A new development on my otherwise bulletproof 2004 SP700 (carbed engine). Since the weather has gotten colder (teens overnight, 20's to 30's during the day) it's very hard to keep the engine running until it's fully warmed up. It starts instantly, but after a couple of minutes the idle RPM's just start dropping until finally it stalls out. It will start instantly again and the pattern repeats. Eventually I have to give the throttle a little pressure to keep the engine idling. No choke setting makes any difference.

Also during this warmup period, the engine wants to lug down at times. Slightly pumping the throttle will usually clear that, and once the engine is warmed up there's no trace of this behavior (or the idle dropoff) at all.

I've heard of rejetting the carb based on altitude, but not based on temperature. It wasn't doing this when temps were in the 40's, and 20-30 degrees shouldn't change the air density enough to throw off the fuel-air ratio to cause this behavior, true? And if that was the problem, why would a warmed up engine fix it?

Thanks for any advice!

 

I have an '05 with the exact same problem in the winter as you describe. I have not done anything with it yet. I assume the carb needs a larger pilot jet for winter or possibly an E-Clip adjustment (clip down), I dont know for sure though but I will agree that it is very cold blooded.

 

What's weird about it is that I didn't encounter this condition last year, when the temps were basically the same.

Further research suggests temperature variations are more important for carb jetting than I suspected. But so far, things I've read seem to worry about changes of many tens of degrees. This thing had no issues when temps were in the 40's, but 10-15 degrees lower and it's complaining a lot. Perhaps the 40's were the low end of its "happy range".

The worst part is that I suspect I have to basically disassemble the whole top of the machine to remove and adjust the carb. I can't see any convenient way to remove it from either side, even with the side panels removed. Therefore the repetitive rejetting process is going to be a huge PITA.

Does anyone know a clever trick for removing and reinstalling the carb on a 2004 SP700?

 

they are not jetted for that cold of temps and your right about being on the lower end w/ 40's. if you just turn the idle up a little does it make it idel fine awhen cold and maybe a little high when its warm? i just turned mine up a little when i used mine in cold weather but granted i wasnt using it alot to warnt a jet change.

 

Yes, as mentioned if I press ever so gently on the throttle (imitating a higher setting on the idle screw) it will hold the RPM's up enough to keep the engine running.

I can believe it's a cold air thing, other than the fact that all last winter - in similar temperatures - it never behaved like this. So I'm not sure.

The local dealer's service guy just finished telling me that Polaris has a "carb update" that involves swapping out the needle and seat, float spring, and a few other components. The fix is specifically to address the cold start problem, so it's apparently not that unusual.

As you said, I may just crank up the idle setting a bit during the cold months rather than go through the agony of rejetting twice a year.

 

Polaris needed to lean out the carbed 700 at idle to get it to meet emission standards. That is why they run better at 1/2 - 3/4 choke in the winter. I know the owner of a performance shop in town & explained the problem to him. Living in Mn, he was very familiar with this problem. This was his recommendation. I had a "dyno-jet" jet kit installed in my machine. The jet kit throws tons of fuel through the machine at idle. I couldn't believe the difference it made!! I can now start my 700 in sub-zero weather at 1/4 choke. Let it warm-up for 1-2 minutes, and push the choke back in. Like WAATV says, the dealerships also have heard from the masses & they have their own jet kit.

 

I have a 2004.5 Sportsman 500 ho and it cranks awhile before it even hits.

 

DynoJet comes up in a Google search but none of the links seem to work. I tried .com and .net in addition to the links offered by Google but they all come back "dead". Do you have any good links to them?

 

Here is the link:

http://www.dynojet.com/jetkits/atv/polaris.aspx


This is who did the work for me:
http://www.straightlineperformance.com/



Hope this helps

 

Try turning the idle speed up to the high end of specs. On my 500, the idle spec is 1,100 RPM +/- 100, so I run it at 1,200 in the winter for a solid idle. Also, an easy way to richen the mixture without rejetting is to wrap the air filter in a shop rag or two. Choking off some air while leaving the fuel the same will give you a richer mixture. I snowplowed all year (250+ inches) last year in some cold temps 0 degrees, and never had a mixture problem.

Good luck!