maybe not sucking enough gas?

jake wilken · Post by **jake wilken** » Sun Oct 09, 2005 5:32 pm

My carb seems to not be pulling gas when I try to start the sled. I have temp. lines hooked up to it and they seem to be pretty tight, I do not have a check valve on the fuel intake. The first time I had it running with the choke open I had to pour the gas into the line and hold it up into the air to let it drain down to the carb and once it started it pulled a little gas to the engine but not a lot, not like a solid stream. Also a lot of gas was going back into tank out of carb drain or return line. Am I not getting enough suction/fuel? My "pulse" line from engine to carb is not blocked or cracked and I took apart carb and it looked alright but could something still be wrong?

:unsure:

Post by **Matt** » Sun Oct 09, 2005 8:17 pm

You definitely need to have a check valve in the tank, or the fuel just runs back down. Did you do anything else with the carb yet? Did you figure out for sure if it is a Walbro or Bendix?

JDFanPa · Post by **JDFanPa** » Mon Oct 10, 2005 12:38 am

you need to rebuild the carb if its the walbro if its the bendix you need a different carb .........what the carb looks like inside is irrevent to how its going to work it only takes a pinhole in a daipram for it to not work......also when you have it running put your finger over the pulse line you should feel air pushing out not like an air compresor but farely light pressure if you feel nothing could be a bad crank seal

400brian · Post by **400brian** » Mon Oct 10, 2005 12:40 am

Come on Matt, keep up, Jake established it as a Walbro in an earlier post

I believe in putting check valves in the supply line, got mine from Central.
However, this is mainly to prevent the fuel from draining back after shutdown.
If your fuel jug is stuck in the engine compartment just ahead of the foot well, it should pull fuel up fairly rapidly even when pulling it over with the rope. With it running, you should see bubbles going toward the tank in the return line.

It is certainly possible that you have a bad diaphram in the carb, regardless of how they looked. Your pulse line could be collapsing internally if it is a rubber fuel line, ( the UL guys run a stiff walled version of the clear fuel line for that reason ). Or you could have crank seals that are bad enough that you are not getting a good pulse.

I would rebuild the carb with new diaphrams, they don't last all that long under any conditions, time is not kind to them. Remember I said: in for a penny, in for a pound?
From what you are telling us, it sounds like you already have it diagnosed.

After I posted this, I see Andy beat me to it again

X's&O's · Post by **X's&O's** » Wed Oct 12, 2005 1:15 am

I agree with both of you (jdfanpa & 400brian) yes you need to REBUILD the carb, especially if its been sitting for a while, but you do not need to change the carb to something else. My sleds run great on there orig. carbs. and your sled should have the bendix carb on that year and model (original) but it sounds like someone has changed it already. Its not that pricy and pretty easy to do, Hell If you ever put together a model or puzzle, well then. The walbro carb comes with a map on how to.

Heres a couple of things to check for and how to.

1)Checking for Spark: lay both plugs (pluged into the wires) on top of the motor and pull it over rapedly. you've got spark GREAT!!!

2) While running: Pull each plug wires separate then put it back on, it should die or run like SH*T and then die when a plug wire is off. Then you'll know if both cylinders are firing that far.

3)Checking your carb for to much air: If 1&2 check out ok while its running cupping your hand and "SLOWLY" cut the air intake off of the carb. If it speeds up then your getting to much air and not enough fuel.

4) Checking your motor seals: while its running spray some starting fuel around "ALL" motor gaskets. If it runs funny (speed up or bog) then theres your problem.

Hope this helps.

jake wilken · Post by **jake wilken** » Wed Oct 12, 2005 8:22 pm

thanks for the replies guys, Im going to order a carb kit for it as soon as I look up what model it is exactly. I appreciate your prompt replies and havent been able to check the sight due to a cold I cant seem to shake

JDXsand00s · Post by **JDXsand00s** » Mon Nov 07, 2005 1:36 pm

I couldn't think of better title for my problem so I'll just post it here. I just got a 73 400, tore the engine apart, replaced the seals, got it to produce all kinds of spark, and timed it as close as I could to .023 btdc. There is compression as well and the pulse line is pulsing. It runs fine when gas is sprayed into the intake. When I bolt the carb on it, the problems start. I just completely rebuilt the carb as well and the engine doesn't seem to want to run. Gas is being sucked into the carb it seems, and bubbles are going out. Both needles are opened to 1 turn. If I spray some gas through the carb, it will start with the choke closed and will rev up some. If I push the choke in a little, it will rev up to several grand I'm guessing, 7 or 8 it seems at times with the choke almost completely closed. It will do that for a couple of seconds and then die. I have been lucky to save it a couple of times by closing the choke and repeating the cycle. If I open the choke, it dies. I haven't been able to start it yet with the choke open. I'm at a loss at what could be wrong. I'll probably take a carb off my 500 to see if it is really the carb or the engine. Hopefully you guys can help and hopefully I didn't miss the solution in previous posts. Thanks.

