JCL MP250A Runs Poorly 0-40 MPH & No Front Brakes By bob123456789 (Read 3,976 times)

[bob123456789]

Went for a good 50 mile ride this morning.

The good:

     The new starter clutch is working well.

     The new rear tire is working well.

The bad:

      1) It has trouble idling even after adjusting idle due to engine dying when braking during stopping.  It still frequently dies when stopping.  The dying at every stop seems to be better after I dropped the idle speed to where the rear tire doesn't spin with it warmed up.

       It runs very poorly up to 40 MPH.  After that it runs fairly well.  It really has trouble getting the bike moving from a stop.  No power at all 0-10 mph and low power 10-40 mph.

Is this carb related?  Where is best to start?  I haven't had a carb apart before.

2) No front brakes.  The front master cylinder has some fluid in it.  I haven 't topped it off since the Phillips screws are partially stripped and I didn't want to damage them more.

Where is the best place to start on the brakes?

With the poor idling the battery doesn't last long when used to restart at every stop.  When it finally is idling through every stop this probably won't be an issue.

[Alleyoop]

Have you adjusted the carbs Fuel Ratio Mixture? And yes the motor will likely die if the idle is to high and the wheel is spinning. braking at low rpms puts a load on the motor and it will die.

On the CENTER STAND the motor needs to idle around 1800 rpms and the rear wheel not spinning AFTER it is warmed up. If it is spinning after it is warmed up you will always have the dieing problem coming to stops.

Just adjusting the IDLE will not fix the problem you need to adjust the carbs FUEL RATIO MIXTURE on the center stand AFTER it is nice and warm. Turning the mixture screw ALL you are looking for is to adjust it where it gets the HIGHEST IDLE. Then after that adjustment is reached you MAY NEED to lower the IDLE so the rear wheel DOES NOT SPIN using the IDLE SPEED SCREW on the THROTTLE CONTROL WHEEL.

I would say it might be your valves causing it to die coming to stops but if you can re-start after it dies then it is not your valves. Running poorly is a fuel and air related problem and may also be a cvt variator problem may be both or just one.


If you had front brakes before and the scoot has been sitting for months then I would say the pistons are just stuck.
Actually I just fixed my Front Disc brakes that way. Sitting in the garage over the winter I never used the front brake to start it every week or so and the front pistons where stuck. I had no pressure at all the handle closed all the way and nothing. I took off the caliper and sure enough I could see the pistons extended out. Got a scraper and stuck in between the pads and pushed the pistons back squeezed the brakes they closed pushed them back several time to free them up and now I have actually more pressure than I had before.

Take the caliper off the disc and if you see the pistons extended out they are stuck. get a scraper or something thin and stick it between the pads and push the pistons back then apply the brakes and they should pop out and when released they should pop back in if they get stuck again do it several times pushing them back and applying the brake SEE IF THAT FIXS the no brake problem.
Alleyoop

[bob123456789]

I have not yet adjusted the carb's air/fuel mixture. Just the idle speed screw. But I do not have my rear wheel spinning when idling on the center stand and it is still stalling when braking.

After it stalls I can restart so you are saying that rules out that a valve adjustment is needed.

It looks like I need to adjust the air/fuel mixture next followed by the idle speed. Mmmm! That A/F screw is in such an accessible place!

I don't know the history of the front brakes. The scoot is new to me. They have been probably sitting for a fair while. I hope you are right that the pistons is just stuck. I'll follow your guidance here.

[Alleyoop]

Do you know what the RPMS it idles at WHEN all nice and hot?

When coming to a stop from higher rpms sounds like it may be running to rich and the idle keeps dropping from the set IDLE. To me that says the Fuel ratio mixture is to rich and needs to be leaned out. But if you follow my 4t carb tuning guide you will get it running much better.

And yes the Fuel Mixture Screw is a PAIN IN REAR TO GET AT, you need something with a 90 degree bend and about 1/2 in length only to get it in there and adjust the mixture.

