Twin Carb envy!

[bikerboy]

Oh and the carbs are 930 concentrics. On my plunger model I have one of the A7 heads with the detachable manifold. I have had this machined out to 70mm and had the valve seats recut to take Super Rocket valves . I also use 930's on that

[muskrat]

G'day bikerboy.
Looks good. Do you have a pic of the head before it went on?
Would love to see your plunger version, I tried a 1102 on my A7 plunger but air flow was too restricted.
Cheers

[Triton Thrasher]

I remember reading somewhere that when Triumph converted the T110 to twin carbs to make the Bonny, BSA tested twin carbs on the A10 and found that it made no detectable difference upto about 99% of full speed and added only a few MPH at the top. My view is that when twin carbs were fitted to the A65's it was more of a fashion thing to sell higher numbers in America. Most of the power gained on the hotter models was from better breathing, higher compression and more sporty camshafts.

Call me old fashioned, but I think a well set up single carb is better than twin carbs unless you are going racing.

Speaking as someone who put twin carbs onto a T110 cast iron head, the difference is gratifying.

[bikerboy]

muskrat

No I dont have a pic of the head off I get so carried away when I am rebuilding anything I always forget and then wish I had taken pics at various stages 

All I basically done was measure the distance from the middle of the combustion chamber to the centre of the carb. Cut the manifold off and milled the surfaces flat. Helicoiled 4 holes in the head and worked out that the T140 manifolds gave me just about the right distance again from the centre of the combustion chamber to the centre of the carbs which saved me machining manifolds.

The plunger is also undergoing a total rebuild and this time I will try to remember to take pics. Its pretty basic tho I made a manfold for it out of steel and had it chromed years ago because at the time I had no alloy welding capabilities. On that one the manifold actually splays the carbs because they are so tight to the frame. It also had high level pipes with no baffling whatsoever and went like the proverbial sh** off a shovel. The foolishness of youth  .

And just to upset the purists this is a pic of another little project of mine that made its debut on the road about 35 years ago. It was totally rebult just over a year ago tho. A10 frame, triumph trident swinging arm, 750 bonnie engine and front end. Lester mag alloys from about 1976. I have also had a with a Triumph Trident 3 cylinder lump in. Damn that flew but again being young at the time I soon blew that to bits racing with the big japanese bikes 

[JulianM]

Cool,

The A10 engine looks great with the 930s tucked in close together!  Very neat!

Julian

[bikerboy]

Thank you Julien

[roadrocket.chris]

http://www.flickr.com/photos/68531324@N03/

Here's a couple of pictures of the twin carb head on m rocket. They are monobloc 389s and they are completely trouble free.

[Billybream]

Found you a complete bike with twin carb,s on Ebay
My dream was just twin clock,s, and now nearing completion just awaiting new rev counter from Ashley Pople
http://www.ebay.co.uk/itm/BSA-GOLD-STAR-REPLICA-Twin-carb-MOTORBIKE-/140953121486?pt=UK_Motorcycles&hash=item20d175f2c,e

[bikerboy]

There is a guy at Kempton Auto Jumble that has a head very similar to RoadRocket.Chris's and he wants about £100 for it. He has been trying to seel it for over a year to the best of my knowledge. It is a 70mm A10 head and the manifold have been welded and splayed out. Not the best welding job I have ever seen but nothing that could not be tidied up and made to look pretty decent. In fact I might grab it myself if it is still there next time.

[JulianM]

Found you a complete bike with twin carb,s on Ebay
My dream was just twin clock,s, and now nearing completion just awaiting new rev counter from Ashley Pople
http://www.ebay.co.uk/itm/BSA-GOLD-STAR-REPLICA-Twin-carb-MOTORBIKE-/140953121486?pt=UK_Motorcycles&hash=item20d175f2c,e

Very nice looking bike!

Rev counter?  3:1?   I need one of them too,  how much and where is best?  (without a bank loan)

Julian

[Rocket Racer]

I must confess I put twin racing 10TT9's on because I thought they simply looked fabulous! 
They also seem to work well enough on Methanol... I have had people tell me I'd be better off with a concentric and wouldnt have all those damn fuel bias issues sidecars can suffer with  but I'm not changing them.
Mine isn't a converted single carb head though but was originally an A7SS one.

For tacho's you can convert a speedo which I did price out then found a real one thankfully before I'd done a conversion