CRF 250 PROJECT

Tyson Henry · Posted: Sun Dec 23, 2012 8:44 am Post subject:

Small needle seat and single pump works flawlessly on my kart. Just saying.

Steve Buckner · Joined: 22 Apr 2003 Posts: 839

Look into my eyes and repeat after me, the GFS system is the only thing that works.

Mike Goebel · Posted: Sun Dec 23, 2012 11:40 am Post subject:

The GFG System is the only thing that works
The GFM System is the only thing that works
The GFY System is the only thing that works
The GFT System is the only thing that works
The GFE System is the only thing that works
The GFB System is the only thing that works

Wait what??

Mike G.
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Chris Reinhardt · Posted: Sun Dec 23, 2012 11:44 am Post subject:

Jimmy McNeil · Posted: Sun Dec 23, 2012 5:08 pm Post subject:

The problem with running the pump directly to the carb is that the psi produced by the pump varies wiith the engine rpm.
If a fuel pump was the optimal set up it would come that way from the factory.
I'm not saying it won't work, im saying it will most likely run better with a gfs

Brian Degulis · Posted: Sun Dec 23, 2012 5:15 pm Post subject:

Ok here's what I've done. I made a resevoir out of some 3X3 square aluminum tubing. It has a 1/4" input 3/8" output and a 5/8" baffled return. It's mounted under the front fairing. So the fuel pump is piped to the 1/4" input then there is a 3/8" gravity feed to the carb and the 5/8" return drops straight down to the tank. With this set up there is no need for a second pump because the return is large and direct. It works great on the stand. The only thing I'm not sure about is how the motion of the kart might effect it. The fuel level in the resevoir is only about 4" above the carb and it's not a sraight shot down like it is on a bike. I'll know for sure when I run it.

Brian

Benn Herr · Joined: 18 Jul 2001 Posts: 1580

Brian,

Interesting! Usually the Magic can is mounted right over the engine but what you have might work.

The usual weakness of the Magic can (in fact any by-pass system) is the return to the tank. Yours won't have that problem. Under acceleration your set up should work fine. There will be a slight rise in head pressure to the carb due to acceleration but it won't be anything the carb can't handle.

The only time there could be a problem will be when you're on the brakes and turning right, and even then you'd have to be on the brakes longer than the engine will run on a float bowl of fuel.

Priming the system might be rather involved if you've run it dry or serviced it. And one other thing to check, at one time IKF had a rule requiring protection for a fuel cap that was the high point on a kart. Not sure how they would deal with yours. Seems like it would be as safe as any existing set up, but you've seen how people deal with something they haven't seen before!
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Sam Zavaglia · Posted: Sun Dec 23, 2012 7:15 pm Post subject:

Howie Idelson · Posted: Mon Dec 24, 2012 9:28 am Post subject:

Man you guys can make something so simple, extremely complicated. One 30 dollar dellorto or mikuni pump works great.
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Chris Reinhardt · Posted: Mon Dec 24, 2012 11:12 am Post subject:

Steve Buckner · Joined: 22 Apr 2003 Posts: 839

Brian Degulis · Posted: Mon Dec 24, 2012 1:58 pm Post subject:

There are lots of carbs that work on a pressure feed like cars outboard motors etc. If you look at one of those carbs and compare it what we're working with you can see the difference. The geometry of the float pivot and the needle is different along with the needle itself. I think it's manufactured that way intentionally I think it's designed to not have a solid open and close action like pressure feed carbs do. I think it's designed to vary restriction and I think it's designed that way to maintain a more consistent fuel level in the bowl.

Can it be made to work with a pressure feed obviously the answer is yes. Will it work as well? Probably not because it's no longer working as designed and the fuel level in the bowl is varying more. Does it make a difference? I don't know and neither does anyone else accept those that feel they know everything and immediately condem anything that challenges they're thinking. People like that are unusually so pre occupied with stroking they're own egos that they wouldn't know a good idea if it bit them in the ass anyway.

Brian

Chris Reinhardt · Posted: Mon Dec 24, 2012 2:55 pm Post subject:

[quote="Brian Degulis" Will it work as well? Probably not because it's no longer working as designed and the fuel level in the bowl is varying more.
Brian[/quote]

I have a really nice Grand National Jacket, and crap load of trophies that says you have no idea what your talking about.... Along with numerous fast laps and track records....

I think the point your missing is these carbs WERE designed for pressure and gravity. That's why they make a needle seat for gravity and another for pressure...

#36 on the fiche reads "For gravity applications use part number...."

http://www.sudco.com/fcrmx.html

Meaning they have a gravity setup, and a non gravity setup.

It really doesn't matter, you're not competing, you have a detuned exhaust, so whatever....

CR
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Brian Degulis · Posted: Mon Dec 24, 2012 3:56 pm Post subject:

I got it we all got you've said it many times. What you may not be getting is the diffrence between a mechanical fuel pump and a pulse pump. I believe you when you say it works I just think gravity works better for the reasons I stated.

I'm sure you've got a lot of nice trophies. Be carefull not to roll over on them when your sleeping.

As for my exhaust unless you've been sneaking into my garage at night you don't know what I ended up with.

Brian