CR125 carb choice

Ace Rossi · Posted: Sun Sep 30, 2012 5:34 pm Post subject: CR125 carb choice

Mine came with a mikuni and thinking about switching to a keihin pump around.
Good choice or not?
Now my question about my mikuni...
Is it possible that fuel could seep from carb past the reeds and into CC causing a very bad flooding situation?
Starts out in am starting easy but then after sitting 20-30 minutes, it is harder to turn over and no start until the 5th or more try at pulling the strap! Then it starts with mega smoke and you have to run it at almost full throttle to clear it out to where it will idle.
We checked the pump, re routed fuel lines and tried every thing making sure all was working as it should. Only thing we noticed as the line feeding the carb has constant bubbles at idle until you nail the throttle. When not running, the line is empty. Pulling the plug and spinning the tire fills the line up quickly!
Out on the track, OGP, a .6 mi sprint track where laps are around 38-40 sec, the motor seems to fall off as if starving after about 5 laps. Running easy for half lap brings it running back to normal and yes the temps are around 125-135.

Steve Buckner · Joined: 22 Apr 2003 Posts: 839

Did you try this yet.

Ace Rossi · Posted: Sun Sep 30, 2012 5:59 pm Post subject:

This is what's on it now and I also have a pump that has two of these back to back

Steve Buckner · Joined: 22 Apr 2003 Posts: 839

The back to back one is for the pump around system. I know you have changed lines, tee back to tank, and still have carb issues. This pump has an internal regulator, all the other pumps dont. I have never heard one person that has used this pump come back and say, It has this prob. For $40.00 you can't go wrong. If there was a better system for that price, I would be the first to say use this one.

Chris Reinhardt · Posted: Mon Oct 01, 2012 4:03 am Post subject:

Everything about those Mikuni's suck with the exception of the fact you change the needle seat. You should be able to run a 1.8 needle seat and fuel pump directly into the carb, no tee's...

CR
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East Coast Super Kart Series
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Mart Roy · Posted: Mon Oct 01, 2012 5:02 pm Post subject:

Chris, by doing that, it wont pressurize the carb itself instead of being gravity feed?

Chris Reinhardt · Posted: Mon Oct 01, 2012 5:38 pm Post subject:

That's kinda the point. Unless you mount the fuel tank above the carburetor, it ain't gravity feed....

Mikuni designed those seats for either gravity feed 3.5 or pressure, 1.8. It's simple physics, x PSI time y orifice will give z volume of liquid. Increase the pressure and decrease the orifice, and you will decrease the volume of fuel.

It works, I ran a Mikuni HSR on my CRF450 Superkart, Mikuni round pump directly into the carb with the pressure seat, I think for that it was a 2.3?

CR
_________________
East Coast Super Kart Series
"This is how we roll!"
www.eastcoastsuperkart.webs.com

CR2 Motorsports
"Home of Cobalt Superkarts"
www.CR2MotorSports.webs.com