer
Post by: bsa-bill on 11.10. 2017 18:50

Hi Peter
I have no idea why but the spacer is often reputed to improve tractability / slug-ability, I 'd see how it goes , not a big job to fit one later

Title: Re: AMAL 275 - spacer or no spacer
Post by: ellis on 11.10. 2017 19:08

Hi Peter
The phenolic spacer is there to keep some of the engines heat away from the carb. If you search EBay you can find spacers from 1/8" to 1/4" inch thick. I try to use the thickest that may keep more of the heat away. As to performance I can't say I have noticed any difference.

ELLIS

Title: Re: AMAL 275 - spacer or no spacer
Post by: pdg on 12.10. 2017 08:51

Many thanks for everyone's comments. The twin carb manifold has an lip around the port, and a corresponding recess in the carb mounting. The spacers don't come with these recesses, suggesting they're not intended to be used ...? I've machined the recess into the spacers, so I'll give it a go and see what we get.

I've managed to drift out the brass jet body and found the pilot circuit recess, complete with 3 holes!, to be a bit grimy and blocked up, so hopefully the cleaning of that will resolve some of my issues - notably that winding the pilot screw in and out made no difference at all prior to cleaning!

Title: Re: AMAL 275 - spacer or no spacer
Post by: BSA_54A10 on 17.10. 2017 08:55

The spacer is needed if the carb has an O ring in the flange.
Otherwise it is good as it reduce the heat flow but not necessary.