2011 Kymco UXV 500 -Replaced Camshaft now it wont fire and wont lose Compression

[CThacker]

Looking for some help here.  We recently replaced the exhaust Camshaft due to a broken decompression cam.  We were pretty sure the linkage on the intake cam did not move so the Piston should be exact where we need it.  However when trying to start back up the cams roll over once but then it stops.  Almost like there is too much compression and it is not relieving through the exhaust. 
It has a new starter, spark plug is good, starting fluid doesn't help, Both cams are at TDC.
We even tried removing the exhaust pipe and no change.  When the Spark plug is removed it turns over just fine and never stops as all the pressure is exhausting through the spark plug hole.

Only thing we can think of now is maybe we slipped the chain on the intake Cam gear and didn't notice so now the Piston is NOT at TDC when the Cam shafts ARE at TDC.  I know to check this we need to open the Crank Case up and look at the flywheel.  Can anybody help on the location of this?   Or are there any better ideas?  My buddy has rebuilt machines more complicated than this and is an Ex mechanic and even he is stumped.....

[300winchester]

I'll try
to find the compression stroke line up timing mark of flywheel with mark on stator case, take out little plug to see.  Yours might have a T,  mine just has a dash,  while rotating exhaust valves will open and close, then  intake valves will open and close,  now watch for that timing mark to appear and line up.  The cam lobes must be down to do valve lash.  .004 both intake and exhaust, cold
also if you dont have the valve cover off and you still cant figure it out there are 2 hash marks on the sprocket side of the camshaft. i had to pull up a little plastic round piece to see,  both those hash marks must be horizontal to the case.  are you turning over by 19mm socket on side of stator cover ?  sounds like a valve is coming in contact with the piston ?  do you have an online service manual ?  when you put chain back on sprocket did you make sure the timing mark was aligned and the hask marks were horizontal ?  hope this helps a little
https://www.azmotors.fr/eclates/MANUEL/PIECES_KYMCO/UXV_700I_SPORT-manuel-atelier.pdf
or
https://www.manualslib.com/products/Kymco-Uxv-700i-9870419.html

[300winchester]

https://www.azmotors.fr/eclates/MANUEL/PIECES_KYMCO/UXV_700I_SPORT-manuel-atelier.pdf

try pages 110 - 119   if dual overhead cam

Piston must be at TDC to set cams

[300winchester]

My first reply was for a UXV 700i single cam, this has the hashmarks at the sprocket side of the camshaft, to see take off cover and pop up that little end cap, 2 hash marks must be horizontal with TDC piston at compression stroke,  the 700i has a dash on the flywheel

For Dual cam,  then line up compression TDC piston and make sure the dots are TDC for both camshafts,  then make adjustments.  I think for the 500i there is a T on the flywheel, if so , use the T , with inspection plug out line up with stator cover mark with T on flywheel.  Also I took out cam chain tensioner prior to removing sprocket and cam chain. Theres an inspection plup on stator cover about 1" diameter for lining up flywheel to cover marks.

If you have to take off side stator cover for any reason do NOT turn over engine, the starter reduction gear uses the stator cover as pin for the reduction starter gear.

always turn over first by hand to avoid bending valves etc if not adjusted correctly.

when did the no sparks start ?

thanks and wish you all the luck

MGM 

[300winchester]

does your stator cover look like this

see that little plug to the left of the oil fill plug

this is the timing flywheel inspection plug

[300winchester]

does your stator cover look like this

see that little plug to the left of the oil fill plug

this is the timing flywheel inspection plug

way left with screwdriver slot in it

[CROSSBOLT]

does your stator cover look like this

see that little plug to the left of the oil fill plug

this is the timing flywheel inspection plug

way left with screwdriver slot in it

See? I told ya! You are NOW the go to guy on UXV 700i machines!

[CThacker]

Hey Guys, 
Sorry for the Delay in responding Work has been crazy busy. 
Yea we are able to manually bar the machine over from the nut where the recoil starter cover is, and we found the T and F mark on my 500.   Unfortunately, it still does not want to fire off.  It almost seems that there are not enough amps to crank the machine over and allow the compression to exhaust out (We even tried a Deep Cycle with 600 CCA).   We marked the chain originally and realigned TDC for both Cam Shafts and the Piston with the T mark on the flywheel.  With the spark plug out it purrs Beautifully so we are super confused of what else it may be that is stopping the exhaust of the compression from coming out.

It does not seem that the valves are misaligned, and my buddy is now thinking that there may be something more internal going on Cylinder or Crank damage???...  We might just go ahead and take the Cylinder head apart and inspect the piston etc.....

Here is the manual we have been referencing.
https://www.manualslib.com/manual/2032784/Kymco-Uxv500i.html?page=112#manual

Any other suggestions would be appreciated.  Thanks Guys!!!

[300winchester]

Were you on the compression stroke ? , 2 revolutions to the flywheel equal 4 strokes of the piston.
Did you hold your finger over spark plug hole ? to make sure your on compression.    wonder if that new exhaust camshaft you put in not working,
Have you turned over with spark plug out to make sure spark is good ?
have you taken compression test yet ?
So when you put on T and on compression stroke with the dots on camshaft indicators straight up you adjusted the valve lash cold to .004 ?
When you turn over by hand with 19mm on flywheel nut what happens ?

[300winchester]

did you make sure the arrow was facinig out on the camshaft holder ?

[300winchester]

This is just a long shot pass to left field. and this happened to me. 
My flywheel key was sheared so no matter what i did to set timing i had a hard stop like you spoke about.  Only until i removed flywheel and found keyway sheared did i truly find out the problem.
Did you put something down spark plug hole and turn over very slowly to indicate that when you hit the T mark the piston was truly at TDC ,   how I found my issue was the piston was already on its way back down when the alignment mark showed up. once again, just thinking out loud.  Before i would pull that top end id pull the flywheel ?  good luck

[CThacker]

Yep,
The spark plug shows good spark.  Cams shafts are installed correctly as well with the indicator Dots on Top. 
We manually moved the piston as well and felt it top out from the spark plug hole and it pretty much matched the T mark.

We even tried putting in the old camshaft and it did the same thing.  So, either we broke something or found another underlying problem that already existed and we didn't know about it.

That is an interesting thought about the flywheel keyway being sheared. We may just have to open this thing up and check for sheared components in there.

Either way I am now borrowing a different 4x4 for deer season so this is now not as much of an urgency as before so I can take my time now.
Time will tell I guess.

[CROSSBOLT]

It will run again if it ran before. When deer season is over, look for some part on thr compression release thingy that can be assembled two ways.....

Just so I understand correctly, it won't start because it stops revolving on the compression stroke, right?

[CThacker]

It will run again if it ran before. When deer season is over, look for some part on thr compression release thingy that can be assembled two ways.....

Just so I understand correctly, it won't start because it stops revolving on the compression stroke, right?

Thats correct once the compression stroke tops out, it just does a hard stop until the buildup of pressure manages to dissipate out (I'm assuming leak by through the exhaust valves).  We did get a small backfire once or twice but no real luck.