The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: flatdeck on 30.06. 2008 21:38

Title: Fitting Exhaust Pipes
Post by: flatdeck on 30.06. 2008 21:38
I was at a little gathering last night and bumped into someone who is well known locally for building and restoring bikes and mentioned to him that the A7 appeared hotter on one side than the other based on the temp readings from the tops of the pipes. Amongst other suggestions he mentioned that if the pipes fitted differently into the head, specifically the length of the pipe inside the head, there would be an effect on the temp of the pipe outside in that the pipe inside tends to return heat back into the head reducing the heat that is released by the pipe outside. Questions ... A. Did my explanation make sense? B. If this is true how much difference would it make and is it measurable? My acquaintance suggested you should have as little pipe as possible inside the head. I said that I didn't have a clue and that mine was dictated by the attachment of the pipe to the frame ...
Title: Re: Fitting Exhaust Pipes
Post by: groily on 30.06. 2008 22:39
I'm sure everything is measurable in this most measurable of all possible worlds! But as long as the basic colour of the pipes up near the head is about right - ie not too blue nor glowing cherry-red in the dark - I'm happy. Efforts to reduce the amount of pipe up the head will almost certainly result in air leaks and backfiring; I like the most I can get up the ports - and the same both sides if possible - a solid mount around the level of the lower engine mounting, a good clip round the silencer/pipe joint at the  gearbox area and the usual solid mount towards the rear for silencers. That way it all stays on. Largely dictated by the frame, as you say Dave. Any variations in temperature or colour are more likely to be due to induction bias with single carb, differences between twin carbs or imperfections in the ignition department. Especially the last. So, if I was trying to figure out a hard thing like varying exhaust pipe temperatures around the head, I'd start with the mag - bearings, cam ring, points gap etc; I'd move to the carb; and I'd only very reluctantly start thinking about the pipes themselves unless I knew I had an air leak at the head joint (which would mess things up a lot and probably start costing exhaust valves in short order).
Title: Re: Fitting Exhaust Pipes
Post by: RichardL on 06.09. 2008 17:01
I think this topic will work for my question.

I bought Asian (Indian?) -made dual exhaust pipes for my '55 swingarm and it seems that the left pipe is not bent properly, as it drops below the frame by about 1/2", while the right side does not. This results in the ends of the silencers being at different heights as viewed from the rear of the bike. Also, I think it would prevent me from using stock mufflers, as the tab would be too far from the pillion-peg mounting hole. These pipes were sold as being for pre-58 swingarm. Does anyone know the difference between pre-58 and 58-62 swingarm pipes? There is a 58-62 left-side pipe on ebay that I will buy if it will solve the problem.


Title: Re: Fitting Exhaust Pipes
Post by: RichardL on 07.09. 2008 19:34
Does anyone know the difference between pre-58 and 58-62 swingarm pipes?

Just restating this question before it falls off the map. I could use some help with this.

Title: Re: Fitting Exhaust Pipes
Post by: Beezageezauk on 07.09. 2008 20:15
Hi Richard,  The pre '58 exhaust pipes are much shorter than the later ones and don't have the kink at the end of the left hand side one.  This is because the pre '58 silencers (more parallel) are much longer than the '58 (bulbous) on type.  Hope this helps. ;)
Title: Re: Fitting Exhaust Pipes
Post by: trevinoz on 07.09. 2008 23:58
Also the mufflers kick up on the pre '58 bikes instead of parallel to the ground.
Title: Re: Fitting Exhaust Pipes
Post by: RichardL on 08.09. 2008 09:59
Trev and Beez,

Thank you very much. One favor, possibly. Do you think you could tell me if I have pre or post 58 pipes, based on the photos at   ???

I am in London, UK, right now, and not Naperville, IL, USA. Otherwise, I would put up some pics that were more pipe specific.

Title: Re: Fitting Exhaust Pipes
Post by: Beezageezauk on 08.09. 2008 20:38
Hi again Richard. 

It's difficult to determine the length of the pipes by the pictures but they appear to be the later pipes to me.  Can you remember if your left hand pipe has a kink in it about 4 inches from the end?  If it has, you have the later pipes.

Enjoy your visit of London.