Sudden change in performance By learae (Read 3,107 times)

[learae]

Hi All! First post!

I recently bought a 150cc Shanghai Shenke and it has been running great until yesterday.

It is cold outside now, and I have to work on it outside, so I wanted to get your opinion before I freeze to death taking things apart.


The scooter usually starts right up, but it has a rough idle around 1000 RPM until it warms up, when suddenly the RPM jumps to 1800 and sounds so much smoother. As I understand, when cold, the enricher should cause it to idle higher before dropping down to speed when it's warm. I haven't taken the enricher out yet to test.

Anyways, yesterday I went for a ride into the city which is about 10 miles. During this time, the scooter was being VERY well behaved, and I felt like I had more power than usual. I wish I had a better description, but I wasn't paying too much attention at this time.

When I started to come home, I let it warm up as usual and it still idles at the same place, about 1800 RPM. I noticed, however, that I was not getting much power. At WOT I was getting only 5500 RPM and couldn't get above 40 MPH even in long straight areas.

It felt like the throttle behaved mostly normally until I hit that 5500 RPM range, and then giving it more throttle did nothing to the engine. But, I did lose power along the entire throttle range.

So I got home and put it up on the stand, and pulled the throttle wide open. The engine revved as normal, hesitated at that same 5500 RPM area for a moment, and then jumped up quickly to 8000+ RPM. I then let it stop and pulled the throttle again, and it quickly throttled up all the way without any more hesitation at 5500 RPM.

Thinking that was strange, I went for another ride and still could not get above 40 MPH and 5500 RPM at WOT.

Since the kick starter doesn't engage, I was thinking I'd take the CVT cover off first and try to fix that while checking on the clutch, belt, and variator.

What should be my next move? Do any of these symptoms suggest a particular fix?

I am pretty handy, but I've never adjusted a carburetor before. I think that might be the next step...

Thank you,

Lea

[Alleyoop]

First thing to check would be your ENRICHER, that should feed it extra fuel for cold starts. The Enricher is held on by two screws holding down a "C" clip on the side of the CARB. The Enricher has two wires that is plugged into the harness. BY DEFAULT the ENRICHER's Cylinder is retracted and in that position it allows extra fuel for cold starts.
Once the Motor is running voltage is supplied to the Enricher and the CYLINDER and along with the needle start to extend to cut off the extra fuel within 3-5 minutes. Once it shuts off the extra fuel then at that point the only other means of fuel delivery is the PILOT JET which the FUEL RATIO MIXTURE screw can control allowing for more or less fuel.
Alleyoop

Here is what the ENRICHER SHOULD LOOK LIKE if you take it off WHEN COLD. The Enricher is RETRACTED which will allow extra fuel to be sucked in for COLD STARTS:



Here is what the ENRICHER SHOULD LOOK LIKE after Idleing for at least 5 minutes.The Enricher is EXTENDED cutting OFF the extra fuel for COLD STARTS:



Your Carb should be similiar to this and the parts are labled:

This is the LEFT SIDE OF THE CARB: Notice the FUEL RATIO MIXTURE SCREW:



This is the RIGHT SIDE OF THE CARB: Notice the IDLE SPEED SCREW:



Here is how to adjust the CARBS FUEL RATIO MIXTURE:

First Start up the Scoot and let it warm up At Least 5 minutes so the ENRICHER cuts off the Extra Fuel.

YOU WANT TO GET THE HIGHEST IDLE OUT OF THE FUEL RATIO MIXTURE:


So from where it is currently set FIRST TRY richening it up more:

1. Turn it 1/4 turn Counter Clockwise and wait about 10 seconds to allow the motor to catch up with the new setting. LISTEN or look at your tach:
a. If the IDLE GOES UP REPEAT #1, UNTIL the IDLE does not change or drops a little THEN TURN THE SCREW CLOCKWISE 1/8 and that should be the highest IDLE from the Fuel Ratio Mixture and go to #3.

**** IF ON THE FIRST 1/4 TURN COUNTER CLOCKWISE THE IDLE GOES DOWN OR DOES NOTHING, TURN IT CLOCKWISE 1/4 TURN TO GET IT BACK TO WHERE IT WAS AND GO TO #2****

2. Turn it 1/4 turn Clockwise and wait about 10 seconds to allow the motor to catch up with the new setting. LISTEN or look at your tach:
a. If the IDLE GOES UP REPEAT #2, UNTIL the IDLE does not change or drops a little THEN TURN THE SCREW COUNTER CLOCKWISE 1/8 and that should be the highest IDLE from the Fuel Ratio Mixture and go to #3.

