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Enduro Engine - 2 stroke Cylinder, Piston, Tranny, Bearings, Clutch, Pipes & Silencers, etc.


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Old 05-04-2016, 07:03 PM
Munch Munch is offline
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Default How to know if the bike is running lean?

Hello GG riders!

I purchased a gas gas ec 250 2006 a few days ago from a family member with a spluttering problem.

Basically it would start first kick every time but the bike would splutter very bad at anything more than 10-20% throttle, I solved this by running a hotter plug (br9) and changing the mixture from 40:1 to 50:1.

Now I am afraid the bike is running lean, I put a fresh plug in and took it for a test ride for approx 5 minutes and the plug was a very light colour, yellow/white colour which I believe means it is lean?

Is there some sort of trick to finding if it is lean? If it is lean how do I go about making it richer?

My settings:
Pilot: 42
Main: 172
Needle: #3
Needle type is "N1EF"


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Old 05-04-2016, 07:14 PM
Munch Munch is offline
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Also something else is that when I first got the bike I tried to set the float however I think I've messed it up somewhere because when the bike is on it's stand leaning to the side the fuel will leak out of the overflow pipe which I'm sure isn't meant to happen?
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Old 05-04-2016, 08:39 PM
Brian VT Brian VT is offline
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Air leak at rubber carb. connection?
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Old 05-04-2016, 09:00 PM
GGRider01 GGRider01 is offline
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Quote:
Originally Posted by Munch View Post
Also something else is that when I first got the bike I tried to set the float however I think I've messed it up somewhere because when the bike is on it's stand leaning to the side the fuel will leak out of the overflow pipe which I'm sure isn't meant to happen?
Your float height is either improperly set, or the viton tipped needle is worn out/hardened.

It's hard to even guestimate whether those jetting settings are lean without elevation, humidity and temperature data. However, if you're below 4000ft, I'm going to say you're lean. However, sputtering is indicative of rich which I'm going to attribute solely to that needle. Drop it (put the clip higher on the needle to lower the needle) one clip at a time without changing jets. This will lean the bike out. If it is bogging however, start raising the needle. Bogging sounds kind of how it is spoken.. "BAAWWWWG.."

If you get to the bottom clip position, you need a richer main jet. If you get to the top of the needle, you need a leaner main jet. (Fixed) More information on this: Clip positions are numbered from top to bottom 1 being leanest, 5 being richest. 3 is, obviously, right in the middle.


Changing from 40:1 to 50:1 increased your FUEL to AIR ratio. The 2 cycle oil in the gasoline is neither fuel nor air. Point here is, you made it run richer by using less oil. The downside is.. you're using less oil...

Finally, your last misconception is that the BR9 is hotter than a BR8. It is opposite. The lower the number on an NGK spark plug, the hotter the plug is. The number indicates the plugs ability to dissipate heat. The higher the number, the longer the insulator is, and the more heat the plug is able to "absorb." You say that by putting a colder plug in, you solved your sputtering problem, but I believe your previous plug was merely fouled. Moving forward, I sincerely suggest you stick to one oil ratio and one spark plug. The BR8 is a perfectly sound plug, and hotter than the one you're currently running. All in all, the changes you've made are minuscule and inconsequential.

Poof. Also, good luck.

EDIT: I just saw another post of yours. You're in England, so I'm going to assume you're fairly close to sea level. Get a 178 or 180 main jet in that bike and your woes may soon disappear. You'll be in the ball park at the very least. Take a look at the jetting database stickied here. There are several members in the UK whose jetting you could copy and modify to your own needs.

Last edited by GGRider01; 05-04-2016 at 10:06 PM.
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Old 05-05-2016, 02:36 AM
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barossi73 barossi73 is offline
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If your heat range is correct the j shaped outer electrode should show a color change in the mid section (between 1/4 and 3/4 of the electrode length)
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Old 05-05-2016, 04:34 AM
Capz85 Capz85 is offline
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I'm in the uk munch, as GGrider said try some richer jets or even a better needle, I used to run a 45pj and 180 main with one of the N3 series needles on my 300 worked pretty well.

Also worth checking your not pulling air in from somewhere, which might be causing it to be lean
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Old 05-05-2016, 06:53 AM
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Jakobi Jakobi is offline
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Quote:
Originally Posted by Munch View Post
Hello GG riders!

I purchased a gas gas ec 250 2006 a few days ago from a family member with a spluttering problem.

