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Carburetor boring

Mxfan

C100

Posts: 5

Joined: 12/2/2012

Location: El Cajon, CA USA

12/9/2012 12:36 PM

Thinking about having my carb bored and a divider plate put in on my yz250. Has anyone done this? Do you recommend it?

lumpy790

C100_image_1388949757

Posts: 4279

Joined: 9/18/2007

Location: York, SC USA

12/11/2012 10:22 AM

how do you ride?

Pro Action used to do a really nice mod called Riffle Bore.

slipdog

C100_image_1391266340

Posts: 3100

Joined: 7/25/2009

Location: Nor Cal, CA USA

12/11/2012 11:22 AM

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.

Sometimes I make jokes, I'm not smart enough to explain them so it's on you if you're too dumb to understand them...

newmann

C100_614585238_1207253287

Posts: 12883

Joined: 4/1/2008

Location: USA

12/11/2012 11:45 AM

newmann

C100_614585238_1207253287

Posts: 12883

Joined: 4/1/2008

Location: USA

12/11/2012 11:48 AM

[img][/img]

slipdog

C100_image_1391266340

Posts: 3100

Joined: 7/25/2009

Location: Nor Cal, CA USA

12/11/2012 11:53 AM

Is that one of those jetless carbs?

Sometimes I make jokes, I'm not smart enough to explain them so it's on you if you're too dumb to understand them...

newmann

C100_614585238_1207253287

Posts: 12883

Joined: 4/1/2008

Location: USA

12/11/2012 12:09 PM

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.

[img][/img]

slipdog

C100_image_1391266340

Posts: 3100

Joined: 7/25/2009

Location: Nor Cal, CA USA

12/11/2012 12:34 PM

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.

Sometimes I make jokes, I'm not smart enough to explain them so it's on you if you're too dumb to understand them...

newmann

C100_614585238_1207253287

Posts: 12883

Joined: 4/1/2008

Location: USA

12/11/2012 12:47 PM

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 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

C100_s36_dsc0358_3

Posts: 981

Joined: 4/1/2008

Location: Cowden, IL USA

12/11/2012 12:52 PM

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 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

C100_image_1391266340

Posts: 3100

Joined: 7/25/2009

Location: Nor Cal, CA USA

12/11/2012 1:07 PM

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.

Sometimes I make jokes, I'm not smart enough to explain them so it's on you if you're too dumb to understand them...

mynewcr250

C100_jakewisdom_1367774019

Posts: 681

Joined: 10/22/2012

Location: CA, USA

12/11/2012 3:04 PM

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.

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

C100_image_1391266340

Posts: 3100

Joined: 7/25/2009

Location: Nor Cal, CA USA

12/11/2012 3:37 PM

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 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

Sometimes I make jokes, I'm not smart enough to explain them so it's on you if you're too dumb to understand them...

neverwasfastenuf

C100_c100_1391279764

Posts: 3698

Joined: 4/1/2008

Location: USA

12/11/2012 3:42 PM

slipdog wrote: Works really well on a 2-stroke.

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 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 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

C100_c100_1391279764

Posts: 3698

Joined: 4/1/2008

Location: USA

12/11/2012 3:45 PM

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 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

C100_image_1391266340

Posts: 3100

Joined: 7/25/2009

Location: Nor Cal, CA USA

12/11/2012 4:53 PM

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 same technology.

They seem pretty interesting to me, but I've not heard anything about how they work.

Sometimes I make jokes, I'm not smart enough to explain them so it's on you if you're too dumb to understand them...

Mxfan

C100

Posts: 5

Joined: 12/2/2012

Location: El Cajon, CA USA

12/11/2012 6:23 PM

I ride Worcs and arenacross

slipdog

C100_image_1391266340

Posts: 3100

Joined: 7/25/2009

Location: Nor Cal, CA USA

12/12/2012 6:17 AM

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.

Sometimes I make jokes, I'm not smart enough to explain them so it's on you if you're too dumb to understand them...

slipdog

C100_image_1391266340

Posts: 3100

Joined: 7/25/2009

Location: Nor Cal, CA USA

12/12/2012 6:26 AM

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 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.

Sometimes I make jokes, I'm not smart enough to explain them so it's on you if you're too dumb to understand them...

Tim507

C100_phpg1iqsvam_1390067275

Posts: 1265

Joined: 6/8/2010

Location: Bend, OR USA

12/12/2012 7:59 PM

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 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!

Germany 1975 250 CZ Centerport, laydown shocks, mikuni with reed valve, Maracohci forks with me as the motopilot

lumpy790

C100_image_1388949757

Posts: 4279

Joined: 9/18/2007

Location: York, SC USA

12/13/2012 4:08 PM

Had a Lectron carb on my 81 RPM KX250 .... seemed to work really well!
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