December 27, 1997
Dear Ralph,
I am replying to two letters that were featured in the October/November 97 issue of SnowTech. While you had some good points, I feel that you left out some critical information in your responses.
First, in regards to Kyle Ohnstad’s questions about the ‘93 750 Storm- Wiseco does not offer pistons or piston kits for this motor. Only Polaris offers pistons for the 750 motor in std, .010, & .020 over sizes, and unfortunately for riders these are quite expensive.
Second, the 750 and 800 motors are quite a bit different, especially from year to year. The 800 cylinders will NOT directly bolt on the 750 cases. The cylinder sleeves and piston skirts need to be machined to make the fit work. Also the 1994 Storm received factory updated pistons (same as the stock 1995 pistons). But the 1995 Storm received factory updated cylinders and pistons (which basically made it a 1996 motor). The 1996, 1997, and 1998 are the same Nicasil cylinders and C series pistons.
Third, the best cure for any Storm is a big bore kit. The cases are quite large and accept big bore kits very well. Both PSI and Legend Performance have quality kits that work wonders on these sleds (especially the ‘93-’95 models). In my professional opinion, Kyle would be better off with one of these big bore kits or getting a new sled.
In regards to the knife edging, if the cylinders are properly size and chamfered and the updated cooling system is in place you should not have a problem with knife edging. We have several Storms in use with over 7000 trouble free miles on them! Although much maligned, the Storm when properly set up and maintained is a powerful, reliable, and fun machine.
Next, in regards to the troubled XCR600SP’s- there is a cure for the stumbling blues. We have spent many many many hours dialing these sleds in, and having run them for the past two seasons are quite familiar with them. First of all the stock clutching was way off. We have assembled a good clutching kit from Polaris parts and Goodwin Performance has an excellent kit as well. Second, regearing does help. I suggest 1 tooth smaller on top. Third is carburetion, they can be leaned out but be very careful here as they will burn down easily! But for 0-3000 ft at -20 to +10 we run Mag 370, Ctr 370, Pto 350, Pilot 35, and needle in #4. We also recommend drilling out the pilot hole to .047″ and running the 3.0 slides (but the slide change is not absolutely neccessary). Fourth, the pipes are flat out wrong on this sled. They are the EXACT same pipes as on the Storm and Ultra SPX, and basic two stroke knowledge tells you that this won’t work. I definitely recommend different pipes or at the least a new muffler from Dyno-Port. It is truly amazing how much this helps. Fifth, I suggest a set of Carbon Tech reeds. The throttle response with the reeds and muffler is tremendous and needs to be heard to believe! Sixth is to roll the timing BACK a bit, yes I said roll it back. Seven, adjust the RRSS block to the back hole like the ‘97 has. This gives a much better holeshot and weight transfer. Last, if you have money to spend, install the 1997 CDI box as it has a different ignition curve and helps prolong piston life under racing conditions. Making all these changes adds up to a completely different sled from stock and makes it very fun to own and ride, not to mention VERY fast!
Keep up the good work, I do enjoy your magazine quite a bit.
Sincerely,
John Ellis
General Manager – F&R Sales & Service
Polaris Master Certified Mechanic & Dealer
Thank you for sharing this excellent information with us John.
December 27, 1997
Dear Ralph,
I own a 1981 440 Yamaha. My problem is that it takes about 40 pulls to start the thing. It’s not flooding, there is no carbon on the plugs and it seems to have a fair amount of compression. It seems to start better when it is cold, but is a bugger when it is warm. What is wrong?
Randall Williams
This is a difficult one to diagnose with such little to go on. Yet…
Remember the requirements to make a two stroke run. 1. Fuel 2. Primary compression 3. Secondary compression 4. Ignition at correct time
What you are telling me is that when the engine is warm it will not start, and that you are not getting too much fuel, correct?
Most basic is to verify the quality and freshness of the fuel. “Summer” gas will not start well in the winter, so make sure you have fresh gas.
How strong is your spark? Gap a plug at 0.125 for test purposes, ground against the head and pull the rope checking for spark. This wide gap will show if the ignition system is strong or weak.
If you have good spark, get the rear of the sled up on a stand and squirt two or three squirts of fuel into the carbs. If the engine starts but soon stops, check the fuel system (lines, filters, pump, impulse line, carbs).
If the engine does not start pull the plugs and check the plug tips for traces of fuel. If they are dry, the fuel is not being transferred from the crankcase to the combustion chamber. this means you have low primary compression- worn rings, leaking end seals.
To prove this, squirt some fuel into the plug hole and install plugs. if it starts then stops, time to overhaul the engine. If it doesn’t start, check secondary compression and confirm ignition again.
Hope this gives you something to work on.
December 27, 1997
Dear Ralph,
A friend is turbocharging a ZRT 800 and we might need a bit more fuel from the power jets than what we’re using. What do the numbers on Mikuni jets (main and power) really indicate? Does it have anything to do with hole diameter, flow rate in cc’s over time, or something else? I have access to a machine shop so drill accuracy and hole size aren’t an issue.
