Carb adjustment? Or is it something else? By apothecary (Read 2,927 times)

[apothecary]

Ok so those following the previous thread, I've FINALLY managed to get her running. I've taken a quick few runs and noticed some things that worry me slightly.

First off, when she's cold, she doesn't want to rev up at all. Give her gas and she stalls out. Once warmed up she runs just fine and the entire time she idles great.

Second, when running (I only took her for a couple of miles nothing incredibly long yet since she's not inspected and missing a mirror) when I get up to speed and let off the throttle she starts popping from the exhaust. I'm assuming I'm running lean or rich (I can't remember which it is) so I'm assuming I need either a carb adjustment or I need a new air filter (maybe both?).

And finally, when at a dead stop I give it some throttle but the response leaves something to be desired. The engine picks up, slows for a second, then revs up normal.

I have a feeling all these symptoms are from the same issue I just need to figure out how to fix it. I've gone through the service manual and they're a little vague on some things and carb settings they tell you that it's set from the factory nothing more is needed.

So where am I going wrong? Is my timing off a tooth? Is it the carb? Valve lash wrong? Where did I goof?

[JR]

I'm going with carb at this moment and going to holler at Alley and get him on board, he's damn good on the carbs and the stall to me sounds like carb and too lean.

JR

[alleyoop]

Apothecary,
Ok, lets make sure you are describing the right sound, because each different sound is a different problem.
So make sure of the sound it is emitting:

BACKFIREING:
It sounds like a gun going off POW= It is running LEAN either to much AIR or NOT enough gas:
LEAN can be caused by AIR LEAKS and or not enough fuel is being delivered at that point.

BRUP:
It actually sounds like a BRUP= It is running LEAN usually richening up the Fuel Ratio is all that is needed when this sound is emitted.

POPPING:
It actually sounds like POP= It is running RICH to much gas period.

1. First thing before adjusting the Carb is to ADJUST YOUR VALVES.
Top Intake Valve to .004inchs and Bottom Exhaust to .005inchs.
Doing this will make the scoot run and idle completely different, and we do not want to be adjusting the carb to compensate for TIGHT VALVES.

Then test it out and see WHAT symptoms still exist or if it is now running good.

If it still Backfires check for AIR LEAKS, First check the Header Pipe FLange that connects to the motor. A nut may have vibrated off and or stud broke and blew out the Header Gasket. Usually you can tell by the different sound than what your muffler puts out.
It will be louder and puffing sounds.

If all is good in that Department then Check around the Carb area.
Check the Intake Manifold for cracks, Clamps tight holding the Carb by the Intake and by the Air Fitler. Check for cracked Air Box tubing or a hose came off.

If it has still some hesistation and or bogging then Adjust the Carb:
Here is how to adjust your carb:

ADJUSTING YOUR FUEL RATIO SCREW:

FOLLOW THIS PROCEDURE, take your time DO NOT Be turning the SCREW fast and wait in between turns otherwise you will be off.

Warm Up the SCOOT for at least 5 minutes.

YOU WANT THE HIGHEST IDLE OUT OF THE FUEL RATIO SCREW YOU CAN GET.

ADJUST YOUR FUEL RATIO:

1. Turn the Fuel Ratio Screw Counter Clockwise 1/4 and wait 10-15 seconds to allow the engine to catch up with the new setting.

** IF ON THE FIRST TURN IT DOES NOTHING OR IDLE GOES DOWN- GO to 2.*** Otherwise GO to a. below.

a. If the IDLE GOES up repeat 1.
b. If the IDLE does not go up or it does nothing turn the Fuel Ratio Screw 1/8 Clockwise that should be the highest IDLE you can get out of the Fuel Ratio Screw-- GO to FINISH UP.

2. Turn the Screw Back 1/4 and GO to 3..

3. Turn the Fuel Ratio Screw Clockwise 1/4 and wait 10-15 seconds to allow the engine to catch up with the new setting.

** IF ON THE FIRST TURN IT DOES NOTHING YOUR PILOT JET AND OR PASSAGES ARE CLOGGED*** GO to CLEAN CARB*** Otherwise GO to a. below.

a. If the IDLE GOES up repeat 3.
b. If the IDLE does not go up or it does nothing turn the Fuel Ratio Screw 1/8 Counter Clockwise that should be the highest IDLE you can get out of the Fuel Ratio Screw-- GO to FINISH UP.

