Ask The Editors: A Tricky Engine Swap
Blame it on the cam?
It starts and runs but stalls after a minute or if given throttle. He is trying to convenience me the cam needs to be changed because the timing is different. I HAVE SEARCHED PART NUMBERS AND BELIEVE THE CAMS ARE THE SAME.
It seems to me the difference is the cam gear to compensate for mechanical timing vs electrical timing. Changing the whole cam won’t do a thing. Can’t swap the pickup coil, its fixed. The flywheels are the same part number – so the only difference has to be the cam gear. I also saw on Youtube where a stall issue turned out to be the cd box after a certain rpm.
If we’re not mistaken, Polaris moved away from the 500cc engine for model year 2014, instead offering the Sportsman in 400, 550 and 570cc packages (then of course 850 and 1000 for the big bores).
As we can’t be sure which engine you actually swapped to, we’re forced to keep the info in this answer fairly generic.
If indeed the cam OEM part numbers match up between the two models in question, then you’d be correct in this instance: They’d be interchangeable. In which case, you’re right, swapping the camshaft would do nothing.
Where your question gets a little fuzzy is that it’s not clear how thorough of a swap you performed. Are you attempting to use the 2009 cam inside the 2014 engine? If you brought over the 2014 engine and transmission wholesale, the problem most certainly is one of ignition incompatibility with the 2009 electronics.
We’re going to assume the latter is the situation, in which case the best course of action would be to run the CDI box, voltage regulator and ignition coil from the 2014 model. It doesn’t sound like a cam issue to us so much as an ignition one. Especially given that you’re playing mix ‘n match.
This would absolutely be our first move. If this doesn’t do the trick, process of elimination would force us to consider that cam gear. We can’t be positive (as again, we don’t know what 2014 engine you’re working with) but if those numbers don’t match up in the OEM parts catalog, and the complete 2014 electronics don’t cure the problem, swapping to the 2014 cam gear would be the right move.
Always remember this – when there is timing trouble at the cam itself, you will typically experience knocking, backfires and immediate shut down, if it’ll even start at all. Ignition timing is usually the harder to diagnose because it can run right until suddenly, it doesn’t.
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