400brian · Post by **400brian** » Mon Nov 07, 2005 9:41 pm

Ryan

Try the carb swap, see if it makes any difference.
If it does not, perhaps you should consider pressure testing the engine.
Harleysportster has done this, maybe we can get him to post this to a FAQ.

We've seen problems like this before, but I don't know if anyone has really solved it yet. It sure sounds like some significant induction problem. Either carb or vacuum leak. Uncomanded rpm surges shouldn't happen.

JDFanPa · Post by **JDFanPa** » Tue Nov 08, 2005 2:44 am

Like Brian said sure sounds like a huge vacum leak. If you have a real bad leak like a crank seal and the motor has enough fuel in it to hits some rpms it will pull so much air through the leak it can actually suck gas right through the carb without throtteling it up. Also if it has a bunch of gas in the crank and a big leak this can happen. Once as a youth just got done bolting a sachs single in a ski doo and was dying to start it but had no carb well inexperienced I decided to spray either in the intake and start it with no carb WOW talk about some major rpms. I thought the sled was going to explode.

400brian · Post by **400brian** » Tue Nov 08, 2005 3:28 am

WOW! Hey Andy, when the sachs took off for max rpm, did that really get your attention?

I've done some less than inspired things as well. Oh well, no matter what school you attend, you have to pay your tuition.

JDXsand00s · Post by **JDXsand00s** » Tue Nov 08, 2005 8:36 pm

I enjoy those max rpms. I always make sure that I clamp the engine with 2 clamps to the picnic table so when it gets up there it don't fly away. I have a squirt bottle with premixed so when I rebuild an engine I can hear it roar. I can't feed it enough gas though to keep it going so it shouldn't be that bad for the engine. There have been a few times when I started the new engine in the snowmobile without a belt; that was scary. It must have been around 8 grand or more for several seconds and the key wouldn't shut it off. I think the kill switch did its job but I learned the importance of a belt in the idle process. Anyway I will trade the carb one of these days when I change my 500's seal and hopefully the carb is the problem.

JDXsand00s · Post by **JDXsand00s** » Sat Nov 12, 2005 5:07 pm

I switched my WDA32 carbs today and it seems to be the problem. My 400 now runs and my 500 will idle only when choked.If I open the choke a little, it will still idle, but when it is open all the way, it stalls. With the choke partly open, I can open the throttle and rev it up. I think my carb is confused as much as I am. I rebult the carb so I could have easily made a mistake putting it back together. My guess is the metering lever. I really don't understand the principles of the carb just how it goes together. In the rebuild kit instructions it says that a new diaphragm metering lever is included, though in my last two kits there was none, so I just used an old one. I didn't think that it pulled out the needle it's attached to far enough so I bent it out some. I was wondering if the needle opening up too far would be the cause of all of my problems. I also wish that someone could tell my its purpose: I know it is a valve but what for. Thanks.

400brian · Post by **400brian** » Sun Nov 13, 2005 2:45 am

I suspect it is not letting the needle open enough if it is bent. Thus you are not getting enough fuel.

My service manual shows adjusting the metering lever. The proceedure is as follows:

Invert carb and lay a straight edge across carb body. The metering lever should be 0.005 to 0.020 inch above the body. Adjust as necessary by bending needle valve tab on metering lever. ( the part that makes contact with the needle )

There is also a spring under the lever, it needs to centered on the dimple in the lever.

As for what this does? It controls the fuel level in the carb just as the float does in a Bendix or Mikuni.

Hope that helps

JDXsand00s · Post by **JDXsand00s** » Sun Nov 13, 2005 2:09 pm

Turns out the lever was the problem. When I bent it, I bent the curved end so it was taller instead of the end holding the needle. It opened up considerably more after I fixed it and now my 73's run like a Deere. Thanks for all of the help guys.

400brian · Post by **400brian** » Sun Nov 13, 2005 9:31 pm

Having a known good unit to try, is always a good thing to have when you are trouble shooting something.

A little success once in a while does wonders for one's morale!

I always enjoy it anyway..