Dead Sled Wrenchers

Add a Primer to your sled

So your sled is hard to start because it sits all the time, or its really cold out. You're tired of yanking that cord a million times to get riding. One night when there was snow on the ground and my '71 Arctic Cat Panther 303 wouldn't start I got thinking there's got to be a better way.


The offender

Well friends there is a better way, its called a primer.

First lets talk for a second about carburetors and the starting circuit. On the older Tillotson and Walbro carbs when you want to start the sled you set the choke. The choke on those carbs is exactly what it say it is, a plate that closes and restricts the amount of air available to the engine. This forces the engine to draw more fuel, which makes the ratio of fuel to air higher, and helps the engine start easier. On Mikuni carbs when you flip the "choke" lever you open the enrichment circuit adding more fuel to the existing amount of air which accomplishes the same thing.
The problem is when your sled has sat for a while the gas in the fuel linea will evaporate or leak out. This leaves you yanking the cord to pull gas from the tank to the carb before the sled will start. This is especially a problem when its really cold and the gas pump at its least efficient, and you're at your most irritable.

So what can you do? There are 2 common types of primer, one is the squeeze bulb primer which pressurizes the gas line, the other pumps fuel directly into the engine intake. The latter type can be subdivided into the push/pull and push bulb. Installation of the squeeze bulb primer is very simple, the hardest part is finding a place to locate the bulb. I'll cover the installation of a squeeze bulb primer in another article. I have one on my '70 Ski Doo and it works well, you may also have seen them on boats with outboard motors.


List of tools:

1. 1/8" drill bit and drill:
The metal of the carb is soft but you don't want to make an oval hole so a sharp drill bit is a must.

2. 4mm-.70 Metric tap
At least thats what size the primer nipple I used was, others will be similar if not exactly the same.

3. Flat head screwdriver:
Small one, the fitting is small.

Pictured above is the Tillotson HL carburetor on my '71 Arctic Cat 303. This carb is a little odd because it has a pipe between the carb and engine. I've seen this sort of thing on Kohler engines too but with the carb pointed straight up. Anyway for the purpose of this installation I pulled the carb with the pipe from the engine.

Then I drilled and tapped a 4mm-.70 hole in the pipe right by the engine and screwed in the barbed fitting and bolted the carb back up.



List of parts:

1. Primer install kit:
The kit itself usually includes the primer, in this case push/pull or push bulb, a plastic t fitting for the gas line, and a small gauge gas line to go from the t to the intake.

2. Primer barb:
The kit usually doesn't include the barb so buy one separately, or if you have access to a sled junkyard like I do, scavange one out of a Ski-Doo from '74ish or later.

3. Locktite:
Both to ensure that barb never comes out and to make sure theres a very good seal to the carb. I expect the color doesn't matter. I used blue and it seems to be fine.

In retrospect I should have located the barb more toward the top of the pipe. As it is the fuel line runs near to the clutch than I'd like. Once I've installed the primer in its final position its pull on the fuel line should keep things safe.

For now I've zip tied the primer in the right footwell. Its safe there and not likely to get knocked around while testing. Since this sled is a pretty good, fairly unmolested sled I'd rather not go cutting it up and I was about ready to start making a braket to mount the primer near where it is now when I happened to take a glance at the sled's dash.


There, in front of my eyes was the word "prime" but no hint of a primer. It looks as though I could easily mount my primer in that panel just above the handlebars. I happen to know where theres a junker '71 and if it has its little panel I'll grab it and mount my primer in it. If it doesn't I'll make a new panel. Either way I'll put mine aside, I'd wager those panels got broken out pretty easily. It would be interesting to hear from someone who actually knows the mystery of the "prime" on the dash.

Whats the verdict?
2 important things learned.

#1 Plan things in advance. I'm still irritated about where I put the barb.
#B Don't blame anything until you've investigated the problem fully.

Early tests indicated some part of this had gone horribly wrong and there was an air leak. The sled idled but died as soon as I opened the throttle. This basically sidelined the machine for the '04/'05 winter. Over the summer the Tillotson decided to stop pumping gas so I rebuilt it figuring that the old carb to block gaskets might have caused the bad running problem.

After rebuilding the carb I found I had the same issue but I managed to adjust the carb to get rid of it. So when I'd been experiencing the issue before it was really a carb tuning problem I'd attributed to my primer installation without investigating fully.
I still don't have alot of test data but early results are positive, the sled starts on the first pull after being primed. The mounting situation isn't even really a problem. I might make some sort of mount but then again I might not.


What do you think about this project? Let me know!