Ski-Doo Snowmobiles Forum banner
1 - 14 of 14 Posts

·
Registered
Joined
·
36 Posts
Discussion Starter · #1 ·
I was just wondering if someone could help explain how power jets work.
Also My seal between the drive shaft and chain case is leaking, can I replace the seal threw the chain
case or do I have to remove the skid and drive shaft to get to the seal/bearing? Any help would be
great.
 

·
Registered
Joined
·
1,433 Posts
I am pretty sure that seal only comes out the back side of the chain case. That is what I found out when I dropped my skid to swap out tracks last winter. The biggest PITA with this was getting the 4 skid bolts to line up with the holes in the tunnel.

A powerjet supplies raw fuel to the engine based on a few things like air temp, throttle position, and maybe pipe temp I think. You add your main jet size to your PJ size and that is your fattest jetting your sled can have. So 100 PJ and a 220 MJ would be like running a normal non PJ carb with 320 mains.
 

·
Registered
Joined
·
815 Posts
The PJ is essentially a fuel injector (electronically controlled solenoid) working in conjunction with the carburetor. The ECM computes a logic output that controls the fuel delivery of the PJ which compensates for changes read by the acting sensors.
For a REV: loosen the track tension (it's easier with the skid out too), speedo housing (nuts on casing behind secondary), remove brake caliper and chaincase (loosen chain tension first), replace seal and put it back together. I put some thick grease like marine grease or bearing grease on the seal to help keep the seal tight and slide in easier with less chance of damage.
Pay attention to the spacers on the gears and behind the chaincase bolts. They are critical to proper alignment. And be mindful of the drive shaft location when reinstalling the chaincase as it could damage the new seal.
 

·
Registered
Joined
·
10 Posts
The PJ is essentially a fuel injector (electronically controlled solenoid) working in conjunction with the carburetor. The ECM computes a logic output that controls the fuel delivery of the PJ which compensates for changes read by the acting sensors.
For a REV: loosen the track tension (it's easier with the skid out too), speedo housing (nuts on casing behind secondary), remove brake caliper and chaincase (loosen chain tension first), replace seal and put it back together. I put some thick grease like marine grease or bearing grease on the seal to help keep the seal tight and slide in easier with less chance of damage.
Pay attention to the spacers on the gears and behind the chaincase bolts. They are critical to proper alignment. And be mindful of the drive shaft location when reinstalling the chaincase as it could damage the new seal.
so when you trail convert, the thread says to run a 300mj, would you run a 100pj and a 200mj=300
or 100pj and 300mj?
 

·
Registered
Joined
·
450 Posts
Read the last sentence in my post. with a PJ I'd run at least 310's. 210+100PJ
Looking for clarification on this thread as it doesnt sound right to me. Just picked up a 2011 RS and converting to trail setup. I have been told to use 300s for mains as I have also found when searching this forum. The answers in this thread completely contradict that. Sled currently have Power Jet still in use.

Picked up some 300 mains to install but this thread explains that maybe I should have picked up 200 mains to install since I have PJ?
 

·
Registered
Joined
·
4,478 Posts
Not an expert here, but I think the advise to run 300 mains is proper, and safe. With relation to fuel quality and octane, you may be able to drop main jet sizes down to 260, with an octane blend of say 98. But if you run pump 92(lowest you should really go), stay around 290 -300 with the power jet system intact. I run 290 on my '10 and am very satisfied with plug reads, etc. If you plug pj, 360-380 mains. This is for trail riding, btw. YMMV.
 

·
Registered
Joined
·
698 Posts
Not an expert here, but I think the advise to run 300 mains is proper, and safe. With relation to fuel quality and octane, you may be able to drop main jet sizes down to 260, with an octane blend of say 98. But if you run pump 92(lowest you should really go), stay around 290 -300 with the power jet system intact. I run 290 on my '10 and am very satisfied with plug reads, etc. If you plug pj, 360-380 mains. This is for trail riding, btw. YMMV.
This info sounds correct, running 300's in my '09 & was told to set my '11 up the same.

BTW, I ran 260's running 50/50 race fuel, 36:1, and hot start connected for a snocross race at mid 40's for temps so I would be leary of dropping to 200's for trail riding.

