Dear Ralph:
I have purchased a set of Delta VForce Reeds for a stock ’96 ZRT 600. I have had all of the updates performed and I am wondering what carburetor changes are needed so that I have the same fuel-air mixture that the sled originally came with.

Len Urban
Duluth, MN

The VForce reeds flow more air, and by doing so will require slightly richer jetting to maintain the same fuel/air ratios. In practice, the jetting chart on your clutch cover has a bit of “safety” margin built into the specs, so you could likely follow that chart and still be safe. If this sled was jetted right to the edge and then had VForce reeds installed you would find yourself jetting up one or two main jet sizes to maintain the proper exhaust gas temperatures. On this engine, VForce reeds are usually good for a 4-6 HP gain from what we’ve seen. You’ll know because you’ll have to re-clutch it to keep the rpms down and get the power to the track.

Dear Ralph:
My sled has one cylinder that is laying down under mid-range operation. It doesn’t completely fall off to one cylinder, but it kind of pops and backfires. The situation will occasionally resolve itself after about an hour of running, or putting in fresh plugs normally cures it. I am confused because the plugs look good, and I am fairly sure that I don’t have fuel problems. I should also mention, this seems to happen after every cold start. Any suggestions would be greatly appreciated.

Dusty Mjoen

First off add some isopropyl to the fuel and see if it works better after the engine has run long enough to work it through the fuel and combustion system. Getting deeper, you could check the compression on each cylinder to make sure they are within 10% of each other. If they are, remove the carbs and check to see that all of the piston intake skirts are intact to allow proper intake vacuum for fuel. This could also be a matter of sucking snow dust into the combustion chamber, giving the impression that a plug is fouling. Plugs can’t burn water, and will act like they’re fouled.

Dear Ralph,
I have a 1996 XCR 600 SP and I’ve done everything that I know to get rid of that one second bog at the beginning of acceleration. I have rejetted, put in Q-8′s (needle jets) and changed needles – installed the almond spring in the drive clutch and #10′s for weights, changed the helix and secondary spring, and replaced the 21 tooth gear with a 19. I live in ND and have been running 330, 350, 350 for jets. Can you recommend something that I may have forgot?

Bummed out Bill

Despite our best efforts, about all you can do is clutch around that bog at 5000-5500 rpm. It seems as if it’s always going to be there. Some of the almond springs are pretty soft (down around 260 pounds which causes the engagement to come in soft at around 4600 rpm) so you could try another almond spring to get the engagement up above 5000 rpm (we liked 5200). Many sleds responded to installing 3.0 carb slides. I would be very curious to see what the ’98 carb specs are for the XCR 600 as the ones we’ve tested seemed to have that bog eliminated.

Dear Ralph:
A friend of mine bought a used ’95 EXT 580 this year. He is having an awful time trying to handle the sled. It doesn’t want to turn. He has installed new ski skins and carbide runners, but it didn’t help at all. We have adjusted the suspension front and rear – it didn’t seem to help that much, either. The sled handles OK at less than 15 mph. Anything faster and it gets to be a guessing game whether it will turn or not. He doesn’t believe it was ever in an accident or raced. It has around 1,000 miles and appears to be all original. Thought maybe you could help us out – any suggestion?
p.s. I suggested he buy a Polaris.

Mike Burke

We had similar problems with an EXT of that vintage. Ours just wasn’t getting enough weight on the skis to get the carbides to bite. Through a combination of suspension adjustments we were able to arrive at an acceptable set-up. The front end was soft so we increased the ski pressure by increasing the front preload. However, the rear skid was a greater cause of the handling ills. Drop the skid, pull all the shafts and get them greased up so that they pivot freely. Shorten the limiter strap length to get more weight on the skis, and you may even want to decrease the spring tension on the center shock, but be careful so that the steering effort doesn’t get too unruly.

Dear Ralph,
I plan to re-ring my ’93 750 Storm. I’m thinking about boring it to 800cc. The question is: does the ’93 750 have the same case and cylinder as the ’94 800 Storm? If it is the same, can I resleeve to an 800 or is there an easier way to do this, via boring 0.010, 0.020, 0.030, 0.040, and putting 800 pistons in it?

Kyle Ohnstad
Mounds View, MN

This seems to be a yearly question – what to do with all of the older Storm engines. There are plenty of used Storms that dealers would love to sell at bargain prices, and a savvy tuner could turn one into a rocket for a lot less than a new machine. First a little background – rumor has the original Storm engine as 800cc with Nicasil cylinders, but was considered too “ballistic” for the market at that time. So to de-tune it and make it less expensive it was delivered to the consumer as an iron bore cylinder 750cc – and that’s when the “heat problems” started. Durability was the key issue as getting pistons to last was difficult.
Can you bore your 750 cylinders to 800? Unless you install new sleeves, I think you are limited to about 780cc. Even then, the cylinder walls will be very thin, the ports will be small, and you’ll still be fighting a heat problem. To install new sleeves and go up to 800cc is an option, but the heat problem will still be there. Another option is to send off your cylinders (with a new set of pistons) to get Nicasiled. But if you use bigger pistons you’re again back to thin cylinder walls and small ports.
Perhaps the best option is to drop on some of the newer ’97 Storm cylinders that are Nicasil coated, along with heads and pistons. This would be the most expensive route, but would be the most efficient. You would have to do some case work to give the larger diameter skirts room to drop into the case, but that’s pretty easy. With this mod you should also want to install the pressurized cooling system to make it right. Since the pipes were originally designed around an 800, they should would work just fine. You could start with the ’97 Storm jetting specs and be pretty close too. The latest Storm engines have been pretty reliable.
Of coure, the least expensive route is to simply clean up the bore, and check the tolerances to see if you can just re-ring. But my suspicion is the pistons in your engine right now will show “knife edging” (a sharp melted edge on the top of an over heated piston [at the exhaust port] that causes the ring to stick so it loses compression). If that’s the case you’ll have to drop in new pistons anyway. Might as well plan on buying at least three new pistons – go with Wisecos if you can get them – they were hard to get last year because of the high demand. They’ll be a bit more durable than the plain cast OEM Polaris pistons. We played around with some Elko (Austrian pistons from the same maker as Rotax, and now what the domestic Polaris engines use), but you might as well stick with what is readily available. They made the power, but still knife edged at about 1000 miles. Bottom line on the Storm is that if you’re investing any large amount of money in it, go with some form of Nicasil cylinders, install the pressurized cooling system update, and get ready to do some clutching.