JCL MP250A stalling at stops and slowdowns  By  4950cycle (Read 5,170 times)

Time to adjust your valves again.

Yes, adjust your valves, it is probably just the exhaust valve which takes a lot of heat and is not closing completely and loosing compression. When that happens the motor will not hold low rpms and or idle. This is caused by the quality metal they used to make the head and or valves. What happens is it gives with every explosion and its like making a bigger hole so now the Valve stem has to move up more and the gap does not allow it to so the valve is left a little open.
Alleyoop

I have the same scooter and i had the same problem at 2000 miles , i seen some short cuts to make adjustment by doing the top valve under the seat and by cutting a hole in the side cover to get at the plug. Taking the covers off is 98% of the job so if you find a shot cut i will sure do that the next time . Try YouTube i think thats where i seen it .

Is there anybody that happens to know how many turns on the valve adjuster = how many thausands of an inch ? For instance , 3/4 of a turn on the adjuster opens the gap .001 .

You missed me allyoop. I have feeler gauges. What color would you like one in ? ;D No, I am developing a quicker method to open up the exhaust valve clearance and button the scoot right back up. And besides , Remember me ? I'm the guy from that other scooter forum that sets both my valves at .008 . Works fine and gives you longer to ride in between these way to frequent necessary valve adjustments. To much valve clearance will never hurt your motor. To little clearance can burn a valve remember. And before I get a bunch of wasted feedback, to much clearance is fine as long as your motor is running good at these clearances I speak of. I never said gap them so wide the motor won't perform correctly. This Linhia runs great and gets dependable 60-67 mpg at this setting.

Here is the tutorial for the adjustment and while it does require removing a lot of things I recommend it for beginners and newbies at least the first time.

itistheride.boards.net/index.cgi?board=250ee&action=display&thread=151

I was asked about a easier and quicker way and I will tell you my way and since I do know the engine well, my last valve adjustment was done in 19 minutes and that doesn't count gathering up all my tools and such, just the time it took to perform the adjustment.

Top view of the carb and battery with the seat and carb cover removed:



Remove the battery and cut a square hole in the bottom of the battery box large enough for your hand to easily go through and expose the top or intake valve cover like in this picture. Leave at least a one inch lip all the way around the box and when you're done just cut a thin piece of sheet metal, galvanized that you can get at the local hardware and put in in the bottom and place the battery back in.





The bottom valve can be accessed by simply removing the belly pan back bolt on each side and it will drop far enough down to expose the bottom exhaust valve cover:




Remove the intake and exhaust valve covers. One bolt on the bottom is very difficult to get too. I use a little box end 8mm wrench get it out and the other two can be removed with a socket/ratchet.

I then remove the spark plug, very tight but can be removed without any plastic removal. This allows the engine to turn over easier and allows me to find TDC.

I then remove the black plastic cover over the variator, not the aluminum variator cover itself and this exposes the variator along with the variator nut. I use a socket and ratchet to turn the engine over.



Now this is what I do different than most. I do not remove the cam sprocket cover.



I do not worry about aligning the cam sprocket marks:



I go to the muffler side and remove the plug with the correct size allen wrench and expose the flywheel that has the "V" notch mark;



I then use the ratchet on the variator and very slowly turn the variator CCW thus moving the flywheel to locate the "V" mark. Remember the slightest turn on the variator makes the flywheel move a lot! In fact if my wife is around I have her turn the variator while I watch for the mark. When it's close I will take a flat blade screwdriver and move it the last little bit until the "V" mark is perfectly aligned.

Then I take a stiff but flexible piece or electrical wire and insert it in the spark plug hole and see how far it will insert. If it immediately hits the top of the piston, I'm good to go, if it goes down in the cyclinder I know I'm on the exhaust stroke and then turn the flywheel another round and check again which will make me on the compression stroke.

Then I adjust the intake valve and then the exhaust. I do not even do it like this:




I loosen the nut, back off the adjuster then place a feeler gauge under the adjuster and screw it back down with my fingers until the feeler gauge will not fall out. I use a over sized guage, (exhaust a 8mm) then I tighten down the nut securely with a wrench, pull the guage out which will be very tight. I then check it with a 5 mm and it'll be right on every time. When tightening the nut it causes the center adjusting bolt to tighten too tight which makes it come out just right by using a too thick guage to start with. The little cresent wrench is just too hard to hold and tighten right with the correct thickness guage.

On the intake I use a 6mm and the check it with a 4mm when tightened. So her back up and you're good to go.

4950cycle, after about 10K in miles the valves settle down and may never need adjusting again, I also told you this the time you mentioned adjusting them so wide too.

The "V" timing mark is the critical mark and you can cut down on the steps by doing it as I have said, never had one issue doing it this way.

JR

Just did my exhaust valve and JCL 250 Linhia took off like a champ. Thanks for all the suggestions and direction Scoot Boyz. Runs great hot or cold now.