Lawnboy 7263 running too lean???

[franchi]

Helloi All:

I am atttempting to get a Lawnboy model 7263 to run well. Right now it is so lean that it only fires about every 12-20 th rotation of the blade. I can start it by spraying carb cleaner into the carb but it will barely run after started. I can cover the carb throat at about 95% with my thumb before it starts to choke from insufficient air supply. I can not get a too rich condition with this engine. It is so lean that it will backfire through the carb. The plug is dry after running. I tried 3 different plugs just for laughs.

I have done the following to no avail:

Checked for a fuel supply at the carb. Plenty of fuel being supplied.

Cleaned all fuel passages in the carb.

Checked the float level and it was perfect.

Checked the needle and seat and they were perfect.

Checked for an air leak in the primer bulb and hose. They were were perfect. Pushing the primer bulb makes no difference! ???????????? It should richen the mixture and cause the engine to gain speed. This may indicate a fuel blockage but I have cleaned and inspected all fuel passages. This may be the key to the problem. I can blow through the primer hose into the carb. This should force more fuel into the carb if it is funtioning and cause the engine to become richer but it does not! ???????????

Checked the reeds and reed plate and they were perfect.

Float pin and float are in perfect working condition.

Checked for an air leak around he carb body and there was none. All gaskets are fine. No fuel leaks.

Position of the throtle makes no difference. It only runs at a very slow speed and sometimes stops.

Any suggestins as to what is wrong with this engine?

Tia,

Franchi

 

[franchi]

Hi All:

I just had a terrible thought! This may be a sign that the crankshaft seals are leaking base compression and not permitting the engine to draw a fuel mixture into the crankcase! Say it aint so!!!!! I have had this problem in the past with model airplane engines!

It is not my mower and I was doing a "friend" a favor by looking at it! He can replace the seals but I want no part of this fun! Lol

Stay well my friends,


Franchi

 

[2smoked]

You might have a short in your ignition system. Perhaps your on-off switch is grounding out. Engine vibration may be playing a role in this, hence the intermittent running. Look at all the ignition wiring and see if the insulation is worn off or broken anywhere.

 

[Grassbandit]

did you already check to ensure the flywheel key is in tact?

 

[franchi]

Hi 2smoked:

Thanks for the reply.

I will check the short idea but I learned that if the engine starts on the third pull after being primed on each attempt, the ignition system is good. The engine starts quickly but runs too lean. Too lean may not have anything to do with an ignition problem. However, I will check it out tomorrow by using a spark tester.

A weak spark may permit the engine to start but under a more severe load, as when running, the weak spark may not be able to light the air/fuel charge. It is worth a look!

Stay well my friend,

Franchi

 

[franchi]

Hi Grassbandit:

I did not check the key/keyway but I did notice that the ignition system produced a good spark when tested. I may be wrong, but if there is a problem with the key/keyway, would not that lead to difficult starting? This engine starts on the third pull everytime after being primed with carb cleaner.

Perhaps I am looking in the wrong place for this soultion. Why would there be enough fuel to fire the engine every 12-20 reveloutioins? Is there a bit of fuel collecting in a place that makes the mixture rich enough to fire?

If the crankshaft seals are leaking, would there be a wet area where there was a leak? Perhaps therwould not be any wet spot due to that leak admitting air into a lower pressure area of the engine. Can one say crankcase vacuum?

This is a D 600 engine with a metal carb and solid state electronics.

Any other comments?

Thanks for the replies,

Franchi

 

[old lawnboy]

You may have 2 problems. The way the engine is running, makes me think you have a bad ignition module (coil) or it is not set correctly at .010 from the magnets on the flywheel. The ignition module has a two stage ignition. It starts with a retarded spark, then advances to run setting at a given speed. This is done electronically and I have seen a couple that would not run on the high speed setting. They sounded like a hit and miss engine. They would start on the low speed setting, then switch to the high speed setting but get no spark and slow back down and the low speed setting would again fire and pick up speed to go to high speed and no spark and go back again. This can also happen if the coil is not set properly, but only on a weak coil. Also have had spark plugs do something similar. If you are choking the engine with you thumb, you might be keeping it form speeding up enough to reach the high speed setting. As for fuel, your engine is going through a intake, compression, power and exhaust stroke each revolution, it should clear each charge of fuel every revolution and not let it build up to get it to fire only every so many turns of the shaft.

 

[franchi]

Hello oldlawnboy:

Thanbks for the reply!

I too am beginning to suspect that the problem is caused by a faulty ignition rather than fuel. I have checked the function of the carb and the fuel system and I can find no reason to suspect that it is faulty.

I checked the air gap on the flywheel and it was right at .010". I am going to get another ignition module and do an A-B test. I bet that your are correct! All things now point to a faulty ignition module. I checked the kill switch and all of the wires that I could see and found no problem. What I can not see is what is going on inside of the ignition module.

I now have a good feeling about this mower.Lol

Again thanks for the information!

Stay well my friend,

Franchi

 

[Grassbandit]

Hi Grassbandit:

I did not check the key/keyway but I did notice that the ignition system produced a good spark when tested. I may be wrong, but if there is a problem with the key/keyway, would not that lead to difficult starting? This engine starts on the third pull everytime after being primed with carb cleaner.

Perhaps I am looking in the wrong place for this soultion. Why would there be enough fuel to fire the engine every 12-20 reveloutioins? Is there a bit of fuel collecting in a place that makes the mixture rich enough to fire?

If the crankshaft seals are leaking, would there be a wet area where there was a leak? Perhaps therwould not be any wet spot due to that leak admitting air into a lower pressure area of the engine. Can one say crankcase vacuum?

This is a D 600 engine with a metal carb and solid state electronics.

Any other comments?



Thanks for the replies,

Franchi

I like the suggestion of a faulty wire causing it to ground out intermittently.
From experience, its best to just go through every aspect and not trust that any area is exactly the way it should be. So just take the time and check every little thing.

 

[old lawnboy]

I should be easy to check out the wiring, as there is only a short wire going to the on/off switch. If you remove it from the switch and keep it away from the metal surfaces, you check the switch circuit also. A good tester is an in line spark tester. One that you hook to the spark plug then the other end goes to the plug wire, It has a neon light in it that sparks each time that the coil send a spark. You can still have a bad plug with it lighting up. I am not sure if the ignition module for the D600 is still available from Toro, The last I checked they were over $100.00 if I remember correctly. I did see a one on e-bay yesterday for around $35.00 though.