Hey Guys -

A question for the anyone who knows the older Polaris engines. My son's '91 488 fan Indy Trail finally died for the last time (the piston blew apart and scattered aluminum throughout the crankcase).

I recently purchased a 488 motor from a seller who claimed that it ran fine when it was removed. The engine looks great, has nice compression, and would appear to be a great fit. While cleaning it up and getting it ready to install I noticed a few things. First I found a data plate which surprised me - the engine looks identical to our 488 but the plate says it is a 433 CC engine. Here is all the info from the plate: Model EC44-2PM-3100, Displacement 433 CC, Motor # 80-00667.

I believe I read somewhere that the first two number in the motor # indicate the model year. Ouch....it would appear that I "traded up" from a 1991 motor to a 1980 motor.

The engine was owned / worked on by a guy in NH who owned a sled repair shop. Unfortunately this gentleman died at a young age in a tragic snowmobile accident last year. I bought the engine from his wife who knew very little about the work her husband did on the sleds....so I'm in tough shape when it comes to getting any additional info about this engine.

I'm thinking that the original owner used the bottom end of a 433 and the top end of a 488. I've read on this forum (and others) that this is possible. One thing that would definitely clear this up for me - do the cooling fins on the head of a 433 go front to back and the fins on the heads of a 488 go diagonal? My original 488 fins go diagonal and so do the heads on this 433. I thought I've seen pictures of 433 heads that had the fins going front to back??? One other thing that may have enticed the previous owner to go with a 433 bottom end is the fact that it has three oil injection ports. One to each carb (as the 488 does) and then one that goes into the crankcase (possible lubricating the crank directly???).

The second thing that was different (and I think this one is what is preventing it from starting) is the two wiring harnesses leaving the engine were both slightly different on the 433 than on the original 488. The harness for the electrical on the 488 motor was a three wire (yellow, brown, and yellow with a red stripe). The electrical harness on the 433 is a two wire (yellow and brown). When inspecting the 488 harness it would appear that the brown and yellow/red wires are connected together so I thought it would not be a big deal to just use the yellow and brown wires. The lights do go on when I'm pulling it over so that would lead me to believe this assumption was a good one.

The second harness leaving both the motors was the ignition harness. Both engines had a three wire harness (black w/ red, brown w/ yellow, and yellow). The weird part was that the harnesses were the same but the gender of the plugs were the opposite - meaning it is meant to have one male and two female connections at the plug and it had two male and one female. When I went to plug the 433 ignition harness into the 488 CDI coil they would not mate (being the same genders). So I cut my old harness off the 488 and (using butt connectors) mated up the ends so that they could be connected. Now all three wires are connected based on their colors.

We tried to start the sled with the new 433 in it tonight and there is absolutely no spark on either plug.

Lots of questions:

1) Has anyone ever swapped / combined 488 and 433 motors? If so - any outstanding issues?
2) Is anyone familiar with the wiring schematics for both engines? Are they at all compatible?
3) Can I use my volt meter to run any kind of test on the three wire ignition harness?
4) I used my 488 CDI on the 433/488(hybrid)engine (it did not come with carbs or a CDI). Is there an issue with using my 488 CDI on a 433 motor?
5) I used the 488 carbs on the 433/488 motor - issues? I don't think so since the top end seems to be a 488.

Everything seems to bolt together very well - I thought for sure the two engines were compatible.....

I apologize for the long post but I wanted to make sure the details were in front of you.

Any help would be greatly appreciated.

Thanks,

Scott

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I think the actual displacement is 432cc,that motor was made up till 1996 in the polaris supersports and use the same 34mm carbs that the 488 uses. I looked up the part numbers for the CDIs and they are the same for both the 432 and 488 so that should not be a issue.

I think I have a wiring diagram for both sleds,I will try and look into it tommarow.

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Sounds good. Thanks RMK.

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i cant imagine why there would be any issues with compatibility. they are both the same motor, its just the 488 has a bigger bore. (its like putting a 500L/C top end onto a 440L/C or 400L/C crankcase. exactly the same motor, just different size bore-- 67.72mm versus 72mm). yes the old 440 fans had fins going front to back

here in the first pic of the 1985 440 fan, you can see the fins are front-to-back. notice the older motors also have the early P-85 clutch (fully enclosed, instead of the 6-tower-style clutch thats used now) and the fan shroud opening above the carbs. this is what the older 440 fans are like, im not sure if the newer 440 fans (like the 1994-1996 supersports) have the shroud and fins more similar to the 488s or the older 440s



here is a 1997 488 fan, you can see here the fins are diagonal, pointing to the fan shroud opening that exits over the clutch belt gaurd.



as for the electrical issues, if you use all the componets from the 1991 (stator, flywheel, and CDI) you should be just fine because you know those three components are made to function together as a unit. and since the stroke (vertical travel of the piston) is the same between the 432 and the 488 (60mm), the timing of the spark shouldnt be messed up.

however, someone please correct me if im wrong.

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I did some more research for you,

Both engines are timed the same way so I dont see why you couldnt swap the stator/flywheel.

Looking at the 1996 433cc diagram it shows it should have the yellow with red stripe that you mentioned the 488 had,that yellow/red ties into the brown that that comes off your kill switch. The yellow and brown controls your headlights so that is why those light up when pulling it over. I wish I had a 80s diagram that showed the 2 wire,unless you are missing a wire?

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That's a good plan - I'll swap the stator, flywheel, and CDI this weekend. I have not swapped the stators on different engines before....but I know there is some adjustment in the stator mounting (to set the timing). How do I know where to lock it down? Last time I did this to the 488 motor - I marked the stator and the crankcase with a marker and then put it right back in the same position but this time I'm switching engines?

Also - anyone have any thoughts as to the function of the third oil injection line that attaches to crankcase on the 432 lower end? I had guessed that it lubricated the crank directly.....???

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It worked...the beast is back running again.

It bogs at low RPM but runs well at higher RPM. Anyone got thoughts on this? I was thinking that the position I mounted the stator in might be too far advanced? Or do you think it is carburetion?

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Good to hear! There should have been a timing mark on it when you took it apart,just have to make sure its in the same spot when you put it back together. The bog could be from either or,is it a bad bog and how long does it take to clear up when you hit the throttle? Does it idle good on its own?

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