Thinking of ordering shift kit and exp. chamber, pros and cons?

rudyauction509 · Feb 11, 2015

I'm thinking about getting a small dirtbike expansion chamber and welding it to the sbp header. Any thoughts? I have access to the tools and a local motorcycle wrecking yard has hundreds to choose from for about $20 each. Anything in particular I should look for, besides the correct shape and size to fit the bike? For example, if the new chamber's header is 2x the size of the sbp header pipe would that cause problems?

Also I'm picking up a dremel tomorrow and am going to open up the transfer ports and smooth out the intake and exhaust. Anything else I should do? I remember a while back looking at a different engine the transfer ports had these ridges in them just below the opening, should I remove them if theyre there on my engine?

mapbike · Feb 11, 2015

rudyauction509 said:
I'm thinking about getting a small dirtbike expansion chamber and welding it to the sbp header. Any thoughts? I have access to the tools and a local motorcycle wrecking yard has hundreds to choose from for about $20 each. Anything in particular I should look for, besides the correct shape and size to fit the bike? For example, if the new chamber's header is 2x the size of the sbp header pipe would that cause problems?

Also I'm picking up a dremel tomorrow and am going to open up the transfer ports and smooth out the intake and exhaust. Anything else I should do? I remember a while back looking at a different engine the transfer ports had these ridges in them just below the opening, should I remove them if theyre there on my engine?

there may be several that have a shape that will allow them to be plumbed up without a lot of fuss, but the one I bought recently that has an excellent shape is pipe off of a KX65.

If you can find one of those you should be able to get it hooked up without much trouble based on what I have seen.

It slips my mind who it is but another member here has the KX65 pipe on his bike and it looks really good and only required a flange fab to get it hooked up.

frank66 · Feb 11, 2015

rudyauction509 said:
I'm thinking about getting a small dirtbike expansion chamber and welding it to the sbp header. Any thoughts? I have access to the tools and a local motorcycle wrecking yard has hundreds to choose from for about $20 each. Anything in particular I should look for, besides the correct shape and size to fit the bike? For example, if the new chamber's header is 2x the size of the sbp header pipe would that cause problems?

Also I'm picking up a dremel tomorrow and am going to open up the transfer ports and smooth out the intake and exhaust. Anything else I should do? I remember a while back looking at a different engine the transfer ports had these ridges in them just below the opening, should I remove them if theyre there on my engine?

-the sbp is a pocketbike exhaust cut into pieces.

-small dirtbike exhuast for the KTM SUZ KAW are all for 16 000 rpm

- get a proma gp clamp on.

rudyauction509 · Feb 11, 2015

got a chamber from a 125cc dirtbike (can't remember what kind), cut the header of the sbp chamber off and welded it to the new chamber, and welded the silencer on to the end. Its a bit ugly, and the exhaust exits in front of the bike, but it pulls hard and gets up to 38mph compared to 29 or so before. I also opened up the transfer ports and matched the intake and exhaust ports, and cleaned all of the carbon buildup.

If I was to open up the ports more, should I widen them, lower or raise them? Looking for low to mid range, not high range.

rudyauction509 · Feb 11, 2015

I should mention that I cut about 5 2-inch cuts in the new pipes header so I could make it match the sbp header's diameter. I hammered the pieces of the header to make a gradual change of size and welded it back together. Also it has insane low end torque from idle to about 4000 or so rpm and then kind of levels off, just like I was looking for.

mapbike · Feb 12, 2015

rudyauction509 said:
I should mention that I cut about 5 2-inch cuts in the new pipes header so I could make it match the sbp header's diameter. I hammered the pieces of the header to make a gradual change of size and welded it back together. Also it has insane low end torque from idle to about 4000 or so rpm and then kind of levels off, just like I was looking for.

thats great.... itsalways nice when you can get something to work like you want it to.

KCvale · Feb 12, 2015

rudyauction509 said:
If I was to open up the ports more, should I widen them, lower or raise them? Looking for low to mid range, not high range.

I'd say leave it be.
You can do over 35 MPH, why chance ruining it?

mapbike · Feb 12, 2015

I agree with KC,

most port work on these engi es is for getting more rpm at the sacrifice of some low to midrange.

a thi ner base gasket or a little shaved off the base along with higher compression will likely add a bit more low down grunt, but if it puls good now and low to mid is what you like, just make sure you have an excellent carb tune, get the exhaust set to you needs and gear it for what you want and then just ride and enjoy.

Its your bike so do what ever you think will work for you, but be careful messing with port timing if you want to keep the power in the low to mid range, you can mess that up especially on the exhaust port if you're not really careful.

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Thinking of ordering shift kit and exp. chamber, pros and cons?

rudyauction509

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mapbike

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frank66

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rudyauction509

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rudyauction509

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mapbike

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KCvale

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mapbike

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