As far as the brakes yea I hope it is as easy as mine was.
Alleyoop

[bob123456789]

It roughly idles at about 1,000 rpm. I had to go that low to get the rear wheel to stop spinning. However, the idle isn't stable. It is usually 1,000 rpm but wanders up to 2,000 rpm.

Where can I find your 4t carb tuning guide?

[Alleyoop]

May 14, 2016 16:10:00 GMT -6 bob123456789 said:

It roughly idles at about 1,000 rpm. I had to go that low to get the rear wheel to stop spinning. However, the idle isn't stable. It is usually 1,000 rpm but wanders up to 2,000 rpm.

Where can I find your 4t carb tuning guide?

Here is the tuning procedure thread:

scooterdoc.proboards.com/thread/1499/4ts-carb-tuning

The Idle is to low it should idle at around 1800 Also if the idle goes up and down MEANS it is LEAN and not RICH like I first thought from the way you described it dying coming to stops. But I can see why it dies your idle is way to low.

If the wheel spins at little over 1000 rpms that means something is not right in the CVT. It could be your Variator weights and or your clutch grabbing to soon which would mean something is broke probably a spring.
Alleyoop

[bob123456789]

It was dying every stop with the idle higher and the rear wheel was spinning. Now with the idle lower it doesn't die sometimes when I stop with the brake. If I set the idle up around 1,800 rpm my rear tire spins and stalls the engine when I stop.

The engine is running so poorly <40 mph that I need to get it running good before I start thinking it is the CVT. You mentioned the CVT. There is a bit of history with it. I sent John my clutch, he looked it over and said he thought he springs were good and couldn't say where the extra clutch spring was from. Boy wasn't that refreshing to see, someone who sells thing for a living says "no you don't need to buy anything from me"! And a really nice guy! I still have pictures of the front of the clutch if it helps. I didn't take it apart. Here is the link to where I had an extra clutch spring for some reason:

scooterdoc.proboards.com/thread/12345/extra-after-belt-change-never

Is the fuel ratio screw easiest to get to from the right side or left side? Any advice on the easiest way to get to it?

[Alleyoop]

Sorry to say but that Spring is a CLUTCH PAD SPRING and if nobody put a new one on that is why your CLUTCH IS GRABBING at very low RPMS. The clutch pads work by centrifugal force and if ONE PAD HAS the spring missing it will be thrown out and grab the bell at very low rpms WHICH IS what your current problem is.

I would suggest you to take the clutch off and check the springs in the clutch and make sure all the springs are on and one not missing. I mean if you found that spring in the CVT that tells me the spring came off and a PAD is without a spring.
Alleyoop

[bob123456789]

I pulled the clutch and shipped it to John and he verified that all the springs were on.

[Alleyoop]

Okey, if he said all the springs are on then it has to be something else. can you do VIDEO? if so take the cvt cover off and start the scooter and video the cvt running. Or at least maybe a picture of the cvt without the belt so I can see how the belt is riding on both the variator and clutch pulley.

Something is not right in the CVT if the wheel stops spinning at 1000 rpms.
Alleyoop

[bob123456789]

How do I add you to some pm's I had with John. There are pics of my clutch in them. I tried to "Forward" it to you but it looks like you can't access it.

[Alleyoop]

I saw the pictures but I cannot see the springs in order to see the springs you need to take the big nut off the springs are on the other side of the clutch.
Alleyoop

[bob123456789]

So to fix the performance issues what is your best guess? Should I focus on the carb or the CVT next?

[Alleyoop]

First focus on the carb issue, and get the motor running good. The clutch is grabbing but to SOON and is causing you to lower the idle to low so the motor dies coming to stops because the idle is to low.

If you can install a Starter Clutch the pulley clutch is a piece of cake.
Alleyoop

[bob123456789]

Ok. Next up adjust the carb following the steps you outlined. Is it easier to get to the A/F screw from the right side or the left?

Then the front brakes as time allows.