Carb and fuel system

Ace Rossi · Posted: Mon Oct 08, 2012 12:23 pm Post subject: Carb and fuel system

Question:

Jason from Swedetech has been very helpful but it has come to decision time again which means more $$$.

Cr125 modded
08 CRG Road Rebel
RLV 5 pipe
RLV silencer

Pump around system

OR

GFS system

Anyone have experience and would want to shed a little light? I know a lot use the pump around but now I'm told the GFS system is far better!

The Mikuni that I have is NOT performing very well!

Thanks
Ace

Jim McMahon · Posted: Mon Oct 08, 2012 1:40 pm Post subject:

If its for cheap kicks\practice days lookup "magic can"
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Ace Rossi · Posted: Mon Oct 08, 2012 1:43 pm Post subject:

Could you possibly be more specific?

Chris Laird · Posted: Mon Oct 08, 2012 3:02 pm Post subject:

This has been debated time and time again but I'll see if I can help you out. The GFS from Swedetech and the pump around are a fix to a motocross carb on a shifter kart. The carb is designed to be gravity fed (gas tank above carb on a bike). In a kart you have to pump the fuel to the carb which creates pressure and the carb doesn't function properly.

The GFS pumps fuel to a "mini" fuel tank. Inside there are a series of hoses that feed fuel to the carb and lets excess fuel drain to a scavenge tank to be pumped back to the main fuel tank. Recreating the gravity feed from the bike makes tuning the carb more consistent and reduces excess fuel "loading up" the motor.

The standard pump around "almost" fixes the problem but is a bit harder to to get dialed in making tuning a bit more inconsistent. The biggest problem with the pump around is trying to get the pressure in the carb "equal to gravity" as your pushing fuel in and sucking fuel out. Some claim it is equal to the GFS and some don't. Also with the pump around you have modify the carb to make it work. Another downfall to the pump around is oil settles in the pumps and you have to clean them out on a very regular basis. The way the GFS is set up, most of the oil ends up in a fuel line. Pull the line off, let it run out and it's done. You rarely have to pull the pumps apart to inspect.

In short here are the differences:
GFS
1. Consistent tuning
2. Less maintenance
3. Basically bolts right on (no mods to carb)
4. Costs a little more than the pump around

Pump around
1. Inconsistent tuning
2. Quite a bit of routine maintenance
3. Have to modify carb
4. Costs less than the GFS

If your really looking to save money some claim that simply placing a tee in one of the lines will fix it. At the end of the day if your not trying to be competitive at the top level any of the three will make the motor run.

Personally I say GFS. Makes for a more enjoyable day at the track because you rarely have to think about it. Less work at the track means more seat time, more chassis tuning and testing time.

Steve Buckner · Joined: 22 Apr 2003 Posts: 839

Dellorto pump $38.00 No carb mods needed. Shocked

Vernon Head · Posted: Mon Oct 08, 2012 5:30 pm Post subject:

I have a Mikuni and was having some real problems with starvation even though it had a Magic Can. Eventually I got rid of the Magic Can, bought a round Mikuni pump with 2 outlets and plumbed it with one return line back to the tank (I used the fitting straight across from the inlet fitting) and one straight to the carb (I used the other outlet that is at a 45 degree angle from the return fitting). I have had no problems since then.

Ace Rossi · Posted: Mon Oct 08, 2012 7:10 pm Post subject:

Ok Thanks for the replies which leads me to another question.

I just bought a brand new stock 38mm keihin carb. Will it work alone without all the mods like gfs or pump around? A little over 200.00 for the carb and Jason says another 400.00 for the gfs! Whew! Or 225.00 for the pump around! Thats 5-600.00 just for a carb! I might just suffer with using the mikuni and try to make it work! I mean it does run the way it is but just hard starting!

Vernon Head · Posted: Mon Oct 08, 2012 7:27 pm Post subject:

I would just keep working with the Mikuni and at the same time look for a used keihin/pumparound system on EKN or eBay. I've seen the whole setup used for under $300.