FINISH UP:
SET IDLE USING IDLE SPEED SCREW:
USING the IDLE SPEED SCREW set the Idle to 1500-1800 where it IDLES the smoothest AND the REAR WHEEL IS NOT Spinning-

TEST YOUR ADJUSTMENT:
Now while on the Center Stand GIVE THE THROTTLE a GOOD QUICK TWIST and Let go,
It should REV UP with with a nice VROOOOOOOOOM with no Bogging or Hesitation and Come back down to where you set your Idle.
DONE RIDE SAFE.

CLEAN CARB:
Take Carb Bowl off and clean Pilot Jet and Pilot Jet Passage and Main Jet and Passage.
Then come back and repeat this procedure.
Alleyoop

[apothecary]

Ok I'll give this a shot in the morning. I've been fighting a few issues with the scoot lately (intermittently working horn, odd issues with the blinkers) so I've been focusing on electrical all day today. I might even take the old Flip camera out and get a video once she's warmed up so you can hear what I'm hearing and give me a bit better of an idea.

I'm thinking it's a popping kind of like a gun but not quite that loud. It's definitely not a BRUP. When I give her gas, she bogs for a second nearly dying (if not warmed up it DOES die) then picks up and revs up fine. When I let off it pops as the engine comes down from the higher revs and then pops once in a while as I coast at speed.

[alleyoop]

Good a Video with sound would help, or just a recording of the motor running with the sound you are hearing. Well the timeing of when it emitts the sounds when letting off the throttle is usually backfires, POPPING usually happens when your excelerating or reach a certain speed and it will go POP. If it makes the sound as your slowing down, if you hold the throttle a little open it should not emit the sound if its a backfire.

Alleyoop

[apothecary]

Ok I'll appologize right now if the sound is off from the video. I guess youtube doesn't handle MP4 well and that's what the Flip records in. Anyways, here's the link for the video giving the sounds that it's making and (hopefully) syncing what I'm doing to the sounds.

The temp gauge stayed low the whole time though. Never above 3 bars.

[alleyoop]

WOW!! That is pretty bad(HAHA).
When I first was listening I did not think you had a muffler on. But one thing I hear is I think it is leaking by the HEADER PIPE FLANGE where it connects to the Motor. Now also that looks like a performance Muffler , do you have the AIRBOX on or a Free Flow FIlter? I noticed it backfires once in a while when you let go of the throttle which means LEAN condition.

Did you Re-jet the Carb.
Alleyoop

[apothecary]

Carb is NOT rejetted and the rest of the scoot is stock. The ONLY performance thing on it is the muffler/exhaust. It IS loud but without it, it's actually MUCH louder.

[alleyoop]

So it has an AIRBOX or a different type of AIR FILTER?

[apothecary]

Stock air box. There's a filter inside the airbox and I mean a regular style filter not the foam sheet the 50cc's use. But the filter is also stock.

[alleyoop]

One thing to try and see if you will have to re-jet is Raise the NEEDLE in the Diaphgram that will give it more fuel when you twist the throttle. Do you know how to do that?
Alleyoop

By the way WHEN DID IT START TO DO THIS, did it ever run right?

[apothecary]

Take off the top cover, pull the needle, take the E clip and drop it down a notch right?

And do you still think the exhaust is leaking at the head? If so, I'll try tightening it down. I actually probably need to adjust it a little as well to line the muffler up a little better.

[alleyoop]

Well it sure sounds like it is leaking I thought you were not running with a muffler when I first heard it and then later in the Video I saw that you have a muffler on it. But it sure sounds like it is leaking. Now be carefull with the Nuts on the Exhaust on the Head Do not crank on the cause you will either strip it or the ACTUAL stud will break off then it is a PITA to get the broken stud out of the head. Snuge them up EVENLY little on one nut then the other the Flange has to come up even otherwise it will leak from one side or the other.

And your correct about the needle Drop the CLIP try one notch if it improves drop it another notch.
Alleyoop

[apothecary]

All right. I'll give the exhaust another shot. Maybe I tightened one side too much when I installed it the first time. I have to adjust it a bit anyways for the muffler . I'll give those both a shot tomorrow don't want to wake people tonight testing it out at midnight. I'll take another video when I get it done to see what, if any, difference it makes.

[alleyoop]

COOL!! If raising the needle improves the situation you will have to get a jet about 2 sizes bigger.
Good Luck tomorrow man hope raising the needle helps it a little. I will watch for your results tomorrow.
Alleyoop