UXV 450i will not start

[nostinkinroads]

I've recently gotten a used 2015 UXV 450i in very good condition. The previous owner said the plug would foul every week or so and would require a cleaning.
It had a celp notification P0410 idle air valve circuit malfunction (previous owner said for some time).
I brought it home, installed new plug, the NGK recommended in the manual, changed the oil and did all service including new battery. Ran great for 3 weeks with no issues.
A few days ago it wouldn't start, still won't start in any gear (brake pedal pressed).
Began troubleshooting...
Strong spark
Nice spray pattern from injector, removed it and watched it spray into a pan while still connected electronically to machine.
Strong compression
No blown fuses
No visible wiring issues (checked every connection visually)
Doesn't even spit or sputter, even starting fluid spray no effect.
If I give it full throttle when I try to start it it does backfire throttle body into airbox.

Has this engine jumped timing? I have no service manual and the nearest Kymco service is 250 miles away.
I'm a better than average mechanic, forever resurrecting peoples old throw away stuff for my own use.
I am hoping I don't have to rebuild this engine since parts seem to be pretty darned hard to find.
couple questions:
How to check timing?
How to clear celp?
Proper valve adjustment specs/method (quite alot of play in the rocker arms)
Identify which module is the idle air valve.

Thanks in advance!

[CROSSBOLT]

I am guessing this will be like all other Kymcos that valve clearance would be .004" for both in and out...

Set at TDC where valve clearance is max.
Do a compression check.
Report here what you find.

Service manual may show at manualslib.com

[nostinkinroads]

I am guessing this will be like all other Kymcos that valve clearance would be .004" for both in and out...

Set at TDC where valve clearance is max.
Do a compression check.
Report here what you find.

Service manual may show at manualslib.com

Couldn't find the service manual at manualslib but I did find one for the MXU 450i which seems to be the same engine.
Valves and compression are within specifications.
No joy, been over everything I can test on this thing today and can't even get a cough out of it.
Solid spark, good fuel pressure and injector action.
Literally can't find anything wrong, which leads me to think once again that it's something simple.
Would love to be able to reset the celp to rid it of the P0410 error but nothing has worked.
Running on a shoestring budget here, at the moment I'm super frustrated and not really wanting to throw a pile of cash at this thing.

[randyo]

Couldn't find the service manual at manualslib but I did find one for the MXU 450i which seems to be the same engine.
Valves and compression are within specifications.
No joy, been over everything I can test on this thing today and can't even get a cough out of it.
Solid spark, good fuel pressure and injector action.
Literally can't find anything wrong, which leads me to think once again that it's something simple.
Would love to be able to reset the celp to rid it of the P0410 error but nothing has worked.
Running on a shoestring budget here, at the moment I'm super frustrated and not really wanting to throw a pile of cash at this thing.

Have you tried simply disconnecting the battery, and reconnecting to reset?

[nostinkinroads]

Have you tried simply disconnecting the battery, and reconnecting to reset?

Yes, as well as disconnecting the display and the ecu and disconnecting and cleaning every connector on the entire machine.
I have it stripped down to the frame at this point for easier access to the veritable smattering of needless electronic foolishness.

[nostinkinroads]

Update:
After tearing the engine down I found that it had jumped time and bent all 4 valves.
Problem was caused by a weak/worn spring in the timing chain guide tensioner assembly that allowed excessive play.

Advice, if you have an older Kymco side by side that is still running buy and install a new timing chain guide tensioner assembly as a preventive maintenance measure, it's an easy external fix and no fluids will be lost.

Will be ordering some parts...will report back.
Any info on a good source for parts that will ship direct would be welcome.

[airshot]

Thanks for letting us know your findings, sorry to hear about your issues, hoping your issues were a rare problem as many of us on this forum have older models, mine is a 2015 model.  So far not a single issue....probably should not have said that !!

[nostinkinroads]

Thanks for letting us know your findings, sorry to hear about your issues, hoping your issues were a rare problem as many of us on this forum have older models, mine is a 2015 model.  So far not a single issue....probably should not have said that !!

Sure thing, I like to be helpful if I can.
I would recommend swapping out the...
"Advice, if you have an older Kymco side by side that is still running buy and install a new timing chain guide tensioner assembly as a preventive maintenance measure, it's an easy external fix and no fluids will be lost."
Comparing my older tensioner to the new one there was a full 1/4 inch of slack being allowed by the old one.

Got the new valves in, installed them and it's up and running again. I'll be reassembling the machine today, still has a code for the stuck Idle Air Control Valve P0410, the old one was in a stuck position almost fully closed, I forced it open just a smidgen so it will stop stalling at idle.
Will be replacing it as soon as I find an cross referenced match from an automotive application that is less than the $103 that Kymco wants.