Tech Tips (Snowmobiles)
New Tech Line Hours (CST) - Updated July 2008!
| Monday | Tuesday | Wednesday | Thursday | Friday | Sat. and Sun. |
|---|---|---|---|---|---|
| 9am-Noon | 9am-Noon | 9am-Noon | 9am-Noon | 9am-Noon | None |
Valve Springs Tech
Over the past few race seasons, Recreational Motorsports has been approached by concerned racers about the valve springs in their engines being ISR legal,due to the discrepancy in manufacturing valves spring lenght can vary, this is a big problem with Polaris or Robins springs not so much with Arctic Cat, a .001 to .002 amount of dia difference can be seen.Wire diameter sizes sometimes see the same difference. Please keep in mind also that when using a dial calipers 4 different people can get 4 different readings. All the springs that Recreational Motorsports sells are genuine Polaris, Robins and Arctic Cat springs, although we check every spring not to be over legal lenght we can not guarantee they will be up to lenght.
120 Carb Tuning Parts Locations
We made this video to help you locate the tuning parts of your carb.
Finding Top Dead Center
This video was made to educate our customers on how to find top dead center for setting the valves on their 120.
Chain Identification
This RecTec video will help you identify what chain you have when ordering sprockets and clutches.
Hilliard Clutch Installation
Service Bulletin - Polaris Champ Engine
NOTE: This bulletin ONLY involves Polaris champ engines.
PROBLEM:
Rocker stud breakage, occurring mostly on exhaust side rocker arm after 1 hr engine run time.
REASON FOR FAILURE:
1. Lack of oil going to rocker arms at idle.
2. Over tightening rocker stud nut when setting valves.
3. Long periods of idling before race.
4. Harmonics for racing camshaft.
RECOMMENDED REPAIR:
1. Increase oil capacity from 18oz to 19ozs.
2. Run 10w30 wt engine oil NO 0 grade oils.
3. Reduce idle time before race.
4. Because breakage seems to occur after 1hr of run time we recommend changing both rocker stud bolts after every long practice session and after every 2 races, use Polaris part# 3086570 or Robins part# 269-35801-03 rocker stud, both studs are ISR/WPSA legal.
PLEASE NOTE; This is not a major engine problem and has happened to a small number of engines, treat this bulletin as a normal maintenance schedule for Polaris Champ engines.
Thank you.
Speed Tips For The 120's
1. The 120's have very small track drivers which cause an excessive amount of friction on the track drive lugs as the track moves, this causes poor acceleration and top speed. The fix for this problem is to run your track with the least amount of tension possible and lube the hyfax and drive lugs with cooking oil.
We have also found a drive cog alignment problem on the Arctic Cat Z120. The only real way to solve this problem is to remove the drivers and grind them to fit. We do not, however, recommend this because it might void the warranty. The Z120 has another high friction problem, that is the lack of track clips on every window of the track, long runs in limited snow or on ice causes excessive heat on the hyfax from the rubber. We recommend contacting your local dealer and having them install the missing clips.
2. Brake band adjustment is very important, not only for stopping, but also for maximum engine performance. A dragging brake can cause serious hp loss. The easiest way to determine brake band drag is to jack up the rear of your sled and run the engine at full throttle for 30 seconds. Then, shut off the engine and feel the clutch drum, it should be cool to the touch. If you feel any heat at all, re-adjust brake band to eliminate drag.
3. Radar testing has shown us that plastic skis will add over 1 1/2 MPH to the Ski-Doo Mini Z and the Arctic Cat Z120. The Polaris XCR120 comes standard with plastic skis.
4. Many hours of dyno testing has shown us that the use of Energy Release additive in the oil will keep the Suzuki, Honda and Fuji engines running cooler, which gives them max hp and torque even when the engine is heavily heat soaked from high RPM running.
Clutch Heat Tips
Clutch heat can cause performance problems on all centrifugal type drive clutches. There are 3 things that we have found in testing that can cause heat related problems:
1. Brake band drag which we refer to in the below tips.
2. Clutch drum bearing drag. We have found that bushing style clutch drums need to be removed on a regular basis and cleaned to prevent heat. Needle bearing drums like the one used on our RC-1335 clutches have much less coefficient drag which greatly reduces heat and need very little maintenance.
3. Clutch shoe slippage, which is caused by too high of spring tension and can be verified by a chattering sound and/or a jerky feel at engagement. This can be cured by going to a lower tension clutch spring. Dirty shoes can also cause slippage and can be fixed by removing shoes from the clutch and cleaning them with a good grade carb cleaner and drying them with air. Then take a small rat tail file and cut two small groves across the width of the shoe. This will give the normal dust and dirt a place to go giving you a more aggressive clutch.
Remember: 1. No brake drag. 2. Clean and lube drum bearing. 3. Clean and groove shoes = LESS CLUTCH HEAT.
Chain Tension Tips
Chain tension is very important for good speed, all sprockets and drive train have some run out. Rotate your track to find the tightest spot on your chain then adjust the chain to have approx. 1/4 inch of slack.
