Homemade T20 expansion chambers

[truckphone]

Hey good morning to the two stroke world! I'm in the process of building a T20 tribute racer and I dont want to spend the $$$ on proper chambers and then have the project go cold. I have a tig welder, metal rollers, and lots of time to plan out the path these pipes will take under my bike. Stock engine, carbs and timing for now so I'm thinking a long skinny pipe. The patient started out as 1966 T20 with lots of rust and dents but seemingly low miles. I'm going to add a full vintage fairing, seat and loong fuel tank, clip ons, rear sets and drum brakes.
My question is can anyone give me the dimensions of a nice mellow chamber for this little 250? I've watched the calculations to design these and it makes my head spin, mathematical stuff isnt my bag. Thanks in advance, when I figure out how to add pics I will show my progress.

[Craig380]

Hi and welcome.

I have a copy of Suzuki USA's tuning bulletin for the T20, which has extensive notes and a schematic of build-yourself chambers. It does warn you sternly that with all the tuning changes, "the engine will not be usable below 4,000rpm"

You should be able to view / copy them from here:

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[daxman]

Interesting stuff the chamber dims aren't a million miles off the one (so far) I made.. 4" 100mm belly etc.. Interesting to not the suggestion
of 22 gauge sheet which I think is only about .75mm. It explains why I found it so hard to hand roll the 18 gauge (1.2mm) I was using
could be tricky to weld with my hobby mig and rudimentary skills though..

I added a stinger and some paint recently and I've just had a tatty T20 exhaust delivered I plan to hack up for the header..

[dollydog]

header pipes? the way i've always been told [going back a long time, so should be good for vintage stuff] to make header pipes was this: do you want it for racing or a good spread of power across the rev range. header pipes will be different lengths.
measure the i.d of your header pipe. let's say it's 40mm just for ease. multiply that by 7 or 8 times for racing, or multiply it by 11 times for easy road riding, which i'll do. so, 40 x 11 = 440mm. this is how long the header pipe needs to be - MEASURED FROM THE FRONT FACE OF THE PISTON - to the first cone in the spanny. so, measure from the front face of the piston to the exhaust flange. let's say it's 50mm. factor that into the total length of the header pipe and we get 440mm - 50mm = 390mm. so your header pipe needs to be 390mm long from the exhaust flange to your first cone on the spanny. hope this helps? with modern spannys etc it's probably totally different, but this is old school
cheers, dd.

[titan performance]

Lets see some pictures...
Rolling 1.2 even from mild will be tough. We use 0.9 in mild or s/s and that will roll ok.
Good luck with your project.

[daxman]

Lets see some pictures...
Rolling 1.2 even from mild will be tough. We use 0.9 in mild or s/s and that will roll ok.
Good luck with your project.

Hopefully something to show soon.. Sadly it will only be one side done. Not looking forward to side 2 although I have some ideas that might speed up the process

[tz375]

Looking forwards to seeing what they look like.

Those race kit pipes are bit "top endy" as I recall, but they could always have the belly stretched to drop peak torque revs.

[daxman]

Ok here's my first effort.. The stinger is quite wide and it's loud for sure, (very 'poppy') but not as loud as i expected.. But then again the other side is still a standard exhaust (obvs not going out on the road like this..!)

[titan performance]

That doesn't look like a bad effort at all....though to me it has a hint of, upside down about it....or is that just me?

[daxman]

That doesn't look like a bad effort at all....though to me it has a hint of, upside down about it....or is that just me?

Thanks - it owes a great debt to the mighty angle grinder and flap disc. I think/hope its a trick of the light it should be symmetrical on the centre axis!

[r5baker_]

Did you ever get a chance to test these?

[Alan H]

Hey good morning to the two stroke world! I'm in the process of building a T20 tribute racer and I dont want to spend the $$$ on proper chambers and then have the project go cold. I have a tig welder, metal rollers, and lots of time to plan out the path these pipes will take under my bike. Stock engine, carbs and timing for now so I'm thinking a long skinny pipe. The patient started out as 1966 T20 with lots of rust and dents but seemingly low miles. I'm going to add a full vintage fairing, seat and loong fuel tank, clip ons, rear sets and drum brakes.
My question is can anyone give me the dimensions of a nice mellow chamber for this little 250? I've watched the calculations to design these and it makes my head spin, mathematical stuff isnt my bag. Thanks in advance, when I figure out how to add pics I will show my progress.

One post on June 16th, last visit on June 17th.
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Why ask then never return to see how folks try to help?

[daxman]

The second one of mine is almost built cones are welded and I have sourced a LHS header which are like hen's teeth. I've also had to get a LHS cylinder rebored and that is at the machine shop now (long story).

I wouldn't attempt to hand build these again those getting everything 'round' enough to match up for welding has been a proper PITA without the right formers. What has taken me days could probably have been done by a fab shop in hours. however finding a shiop to take on a small job is tricky unless they have an interest in the subject.

[daxman]

Did you ever get a chance to test these?

Next sunny day I hope they are both fitted now at least - just nee to remove the centre stand!

[r5baker_]

Thanks for keeping with it and looking forward to the results.