A few upgrades for the polaris 120

Mar 13, 2019
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yup.

@Reeb find yourself a mild cam. I put in this one. http://www.nrracing.com/product-p/dynomod2.htm?1=1&CartID=0

From what I saw today this would be my recommendation for a GREAT back yard engine build:

upgrade carb with intake
upgrade valve springs to 22lbs
upgrade cam
remove governor

I only ran the engine for about 20 minutes and I haven't had it on the snow yet but I can tell you it revs WAY higher (couldn't get my tach working) and is WAY smoother and there is almost zero backfiring like the stock unit. And it is snappy. Like REALLY snappy. Should be fun. ? Not sure if I will put all the race parts in the other sled or wait til next season...


I also added a pair of 3 amp charging coils. The stock princess auto unit is only about an amp it wasn't cutting it. Got about 30 volts out of them so I am also adding a dc-dc regulator. pic to follow.
 
Mar 13, 2019
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dang it bugs me I can't edit old posts....

Here are the charging coils. Pretty basic. I will have the lead go into the DC-DC converter (silver box) with the output from that going into a diode to prevent back feeding from the battery before it goes to the fuse block. It should work great. FYI I was getting a full day of riding with the hand warmers on high. I do need to track down warmers for the throttles.



 
Mar 13, 2019
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So our little crash did more damage then I thought. Cracked the fly wheel. Kinda scary. Glad I found it before we hit the snow again. New one is on it's way. I suspect a casting flaw as well but the ign coil did hit the fly wheel too. I will make sure and torque all coils to spec and have lock tight on them as well.

Make sure you lap your flywheel and torque to spec, 55ft-lbs Use a rope in the sparkplug hole to prevent the engine from turning to reach spec.





The good news is skis are on there way and improvements have been made to the bulk head and running boards.

For reference, the 208 pro point runs a 1.180" crankshaft and a .716" wrist pin in standard length of 3.308"



I also got the charging figured out. I added those dual three amp charging coils but you have to add diodes to each coil to prevent back charging... I also added a diode to the output of the DC-DC regulator. Everything is working nicely. The fly wheel has me a bit freaked out so I added some belting to the top of the shroud. I did some testing with high velocity projectiles and was happy with the results.

 
Mar 13, 2019
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so Kimpex screwed up and sent me two PAIRs of mini skis. I had only bought one pair to replace the broken skis from the crash. They didn't send out the install kits.

They look significantly better then the OEM skis.... Might have to keep both sets. Damn these minis are $$$$$$$$

I am def considering modding the keels on the bottom to match the rec supply race modifications.



 
Mar 13, 2019
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Well the lights aren't working again. Not sure if it's the charge coil or the DC-DC or what. Might be time to say forget it on the charging system and just go with charging the battery after the rides. PITA .

Got the wear bars made for the new skis as well. A little time with the welder and grinder and I have two sets made for a couple bux each. Hope to have the install kit here this weak. I think I have enough parts to make one kit except for the rubber.

oh, and Jack got a early birthday present:

 
Mar 13, 2019
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Nothing worse then waiting on parts. New flywheel still not here and dealer that I bought the skis from has gone MIA and no install kits for them. We have races on the 22nd. Hope they get some seat time before then.... Not sure who is more frustrated, me or the kids! haha

pictures just cuz.







 
Mar 13, 2019
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HOLY MOLY. Geared the XCR down to 2.5:1 It hauls A$$ seriously fast. 6800rpm max. It's going to be fun.

Also got the skis on, they sure did feel "heavy" but with a kid on the sled no one complained.

Picked up a pair of used Powermad Star handguards with a polaris mount. I hope they really cut down the wind on the little ones hands. I didn't like the width of the pro tapers for the kids so ordered a set of Moose Mini bars.



 
Mar 13, 2019
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Well, I am going to have to do something about the steering. After an hour out today Jack is complaining his arms are sore and the sled is hard to turn. Might be the angle of the handle bars too. Handguards worked great. Just need some fresh snow, it's pretty bumpy out there.

I can never get him to do the cool stuff for the camera...

 

Reeb

Modding mini's
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The Rec motors mod helped to the skis. Doesn't take long and while I didn't notice a difference, my then 12yo said it helped. My 7yo doesn't care, he rides till he damn near falls off the sled from being so tired. My 3yo literally tries to make deals with me to sleep on his Kitty Cat. Crazy kids....
 
Mar 13, 2019
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I did the front part of the keel but I will do the back as well. I think my runners were too long so I cut those back as well. I put the old skis back on today and it turns easy. BUT, I think a bigger problem was/is the spindles are not perpendicular to the ground. I am not sure if he bent them yesterday doing jumps or if they were bent before and I just never noticed. The skis almost looked like a kid wearing skates that weren't tied up tight enough. Could be sloppy bushings too. I think I am going to make the top arm adjustable just cuz. I thought about widening the suspension but I really don't think it's needed for the riding we do. The sled is 20 years old and been in a crash or too so I am not surprised something bent... Didn't get a picture as sleds are in different shops.

I did put them on the Indy and they turn fine on the cement. (they didn't on the XCR) And as you can see the spindle is straight up and down and ski is level side to side.



