expansion chambers

was just wandering if anybody local makes decent expansion chambers as both me and my dad need some making up? preferably in the lincs area thanks!! also any info on bantam pipes would be much appreciated

Try Nikkon Exhausts. I think they would make one-off exhausts if you contact them. Other than that I can't think of anyone else. Or try modern scooter exhausts.

Tim

thanks for that. what type do you racers use on your bantams then?

I am thinking of using probably Nikkon, old Japs or scooter exhausts. I'm in the middle of building my Bantam. Just need the forks and carbs to complete. Then off for some bodywork from Jimmy.

Hi we make are own exhausts
but you could go to gibsonexhausts.co.uk

Hey Robbie,

Any suggestions on formulae, lengths for a 175/185 pipe ?
My dyno experiments indicate science does not always produce the practical results. I have used Bett's old Sprint pipe - 200mm on cast iron barrelled long stroke, 174 degree exhaust; but nothing over 8500 rpm. Someone did hint at your pipe dimensions, will try on an alloy BTW barrel with ? TM porting.

cheers

John

John, if you pm me some variables i can come up with pipe dimensions, but you'd have to find someone to cut it

Hi All,

Wishing you all an excellent 2010 and a safe and fun racing season. During my time bantam racing and making my own exhausts I always has issues laying out the cones and cylinders. With some help from my wife we came up with an excel tool to help with the drawing of the cone in the flat form. I have used it several times over the years and if you layout the cones and cylinders accurately it all lines up.

Here is a picture of the excel sheet:-



Whilst I cannot attach the excel sheet to this post I would be happy to email it out to anyone who wants a copy. Just send me a PM with your email address.

Of course the magic is in the design but I hope this helps with the fabrication.

Dear Zac,

Tried pm, but the site reckons you don't exist !

Thanks for your offer of help. I am away from home at the moment; keeping the missus happy at the beach. So next week I can work 20 hours a day in the garage getting two bikes ready for our big Pukekohe festival. All my data is at home, guessing the short stroke 56 * 54 looking for peak power at 10,500 = exhaust timing 191 degrees, port 35mm at piston face to 37 x 35 at exhaust flange to exhaust stub 38mm at 106mm from piston face. The best dyno experiment was a 1980 RS125 Honda pipe that was 530mm to middle section, 100mm diameter middle 75 long, with 250mm diffuser and 270 * 25mm tail pipe; Lt 770mm. My 1980 BRC pipe has wide torque, good lap times on short circuits, but only has peak power at 8,500. Also using a modified 1990 RS pipe peaky power at 10,000; Lm ~ 400 on long fast GP circuits . I can't quite remember 175 long stroke data, E = 174, looking for power at 9 or 9.5K. Currently using a shortened version of the old Betts BRC Sprinter pipe.
No problems cutting, two local firms have CNC water and laser cutters.
Cheers

John 8 {)}

Being as there is already a thread on exhausts. As I have mentioned before, I am building a road racer bantam. I will be using standard stroke with a TS185 piston to give 185cc and at the moment standard porting. Does anyone have an old pipe that, whilst not good for racing would be suitable for road use? I don't want the engine revving too high, and a reasonably wide powerband. Thought it worth asking here before I make my own, I could save myself some trouble and give someone else more shed space!
Cheers
Phill

Hi John, i'll work it out this afternoon