3. If the idle is TO HIGH NOW LOWER the IDLE USING the IDLE SPEED SCREW so that your REAR WHEEL JUST WANTS TO TURN... Go to #4.

4. Now give the Throttle a quick twist and let go, the Motor should Rev up nice with no sputtering or hesitation and come back down to where you set the idle.

*** IF TURNING THE FUEL RATIO SCREW Clockwise or Counter Clockwise DOES NOTHING Then the Pilot Jet AND OR ITS PASSAGE ARE Clogged and you will have to clean the Jet and CLEAR OUT THE PASSAGE. And go through the Procedure again***

[Alleyoop]

Just a note, when temps go down around 60 or lower the motors need more fuel. Also if you just start the scoot and jump on it and take off the ENRICHER is feeding it extra fuel along with the PILOT JET and MAIN JET So at that time it may be getting to much fuel and it will be sluggish and may hiccup on you the first couple of minutes or so, then when the ENRICHER finally cuts off the extra fuel it is now running on the PILOT JET and the MAIN JET. So as you can see it could just be to much fuel for the first few minutes.
Alleyoop

[Alleyoop]

Normally when Cold and the ENRICHER is retracted feeding it extra fuel your rpms will be high around 2000 or so then as the ENRICHER starts to EXTEND cutting off the extra fuel the RPMS will start to drop to wherever you have set your IDLE at. So if it starts up with low rpms and then the rpms rise as it warms up indicates not enough fuel for cold starts.

So first check your ENRICHER then try adjusting the Fuel Ratio mixture.
Alleyoop

[terrilee]

hi

i have a Shanghai Schenke 150 also


got a few miles on her


your description does sound like the enricher
like alley says---hes very smart listen and do what he tells ya
and once that is fixed , the a/f screw needs adjusted along with idle

good luck

[learae]

Thanks for the quick replies

I took the enricher off and found the engine wouldn't even run. I held the enricher in place and got it started and warmed up. it idled slow until it warmed up, but then idled at 3200 RPM. Wow! I slid the enricher off and the engine died, but it was extended properly. While putting it back in, i discovered that the top hole holding the enricher in is stripped out big time. I took the carb out and I'll get a mechanic to put a helicoil in that hole and get a shorter screw... The screw was bottoming out against the carb so the last person to work on it probably messed it up.

I am guessing that repairing that will fix part of my problem; I will then adjust the mixture and hopefully get my power back :-)

So, while i have the carb out, should i open it up for a cleaning? Or would i be better off leaving well-enough alone?

[Alleyoop]

Sorry, I forgot to mention if you take off the ENRICHER and then want to start it you have to cover the hole. Just holding your thumb over the hole while the motor is running will work. If you leave it open it will suck in to much air and like it happened to you the motor died.

You can take the GOOD SCREW to the hardware store and get a NONE METRIC one and it will screw in modifing the metric threads a little as you screw it in because the american screws are just a tad bigger.

The ENRICHER has to seal good, if you look it has an O-RING about 1/4 of an inch from the end to seal it. If it does not seal good it will suck in air and not feed it fuel like it should as you found out when you took it off and did not cover the hole.
Alleyoop

[learae]

Alright I swapped that enricher casing(?) for one I had in another scooter

I got the engine tuned, I had to go about 2.5 turns in with the ratio screw. It's idling at around 2500 RPM now, but sometimes it bogs down for a few seconds to 2000 RPM before going back up. Any idea what could be causing that problem?

I went for a test ride, and got it up to 50 MPH after a 1/2 mile straight away at WOT. It's still not doing as well as it was just a few days ago. I used to be able to get up to 50 pretty snappy, and still had 1/4 throttle left if I needed it.

So, what should I check out next?

Thank you!

Lea

[Alleyoop]

That is good news,

If the IDLE BOUNCES UP AND DOWN it is TO LEAN, turn the FUEL RATIO screw Counter Clockwise 1/4 at a time and check it out. Also 2500 rpms is a little high, normally the 150s idle is 1500-1800 after nice and warm. Is the Rear wheel spinning at those RPMS?


On the center stand give the throttle a quick twist and let go.

If the RPMS do not drop quickly they sort of come down slowly it is LEAN.
Alleyoop

[learae]

I adjusted the ratio 3/8 of a turn richer and dropped the idle screw to idle at about 1900 RPM. If I go any lower, it's not a very smooth idle. It seems to be running good and the idle is steady when sitting and warm. After the adjustment I got some more power and speed back, so much better! I think I will go another 1/8 turn richer before I go home tonight and see where it puts me.

