Carburetor boring

Mxfan
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Mxfan
Edited Date/Time 5/9/2019 6:27am
Thinking about having my carb bored and a divider plate put in on my yz250. Has anyone done this? Do you recommend it?
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lumpy790
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lumpy790 12/11/2012 10:22am
12/11/2012 10:22am
how do you ride?

Pro Action used to do a really nice mod called Riffle Bore.
slipdog
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slipdog 12/11/2012 11:22am
12/11/2012 11:22am
lumpy790 wrote:
how do you ride?

Pro Action used to do a really nice mod called Riffle Bore.
Works really well on a 2-stroke.

The Shop

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slipdog
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slipdog 12/11/2012 11:53am
12/11/2012 11:53am
Is that one of those jetless carbs?
newmann
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newmann 12/11/2012 12:09pm
12/11/2012 12:09pm
Yeah, PSI Big Air. Got one to try on my KX150 AF project. Taper bored 30-38mm. Need some radiators made to fit and I'll be motivated to finish it.

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slipdog
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slipdog 12/11/2012 12:34pm
12/11/2012 12:34pm
That's going to be a nice ride!

I have a few cool 2-stroke parts floating around my place, a few turbo cranks and a Polini reed block with 14 vertical petals.

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newmann
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newmann 12/11/2012 12:47pm
12/11/2012 12:47pm
slipdog wrote:
That's going to be a nice ride! I have a few cool 2-stroke parts floating around my place, a few turbo cranks and a Polini reed...
That's going to be a nice ride!

I have a few cool 2-stroke parts floating around my place, a few turbo cranks and a Polini reed block with 14 vertical petals.

Those turbo cranks work well? Any of them fit a KTM150?? I have one trick crank, but nothing to fit it in...came from what I believe to be a 1982 RC125 Honda. One of the hollow laser welded, balanced , stuffed, polished, every bit numbered.....Someone spent some time on the workbench type of cranks. Think all those holes in the other crank could be why my 81 YZ250 is so damn weak??

motofab36
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motofab36 12/11/2012 12:52pm
12/11/2012 12:52pm
slipdog wrote:
That's going to be a nice ride! I have a few cool 2-stroke parts floating around my place, a few turbo cranks and a Polini reed...
That's going to be a nice ride!

I have a few cool 2-stroke parts floating around my place, a few turbo cranks and a Polini reed block with 14 vertical petals.

I assume the 2 in front are turbo cranks? Whats the theory? The notches pick up more air/fuel mixture forcing it up through the transfer ports? I've heard the term but never seen one.
slipdog
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slipdog 12/11/2012 1:07pm
12/11/2012 1:07pm
These cranks work very well. The term turbo crank has been used loosely over the years and most don't really work very well. They are machined like a centrifuge so as it spins, it creates vaccum in the center of the crank. They pull more fuel into the cases and exhaust it up the transfer ports.

mynewcr250
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mynewcr250 12/11/2012 3:04pm
12/11/2012 3:04pm
lumpy790 wrote:
how do you ride?

Pro Action used to do a really nice mod called Riffle Bore.
slipdog wrote:
Works really well on a 2-stroke. [img]https://p.vitalmx.com/photos/forums/2012/12/11/vortex2_919100.jpg[/img]
Works really well on a 2-stroke.

can you give us some more info on this? been thinking of doing an oval bore on my '13 250sx but this sure looks interesting as well
slipdog
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slipdog 12/11/2012 3:37pm
12/11/2012 3:37pm
mynewcr250 wrote:
can you give us some more info on this? been thinking of doing an oval bore on my '13 250sx but this sure looks interesting as...
can you give us some more info on this? been thinking of doing an oval bore on my '13 250sx but this sure looks interesting as well
That's the Pro-Action Vortex carb mod. They riffle the bore to help increase the intake velocity. It helps with throttle response and acceleration. You might be better off with the oval bore on the KTM because it has a the 36mm carb, which already has good low to mid response.

I operated a Pro-Action shop for 5 years and always had positive feedback from that mod. It's great for 38mm carbs as well as the minibike carbs. Give them a call if you want more info, they're good people.

http://pro-action.com/index.html
neverwasfastenuf 12/11/2012 3:42pm
12/11/2012 3:42pm
mynewcr250 wrote:
can you give us some more info on this? been thinking of doing an oval bore on my '13 250sx but this sure looks interesting as...
can you give us some more info on this? been thinking of doing an oval bore on my '13 250sx but this sure looks interesting as well
slipdog wrote:
That's the Pro-Action Vortex carb mod. They riffle the bore to help increase the intake velocity. It helps with throttle response and acceleration. You might be...
That's the Pro-Action Vortex carb mod. They riffle the bore to help increase the intake velocity. It helps with throttle response and acceleration. You might be better off with the oval bore on the KTM because it has a the 36mm carb, which already has good low to mid response.

