[Gary Smith]

Are you running a Mikuni TM28 carb? If so, what are the pilot jet and main jet size? Are you running an airbox or a K&N style air filter?

As far as fuel mixture, I run 6 OZ Motul 800 2T synthetic oil per gallon of 110 leaded fuel.

The only time I had a problem with a bog out of a corner was during break-in of a big bore kit that the guy told to go massively rich from the settings I was accustomed  to. I figured too rich , no problem, can always lean it out after break-in!

Gary

#55 Honda CR80

[Manny Dial]

Thanks for the reply.  K&N style filter with a Flat Slide type Mikuni Carb.  I went out to Prairie City today which is a tighter course and it was VERY apparent around all lefts.  I’ll post vid on it soon.  I just got done taking apart the carb. Pics below of the setup.  Can anyone help verify the lines and if this is truly a pump around setup?  The pilot jet looks semi clogged as the light passing through the main hole is barely a hair size.  Can’t tell the size but I’ll double check to see if anything is written on it.  Any other tips are appreciated.

This pic shows the carb.  It looks like the fuel pump line goes up into this cylinder regulator (?) then down into the carb.  The cylinder also has a nipple facing outward that goes to the bottom of the tank.

[img]http://i640.photobucket.com/albums/uu122/my3awds/8DB8D4FC-866C-4330-8587-AC6F8F061B6E-1834-0000029F083F0278_zps2f2d61bb.jpg[/img]

Picture of the nipple going to the bottom of the tank

[img]http://i640.photobucket.com/albums/uu122/my3awds/B7822511-16DC-46F4-894C-69A996DFAB0E-1834-0000029F2A710CB4_zpsb8037936.jpg[/img]

Fuel tank.  Didn’t notice any vent line?

[img]http://i640.photobucket.com/albums/uu122/my3awds/23058050-2B54-43FB-8CA0-925D08E5C19F-1834-0000029F75111788_zpse7f32d05.jpg[/img]

The carb has a vacuum line that loops back to the other side of the carb?  Bottom line just vents to the ground.

[img]http://i640.photobucket.com/albums/uu122/my3awds/CF5AAD5B-4616-41CD-9EFC-26089FA4906B-1834-0000029F41890B53_zps4f9aa214.jpg[/img]

[Gary Smith]

From what I can see, this is not a pump around system. Have you taken the float bowl off? Do you have a float in the carb? A pump around system does not have a float. There is a fuel line in and a fuel line out, with coarse foam and a brass plate in the place of the float. Seems to me you have a sticking float.

The pilot jet size is difficult to read, it is written on the side of the jet, main jet is easier to read on the head. Being an old fart, I need a magnifying glass to read the numbers.

Gary

#55 Honda CR80

[William Martin]

Manny,

That looks like a DIY version of the old “magic can” fuel system. The can is just a reservoir to simulate a gravity feed like on a bike. One thing that seems wrong about the carb plumbing: the line looped under the carb, from side to side, should go over the top of the carb, and have an air vent snipped in the center of the loop. The way it is now, there is no venting of the float bowl. Not sure what that bottom hose is about, never have seen one of those on a shifter engine carb.

 

[Manny Dial]

Ah thanks William.  Here’s some progress info & pics.

Main Jet: 180

Pilot Jet: 30 (?? Impossible for me to read and thats a guess with the jet pointing down)

Visual Plug: Dark Brown/Black (Rich)

Cleaned the heck out of the carb.  I can see better through the Pilot, and the float seems to move freely.  The needle tab seems ok as well.  I notice that it seems like the Pilot is too fat / rich?  I start the kart and rev it to keep the idle up for about 5 mins, then let it choke itself out.  I can’t restart it without a few wheel pulls and the throttle has to be about 15% down.  I also notice fuel is coming out of the drain nipple at the bottom of the carb while I’m having difficulty starting.  Once it fires up it sounds good though.  I plan on taking the Kart out this week to see if cleaning it helped any.  I’m really hoping it was just a sticky float on high G corners.  What would you guys recommend for a Pilot at this point?  With a black plug sounds like I might have some room to lean.

I took your advice and cut/routed the loop line.  This is how i’ve seen it on 125 shifters

[img]http://i640.photobucket.com/albums/uu122/my3awds/A_zps4f085831.jpg[/img]

Bottom all cleaned out

[img]http://i640.photobucket.com/albums/uu122/my3awds/B_zpsca8037df.jpg[/img]

Float looks to be parallel

[img]http://i640.photobucket.com/albums/uu122/my3awds/C_zps2b9e4de7.jpg[/img]

The bowl was about this clean before washing it out

[img]http://i640.photobucket.com/albums/uu122/my3awds/D_zps1b7017eb.jpg[/img]

Jets cleared out

[img]http://i640.photobucket.com/albums/uu122/my3awds/E_zps0a4debe0.jpg[/img]

 

[William Martin]

Fuel dribbling out the lower fitting on the carb while starting? That sounds like too much pressure in the fuel system. I see there is a tiny vent in the fuel tank cap, likely not enough for the size of pumps used on shifter karts. Guessing your pump is a 52mm Mikuni, can’t see it in the pictures. Did you check the needle & seat carefully for any sign of wear? If it’s leaking, that could be part of your over-rich condition.

 

[Gary Smith]

Does the fuel line on the top of the can go back to the top of the tank? Does it flow fuel unrestricted? There should be no restriction in this return line.

Do you have a fuel filter? It should be on the inlet side of the fuel pump.

There is an air screw for idle mixture, right hand side of carb near the air horn, should be turned out about 1 turn. The more you turn it out, the leaner the idle mixture.

Get your kart to idle, adjust the slide screw, that’s the screw on the other side of the carb with a lock nut and a thumb screw head, back it out just to the point when the engine stalls. Now to restart, just a little throttle needs to applied.

Like William said, the vent hole in the cap is too small, mount a 1/4 inch barbed fitting and run a 1/4 inch ID hose into an overflow bottle above the fuel tank.

My jetting with a K&N style filter is 37.5 pilot, 195 main, my tracks are about 1,000 above sea level.

Hope this helps,

Gary

#55 Honda CR80

[Manny Dial]

Thanks Gary! Between cleaning the Carb and rerouting the vent lines, the kart drives great now with no bogs! Appreciate everyone’s advice. Now I can setup the kart to idle as well! One quick follow up question: is it recommended to empty the bowl after racing? I don’t plan to take it out again for a week and wasn’t sure if my gas mix will possibly clog the ports again (20:1 redline 110oct). I’m thinking it originally got clogged due to the old 927 mix just sitting in the carb for a few months from the previous owner.

Thanks

Manny

[Gary Smith]

Your welcome Manny, If the kart was going to sit for more than a couple months, yes I would drain the carb bowl as well as the fuel tank. For just a week, I wouldn’t bother. I always siphon the fuel out of my tank after a day at the track and store it in a sealed fuel jug for the next time I go out. I try to mix just enough fuel for the day, usually have between a quart and half gallon left over.

Gary

#55 Honda CR80

[Dave Holstein]

Great now you can take it out to the next RedLine race at Sonoma!

[Author]

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