The BSA A7-A10 Forum

Technical (Descriptive Topic Titles - Stay on Topic) => A7 1946-1950 => Topic started by: Stephen Foster on 24.05. 2014 18:07

Title: Seeking flame traps for "Star Twin" (longstroke) ?
Post by: Stephen Foster on 24.05. 2014 18:07
Desperately looking for a pair of the above to fit 275 pre-Monobloc carbs .
They are the gauze type which would have been fitted to the short bellmouths .

Alternatively any pictures , etc please for Me to make My Own ?

Thanks in advance
Title: Re: Seeking flame traps for "Star Twin" (longstroke) ?
Post by: muskrat on 24.05. 2014 21:42
G'day Steve. Could you make them out of these on ebay  http://www.ebay.com.au/itm/6-038-AMAL-TYPE-6-76-276-CARBURETTOR-AIR-INTAKE-TUBE-BELLMOUTH-/400389830735?pt=UK_Motorcycle_Parts_13&hash=item5d3917f84f
Cheers
Title: Re: Seeking flame traps for "Star Twin" (longstroke) ?
Post by: trevinoz on 24.05. 2014 23:37
http://amalcarb.co.uk/pre-monobloc/75-275-series/air-intakes/274-275-gauze-intake-assembly.html

Have a look at these, Steve.
Not cheap but could save an expensive bike from destruction.
The ones on my carbys came with them, don't know whether they are original or not.

Trev.
Title: Re: Seeking flame traps for "Star Twin" (longstroke) ?
Post by: wilko on 25.05. 2014 00:35
The last time a mate fitted one of those mesh bellmouths it ran like shit. He took it off and it was fine.
Title: Re: Seeking flame traps for "Star Twin" (longstroke) ?
Post by: muskrat on 25.05. 2014 03:36
I would imagine the gauze would richen the mixture a tiny bit but not enough to be noticeable. I wonder why it was so wilko?
Cheers
Title: Re: Seeking flame traps for "Star Twin" (longstroke) ?
Post by: Stephen Foster on 25.05. 2014 08:43
I have been told twice that this model were known to catch fire in certain circumstances & B.S.A quietly retrofitted the gauzes .
I believe the ones on Trevs bike are the original ?

I contacted Burlems & they have none left so I am scratching My head ?
I have the original bellmouths although the gauzes are long gone , still searching .
Thanks for the responses & I hope highlighting this point helps Someone else ?

I cant think of a way to make a swaged piece to fit around the outside edge of the bellmouth which would hold the gauze ?
I am open to any suggestion or offer ?

Steve ..
Title: Re: Seeking flame traps for "Star Twin" (longstroke) ?
Post by: Stephen Foster on 25.05. 2014 08:45
"Wilco" , If Your friend still has the bellmouths with traps I would buy them from Him & take the chance on setting My "Star Twin" up accordingly ?
Title: Re: Seeking flame traps for "Star Twin" (longstroke) ?
Post by: Triton Thrasher on 25.05. 2014 10:52
Quote from: trevinoz on 24.05. 2014 23:37
http://amalcarb.co.uk/pre-monobloc/75-275-series/air-intakes/274-275-gauze-intake-assembly.html

Have a look at these, Steve.
Not cheap but could save an expensive bike from destruction.
The ones on my carbys came with them, don't know whether they are original or not.

Trev.

It's noticeable that this is substantially larger than the intake area,  so at least Amal in 1940 gave some consideration to the restrictive effect of gauze over the intake.
(https://www.a7a10.net/forum/proxy.php?request=http%3A%2F%2Fi257.photobucket.com%2Falbums%2Fhh236%2Ftritonthrasher%2Fimagejpg1_zpsf4fafb0d.jpg&hash=4e6768d51799842f0eafa99ba9c6d1cf71c9f273) (http://s257.photobucket.com/user/tritonthrasher/media/imagejpg1_zpsf4fafb0d.jpg.html)

The small bellmouths with gauze, that you see on "cafe racers" must be seriously restrictive.
Title: Re: Seeking flame traps for "Star Twin" (longstroke) ?
Post by: roadrocket.chris on 25.05. 2014 18:09
tried it on my twin carb rocket it went like crap i figured that if the gause was crushed to a solid it would make quite a restriction in the  venturi.
Title: Re: Seeking flame traps for "Star Twin" (longstroke) ?
Post by: Stephen Foster on 25.05. 2014 20:03
Appreciate Your answer Chris .
I wouldnt bother with them except for the warnings I have been given regarding them catching fire .

Has Anyone else heard of this problem with the "Star Twin" please ?