'73 Cheetah 440 carb trouble

[Reeseholler]

Hi folks!

I discovered this forum while deployed (ironic as I was in the desert), but waited until I got back (Wednesday) to post so I can be of more help answering questions.

I brought home two vintage sleds (the 73 cheetah 440 and a 72 Deere 400) and did a quick once over on them and all seemed fairly well with them. That's to be taken lightly as I know next to nothing about snow machines and know more about old tractors and pickups. I pulled the carb (WD) on the cat and while it was soaking, I checked for spark. Wasn't any, so I touched up the points and she throws a nice bright spark now. Threw the new kit in based on pictures I took and the one thread on here. It pumps fuel to the carb and back to the tank so I know that part is working, but doesn't seem like it's making it through far enough to be drawn into the engine. I've choked, messed with needles, but to no avail. Put some gas in the cylinders, put the plugs back in, and it'll start and run until there's no gas left.

I disassembled and double checked to make sure I had the right diaphragms and gaskets in the right place, and all appeared correct. Any places where I might start looking to find the culprit?

Thanks,

-Brandon

[Vintagesleds.com]

[moose17n]

welcome to the site, and welcome home-been there- my advice is to put a tillitson on er brother. someone will pop up on here and help you through the wally i'm sure just give it a day-moose us airforce/usarmy retired-one 03-04, oif 08-09 welcome home brother

[Reeseholler]

Thanks Moose for the reply. Any particular tillotson I should be on the lookout for?

[Desmo878]

The Walbro carbs are a little more finicky than Tillotsons, but if they work right, run great. There is a tutorial on here by Wankel303 about the Walbro's, be worth looking into. Pictures got lost in that Photobucket deal, but here it is; https://vintagesleds.com/bs/index.php/topic,49980.msg566663/topicseen.html#msg566663.

I only have 1, but have worked on a few. If it's not quite right, won't run right. If you do go looking for a Tillotson, this may help;   http://www.vintagesnow.com/Carburetors_files/app%20and%20desc.pdf
Source one that has an external pulse connection, but other than that, basically all the same. Do not lose the original hi/low screws!! If you rebuild one of these, use the original adjustment screws, & throw the ones in the kit away.

[Reeseholler]

Thanks for those specs Desmo, it helped quite a bit when looking at alternatives. I think I'm going to try a tillotson at this point, as I haven't been able to make any progress with the walbro.

I went through the walbro carb off of the cat, cleaned, kit, put back on. No fuel through it. It was pushing back to the tank but it wasn't moving through the needle. Took it apart and compared it to the same carb off of the deere and everything was put together the same. Looked at it again, and the new needle has a slightly wider groove cut in it for the metering lever, so I thought what the heck, put the old needle back in.

Meanwhile, I had put the old deere carb on it for the heck of it, and was able to get it to run, although it would just idle and spit gas on the floor. It would four stroke at idle, but wouldn't accelerate. Put the worked over carb back on, 3rd pull it started up, blew gas all over the floor, ran for about 20 seconds fairly cleanly then shut off. I changed the gas out for fresh, and I turned the adjustments out until I got something (about 1 3/4 out). Got a second or so of running and that was it. Went out and started my 65 pickup and let it warm up, came back in and it started and ran for about 5 seconds, then nothing. Took the pickup out for a drive before I parked it in its new place before this new snow falls, and when I came back after a couple pulls it ran at about a quarter throttle, no skips in cylinders or variance in RPM. After about 20 seconds it died off and quit, and wouldn't start again. This is becoming quite the enigma to me.

I've tried seemingly a million combinations of choke, no choke, idle screw in, out, anything I could possibly think of to try to figure out the magic combination. So at this point I'm willing to try about anything, and find a tillotson carb to see if I can regain sleep

[Desmo878]

What you have described is my story when I got into vintage sleds. Had been messing with Mikuni carbs on bikes all my life, but theses were different, in that they are "pumper" carbs. Rebuilt a carb , wouldn't run, just spit gas on the seat!! After many, many tries, & lots of frustration, I got to a point where I finally got it. These carbs, both Walbro & Tillotson, are very finicky. If 1 thing is off, won't run right. On the Walbro, if the wound spring on top is off 1 revolution, it will never run right, found this out the hard way on a 440 Cheetah. Ran almost like you have described, would run a bit, then die.

Questions;  Do you have 1 Walbro, 1 Tillotson, or 2 Walbro's? Did you change the check valve in the Walbro? These are not available in the kit anymore, but there is a Holley carb # that is a direct replacement. Don't have it handy though. Haven't played with a Walbro in awhile, little hard to diagnose it online. If needed, I have quite a few Tilly's on the shelf

[Reeseholler]

I have two Walbro's. The one off the deere I believe is a 34 and the one I pulled off the cat is a 34 (off of the top of my head).

I purchased the kit from rt 21, and it came with the check valve. I did pick up an additional two check valves from napa though, because I was just going to disassemble the deere one and clean it, and put it back together. I know that one ran, the gentleman said he just touched up the points before he got it out every year. The cat belonged to a relative of his, so he couldn't tell me any history on it.

Thanks again for the reply