snowmobile motor on dune buggy help - Snowmobile Forum: Your #1 Snowmobile Forum

TheyCallMeCrazy · 07-11-2006, 07:06 PM

i have a 1971 or 1974 Keihin carb with fuel pump on a dune buggy
its a 340cc 2 cylender yamaha motor
i just rebuilt the whole carb & pump and i made 100% sure i put all gaskets in properlly

heres the problem

i have the motor on a slight tilt with the exhost end down lower than the carb end thus putting the carb in the air....

when i mount the gas tank above the carb and motor, the motor floods out big time.
when the tank is below the motor the motor starves for gas.....

i had the motor running with the tank in both locations. the last time i had the motor running i forgot to tighten that screw under the pump and it vibrated loose and shut the motor down, i wasnt able to get it started again after that

is the tilt on the motor effecting it from running properly? or
is my pump not pumping?

i also need the tuning specs on a carb such as this

edit:::
i just read that
"These carbs have a real big problem with sticking inlet needles. "

anyway around that? i think thats my problem!!!!

update::::::::::::::::::::::;

i moved the gas tank to the front of the dunw buggy, made made the fuel line run like they do on sleds, since my carb has a fuel pump.

now it seems to stave for gas.

i need the proper setting for the 3 screws on the carb

high speed
low speed
and the one on the very bottom of the carb

IndianRvrShiver · 07-12-2006, 06:19 AM

If it's a float carb, it must be level in order for it to meter the fuel correctly. You can tilt the engine anyway you want, but the carb MUST remain upright/level. Try h/s at 1-1/2 turns, l/s at 1, and bottom at 1. To be honest, I 'm not sure what the bottom one does, but you must start somewhere. You can always adjust it later. Good luck!!

BTW - Welcome to SF.com!!

TheyCallMeCrazy · 07-12-2006, 09:10 AM

this is a non float carb.
fuel pump style
i did have a gravity system, but i removed it and ran the fuell ine diffently. flooding has stopped but now it seems to be starving for gas......
any tips?

ITriumph · 07-12-2006, 12:24 PM

Do you have any pics that you could post on here to give us a better idea of what the carb looks like. I did a search, but not sure exactly what 340 motor you have on your buggy. I found a few microfiches of some carb, and the only screws i see are you HS, LS, and yur idle. Your fuel pump could be shot, or your diaphrams are shot.If they get as much as a pinhole in them they are junk. I would try rebuilding your carb, and fuel pump. The parts don't cost very much.

letitsnow · 07-12-2006, 12:29 PM

take the return line off and see if it sprays gas out when you pull it over, if it does your pump and lines are fine and you need to adjust the needle, if not then you have a problem with the pump or lines. have you checked the pickup in the tank? do you have a fuel filter?

IndianRvrShiver · 07-12-2006, 12:33 PM

Quote:

Originally Posted by TheyCallMeCrazy

this is a non float carb.
fuel pump style
i did have a gravity system, but i removed it and ran the fuell ine diffently. flooding has stopped but now it seems to be starving for gas......
any tips?

I get it now!! I mis-interpreted your first post....sorry! Not familiar with that brand carb

.....if it was a Tilly or Walbro, I might be able to offer some help.

TheyCallMeCrazy · 07-12-2006, 01:12 PM

top image ill have to get more pics when i go up to my shop later tonight
http://www.mixed-drink-recipes.com/buggy/IM001788.JPG
http://www.mixed-drink-recipes.com/buggy/IM001783.JPG

the pump has been rebuilt $20 for the kit and i put it in

the pick up in the tank is nothing m ore than a fuel hose in the bottom of the tank.

no fuel filter

**RJ Gleason** · 07-12-2006, 01:50 PM

That looks like it came out of a SnoJet, the Yamaha 340 fan cooled. The carb that you have does have a float in it and needs to be mounted level to work correctly. I would also get the shroud back on the cyls. to cool them better. I will look up the specs for that type of carb tomorrow when it stops raining long enough to go outside to my shop and get the book out.

TheyCallMeCrazy · 07-12-2006, 01:56 PM

wow good call i had no idea what model sled i had, i looked up sno jet and found this
http://www.vintagesnowmobiles.50megs...2B_1_PP209.jpg

this is the sled i had

but the carb doesnt have a float, not a normal one anyhow.

**RJ Gleason** · 07-12-2006, 02:00 PM

Linky no worky

TheyCallMeCrazy · 07-12-2006, 02:02 PM

works for me

TheyCallMeCrazy · 07-12-2006, 02:06 PM

the only pic i can find of a similar carb
http://i17.ebayimg.com/03/i/06/5c/8d/ee_1_b.JPG

**RJ Gleason** · 07-12-2006, 02:42 PM

Ok, it stopped raining long enough and I got my book out. Needle valve settings for Keihin diaphram carb; Idle mixture needle...1 1/8 turns out. High speed needle....1/14 turns out. Fuel level@ 39mm. Inlet lever (the arm that moves the fuel metering needle open and closed) height 5.7mm. On the bottom of the pump section there is also a screw called the adjusting stud. this is used to set the fuel level. turn it in to rais the fuewl level and out to lower it. If the engine is starving at mid throttle, you need to raise the fuel level a bit.

Depending on which sled it came from, you have either 24hp at 5500 rpm or 36hp @ 6500 rpm. the later is from an SS or GP It is likely and 338cc model#810.

TheyCallMeCrazy · 07-12-2006, 03:03 PM

Quote:

Originally Posted by RJ Gleason

Ok, it stopped raining long enough and I got my book out. Needle valve settings for Keihin diaphram carb; Idle mixture needle...1 1/8 turns out. High speed needle....1/14 turns out. Fuel level@ 39mm. Inlet lever (the arm that moves the fuel metering needle open and closed) height 5.7mm. On the bottom of the pump section there is also a screw called the adjusting stud. this is used to set the fuel level. turn it in to rais the fuewl level and out to lower it. If the engine is starving at mid throttle, you need to raise the fuel level a bit.

Depending on which sled it came from, you have either 24hp at 5500 rpm or 36hp @ 6500 rpm. the later is from an SS or GP It is likely and 338cc model#810.

Thanks!
i will try this out

TheyCallMeCrazy · 07-12-2006, 03:05 PM

Quote:

Originally Posted by RJ Gleason

High speed needle....1/14 turns out.

is this 1 1/4 ?
or 1/14 as stated

**RJ Gleason** · 07-12-2006, 03:24 PM

sorry, fumble finger typing 1 1/4

**RJ Gleason** · 07-12-2006, 03:31 PM

Handy to have book, Snowmobile service manual(from Intertec), covers most sleds built from early 60's to late 80's. ")

IndianRvrShiver · 07-12-2006, 04:58 PM

Good job, RJ!!

TheyCallMeCrazy · 07-12-2006, 06:11 PM

Quote:

Originally Posted by mouse72

I'm pretty sure he meant 1 1/4 turns.

i figured so
yes very handy book and thanks, ill let you know how it goes.
this motor runs very well when running but its so hard to get it going for the first time, i was hoping the rebuilding of the carb would have helped.

if this motor refuses to run i will get an arctic cat 440 motor
or new duel carbs.

i have only ridden this thing for about 45 minutes so far and its crazy fast.
anyone have any parts for sale?
carbs motors?

image
http://www.mixed-drink-recipes.com/buggy/IM001785.JPG

**smallengineguy** · 07-12-2006, 08:30 PM

Good job, RJ! Can you mount the engine straighter?