Need help or ideas - 94 XLTSP

[cat5752]

I have searched all over the Internet and there are 100s of threads about this, but every one I have read a guy will state what his problem (or problems) are, every one will chime in, original poster says "I'll try all that and report back" and they never do. So I promise however this turns out I will come back here and finish this. I'm going to lay out where I'm at and what I've done so we can skip a lot of the usual things. As the title says it's a stock 94 XLTSP, a little over 2000 miles.
1. Compression from left to right is 115 psi in all three
2. New BPRE8s gapped at .028"
3. New Non Ethanol Premium, 3/4 tank full, new fuel filter and lines, filter arrow pointing correctly
4. Pickup line inspected, clunk cleaned. Can blow in the fuel line at the fuel shutoff and get bubbles in the tank. Can also take the same line, hold it lower than fuel level and get a steady stream
5. Fuel pump rebuilt with new gaskets. Matched gaskets to metal parts of the fuel pump plus I labeled all lines prior to removal. No junk in fuel pump
6. Wadded up some string and put it in the pulse line. Pulled sled over and it blows the string out
7. Carbs synced with drill bit method
8. New choke plungers, springs and choke cable. Have right in between 1/8" to 1/4" freeplay at lever
9. Carbs have been rebuilt. I've tried book recommended 200 mains and what the sled had in it when I bought it (160s) Needles set in 3rd clip and what it had in it originally, 2nd clip
10. Carb floats float, new float bowl needles (viton tip) and seats, when held upside down the float plate is square with the carb body
11. Bright blue spark
12. New coils, wires and plug caps - all pass the book specs
13. Cylinder drain plugs in front of block removed, no buildup, replaced them. They have the little aluminum washer on them

Now here's the weird part. I can pull until I'm blue in the face, with max choke and nothing. I pull the plugs and they don't even smell like gas. Nothing smells like gas. I can put about 1/2 tsp of premix in each cylinder, pull and it fires right up and idles beautifully, right on the money at 1800 rpm. Until it dies, which is about 45 seconds. Why isn't gas getting to the cylinders? The bowls are full. I can pull the fuel water separator hose on the float bowl and drain it. They've got gas in them! What the hell am I missing? Thanks in advance for ANY ideas anyone has.

 

[retiredpop]

If you pull the airbox and hold your hand over each individual carb throat do you feel any suction when pulling the motor over?
If there is no suction then it could mean the inner seals on the crankshaft that separate the cylinders are leaking. Without suction you won't pull any fuel from the carbs into the crankcase.

 

[Bushwacker1]

Seems strange that all three carbs would have a no flow issue but you need to determine if this is only due to the idle circuit being plugged. Can you get it to run at a higher rpm than just idle by adding fuel to the carb throat. You can use a spray bottle to squirt some gas in and try to get the main fuel circuit to take over. If it takes over and runs on the main circuit at higher RPM and then dies at idle your pilot circuits are plugged. Check to be sure the pilots are the correct size and that they do not have a film of dried fuel residue on them that is reducing their size. Check the needles and the needle jet tubes for this film also. Just spraying carb cleaner will not remove the film it needs to be scrapped off. I had a sled that would not idle but would run at higher rpms. After I took the carbs apart for a second time and ran some .023" wire thru the pilot passages and replaced the pilots with new it ran as it should. I also found a heavy film on the pilot air screw tip and shaft that could have been affecting the pilot circuit adjustment.
You may want to check your exhaust for a restriction like a broken baffle in the can or a mouse nest in the can or pipe. I had a sled once that I could not get to run and when I swapped the exhaust out with another sled it ran just fine. It took 180 PSI of air pressure and some probing with a rod to blow out a huge mouse nest from the exhaust. If you don't have a pipe to swap out you could try to run it with the exhaust off for a short time. Some Y pipes were made with an inner layer and an outer skin structure, check the y pipe to be sure it has not fell apart causing a restriction.
As retiredpop said Crank case sealing issues could also be the problem but I would not want to go there until all other potential problems are ruled out.
Hope this helps you to find your problem.

 

[cat5752]

I just learned a new way to adjust choke (enrichener) plungers. I checked mine with an artist's paint brush poked in to the enrichener hole in the carb throat. Marked how deep it would go, verified all three carbs are the same depth with choke lever off. Set choke lever to max choke, no change in the depth on any of them. I might be on to something. Thanks for all the ideas. Will let you guys now.

 

[cat5752]

Got it! Choke plungers were way out of adjustment. Using an 1/8" brass rod inserted in the choke enrichener port in the carb throat to adjust the plungers makes it super easy. Thanks to Jack on Vintage Snowmobiles! And Brokenleg for pointing me in the right direction. Now for jetting and carb adjustments.

 

[cat5752]

Double post, sorry.