488 fan vs. 433 fan - compatible ??? - Snowmobile Forum: Your #1 Snowmobile Forum

Phillips_ME · 11-02-2009, 08:04 PM

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 guy 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.

What was this engined called? 440 fan? 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 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 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 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 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 motor - issues?

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

Any help would be greatly appreciated.

Thanks,

Scott

Phillips_ME · 11-02-2009, 08:48 PM

It gets even more weird.....from further research tonight it would appear that a "standard" 440 fan had cooling fins going front to back. The top end of this 433 engine (cylinder heads) look identical to the original 488 with cooling fins going diagonal.

Can you use the top end of a 488 (jugs, pistons, and heads) on the bottom end of a 433?

**RJ Gleason** · 11-03-2009, 11:18 AM

Quote:

Originally Posted by Phillips_ME

Can you use the top end of a 488 (jugs, pistons, and heads) on the bottom end of a 433?

The bore is the same, but the Stroke is different, so, No you can not swap them over.

Phillips_ME · 11-03-2009, 07:25 PM

I've done a bunch of research tonight on three different forums - everything I've read tells me that the 433 fan and the 488 fan have identical bottom ends (using the same crank i.e. the same stroke). Many people have mentioned that they are using 488 top end and bolting it directly on a 433 bottom end since it is cheaper and easier to find the parts (and it gives them 56 more CCs). They are saying the only difference between the 433 and the 488 is the bore size.

RJ - Am I reading your post wrong or am I misunderstanding what I'm reading on the other forums???

Thanks,

Scott

**RJ Gleason** · 11-04-2009, 06:47 AM

Unless I read my book wrong, the bore is the same (60mm) and the stroke is different (78mm vs 72mm).

jamesu9165 · 11-14-2009, 07:49 PM

if the connector from the motor to the sled is connected it should start (but not shut off as polaris uses open to run (or atleast the older ones do)). make sure that both plugs are grounded when you check for spark, in my 94 488fan the left plug will not fire unless the right is connected. as far as bore vs stroke i dont have my book here to see what they should be. clymer makes a real good manual for those sleds and i used the wiring diagrams many times as that 94 motor is the donor engine in my 85 indy trail which came stock with 440, wiring didnt take much to change tho