This will give you the BEST PERFORMANCE.
Rear Sprocket Break In Tips
By taking your rear drive sprocket and wire brushing the edges of the teeth on a wire wheel before installing you reduce chain side friction and have a smoother rolling chain this = MORE SPEED and BETTER TAKE OFF.
Grass Drag Tech Tips
GRASS DRAG WHEEL ALIGNMENT TIP: WE DO A LOT OF TESTING IN THE SUMMER ON OUR LITTLE SLEDS AND HAVE FOUND ONE AREA THAT MOST PEOPLE MISS WHEN SETTING UP FOR RACING AND THAT IS WHEELS ,WE FOUND THAT GETTING A PAIR OF 8 INCH AIR TYPE DOLLIES WHEELS AND MOUNTING THEM DIRECTLY TO THE SPINDLES WORKS THE BEST YOU CAN FIND THESE AT ANY TRACTOR SUPPLY STORE . MOST LITTLE SLEDS HAVE A LOT OF STEERING PLAY THERE FOR THE WHEELS TRY TO TOE OUT WHEN DRIVING CAUSING DARTING AND SCRUB SPEED LAY A 2X4 ON THE GROUND AND ROLL YOUR SLED WHEELS UP AGAINST THE 2X4 WHILE HOLDING THE SLED HAVE SOMEONE ADJUST THE ALIGNMENT PERFECTLY STRAIGHT. THIS WILL GAIN YOU QUICKER ACCELERATION AND MORE TOP SPEED.
Arctic Cat Z120 New Drivers
Have your local ARCTIC CAT dealer order the 2001 drivers for your 2000 sled it will reduce track drag and increase speed.
Polaris Xcr120 Plug Indexing
We have seen a improvement in performance on the Polaris XCR120 when indexing the spark plug , this means removing the plug,marking it where the plug gap is then reinstalling it so the plug gap faces toward the piston you might have to add 1 washer to the plug or try other plugs to achieve this.
Best Kept Speed Secret
There are many things you can do to your track to reduce friction but one of the main areas overlooked is the drivers the problem they have is there diameter it is very small which means their lugs stay in contact with the track lugs a lot longer, which causes the track to heat up and get sticky,causing drag and that causes lose of speed. Heres the tip COOKING OIL go to the local groceries store and by a gallon of cooking oil put it in a garden sprayer or hand spray bottle and spray large amounts of oil on the drivers ,bogie wheels,and track lugs. you will see a big improvement in performance and speed.
Clutch Problems 101
ONE OF THE MOST COMMONLY ASKED QUESTIONS I GET ON OUR TECH LINE IS, WHY WHEN MY SLED TAKES OFF DOES IT SOUND LIKE THE CLUTCH IS RINGING or THE TRACK IS JUMPING COGS. ESPECIALLY AFTER YOU HAVE JUST INSTALLED DIFFERENT GEARS FOR MORE SPEED.
(ANSWER) A CENTRIFUGAL CLUTCH ENGAGES AT A CERTAIN RPM, WHAT THAT RPM WILL BE IS DETERMINED BY WHICH SPRINGS OR SHOES YOU HAVE IN IT AT THE TIME. THE ABOVE PROBLEMS USUALLY OCCUR WHEN YOUR ENGINE DOES NOT HAVE ENOUGH POWER OR (torque) TO ENGAGE THE CLUTCH AND MAKE THE SLED MOVE. HERE ARE JUST A FEW THINGS TO TRY (1) GO TO A LIGHTER TENSION SPRING IN YOUR CLUTCH, (2) MAKE SURE YOU HAVE NO BINDING IN YOUR TRACK AND IT HAS BEEN LUBED ( as per our tech tip) (3) CHECK TO SEE THAT YOUR DRIVE CHAIN ISN’T OUT OF ALIGNMENT OR TO TIGHT (4) CHECK TO SEE THAT YOUR BRAKE BAND ISN’T DRAGGING ON THE CLUTCH DRUM (5) RUN NO HIGHER THEN 87 OCTANE FUEL. OH AND ONE MORE THING THESE LITTLE SLEDS WERE NOT DESIGNED TO HAUL AROUND ADULTS LET THE KIDS DO THE TESTING.
Power Charts For The 120 Engine
PLEASE NOTE THAT THESE RESULTS ARE FROM OUR DYNO TESTING, AND OTHER PEOPLE OR THE FACTORIES MAY GET DIFFERENT RESULTS. ANY QUESTIONS REGARDING THESE RESULTS CALL OUR TECH LINE 319-365-5391.
| Stock XCR 120 | Stock MINI Z 120 | Stock Z120 SnoPro |
|---|---|---|
 |  |  |
| Stock Z120 77.5 jet | Stock Z120 90 jet | |
 |  |
The Answer To The Most Commonly Asked Question
The most common question I get asked on our tech line is how much HP does my sled have? Here is the answer everyone has been waiting for, out of all the engines sent to us for modification we tried to be very fair and pick one of each brand that had close to the same amount of run time and type of use. We then installed our governor spring and pipe, which was set to the same back pressure as the stock pipe. We ran inertia dyno tests on all three of the engines and these are our results. You will also note that there are 3 dyno runs on the Z120 Cat, the only difference is the main jet size. This was done so Z120 owners could compare to the Z120 SnoPro.