I also started on the steering adapter to go to a proper riser and the pro taper bars. It should be sweet

 
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Mar 13, 2019
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getting closer. Engine tune up tomorrow morning and some electrical work then off on holidays! Coming back a day earlier to get sleds ready for the drags. The things we do for our kids ( I love it)




 
Mar 13, 2019
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And he's rolling. Beautiful day today but really showed the weaknesses of the the clutches. -1* C and the snow is sticky. One foot rise and the Indy bogs out and won't spin the track. Black soot out the exhaust from running so rich. These are a -10 C or colder machines. Jack loves the pro taper bars and the skis. Emma digs the handguards too. I am going to talk with Rec Motors about clutch options for next year. Not sure if a $200 clutch will help VS the $45 rotor tiller max torques we are using now. hahaha Off to the drags this afternoon!




 
Mar 13, 2019
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2nd and 3rd place behind a ZR200 It looks like you either go fast or have power and good hole shot and lose top end. Sent emails off to MAx torque to see about upgrading over their SS clutches we have now. Might try the Draggin Skin for a higher engagement RPM. I think we are losing power on the lower end when it's warm with the engines... I think the draggin skin are a cartridge style clutch that lets you change springs and perform maintenance on them without removing the drum and sprocket.

Sorry for the poor video.

 
Mar 13, 2019
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Just a quick update. I am trying to keep this thread going because I find 120 info so hard to find all in one spot.

DC-DC converter blew, again!. No idea what I am going to do there.

Jim Donovan of Max-Torque sent me some great info and I am going to try and tune up the SS clutch. He doesn't recommend the Draggin for snowmobiles.

His recommendation is to use their wedge shoe and their light weight shoe (three of each ) with a black spring. With the wedge shoe going over the cut out hole in the drive plate. So go light/ heavy; light/heavy; light/heavy. Interestingly each clutch I am using had a set of each in it. So it will be easy to mix and match the two sets.

hhhmmmm Wonder why we where having trouble with the XCR. Spring is POOCHED.

 
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Reeb

Modding mini's
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Keep it up! I have to go through this thread with a comb soon but so far I haven’t had a chance to swap engines. I’m thinking of trying to run extra dummy drivers because it feels like it ratchets off the line. There’s no wear on the 200 drivers to indicate its ratcheting so I don’t know.
I’ll have to add the clutch onto my list.

Thanks for the great thread!


Sent from my iPhone using Tapatalk
 
Mar 13, 2019
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clutching! It's all about CLUTCHING!! hahaha These little rototiller clutches rock.

Sooo After many emails back and forth with Mr. Donovan, here is what I have come up with:

Chain maintenance is key. I melted up a pot of 30W oil and some paraffin wax and let these chains soak for 3 hours. My plan is to have two sets of chains for the gearing we eventually go with (trails and the pow) for each sled. I think this is key on snowmobiles. These chains get wet and cold and are treated different then on a kart.

If you are interested go read this: http://www.maxtorque.com/chain.php

This is what the goop looks like cold, it's reusable so make sure you clean your chains well first.



Watch out for max-torque rip off clutches. They are not hardened and well suck. Both these gears have the same amount of time on them. Check out the crap bushing too.



I went with wedge and light shoes. I actually cut the wedge shoes in half and placed the light shoes (full length) over the openings. I ended up cutting 4 loops off the spring. I didn't get a picture as it was a bear to put together and I forgot to get a picture before I did. I still don't have the black springs but will install those when they get here.

check out these two great links for clutch modification and assembly:







We haven't had a snow test yet but I geared down the XCR to 2.2:1 and pinned it on my garage floor, and well.... It's a beast. Those carbides grooved the concrete and lifted the front end. I am extremely pleased. They wouldn't move themselves on the concrete before.

 
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Mar 13, 2019
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-10C today. The engines pull so much better in the cold! Jack turned 6 this morning and we went for a dig.

Looks like the XCR will be geared at 18/36 for 2:1 and the Indy will be at 13/28 for 2.2:1 This should be good for ripping in the yard/field/moderate snow. Had the XCR down to 1.55 :1 and it hauls on the hard packed. Too fast.

Looking for Switchback assault stickers for the indy. hahaha Kids are funny.
 
Mar 13, 2019
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opened up the XCR to install a billet connecting rod. Glad I did. The old one is completely pooched. Piston skirt isn't great either. Everything else looks OK.

These pro point 208 engines are a Ducar engine. Takes a 70mm piston. New one is on its way with new rings.





Here is the new con rod cap. Has a bearing and better oiling. I will need to polish the crank before install.

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Mar 13, 2019
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Still waiting on new rings and piston... but hey, that gives me time to polish and blue print my crank and mate it to the ARC billet connecting rod. Snow is still Ok here and I hope we get one more shot before it melts away!



only real upgrades we want to do before we put the sleds away for the season is to install stiffer foam in the seat on both of them. The stuff I used is pretty soft (it was the egg carton style??) and we need to go to a higher density foam. I also need to get the C&A skis on the XCR. I had the trailing arms on the press today and straightened everything out. Gained about 3/4" of camber and spindles now sit straight up and down. I also have an adj RTS for the Indy on the way. Should help alot.

Next year both sled will get new adj front shocks.
 
Mar 13, 2019
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Still no parts for the XCR. I will probably track down more spares over the summer so that we don't get into a no riding situation next winter.

The indy is working great and is now fast enough that my youngest is learning GOOD throttle control. It did 32 mph on the GPS today and the clutch is working great. New rear shock still not here. I hope it takes some of the bounce out of the ride. Will be nice to dial in the stiffness.




 
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