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mmaleh

Did I mix poorly?

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So my newly restored Li150 S3 has been running great. I had a full tank of gas in it from the shop that worked on it.   I just premixed my own and I thought I did it at 40:1 things seemed to be going well but then towards of the end my ride last night she stalled out coming up my steep driveway (in 1st gear) and then even when I got her to fire back up she would not make it up.   A few things to note. 

1. When I started it cold that day she was producing a lot of smoke but then when warm was fine. 

2. It was really really hot here. Like 100 outside not sure if that would be an issue. 

3. When I originally tried to make it up the steep driveway I had my 150 lbs brother on the bike as well.  But then on second attempt it was just me and did not make it. 

4. I am using Castor 927 Pro Series as my oil

 

Appreciate any advice for this newbie.  

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Check your spark plug color first. Is it greasy/black(rich), chocolate brown (just right), chalky grey (lean)? What spark plug are you using? Try swapping it out for a new one. Gap it correctly before installing.  Is it totally stock? What are your (stock?) carb settings, timing (points or electronic)? Since it is carbureted and the weather is extremely hot and humid that can make your carb settings rich. Especially if the shop tuned your carb when the weather was cooler and dryer.  I think a lot of people on here follow the 3, 3.5, or 4 oz.. per gallon of gas depending on the top end/ state of tune. Have you spoke to the shop to get their thoughts? Keep us posted

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Okay update here.  She started after a few tries today in the driveway.  A lot cooler here but then after getting warm she died.  Pulled the plug and it was black and greasy. I did not have a spare handy but I cleaned the plug a bit and put it back and it started right up.  So what do we think this means?

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It would seem to be rich. At least at idle. Choke off? What plug number is it? What carb and what are your carb settings, electronic ignition or points and what is the timing set at ? If you post that info (or some of it), people with similar set ups can chime in with what works for them. Did you mix your gas correctly? I'd say for yours 3oz. or 3.5 oz per gallon. Also, buy 5 plugs keep two with you when you ride... Extra things to bring is a whole other topic

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Since the bike is not in front of me and I am a rookie I will answer what I can. 

The choke was off (after it warmed up) and it ran but I was constantly giving it a little bit of gas maybe more out of fear that it would die.  It is on coil and points not electronic ignition.  The only two things that really have changed are the outside temp and humidity and the fuel mixture.  This time the fuel mixture was done by me rather than the restoration shop.  So not sure if the richness has to do with the oil to gas ratio rather than the gas to air mixture even though I know they are all tied together!   But this is why I love the help this forum provides.  :) 

Carb - Dellorto SH1-18/20 Carburetor - fully rebuilt, cleaned, new gaskets etc only 4 months ago with about 40 miles driven. 

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Read the Manual on this site from cover to cover.  Use the indicated mixture. spark plug etc.

 

WW

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Thanks. 

Those documents state 4% on run in and then 2% after that. I went 2.5% aka 40:1 on this but was that wrong?  Would that cause the black spark plug?

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No. Your plug is black because your jetting is off, or your timing is off

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Was also reading this for what it is worth.   http://www.lambretta.co.uk/downloads/sparkplug.html

We did experience a large change in heat and humidity in the north east

Fouled Plug

Wet fouled plugs are normally caused by rich air/fuel mixtures, these must be changed as the plug will not operate. The richness is more comonly caused by jetting, but can also be caused by an incorrect fuel to oil ratio. Fouled plugs can also be caused by selecting to colder grade in spark plug which will not allow the plug to burn the mixture efficently. Dry-fouled spark plugs can sometimes be cleaned by bringing engine up to operating temperature.

Before changing fouled spark plugs, be sure to eliminate root cause of fouling. Running rich can also be caused by a number of other factors, Change in Ambient air conditions, altitude, humidity

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16 hours ago, DerekM said:

No. Your plug is black because your jetting is off, or your timing is off

its worth repeating. 

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16 hours ago, mmaleh said:

Thanks. 

Those documents state 4% on run in and then 2% after that. I went 2.5% aka 40:1 on this but was that wrong?  Would that cause the black spark plug?

Stick to 32:1 fuel mix (I use yamalube R)

For stock I like a B8ES spark plug

Make sure the plug is gaped to the correct spec (.02"- .024") 

Ride the bike, once it's warmed up then correctly set the idle and "usually" the air/fuel mix will sort its self out. 

Big shifts in heat/humidity can and do affect how the motor will run. 

 

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