Tim Salvino · Joined: 20 Nov 2010 Posts: 257

First, try routing the fuel lines like Vernon mentioned. If that doesnt work for you, get the Dellorto fuel pump.

If for whatever reason neither of those work out for you, THEN think about dropping all that money for PA or GFS.

Benn Herr · Joined: 18 Jul 2001 Posts: 1580

This is from a few months ago:
Keihin PWM $219.95
Plastic "tee" $0.50
Fuel Line $2.00
Mikuni Round Fuel Pump $32.99
Total $255.44

Keihin PWM $219.95
Fuel Line $2.00
Dellorto Bypass Fuel Pump $48.69
Total $270.65

Keihin PWM $219.95
Small Inlet Seat $24.95
Fuel line $2.00
Mikuni Round Fuel Pump $32.99
Total $279.89

Keihin PWM $219.95
Magic Can (used) $25.00
Fuel line $2.00
Mikuni Round Fuel Pump $32.99
Total $279.94

Keihin PWM $219.95
Pump-Around Conversion $179.00
Fuel line $4.00
Mikuni Round Fuel Pumps (included in conversion price)
Total $402.95

Keihin PWM $219.95
Swedetec GFS System $399.99
Fuel line $4.00
Total $623.94

Side note: The PWK is $10.00 cheaper.

There is your comparison. Some people spend more money on their kart, it's because they want to. Nobody is making them.

Any of the systems will work if you take care of them. Any of them will let you down if you don't take care of it.

You pays your money and you takes your chances!

You can read the whole thread here:

http://www.ekartingnews.com/viewtopic.php?t=111230
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Ace Rossi · Posted: Tue Oct 09, 2012 4:37 am Post subject:

WHEW!
Thanks for the many many replies and pm's! I gotta tell you, after reading 10 pages of postings regarding fuel systems blah blah blah, im more confused now then ever before!
What I did learn was any system has to be plumbed correctly and vented sufficiently to keep the carb full at all times without starvation. I also read a LOT of debate on who is right and who is not! That was discouraging to say the least!
Look, I'm just a recreational racer hoping to get the bugs worked out this year in hopes that I can race a REAL race schedule next year! What I dont want is to go broke trying every gadget made just because someone says 8-10 big names use that gadget! Good for them that they have the gadgets to use! I know all too well how they acquire them to begin with regarding sponsorships etc.. Nobody ever gave me anything to just try. I pay for everything i have and i guess im one of those that keeps others in business!
Anyway, thanks again for the help...i think!

andy graham · Posted: Tue Oct 09, 2012 5:19 am Post subject: honda carb

for what it's worth, I remember back in the 90s when I was racing MX, I raced honda CR125 for about three years. I think it was `95, there was a tech bulletin from Honda that I received in the mail that addressed a bogging issue in corners, dont remember if it was lefties or right handers, but it was specific to the problem and where it occured....What I do clearly remember was they gave instruction to re-vent the carb with tee fittings and additional hose that was supplied withe the letter...I do remember making the suggested mod and the bogging went away.....for what it's worth...

Ryan Leger · Joined: 19 Jul 2012 Posts: 133

Your are correct andy ot was when turning right they had a similiar problem with 06

Jimmy McNeil · Posted: Wed Oct 10, 2012 10:01 am Post subject:

Alex King · Posted: Wed Oct 10, 2012 11:12 am Post subject: Re: Carb and fuel system

Ace - If you have a '99 engine, I would recommend going w/ what SwedeTech is recommending you. And if GFS System is what you are looking for, I have one for sale. I bought a brand new SwedeTech engine pakcage (you can verify that w/ Jason) and I am selling the GFS System along with the complete '99 Cylinder (etc...). I only used it for 3 races. It worked and works perfectly. I am technically challenged and a mediocre driver so I had to 'hook up' with a local team for local support, the team runs a different system so that is why I made the change; otherwise...this would be it! I am also selling the SwedeTech engine mount and silencer (all purchased brand new as a package at the beginning of this year, 3 races on it). Email - aking888@yahoo.com