Basically it would start first kick every time but the bike would splutter very bad at anything more than 10-20% throttle, I solved this by running a hotter plug (br9) and changing the mixture from 40:1 to 50:1.

Now I am afraid the bike is running lean, I put a fresh plug in and took it for a test ride for approx 5 minutes and the plug was a very light colour, yellow/white colour which I believe means it is lean?

Is there some sort of trick to finding if it is lean? If it is lean how do I go about making it richer?

My settings:
Pilot: 42
Main: 172
Needle: #3
Needle type is "N1EF"
With todays fuel blends (detergents etc), synthetic oils, and not to mention 5 minutes ride time.. I'm not surprised you have very little colour on the plug. It started out white. If you fear you are lean get a well used plug that's nicely coloured and do a run on it. If you're lean you'll turn whatever colour/carbon is on it white and ashy.

Lean symptoms are as follows
- Hard starting when cold. Needs choke, and needs choke for a long while before continuing to run.
- Once hot you could see weak flat power, hesitation and cold stalling when cracking the throttle open (BOOOWAAAH sound) that drops rev and sounds like its gasping for fuel. Backing the throttle off the engine will want to surge or run on for bit before the revs drop. Pulling the clutch the revs won't drop immediately. At idle the engine will surge, race, and resist settling into a steady idle.
- The engine will run very hot. Pipe may discolour. Coolant may be expelled.
- The throttle response will sound sharp and crisp. If too lean you'll note that it appears the bike makes more noise but doesn't go any harder or faster.

Rich symptoms are smoke, spooge, blubbering wet sound (similar to what you feel when you forget to take the choke off, or ride around too slow and load the engine up with fuel).

A lean setup will typically run like a cut snake for a short period of time and then the power will flatten right out as the engine gets too hot and the symptoms will show.

A rich setup will run poorly in general. Depending on where it is rich it won't take throttle well.. but if transitioning into a leaner area of the jetting it can work through and run ok at certain throttle positions.

After all that, you can be rich in one throttle position, and lean in another. You could be rich across the board, or lean as well. Work methodically and adjust each circuit to seek improvement. If you go lean and pick up symptoms move back the other direction.
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Old 05-05-2016, 09:36 AM
Munch Munch is offline
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Wow I got a ton more information/replies than I expected, thanks all!

Because of all the info I will explain below exactly what I have done and then hopefully I can be given advice on what step to take next.

A family member bought the bike for super cheap from a friend, it was stood for approx 3 years without any use, old fuel still in the bike. He doesn't know much about bikes and only rides so I was doing all the work for him.
  • Emptied tank
  • Put straight fuel in and washed it out making sure tank is clear
  • Cleaned the carb with carb cleaning, including jets ect
  • Fresh plug (BR9)
  • Fresh mixture, 40:1 putoline oil

After all of the above it still spluttered so I did a lot of researching and did the below:
  • Another fresh plug
  • Checked reeds
  • Leak down test on the inlet with carb cleaner
  • Checked for any obvious sign of damage to electrics
  • Tried a different muffler

I also purchased a few jets both bigger and smaller pilot and main ready to try.

The splutter was extremely bad, right through the range too and the bike smoked a lot (blue smoke though)

I was reading the manual and noticed it recommends 50:1 so I tried that with a different type of plug (br8) and it seemed to do the trick, the bike is hitting powerband in every gear, zno spluttering at all.

I don't get to ride the bike until Sunday but my plan is to run it and see how it rides, check the plug after some more riding. If the plug is lean what steps should I take to make it more rich?
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Old 05-05-2016, 09:47 AM
95jersey 95jersey is offline
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I have learned not to bother with the plug. It is too vague to read 1/2 the time.

I go by sound and feel. Lean has a high revving pinging sound. Also, the throttle will hang. It will also be down on power but may hit hard on the top out of no where.

Richen it until it gets blubbery then go one step back.
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Old 05-05-2016, 09:56 AM
Munch Munch is offline
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Quote:
Originally Posted by 95jersey View Post
I have learned not to bother with the plug. It is too vague to read 1/2 the time.

I go by sound and feel. Lean has a high revving pinging sound. Also, the throttle will hang. It will also be down on power but may hit hard on the top out of no where.

Richen it until it gets blubbery then go one step back.
Yeah it sounds very snappy and loud right now, almost like my kx 125, I'm sure they are meant to sound a lot more tamed because of the longer muffler right? I also noticed inside the muffler only around 30% of the length of it was packed, the rest empty.

How do I go about richening it?
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