I could be wrong.... Wouldn't be the first time :)
 

·
Super Moderator
Joined
·
3,632 Posts
Nope, not even close to fuel injection, more like a valve. There is no pressure, no rail, no mist from an injector. It is simply a power jet, a jet controlled by power, not by vacuum, flow, pressure or anything else, but by power.

It gets it's power from the ECM. The ECM monitors TPS, engine coolant temperature, exhaust temperature, air box temperature, crank position and decides on how much to open the PJ, and when, using the data and built in fuel maps.

It adds to the main, so fully open a 100PJ would add to a 300MJ and give you very close to a 400MJ uncorrected.

It does no more, no less, and is not fuel injection.

It means you don't have to change jetting for a change in ambient air temperature. Barometric temperature correction is not in the 2011 and earlier models of the RS.

The PJ is essentially a fuel injector (electronically controlled solenoid) working in conjunction with the carburetor. The ECM computes a logic output that controls the fuel delivery of the PJ which compensates for changes read by the acting sensors.
For a REV: loosen the track tension (it's easier with the skid out too), speedo housing (nuts on casing behind secondary), remove brake caliper and chaincase (loosen chain tension first), replace seal and put it back together. I put some thick grease like marine grease or bearing grease on the seal to help keep the seal tight and slide in easier with less chance of damage.
Pay attention to the spacers on the gears and behind the chaincase bolts. They are critical to proper alignment. And be mindful of the drive shaft location when reinstalling the chaincase as it could damage the new seal.
 

·
Registered
Joined
·
15 Posts
Nope, not even close to fuel injection, more like a valve. There is no pressure, no rail, no mist from an injector. It is simply a power jet, a jet controlled by power, not by vacuum, flow, pressure or anything else, but by power.

It gets it's power from the ECM. The ECM monitors TPS, engine coolant temperature, exhaust temperature, air box temperature, crank position and decides on how much to open the PJ, and when, using the data and built in fuel maps.

It adds to the main, so fully open a 100PJ would add to a 300MJ and give you very close to a 400MJ uncorrected.

It does no more, no less, and is not fuel injection.

It means you don't have to change jetting for a change in ambient air temperature. Barometric temperature correction is not in the 2011 and earlier models of the RS.
 

·
Registered
Joined
·
15 Posts
Mark, I am looking at a 2010 with the powerjet unhooked with 370 mains. I am a little leary not knowing much about the powerjet. Your post definatly put some questions to rest but leaves me with a few. The guy has the sled jetted to run perfect at -10-0 which i would assume is to stay on the safe side. My question is: without the powerjet how big of temprature swings will the sled run right without rejetting? Is it a costly fix to replace the powerjets? He says everything is still there to hook them back up but doesnt dare because he suspects powerjet failure is the reason for recent blown motor. He did say his plug on the side of the cylinder that melted down was much lighter in shade. He also said that the compression was like 160 and questioned that and for good measure got new stock domes and brought compression down to 135ish but he did this after the blow up. I just wanted your thoughts on this and any help would be greatly appreciated!
 

·
Super Moderator
Joined
·
3,632 Posts
PJ is a very simple circuit, very trouble free for the most part. Stock compression for a 2010 was about #145. If you are doing a trail conversion, look in the FAQ, all the details are there. Without the PJ system, you are like any Polaris or Arctic-Cat, no temperature compensation. Grab a RAD gauge, or a Mikuni slide rule and tune from there. PJ is the way to go. No PJ, assuming with 370's safe at 0 degrees, you will need 330 at +60, and 420's at -60 degrees. Changing depends on you. How important is optimum gas mileage or performance? How aggressive is the clutching or studding? How much do you weigh, how do you ride, where do you ride, what is the elevation? What fuel, what belt? You get the idea.
 

·
Registered
Joined
·
1,433 Posts
for the record the MJ sizes i was stating were for 440's, OP had a 440 at the time of the thread. 600RS riders disregard.
 

·
Registered
Joined
·
7,764 Posts
some guys ran 350-360 mains with a 0 power jet on the 08's and 09's
 
1 - 14 of 14 Posts
Top