Oval mods to a 79 Polaris Cobra

[RootsTXL]

It's been years since I posted here. I miss this site and wrenching on sleds. My barnyard oval race buddies have decided to dust off the sleds for a March paint swap in a farm field. I found a 79 Cobra 440 basically free. It needed the basic fuel system cleaning, point cleaning, handlebar welding, brake line repair, a new throttle lever, and some cleat repair.
I know this thing isn't intended to be a rocket ship but it's all I have these days. I sold off my previous collections. I'm trying to stay at zero $$ invested so I'm not looking to port and pipe or anything of that nature. I highly doubt there would be much to gain anyway?

I'm more interested in simple mods like if a stiffer spring in the primary or another 1/2 turn of the secondary might be worth the effort. I will likely widen the ski stance too since it is narrow as can be in stock form. I already have plans to make custom wear bars that will corner well in deep loose snow.

My past history with these guys shows a better response in the turns produces more checkered flags!! Granted the last time we got together it was 10 years ago and I was rocking a sweetly ported and piped TX440 with a few years of test and tune.

My other option is to pick up a 440 Exciter for $100. I'm not sure if there is much to gain by this though other than wider stock ski stance?
Honestly though I am not familiar with Exciters. Mods would still need to be low $$.

For the loose deep snow the cleated track on the Cobra seems advantageous. Seems the twin round slides on the Cobra would be more responsive than a single butterfly also?

I'm looking forward to seeing your suggestions!

[Vintagesleds.com]

[8A8340]

An Exciter should run circles around that, and handle better to boot.  Good luck either way.

[RootsTXL]

Oh no. Is this the general consensus? I am a Polaris guy and the thought of this hurts my soul. But, I am also a realist. If most believe the Yamaha is the way to go then I will pick it up this week and sell off the Cobra once I get it running.

Looks like it is time to learn the low budget garage secrets with Exciters.

[RootsTXL]

Disregard the consideration on the Exciter. Someone else got to it before me.

[Brettm57]

I say dare to be different!  Give the Cobra a go!  I'm guessing with it being a barnyard race (My favorite kind!) they won't be using the ISR rulebook to tech your sleds?  It's probably not $10,000 to win either?  You'd be surprised what you can accomplish with some "imagineering".  Think outside the box.  Be creative. 

Since I started racing in 1983, I can't count the number I've times I've been told "You'll never beat this or that with what you're running, you need to get a Xxxxxx if you want to win."  Well, I'm just bullheaded enough that I stuck with what I had, and with enough patience and perseverance, I more often than not made what I had competitive.  Believe me, a race win - or even a decent placing - is much more rewarding on the underdog!

[snowracer]

My opinion, you can achieve some big gains through clutching. In your case running the Cobra, don't ask me what changes to make. Just keep trying different setups until you are satisfied with one.

[toocheaptosmoke]

Roots!!  Glad to see ya back.   I think the Cobra is a bit of a potential sleeper, there was a guy that ran one at the coudersport oval races and did pretty well from what I remember.   The porting on that 440 fan was surprisingly decent for what it was, fairly close to TX 440 but with just a bit less exhaust timing.  If you believe the 1979 service manual notes, the cobra was 50 hp at 6500 rpm and the TX 440 54.5 hp at 6750 rpm.   


Suspension tuning and adjustments may be limited, can't remember what type of suspension came under those?   Would at least make sure there's no broken springs.   

[SirSpamalot]

Free is great! Yeah go thru the Cobra and just chase down parasitic drag ( bearings sliders skid etc) and freshen up the clutching and overhaul the fuel system. I remember those as fairly zippy. You can gain so much just by taking it back to original first then go from there.

[RootsTXL]

Brett you are correct. No rules and no tech. Unfortunately my test and tune time is almost non-existent.
Vinny, good to hear from you too. I'm very encouraged to see your comparison to a TX 440.
If I don't blow it apart this year, I might tear it down and see what I can squeak out of it.

I like the advice to go back to original and look for parasites. I don't believe there is any drag currently.

After doing a bit of digging it seems like a good starting point is to stiffen up the primary spring while drilling an extra in the secondary to tighten that one up. I will tear both apart and polish them up nice while treating it to a fresh belt!!

[gtsdude]

Sounds like fun! A group of us used to do something similar on a small boot shaped track. Never got much speed but was a lot of fun. First sled I got ready was a Polaris galaxy that had been sitting. I fixed a few cleats and went through the fuel system. Took it out on a small pond to try it out before changing anything and it blew just about every cleat off the track in the first 30 seconds! I ended up with a 74 ski doo tnt 340 fan that worked well. Only mod to that was an extra hole for secondary spring and wound it a little tighter. The track was small enough it didn’t really matter what size sled you ran as long as you could make the turns.