Expansion chamber swapout

[gus58]

Can I cut and shunt an expansion chamber off one bike onto another ie yamaha onto Bultaco if its the same cc capacity motor? or is it a lot more complicated maybe coming down to things like  port opening and closing etc?

[pokey]

Sure you can do it but how the bike will perform is a different matter.

pipes are 'tuned" to a specific peak RPM that matched the particular engine, You also have cones of a specific length for a specific style of power and width of band , Over all length is also part off the equation.
 
im fairly sure if you want to stuff around enough you could put a chev conrod in a victa but why would you want to?

[oldfart]

a Victa with a Chevy rod ..... this I would have to see 

[Momus]

Can I cut and shunt an expansion chamber off one bike onto another ie yamaha onto Bultaco if its the same cc capacity motor? or is it a lot more complicated maybe coming down to things like  port opening and closing etc?

The French say "ahh we know it works in practise, but does it work in theory?"

It can be complicated if you let it; don't let it just do it and find out.

Plenty of people have done realistic chamber swaps and had very good results.

[GMC]

Pretty much what Pokey said, there's a lot of science goes into chamber design and often when you need to cut & shut to make something fit you will lose some of the length which will effect the original intentions.

You can always make something fit so it comes down to what you want to achieve.

What model Yamaha onto what model Bultaco?

[matcho mick]

my pre 75 dirt track ossa (phantom t/end on super pioneer b/end) runs a 92 FMF KDX 250 pipe,works for me  ,

[gus58]

No real idea yet, but think the IT or yz models might go close to fitting frame lines....

[jimg1au]

what about
yz490 pipe complete with muffler on a 1978 bultaco 250

[gus58]

what about
yz490 pipe complete with muffler on a 1978 bultaco 250

Have you done this?

[GMC]

what about
yz490 pipe complete with muffler on a 1978 bultaco 250

That would be all wrong in my opinion.
Big bore chambers are designed for a broader power spread which wouldn't work that well on a 250.
Also stinger & header diameters would be wrong.

Best to try and swap pipes of a similar capacity.

Also I think a pipe from a modern could possibly be a bit peaky on an older bike as moderns may rely on the power valve for a broader power spread.
Might work alright in dirt track but not so well for a trail bike

[Momus]

My ancient experience was with swaps like a CT175 Bassani onto a TS185 and a pipe made for a 500 triple Kwaka onto a MT125.

[vandy010]

It can be complicated if you let it; don't let it just do it and find out.

Agreed
Just do it if you have the skills and what you'll learn will make the next one even better

[80-85 husky]

I made a ts rm hybrid years ago with a hotted up ts 125 in a rm 125s frame. the rm pipe was too loud and too pipey with absolutely no low end but the ts pipe killed the top end I was expecting but was suitable for the road.

I put the rm motor in the ts frame and the ts pipe gave some amazing low end power from an rm but shut the tap just as it started to hit the band.

the rm in the ts frame with rm pipe was scarey!!