I gave it a quick twist of throttle while it was warming up this morning and the RPM came down so low that the engine almost died. Once it warmed up, the engine didn't try to die anymore, but I am unsure how quickly it should be coming down. It seemed to come down at about the rate the tire slowed, which makes sense. I think.

The rear wheel doesn't start spinning until around 2800-3000 RPM. Should it be sooner?

It's still having trouble starting cold. I need to give it constant throttle to keep the RPMs high enough so it doesn't stall out. It seems especially bad when it's only cooled down some - like at the gas station where the engine is off for just a couple minutes. It starts better when it's completely cold, say after a night of sitting.

[Alleyoop]

Good, what is happening now is a sign that the valves need to be adjusted. When hot they are expanding and tightening up and leaving the exhaust valve a little open and you loose compression. When it is nice and cold the valve has cooled and the metal retracted that is why it starts up good when really cold.

Adjust your valves to .004 top intake and bottom exhaust and it should act much better for you. You may have to tweak your carb as well once the valves are adjusted.
Alleyoop

[learae]

Alright, before I adjusted the valves I tried to ride the scooter to work. I got about 4 miles down the road when I lost all power, couldn't even move, and the engine died if revved beyond 3000 RPM. So I pulled over and, after a bit of walking and a no-fun day, set the valves.

The exhaust valve was tight! After resetting both valves to .004, the engine runs good and I got my power back. I did have to adjust the carb some more as well, and I think I am going to tinker with it a little bit still. I also replaced the spark plug while I was at it.

I can hear the valves clicking now inside. Does that mean the spacing is too big? It's at .004 and I reconciled that against the .005 which does not fit.

In order to warm the engine up, I still need to give it a lot of throttle for the first 5 minutes. Once the engine is warmer, I can let off the throttle and it idles poorly around 1000 RPM until finally coming up to idle at about 1500 now. If I let off the throttle while the engine is cold, it dies almost immediately.

When idling and warm, the RPM still hiccups sometimes. You said this was caused by the mixture being too lean, but it seems to get worse when I richen the mixture. Could this be caused by something else?

[Alleyoop]

If the valves are CLATTERING that means they are to loose. But a TICKY TICKY is fine as they say a LITTLE LOOSE VALVE IS A HAPPY VALVE. You done good rechecking trying the next higher feeler that is what I also do. I also turn the motor over a couple of times and recheck them, it is not fun taking stuff off putting it back on and then taking stuff off to re-do.

Something is not working right, it is either getting to much gas or not enough for cold starts.

Q1.
Does the scoot start with 1 or 2 hits on the start button or do you have to crank it quite a few times before it catchs?

Q2.
When you turn the FUEL RATIO mixture screw IN EITHER direction DOES the IDLE CHANGE or NOT.

Next time let it die and take the plug out and check if it is WET OR DRY, that will help determine what it needs.


The Carbs are pretty simple but they do have tiny passages and can easly get clogged if the fuel filter and or air filter are not doing their job.

It could just be that the AIR and or Fuel Passages are clogged and is throwing the mixture off. You may need to take the Carb off and CLEAR out ALL THE HOLES in the CARB, when you take the Carb off you will see some holes where the AIR FILTER attachs to THOSE are AIR HOLES and can get clogged as well as the PILOT JET PASSAGE and ENRICHER PASSAGES.

Here are the Carb HOLES for the ENRICHER that must be clear:


Air Passages for the Carb to work properly:


Pilot Jet Main Jet, in your case the PILOT JET and PASSAGE which is controlled by the FUEL RATIO MIXTURE may be clogged.


When you clean out the PILOT JET PASSAGE Controlled by the FUEL RATIO screw fuel is sucked out of the following TINEY HOLES which must be clear.


When you clean out the MAIN JET here is where Spray should come out:

[learae]

The valves are making a pretty loud ticky ticky, but I'm not sure how loud a clatter would be considered. I can hear the valves over the engine when stepping away, so I think that's too loud and I'm going to try tightening them up to .003" to see where it's at then.

The scooter usually starts right away if I roll the throttle back as I push the starter button.

The fuel ratio screw doesn't seem to have much of an effect on the idle speed. Not as much as it should, I think. I had more of an effect after I adjusted the valves.

I pulled the carb and started cleaning it out, and a small flat washer fell out while I was spraying down the carb body. It's really small. Any idea where it came from? All of the external screws have their lock washers, but the missing washer is too small to fit on any of those, anyways.

Thanks again!

[terrilee]

hun

all i can tell u is this....
its gonna take alot of fiddling to get it to
really well running
i had to also.
but once its done its fine.
when it gets really cold i have to mess with the carb
a bit to get it running great in cold
and then again once it gets very hot again
but its well worth it