Author Topic: Anyone know about old skidoos? (Read 2224 times)

wyo969 · « **on:** Feb 13, 2014, 08:42 AM »

I recently bought an 88 formula mx. I went through and cleaned the carbs spotless but yet for some reason I'm not getting any fuel to the motor just to the carbs. Any of you guys might happen to have any insight?

Turk · « **Reply #1 on:** Feb 13, 2014, 09:24 AM »

Is the motor turning over at all?
Do you have spark?

wyo969 · « **Reply #2 on:** Feb 13, 2014, 10:27 AM »

Motor turns and I have spark my only problem is the fuel delivery. Its got me baffled. If I take and use a spray bottle a give it a shot of premix in from the top of the head it will fire up and run until that's burned up. If I don't do that and just pull on it when I pull the plugs to get for fuel there bone dry.

Turk · « **Reply #3 on:** Feb 13, 2014, 10:47 AM »

It sounds like you do but can you see fuel getting to the carbs though the fuel lines?

wyo969 · « **Reply #4 on:** Feb 13, 2014, 11:00 AM »

You can fuel in the fuel in the lines and if you pull the carbs the bowls are full as well.

moneypit2 · « **Reply #5 on:** Feb 13, 2014, 11:03 AM »

time for a fuel pump rebuild or replace

Turk · « **Reply #6 on:** Feb 13, 2014, 11:10 AM »

I would check the fuel pump, inline filter and the fuel line in the tank. Sometimes the fuel line in the tank will get cracks in it and start sucking air. Did you make sure to clean the pilot jets? They are not in plane sight and can be missed when cleaning the carbs.

Fisherman 1 · « **Reply #7 on:** Feb 13, 2014, 11:30 AM »

If he gets fuel to the carbs, then it's unlikely there's anything wrong with the fuel pump. Floats and needles are obviously working because they are letting fuel into the bowls. You most likely have a blockage in the carb's internals. Take them apart and soak in carb cleaner, take the jets out too. Sea Foam is a good quality cleaner. Let them soak overnight.

wyo969 · « **Reply #8 on:** Feb 13, 2014, 11:37 AM »

I checked all the lines and replaced all one that was cracked and any that looked like they could be short lived replaced the filters. Cleaned the main the pilot the air screw the slide needle the idle screw the float shut off. I'm pretty good with carbs. I' starting to wonder if there is any way the rotary valve on it could get out of timing. Or if there is some other quirk that the old skidoos have

Fisherman 1 · « **Reply #9 on:** Feb 13, 2014, 01:50 PM »

Crank seals? If they not sealed then you may not have enough vacuum to suck in the fuel/air mix. Upper cylinder compression may however still be good.

wyo969 · « **Reply #10 on:** Feb 13, 2014, 02:13 PM »

Ill have to check. That would make sense on an old sled like it.

Turk · « **Reply #11 on:** Feb 13, 2014, 04:22 PM »

You could always ask the boys over on DooTalk.

Fast jack · « **Reply #12 on:** Feb 13, 2014, 04:29 PM »

If that is a rotary valve intake -the rotary valve may have broken the center out . If there is a large round cover on the engine behind the carbs -its a rotary. Pull a carb out of the boot and turn the motor over , you should have an opening into the crankcase open and close.

wyo969 · « **Reply #13 on:** Feb 13, 2014, 04:52 PM »

Ya I can see it when I turn it over slowly. I kinda wonder if it is 180 degrees out? Turk I have a few other people I gotta get ahold of but after that if all else fails ill head that way.

CMMahy · « **Reply #14 on:** Feb 13, 2014, 07:32 PM »

Are you getting fuel moving through the primer lines? (i'm pretty sure that sled should have a primer, not a choke...) Ski-doo's of that era tend to like 3-4 full primer shots before you try and start them. Usually the o-rings inside the primer dry up and it doesn't draw any fuel. Work the primer and look at the thin lines that run to the carb, you'll see the tiny air bubbles moving along the lines with each prime.

If the primer isn't working, it's a cheap fix, usually less than $30.

As for the rotary valves, you have to do quite a bit of dis-assembly to even get at it, so it's unlikely that it's out of time.

wyo969 · « **Reply #15 on:** Feb 14, 2014, 09:06 AM »

I believe its working CM ill have to check again tonight. I took Last night off from screwing with it before I stated loosing hair. I have a hard time as seeing it as the primer though cause its not drawing any gas at all into the motor.

CMMahy · « **Reply #16 on:** Feb 14, 2014, 03:02 PM »

If it is working properly, then the engine will usually run for a second or two after you pull it, just on the fuel you manually pushed into the carbs with the primer. Ski-doo carbs don't typically send much fuel into the engine at starting speeds, in my experience, which might explain why your plugs are staying dry.

Good Luck!

wyo969 · « **Reply #17 on:** Feb 14, 2014, 04:03 PM »

I've manually put fuel into though and got it fired but then it just dies out after that burns up. If all else fails atleast it was cheap to gamble on. Thanks for your insight.

CMMahy · « **Reply #18 on:** Feb 14, 2014, 06:46 PM »

No problem, I hope you get it figured out!

Another thing to check, are the carb vent lines. There should be 2 on each carb, they come up from a nipple on the top of the float bowl flange, loop over the cab body, down through little tabs on the opposite side float bowl screws and usually hang down into the belly pan. If those lines are kinked, or blocked somehow, you get a vacuum in the float bowl and the engine can't draw fuel up through the jets.

The black rubber impulse line from the crankcase to the fuel pump can swell up internally and prevent the fuel pump from working properly, while still looking ok on the outside. You can replace it with some black rubber fuel/emissions line if it's suspect.

Any fuel coming out through the tiny weep hole on the top of your fuel pump, means the diaphragms have cracked. You can either rebuild, or replace the pump for pretty cheap.

Good Luck!

wyo969 · « **Reply #19 on:** Feb 18, 2014, 12:07 PM »

Well CM I put it back together and did everything as I had been doing and if finally decided to cooperate. Makes no sense to me but hey I'll take it lol.

CMMahy · « **Reply #20 on:** Feb 18, 2014, 03:09 PM »

Glad to hear you got it running!

wyo969 · « **Reply #21 on:** Feb 18, 2014, 05:16 PM »

It made absolutely no sense but I guess some times they just like to be fickle. Now if we can just get that snow later this week that there talking about.

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Author Topic: Anyone know about old skidoos? (Read 2224 times)