I operated a Pro-Action shop for 5 years and always had positive feedback from that mod. It's great for 38mm carbs as well as the minibike carbs. Give them a call if you want more info, they're good people.

http://pro-action.com/index.html
Looks sweet. Have you had an opportunity to test or hear how the APT smart carbs are working? They all seem to incorporate some of the same technology.
neverwasfastenuf 12/11/2012 3:45pm
12/11/2012 3:45pm
slipdog wrote:
These cranks work very well. The term turbo crank has been used loosely over the years and most don't really work very well. They are machined...
These cranks work very well. The term turbo crank has been used loosely over the years and most don't really work very well. They are machined like a centrifuge so as it spins, it creates vaccum in the center of the crank. They pull more fuel into the cases and exhaust it up the transfer ports.

These are cool and it sounds like they work too.
slipdog
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slipdog 12/11/2012 4:53pm
12/11/2012 4:53pm
neverwasfastenuf wrote:
Looks sweet. Have you had an opportunity to test or hear how the APT smart carbs are working? They all seem to incorporate some of the...
Looks sweet. Have you had an opportunity to test or hear how the APT smart carbs are working? They all seem to incorporate some of the same technology.
They seem pretty interesting to me, but I've not heard anything about how they work.
Mxfan
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Mxfan 12/11/2012 6:23pm
12/11/2012 6:23pm
I ride Worcs and arenacross
slipdog
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slipdog 12/12/2012 6:17am
12/12/2012 6:17am
Mxfan wrote:
I ride Worcs and arenacross
If you want to shift the power more to the top end, boring your carb might work out for the longer WORC races. It isn't something you would really want to do for Arenacross where throttle response is much more important. For that you should consider just the power wings or the Pro-Action Vortex mod.
slipdog
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slipdog 12/12/2012 6:26am
12/12/2012 6:26am
newmann wrote:
Those turbo cranks work well? Any of them fit a KTM150?? I have one trick crank, but nothing to fit it in...came from what I believe...
Those turbo cranks work well? Any of them fit a KTM150?? I have one trick crank, but nothing to fit it in...came from what I believe to be a 1982 RC125 Honda. One of the hollow laser welded, balanced , stuffed, polished, every bit numbered.....Someone spent some time on the workbench type of cranks. Think all those holes in the other crank could be why my 81 YZ250 is so damn weak??

Wow! I've never seen a crank that was that bad, it must be Swiss made. Lol.

Just stuffing that bad boy would make a world of difference.

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Tim507
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Tim507 12/12/2012 7:59pm
12/12/2012 7:59pm
Mxfan wrote:
I ride Worcs and arenacross
slipdog wrote:
If you want to shift the power more to the top end, boring your carb might work out for the longer WORC races. It isn't something...
If you want to shift the power more to the top end, boring your carb might work out for the longer WORC races. It isn't something you would really want to do for Arenacross where throttle response is much more important. For that you should consider just the power wings or the Pro-Action Vortex mod.
I put a Boswell Carb on my 97 Suzuki 250. Was awesome for arena cross as it pulled off the bottom like there was no tomorrow. I pulled almost all the holeshots in the 40 class and the 30 class. Took the same carb to Washougal and about half way up horsepower hill she signed off....shit!
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lumpy790
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lumpy790 12/13/2012 4:08pm
12/13/2012 4:08pm
Had a Lectron carb on my 81 RPM KX250 .... seemed to work really well!
PJSMAN
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PJSMAN 5/9/2019 6:27am
5/9/2019 6:27am
Mxfan wrote:
I ride Worcs and arenacross
slipdog wrote:
If you want to shift the power more to the top end, boring your carb might work out for the longer WORC races. It isn't something...
If you want to shift the power more to the top end, boring your carb might work out for the longer WORC races. It isn't something you would really want to do for Arenacross where throttle response is much more important. For that you should consider just the power wings or the Pro-Action Vortex mod.
Tim507 wrote:
I put a Boswell Carb on my 97 Suzuki 250. Was awesome for arena cross as it pulled off the bottom like there was no tomorrow...
I put a Boswell Carb on my 97 Suzuki 250. Was awesome for arena cross as it pulled off the bottom like there was no tomorrow. I pulled almost all the holeshots in the 40 class and the 30 class. Took the same carb to Washougal and about half way up horsepower hill she signed off....shit!
Hello Tim, Do you have any of the Boswell Tuning instructions for the MX carbs? thanks

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