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470 Rotax issues

470 Mx formula skidoo carb

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#1 matthewharrison2011

matthewharrison2011

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Posted 01 March 2021 - 12:30 AM

Hey guys, for starters I’m sorry about the long post, just want to include as much info as I can.

I have a 95 MX 470 I picked up, hasn’t been running since a couple years & I haven’t had it running right yet.

When I pulled it home I got it running to find it was only running on 1 cylinder. Found little to no compression on PTO side. Pulled top end apart & found the PTO side had leaned out and burnt out the piston, but the cylinder was still good. Replaced piston, new rings for both, and honed cylinders. Also installed both outer crank seals.

Pulled carbs apart to clean & found clip off needle on the PTO side. Fixed that up & cleaned the carbs which got me running on 2 cylinders. Now that it was finally running I took it for a run. It worked, but not exceptional. Often hard to start after shutting down & very boggy on initial startup. Noticed lots of oily residue coming out of exhaust right onto the ground, and I do mean lots. Also a LOT of blue smoke, makes sense with the oil coming out of the exhaust. Since the kit I got included rotary valve seals, I decided to do them.

Immediately after doing rotary valve seals the sled started up a lot easier, no more oily residue, didn’t smoke real bad anymore, and it ran a little better, but bogged out like it was starving for fuel after full throttle for approx 10-20 seconds.

I decided to go after fuel next. Swapped fuel pumps with a USED one that I had here, still acted the same. Inspected all the fuel lines, cut the ends off that were stretched from the nipples & reinstalled. Pulled filter out of tank, check valve seems to work, cleaned & reinstalled. Got new hose and replaced pulse line, used hose clamps to make sure it was tight.

After clipping fuel lines & replacing pulse line it ran a lot better, still had full throttle issue but not as bad, started pulsating slowly rather than completely dying out on me.

Next day I was trying to figure out the full throttle issue & everything started going backwards again. Very hard to start sometimes, a small amount of oily residue out of Y-pipe, and not running like it did before. I decided since I had an extra oil pump I might swap that out, took everything apart to find that the pump I had wouldn’t work as it was opposite orientation. While I had the rotary cover off I noticed a small amount of oil near the carbs & directly below the rotary valve shaft. Now I’m wondering if the seal I installed failed, I did have a bit of trouble getting it all back together. Is it normal to see oil here? It was a pretty small amount, but didn’t seem right to me.

It now bogs really hard after startup for about a minute before it clears up. I’ve also noticed that the fuel seems like it’s disappearing faster than it should out of the tank, so I’m wondering if I have a potential fuel pump problem. Could be needle & seat too I suppose. It has a fuel shutoff that I do shutoff every night or after use.

I should mention that when I did the MAG side seal I noticed that the stator had some bubbling on that plastic as well, as if it got hot. I do plan to replace this, just don’t have the parts at hand yet,

Just hoping someone has some insight or ideas to help get me back on some sort of track as I feel like I’m all over the place right now.

Any help is appreciated!

#2 David H

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Posted 01 March 2021 - 09:51 AM

I'll be watching this.  Been working on mine for 2 years.  Think I've done everything but the stator.


David H
Excelsior, MN
 






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