Lee Sledjeski
As far as I know, the Mikuni jet numbers are definately an orfice size indicator. With a numbered set of drill bits you could gauge the difference from one size to the next and “make your own” to whatever size you desire. I would recomend that you use a belt sander or something similar to remove the “old” jet size number to avoid any confusion and mark your new jets in a manner so you know what you have.
I can tell you that when it comes to non-Mikuni jets that the sizing is not as accurate as what Mikuni makes. For example, a non-Mikuni jet size 350 may not nesecarrily be 1 size bigger than the Mikuni 340. I’ve seen it where the 350 in question acts more like a 330 Mikuni. The moral of the story here is to stick to genuine (Mikuni or Kehin) jets for general tuning. The Mikuni ones always have the little emblem or insignia stamped on them so you know that they’re the real McCoy.
December 27, 1997
Dear Ralph,
I recently ran a compression test on my ‘97 Powder Extreme and it read 97 pounds per cylinder. Just as I thought that the motor was junk we tested the neighbors ‘97 EXT 600 and his read the same. What gives?
Greg Olespad
How are you checking the compression? If you’re only pulling on the rope once or twice then you’ll get inaccurate low readings like this. You want to keep pulling on the rope until the compression isn’t going any higher. I hold the throttle wide open (easier to pull over, takes less pulls) and pull on the rope at least five times. The compression will usually peak by five pulls, but if it is still going up on the gauge keep pulling. You could do the check with the throttle closed, but it’ll take more pulls to get an accurate reading. It really doesn’t matter if the engine is warm or cold, but if the engine is flooded you will get a lower reading because the fuel washes all of the oil off the cylinders and the rings won’t seal very good. If the engine is fogged, you will get a higher reading because of all of the fogging oil. Next time you do a compression test, see what kind of a reading you get with the throttle closed and only pulling on the rope twice; then hold the throttle wide open and pull on the rope five times. What a difference!
Is 97 pounds of compression low? You bet it is. You really need at least 110 pounds for the engine to run decent, but perhaps more important is that the readings are all within about 10% of each other. We always record compression out of habit to give us an idea of what kind of shape each engine is in as the miles accumulate.
December 27, 1997
Dear Ralph,
I have a slightly used Vmax 700 SX with 120 studs. This is not enough for the kind of riding that I do, nor is enough for the power output of the sled. The studs are placed in Woody’s standard 120 stud layout and I would like to increase to 168. Is there a good source of advice on adding the 48 studs and where to place them?
Brian Howenstine
Wabash, Indiana
Perhaps the best source of advice is to check with what Woody’s recomends? By looking at the latest Woody’s studding template, the 168 stud layout is simply an addition to the 120 stud pattern. Here is the 120 stud pattern, and the 168 stud pattern, as recomended by Woody’s.
December 27, 1997
Dear Ralph,
We seem to be having a problem with our Polaris 500 carbed machine as it bogs down rather often. After he rides for a while it seems to bog down very often. I have had the sled back to the dealer three times now and they’ve been adjusting the clutches, and the last time when I picked the sled up they said that they had adjusted the motor mounts. My son rode it for another 100 miles and he said that it is still bogging as much as it ever did. This son is 15 years old and has been riding since he was 8 years old and does have a fairly good understanding of the machine. My XLT Touring hasn’t had aby problems, and one of my other sons XCR SE has worked fine, but the 500 Carb has us wondering. I would appreciate any ideas or suggestions.
Patrick Maillett
My first reaction would be that the carbs are not synchronized, or the secondary clutch is ending up in too high of a gear ratio for the engine to pull the load, causing the bog. First, verify that the carbs are synchronized, then let’s get into the secondary clutch. Check the belt “ride-in”; the belt should be riding about 1/8″ above the top of the sheave of the secondary clutch. If it is lower than this, you are in “too tall of a gear” that could contribute to the problem. Check the belt deflection, as this could be what the dealer was tryiong to fix by adjusting the motor mounts. Place a straight edge across the top of the belt from one clutch to the other, and measure the amount of “flex” in the belt. The belt should be deflect about 1 1/4″ with 10 pounds of force. It is possible that the secondary could be too loose, allowing an upshift to occur at the wrong time. It would be a good idea to try a different Polaris red secondary spring in hole # 2, as springs do vary and the one in the sled could be weak compared to what it is supposed to be. Then again, it would be wise to verify the gearing in the chaincase – maybe someone has made changes to the gearing in an attempt to get more top end out of the sled before you got hold of it. Verify that the helix is a straight 36 degree, someone may have made changes here in an attempt to get stronger upshifting. It could also be something as simple as the secondary clutch being dirty, and not backshifting like it should. A good dis-assembly and cleaning should eliminate this. If the buttons are significantly worn the clutch would also act like it was in a taller gear.
