150cc racer ktmmx running and idoling rough By squall8ball (Read 917 times)

[squall8ball]

hi! i am new to this board, and i am kinda new to scooter repair as well. I have a major issue with a 2008 ktmmx 150cc racer scooter where it just idols rough all the time. even on throttle it just has a hard time getting up to speed. it acts like it is not receiving enough air. when i pull the vacuum line of the manifold, it idols up, but does not fix the problem. i have adjusted the valves, replaced the cdi, replaced the spark plug and wire, new carb, new choke, but all still to no avail! i have also checked the a/f mixture, and checked exhaust thoroughly, along with vacuum lines. checked fuel filter, and gaskets throughout. please help me! as i am lost, and so is my mechanic! he has over 25 years in this field!



thank you in advance for any and all help you might be able to give me! here is a short video of what it is doing.

[kz1000st]

Check the intake manifold for cracks. Also look and take a plug reading. It sounds like it has a vacuum leak. Is there an air filter? Most times in my experience when an engine sounds like that it's starving for fuel, hence too much air. I also thought I heard a slight backfire in the exhaust pipe. That says air leak to me.

[squall8ball]

i yamaha bonded the intake gasket to the carb, and at the moment it is running of strait carb. still nothing...

[Alleyoop]

Check your plugs gap and what is the number on the plug.

Also check the timing, aline the cam as if going to adjust the valves and look at the flywheel and see where the CASE pointer is pointing to on the flywheel.

If you can put a pic of the flywheel timing position.
Alleyoop

[squall8ball]

 the spark plug is brand new and gaped properly, one other thing i forgot to add in was this started suddenly while i was riding it.

[Alleyoop]

Well the timing looks good but it is definitely missing and badly. Before this happened did you put a new head on it or any changes. Also check the GROUND wire from the VALVE COVER to the FRAME if loose or sometimes not grounding to to vibrations it will cause missing. The other thing it could also be your PICK UP COIL if not that it could be the stator.

Now if you have multi meter the COIL and the PICK UP coil can be tested.
Alleyoop

[squall8ball]

well there is no ground from the valve cover to the frame at all! there is one from the tank to the frame, and this is a rebuilt motor prior to me buying it. no new parts since i bought it minus a tire. no multi meter on hand. will get one tommrrow and test those, will get back to you when i test them... what should i be testing for exactly?

[Alleyoop]

Before you even go and spend money, GET a nice piece of WIRE and put one end on the Valve cover and one a NICE CLEAN SPOT on the frame(BARE METAL) not over paint. We may have just found the cause of the missing.
The tank to frame is not going to do it. What you should have is a GROUND WIRE FROM the NEGATIVE battery post to the FRAME. Try to put both of the grounds I mention on the same BOLT on the frame.
Alleyoop

[Alleyoop]

Another bit of info since it was rebuild is the head. The head could be thicker where plug screws in and what happens is the plug does not extend far enough into the Chamber and it grounds itself out on the head.

You can also check that out with a piece of wire just put bend on the end of the wire and then grab the end of the plug with it the ROUND OPEN end and then put a mark on the wire at the washer. Then stick it into the head hold and grab the inside of the head and get a flashlight or something and see if the mark is at the top of the hole. Or you could put a little grease on top of the hole and then hit the wire with it the grease mark will be on the wire. That will tell you if the plugs Eletrod is reaching far enough into the camber.
Alley

[squall8ball]

well the new ground didnt help, and its getting a good hot spark to the plug and the plug is extended to it correctly too...

[Alleyoop]

Like to see some pics of your grounds, Now I hope you grounded the two I said to the actual frame AND not on the swingarm that the motor is mounted to. What plug have you got in there the number also the gap. If all is good then it has to be your stator and or pickup coil to be missing so badly to test you will need a multi meter.
Alleyoop

[squall8ball]

[Alleyoop]

That my friend is NOT grounded to the frame, all you did is attach the batteries neg to the motor. You need to take another piece of wire and use a thicker wire and attach it to where you have it on the motor and bolt it to the FRAME that your seat is bolted to. And what is that THIN RED WIRE coming from?
Alleyoop

[squall8ball]

found the issue! its the stator! its catching on something inside the motor! taking it to a shop 2morrow to get it fixed! thank god! thank you alleyoop for all your troubleshooting help!

[Alleyoop]

Take a pic of the stator you probably can fix it yourself. Is it a wire that is rubbing on the FLYWHEEL? Also a pic of what is wrong may help others with the same missing problem. What I do is copy those nasties and when someone has a similiar problem I put up the picture of someone that found the problem pointing to the problem to help them out.
Alleyoop