96 XP backfiring

[txhellraiser]

I'm having hell here with this ski. Put a new trigger and MPEM in and finally got it to fire off. Have rebuilt both carbs. Verified pop off pressure at 38 & 40 psi. LS jets at 1 1/8 turn, HS at 0. Coil OHM's out per specs. Have snipped wires back a little. Ski idles good but starts to backfire with anything more than 1/3-1/2 throttle. What am I missing? Any help would be appreciated. Video below.

 

[mikidymac]

What MPEM did you buy? OEM or aftermarket?

 

[txhellraiser]

What MPEM did you buy? OEM or aftermarket?

OEM.

 

[txhellraiser]

OHM'd out the stator while i was replacing pick up. Its within spec. Rectifier seems to be doing its job also but unplugged red wire off it also, no change.

 

[Austrian Rotax]

Check your rotary valve timing, based on the way its running backfiring like your getting and at those throttle positions is a symptom of RV gear partially stripped and jumped a couple teeth (maybe debris or lack of lube who knows), at least in my little bit of experience.

 

[txhellraiser]

Check your rotary valve timing, based on the way its running backfiring like your getting and at those throttle positions is a symptom of RV gear partially stripped and jumped a couple teeth (maybe debris or lack of lube who knows), at least in my little bit of experience.

Appreciate the advice. I ordered the RV timing wheel today. That was my next idea. After that, was going to pull front cover off and make sure the key is still intact and not slipped.

 

[jts32]

A backfire through the carbs is usually a timing issue. Definitely need to verify RV timing

 

[txhellraiser]

Anybody have any tips on how to do it w/o timing wheel? Mine will take a few days to get here. Know mag cylinder has to be at tdc. Lost after that. I'll pull intake real quick.

 

[txhellraiser]

Cover and mag side at TDC.

 

[txhellraiser]

PTO side at TDC

 

[txhellraiser]

After doing a little digging, it appear the RV Plate needs to be flipped. From what info I'm seeing, the plate needs to be set at 146.5. The plate appears to be at 90-100 degrees. Can anyone confirm what I'm seeing?

 

[txhellraiser]

After doing a little digging, it appear the RV Plate needs to be flipped. From what info I'm seeing, the plate needs to be set at 146.5. The plate appears to be at 90-100 degrees. Can anyone confirm what I'm seeing?

Nevermind. I head my head up my arse. Used my front camera on previous images. Below is the "correct" RV image with mag/flywheel side at TDC.

 

[txhellraiser]

Timing tool game in. RV was in the correct spot to begin with. Any other ideas?

 

[mikidymac]

The 1996 XP's are know to have a bad pickup coil mounting bracket in the MAG cover. I would pull the front cover and check the timing pickup.

 

[txhellraiser]

Brand new. Not saying it cant be bad but it ohms to spec