RXP X won’t start backfires through exhaust

[spx1997]

2008 RXP X 75 hours won’t start and backfires through the exhaust. I just reinstalled the engine after pulling it to diagnose severe smoking issue. It was exhaust valve seals that were leaking. Took the head to a machine shop for new valves, new seals and the head milled. New head gasket, bolts, front and rear oil pump assembly. I also replaced the starter double gear (ring gear) and Bendix Starter because of wear.
Timing, I used the cam and crankshaft locking bolts, marked the timing chain while 3# piston was at TDC. I even checked it again after backfiring and while harder to figure out TDC with the head on the camshaft sprocket lines appear to line up. Replacing the starter double gear (ring gear) requires removal of the stator, I lined up the location pin on the crankshaft end and ring gear but don’t remember if the trigger wheel had one. I do remember placing the cut out on top. I didn’t find a mark on the stator so I positioned the number stamp on the stator between the trigger wheel cut out. Thoughts on what to check?

 

[Greg Moore]

Run a compression test first, either valve timing, valve lash or ignition timing will cause your issue. A compression test will point at or clear valve timing or lash. If valve timing you'll have equal compression across the 3 but either higher or lower than spec. Valve lash (not closing on exhaust) will produce nearly no compression. If these numbers are good then you screwed up ignition timing and will have to pull the PTO housing and re-check the triggers, they will only go on one way..

 

[spx1997]

Compression is 120 +/- 2 pounds across all three. I thought that the valves are hydraulic so there is no lash to set. I read the manual and didn’t notice any ignition timing setting. I’m assuming that is controlled by the stator? I thought it would only go on one way but I didn’t try 180 degrees (upside down.) I don’t think I can check it without pulling the engine again. I read another post talking about the cam position sensor, not even sure how to check that.

 

[68ragtop]

Was thinking you mixed up your coil wires, but hat engine harness fits like a glove. I'm not even sure they would reach the wrong coils. If you want to check (#1=BR/BK, #2=BR/OR, #3=BR/YL) If you have the locking pin in the case to lock the crank & the pin in the head for the cam, the two can't be 180 off from each other. This would give you the correct compression you are seeing, But You could install the cam gear incorrectly with the locking pins in place. There is a pin on the top gear that needs to pass the position sensor in the head at the correct time (+/-) to let the computer know what phase its in. Sounds like your top gear might not be indexed correctly. There are three positions it will install. I'll see if I can dig up a picture.

EDIT: I digress, Looking at one picture would show the gear won't install in other positions. Hold that thought, I might have picts on my PC somewhere.

 

[68ragtop]

Nope, guess you can't install the gear 120 off. My next guess would be you either didn't have the crank locking pin into the detent on the crank, or if you used the TDC method instead of the locking tool. you used the wrong cylinder for TDC.

 

[spx1997]

I had the crank locking pin in place, I also verified 3# piston was at TDC which is the cylinder closest to the front of the ski while the alignment lines lined up as your picture shows. I'm in the process of pulling the engine again with the thought that the Trigger wheel wasn't reinstalled in the correct position. The cut out in it must effect the stator and I'm guess that is causing the problem. Not sure though... I'm open to any ideas

 

[68ragtop]

On my first read, I missed the part where you removed & replaced the flywheel
What parts did you replace & from what year? is the trigger wheel/flywheel from a pre 2006 by chance? or is it the same wheel that was in the engine? also, any chance any of the fingers on the wheel might have got bent?

 

[spx1997]

I replaced the double gear aka ring gear and the bendix starter because of wear, they were both the correct year OEM from Riva racing. The ring gear has a location pin in it so it is installed correctly. I didn't notice any marks on the trigger wheel or stator. With the trigger I placed it with the cut out closest to the top of the engine. I didn’t find a mark on the stator so I positioned the number stamp on the stator between the trigger wheel cut out.

 

[68ragtop]

There's an alignment hole in the trigger wheel that is supposed to line up with the pin that is in the crankshaft gear & passes through the flywheel. If you don't recall seeing it, that's very likely your issue, because the spacing on the 6 bolts are uniform it can be installed wrong. I'll see if I can find an image those would show the indexing of all of this in relation to where you placed it. Provided #3 was still at TDC at that time.

The reason I asked about the year of the parts is because in 2006 the CPS was moved from inside top center of the PTO housing to external and to the side of the housing. When they did this the location of the pin changed. Yours should be on the outside though, 2006 and up. Also, I would not re-use the bolts. They are a one time use torque & final turn stretch bolt. I'm guessing you might now that, but if you re-used them last time, you sure don't want to stretch them 3 times Worth mentioning anyway.