I posted in the engine forum about sluggish 120 out of the hole. Bob suggested I post here after I have gathered a little info. Purchased last year and used a bit not racing just recreation. Well this is what I have, used 03 AC 120 currently running the 2 shoe 13 tooth clutch, green spring, heavy shoe's in #2 slot, 51 tooth rear with 35 chain. a seeming 392GR and 3200 rpm from what I can gather. I also have a Max torque clutch w/10 tooth, 45 tooth rear gear for 420 chain a seeming 450GR not on the sled not new has been used, I didn't get the chain with it. The issue is out of the hole my 60lb daughter has to bounce on the sled to get it rolling, once rolling the sled goes pretty good. Seems to start fine on choke idle fine off choke and on stand seems to run up fine. Question is should this 392gr set up be fine and look for another problem relating to the lack of torque or make some changes like get a 420 chain and go back to the 450gr or maybe get a 55 tooth gear and light shoes for the 35 chain, keep this set up and get blue springs to lower the rpm?
Post by Jim Donovan on Jan 7, 2011 16:41:18 GMT -5
If the clutch gets you going, it is locked up and doing what it should. If it gave you problems before you got started then we could see what is the problem. I am going to say it is an engine/carburetor problem.
When you say it seems to stall after she gets going and she has to rock the sled to get it to start to react then I would look at fuel filter, carburetor, and maybe the gas tank. It is easy enough to get moisture in the gas tank because the kids will ride it until it runs out of fuel, then you go down to fill it and it is snowing and some snow gets into the tank while you fill it. It doesn't take much to give you fits. I always add some SeaFoam to my gasoline container just so I don't run into these types of problems.
Since the clutch is a two shoe, take a flashlight and take a good look at the shoes. Are they blued? Does the outer edge have a little tinge of blue from heat? You are going to have more slippage with a two shoe, than a three shoe, four shoe, six shoe just because there is fewer pressure points to the drum. Nothing you can do about that but the things you don't want to do is hold the brake and give it gas. Don't ever brake torque the engine you don't gain a damn thing but we sure love you to do it because we get to sell you a new clutch.
I like pictures so if you want to take the clutch off and send me a side view of the shoes as well as one from the bottom looking toward the drum & sprocket it sure saves a 1,000 words. Just e-mail to me at email@example.com Be sure to put a subject in your e-mail because I don't open a lot of things unless I know what they are first.
Post by Jim Donovan on Jan 7, 2011 16:57:35 GMT -5
I reread your question again and if you are not racing with it and you haven't done anything to the engine you are coming in way to high an engaement if you are telling me you are coming in at 3,200rpm. Simple thing to do and not a lot of money in just buy a 13 tooth drum and sprocket for the Max-Torque clutch and put that drum and sprocket in place of the 10 tooth on it right now. This way you have the exact gear ratio and see if it locks up better. The Max-Torque is coming in about a 1,000 rpm lower than the 3,200 number you gave me. If you haven't done anything to the engine, and the govenor is still in it coming in at 3,200 when the engine only goes up to 3,600 to 3,900 you are asking for over heating problem to the clutch.
Thanks for the reply, the 3200rpm number is what I have gathered from the clutch sheets based on spring color not from a tach. Im not sure of the actual engagement RPM. THe only things I know the previous owner did to the sled is, what he called, "The speed gear kit, adjustable main jet, velocity stack and linkage. I have the old governor spring with wire ties on it in a box not in the sled. I have the 420 10 tooth max-torque clutch with 45 tooth rear sprocket, no chain in the box (used). Did these come stock on this or did it come stock with the 2 shoe clutch? and I havent made any changes to the sled since I have owned it and this is the second year of her using it, she doesnt notice and loves it but I do. I just want it righ. It does go, just on initial engagment it seems to just "BLAAAAAAHH" and if she gives it a bounce on the seat while it's going "BLAAAAAHH", track starts to spin, rpms come up and away she goes. As long as she continues rolling, it seems ok, just when it goes from stoppped to motion it struggles. There might actually be a little skipping/slipping to the clutch going on while moving and engaged as well now that I think of it. She has to bounce the preasure off the track to get it spinning and then she is off on her way without any sort off stalling from the motor.
Post by Regan Vehring on Jan 8, 2011 22:25:27 GMT -5
One other thing to think about is the track drivers that drive the track might be skipping. If the drivers drive off the lugs and not the windows of the track they could skip, the main reason that this would happen is if the track tension is to loose. This mainly happens when taking off from a standing start.
Post by Jim Donovan on Jan 10, 2011 8:11:57 GMT -5
Check out what Regan suggested.
The clutches stock on the 120's ( Arctic Cat, Polaris and now replacements on the SkiDoo) are Max-Torque SS1034IKW. The #420 chain would mean you have an Arctic Cat 120 (#420 chain is #41 chain that has been pre-stretched). Polaris uses #40 chain that would have wider sprockets .284 in width versus .227 for the #41/#420.
This site is meant to educate so I always throw in some extra learning material. Buy a #41 sprocket will handle any of the 1/2" pitch chains but if you buy a #40 sprocket then you have to buy #40 chain. All chain with the exception of 219 chain is designated using the 1/8 rule -- the first diget in the chain is substituted for the 1 in the 1/8 and that gives you the pitch -- #35 = 3/8 pitch, the #40, #41 or #420 all put the 4 over the /8 =4/8 =1/2 pitch. The same thing for #50 chain , etc. You guys will be the smartest in the industry before you are done and will know as much as me.
The universal 3/4" gage we all carry around with us to verify the bore of a 3/4" clutch??? a penny is exactly 3/4" .750 -- When they made the Lincoln head penny in 1909 (VDB) wanted everyone to have have a measuring device in their pocket so they could measure a clutch so it was decided the penny would be the universal gage and now you now "the rest of the story".
I noticed the drivers were not set in the middle of the drive shaft and the track was slightly further to the sprocket side of the shaft. The drive shaft bearings sound a little noisy also so I am going to replace the bearings. I suspect I am getting a bit of binding from cog misalignment and bearings. I also notice it sounds like the chain is binding when the clutch gets up to speed and the sled is rolling. Doesnt do this on the stand though so it happens under a load when up to speed. What is the best way to check the clutch gear and drive shaft gear alignment?
Post by Bob Vehring on Jan 10, 2011 9:47:25 GMT -5
Most racers understand what Chassis Blueprinting is. It doesn't matter if its a sled, big or small, a kart, or a car. Anything that is mis-alined, causes fricton and shows up as a HP loss or drag. Sleds are the worst because of the massive track they must turn. You start with the part that is most complex to move, on a big sled usuallt the chaincase. You get this square and true in the chassis, sometimes it takes openning up or oblonging bolt holes. From here you work back to the rear of the sled and up to the engine making sure each part is aligned to the part before it. Regan designed and had made CNC alignment fixtures that are used forn engine and clutch set up. Most of what we do is with belt drive clutches. We sell the fixtures but they are pretty exspensive and meant for race teams. For the guys that will only do this once or twice, you can use small rullers and small L squares, the now somewhat cheap digital levels and lasers also come in handy