December 27, 1997
Dear Ralph,
I am looking into purchasing a set of performance pipes for a ‘96 Indy XCR 600 (XLT engine), and I am wondering the main difference between the different types of pipes available. For example, I understand there are both Stockblaster and Modblaster pipes from PSI. What is so different between these? I will be porting my engine and I am looking for the pipes (and any other mods) that will give me more power towards the top end.
Ryan Valin
The difference between the “Stockblaster” and “Modblaster” pipes from PSI is that the Stockblaster pipes are designed to work with a stock engine, one that has not been ported. Each set of pipes is RPM sensitive, and the RPM that a stock engine configuration is going to breath the best and make the most power is very different from the RPM that a ported engine will spin best at. The Modblaster pipes therefore are dimensioned for a higher operating RPM that a ported engine is going to breath better at. In both instances, the pipes are designed to make the most power for the operating RPM of the engine configuration. In the case of these exact pipes from PSI, there is no real difference between the silencing systems used on the pipes. However, on pipes from many aftermarket manufacturers (including PSI) for the newer engines you now are being offered more choices of silencers. Take a look at the “Silencer Science” article in this issue of SnowTech to gain a better understanding of how silencing the exhaust effects power output levels and you may be surprised.
You didn’t mention what you would be using your sled for, but you did mention that you plan on porting the engine. This XLT engine is very solid and reliable when limited to basic bolt-on mods, but porting and big bores tend to greatly reduce the reliability of this particular motor. I do recomend changing the heads, they help quite a bit. As far as changing the airbox or installing cone type filters, I do not suggest it for trail riders with this engine. The increased airflow really makes dialing in the jetting difficult and slight temperature changes really upset the balance here. Beyond pipes, heads, clutching, and gearing there is not much else that I would recomend for trail riding.
December 27, 1997
Dear Ralph,
I have a ‘94 XCR 600 that is pretty much stock except for the ports have been polished and it has a 133.5″ track on it. The problem is that I can run the tach past 10,000 rpm at will on hardpack, at almost any speed. So I installed a set of #10 weights from an Ultra and now the rpms dropped to a steady 8500 (which I figure is where I’m supposed to be) but my bottom end and top end is weak, and the clutches are not shifting all the way out. I ride at an elevation of about 2,000 feet, the gearing is 20/39, I’ve got a white/blue drive clutch spring, yellow Erlandson secondary spring, stock 36 degree helix, and I ride on both trails and fields. How can I get my power back and keep the rpms down?
Evan Empey
The yellow Erlandson secondary spring is a good product, but you’ll need at least 54 gram weights to make it work right and keep the rpms down. The problem is that your engine doesn’t have enough power to pull this combination. I’m not sure as to what the white/blue spring rate is in the drive clutch, so I would try a Polaris almond/yellow that is a longer version of their blue spring. This will bring the engagement up but still allow you to shift out at the right (8500-8700) rpm. Since the ports are polished you can spin it this high. The #10 weights are only 51.5 grams, go up to the #10 ALs that are 53 grams. I would change your gearing to 21/39 (at least, maybe more). Install a silver Polaris secondary spring (in hole #2), a Polaris T1 helix (old Storm helix) and hang on. Your engagement should be 4500-4900, shift out should be 8500-8700, and it should pull harder than any other “stock” XCR you’ve ever ridden.
December 27, 1997
Dear Ralph,
I have a 1997 Polaris Sport with a 440 fan cooled engine. What kind of top speed should I be getting out of it? When I ride it the fastest it will go is about 65 mph. I’m a big guy, about 190 pounds, but I think it should go faster. What kind of mods would help me get even more power and speed out of it?
Paul Brown
Dundas, MN
On the ice we can get an XCF (with the same 440 fan engine) to show 76-77 mph on the speedo. The first place I would start looking would be in the clutching; are the clutches shifting all the way out? Verify all of the basic clutch adjustments such as the alignment & belt deflection. Take apart the secondary and verify that the spring is at position B-2, as some of the ‘97 Sports were set at B-3 which wouldn’t allow the clutches to shift out completely.
Want to go faster? Would you believe that you can drop on a set of 1985 440 cylinders (Polaris part # 3083441) that have a different port height and really make power at 7200 rpm, in comparison to the 6800 rpm that your 440 runs at now. Of course, you’ll have to re-carb and re-clutch the package, but you’ll gain 4-5 hp in the process, and that’s a lot for a fan cooled engine! I know of a few XCFs that are running this set-up that really scream. It’s not the least expensive route, but it works.
December 27, 1997
Dear Ralph,
Will the larger diameter recoil used on many of the ‘97 Ski-Doos retrofit to a ‘96?
Jeff Bottom
Cheyene, Wy
Jeff,
Yes, you could do it, but it would be cost prohibitive. From the looks of the newer engines, you would have to replace the entire recoil housing and mounting, which would be over $500.
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