Wheel Kit Speed Secrets
MOST PEOPLE DO NOT KNOW THAT THERE IS A RIGHT WAY AND WRONG WAY TO INSTALL A TRACK WHEEL KIT. WHEEL KITS COME WITH ONE OR TWO SETS OF WHEELS DEPENDING ON THE BRAND AND THE INSTRUCTIONS TELL YOU TO MOUNT THEM IN THE HOLES THAT OUR ALREADY IN THE SLIDE RAILS, THIS IS OK IF YOU ARE NOT LOOKING FOR TOP SPEED ON YOUR SLED, BUT IF YOU WANT TO FIND THAT LITTLE EXTRA SPEED ADVANTAGE PROPER WHEEL PLACEMENT IS VERY IMPORTANT. PLEASE REFER TO THE FOLLOWING DIAGRAMS BELOW FOR A BETTER UNDERSTANDING OF WHAT I AM TALKING ABOUT.
Fuels Which Type Is Better
THIS IS A QUESTION THAT WE GET ASKED ALLOT AND WITHOUT GOING INTO GREAT DETAIL I WILL ANSWER IT. IF YOU HAVE A STOCK 120 SLED WITH NO HEAD CHANGES USE 87 OCTANE FUEL, YOU WILL HAVE EASIER STARTING, THE ENGINE WILL IDLE BETTER, AND MAKE MORE HP. IF YOU HAVE A 120 WITH ANY OF OUR HIGH COMPRESSION HEAD MODS USE 92 OCTANE. WE RECOMMEND AMOCO BRAND ONLY BECAUSE THIS FUEL IS MARKETED WITH NO ALCOHOL IN IT. HIGH OCTANE RACE FUEL WILL NOT MAKE MORE HP IN A STOCK ENGINE WE HAVE PROVED THIS MANY TIMES ON THE DYNO.
Gearing Tips For Changing Snow Conditions
We have been getting a large number of phone calls lately from customers asking about gearing for different snow conditions. The following items need to be kept in mind when picking gearing. Under wet snow conditions, which usually occurs during warmer temperatures, the following things happen: warm temperature decreases engine performance even when jetted properly, it also creates more under hood heat which decreases engine performance more yet. So, the proper gearing selection for this condition would be to gear down or put a bigger sprocket on the drive axle, which will allow the engine to have less load placed on it and give it the ability to rev higher, which will let your sled go through heavier snow with less effort. Your top speed will be reduced by a small amount but low end and mid range performance will be increased. This set up works very well for snowcross applications and normal play riding.
Valve Spring Survival Tip
Racers! One of the major governing factors in good engine rpm is valve spring tension. To keep valve springs from fading out and lasting longer, try this tip: At the end of each race day, turn your engine over to top dead center (TDC) on compression stroke this will put your springs in the most relaxed position causing less fatigue and spring sag when sitting over a long period of time.
Rocker Arm Breakage Tip
We have found away to gain some performance and reduce rocker arm breakage. Here's your tip, take the adjusting nut from your rocker and mount it in a lathe or drill press then apply a small amount of valve lapping compound to the end slide your rocker arm over nut like it is in the engine and move it in a rocking motion while spinning nut this will match the arm to the nut and give you some hidden rpm.
Under Hood Heat
The best way to get a good hole shot with your 120 is to warm up your engine 5 to 10 minutes before the start of the race, the reason for this is to let the engine oil have time to thin out causing less oil drag and build good combustion chamber heat to burn the fuel better which means more HP and better throttle response, BUT what most racers don't realize is there is a right way and a wrong way to do this. the right way is to always let your engine idle with the hood up so the air under the hood stays as cool as possible, this will allow the engine to breath cold air until the start of the race, cold air has more oxygen in it than hot air, more oxygen means more combustion heat more combustion heat means more HP more HP means better hole shot.
Valve Clearance 101
I am going to keep this simple, valve clearance can change the performance of your engine heres how.USE THIS TIP ONLY ON STOCK ENGINES: 1) By tighting the clearance on both valves to .003 you will retard your cam timing which will give you better top end performance; and 2) By loosening the clearance on both valves to .007 you will advance your cam timing which will give you better take of or bottom end.
Fast Track Slow Track
Here's a little trick you have probaly seen the fast guys doing at the race track but did not know why, Its called heating up the track. When your 120s track sets on the cold snow it takes a set by raising the track off the ground (ON A STAND)and running it while your warming up your engine you warm the track up making it easier to roll which means less drag, which means less work for the engine, which means a better hole shot off the start, the only thing to remember to do is lube the track with COOKING OIL so you do not heat up the hifax. We tested this tip on our track dyno it is good for a couple tenths of a second in 100 ft that's 1 sled length.
