Scooter stopped running
 

I'll try to make this as short and specific as possible.
I have a JCL-MP-150R (150cc, 157QMJ engine with EGR). A day or two before it completely stopped running, it started making what I can only describe as a almost sucking sound near the cylinder head area. Took a few things off and apart but couldn't find anything loose, broken or otherwise damaged. I suspect it's a compression problem (the valves not completely sealing). There was quite a bit of carbon build up on the head of the piston and the surface around the valves. My question is:
Would my best option be to buy a rebuild kit and replace the whole top end (cylinder head & cams, cylinder, gaskets & piston w/rings)? It's a 2008 with roughly 4000 miles on it.
Any advice is good advice. I know my way around cars and simple repairs ubt I'm a little green when it comes to scooters as I've only had it for just under a year.
Thanks for the help!
N8

I think you are the only one, who can answer that question. How attached are you to this scooter? How much money are you willing to put into a 9 year old.... About $100 for a top end kit....about $300 for a complete, new 157QMJ unit, or 3 times that for a new scooter.

Properly cared for, they will run trouble free, much, much longer than your's has.

If the rest of the scooter is in good shape, I'd be inclined to go with a rebuild. A lot depends on what you intend to use the scooter for and if it's critical for transportation. Be sure to check out the air cleaner and connecting duct if you keep it, clean air is vital for engine life.

I agree except that I'd rebuild it myself! That way , you know that it's correct. Not knowing what your mechanical abilities are ,it's up to you.:hmm::shrug: Irish:scoot::nuts:

Well, as far as how attached I am to the scooter, I need it since it's my primary source of transportation. I'm pretty at working on mechanical things so I know I am capable of doing the work myself. I guess my Makin question is, will replacing the top end fix the problem or do you guys think it could be something else?

I'll admit I've been absent when it comes to maintaining it, I've done a couple of oil changes but that's it. I realize now that there's more to it than that to keep it running good.

Just thought I'd post again to try to get some additional info. My engine starting making a weird sound that I can only describe as a kind of sucking or vacuum or chirping sound and then eventually will not start out stay running. Can anyone give me advice as to what they think it is? I can post pictures of the disassembled top end of need be. I can't find any other things that might be wing other than the valves not completely closing.
Thanks

Air leak? Check intake manifold for cracks, check cylinder head and jug, check gaskets, or spray soapy water all over the engine and crank it over seee where it bubbles from

So I got my rebuild kit today. Got everything ready and commenced to assembling. After I got the assembly back together I realized I have another problem: my patron rod seems to be stuck on the crank shaft. It will only turn so far then it gets stuck. Is my only solution to take the engine off the scooter and pull the halves apart and figure out what's wrong? Or is this somewhat common and there is an easier solution?
Patiently waiting for answers...........

If it would turn over problem free before you disassembled it, and now that it's been put back together, it won't.....my guess would be valve timing. It has to be right, in order for the piston to reach the top of it's stroke.

I thought it was the valves but I took the cylinder head back off to make sure and it's still not moving. It seems like the big end of the piston roof is stuck or jammed on the crankshaft inside the engine.

I'd take the cylinder off and see if the crankshaft will turn (hold on to the timing chain) . If it won't make it all 360 degrees around it sounds like the piston might be hitting the crankshaft? Anyway if it turns OK, start putting it back together piece by piece checking that the crankshaft will keep turning as you go. Leave the spark plug out and keep the cylinder oiled to help things along. Are you using the starter or turning it by hand?

I'll give that a try tomorrow... full day of working today.
Thanks

As suggested, I took the cylinder off and tried turning the crankshaft. I could barely turn it by hand. I put a socket and ratchet on the outside of the variator. It will turn with some effort but the piston rod seems to be stuck. When I try to turn the crankshaft, the piston rod just smacks the top or bottom of the opening of the engine. Looks like I definitely have a bad crankshaft. I guess my next step is taking the engine completely off the scooter and replacing the crankshaft. This bites!

I'd put out the word and look around for a used non running scooter, intact and check it out if the engine is any good. They are around just sitting, all you have to do is find them and make an offer. Piece together a good running scooter with the best parts from each and buy new what you have to. We all do things differently but that's what I did. If you do change the crankshaft view a few youtubes to see how to deal with the pressed on bearings.