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Very frustrated with D-engine mower

#1

P

Phototone

I've got a late D-series engine mower. It is an International, but it was made by Lawnboy, and is Lawnboy thru and thru. I have replaced the rings, new seals, gaskets, new reeds. It has good compression, and it has spark. The darn thing won't start. I'm tearing my hear out. It is an early electronic (pointless) ignition..much longer coil than later ones. (if that matters). It gets spark when I hand rotate the flywheel, holding the spark-plug against the head. Sparks every revolution. The carb is clean, new needle and seat, it's getting fuel.


#2

L

LB8210

How many lbs. compression?


#3

beg

beg

what kind of spark?:is it snappy or just sparking a weak blue?you done replaced everything so I assume it has great compression.Is the plug wet?I would pop for a new coil if you can find one otherwise you have to use the newer one with is ***** backwards on the on off switch wiring Is it the cool looking International with the cub cadet style shroud?


#4

P

Phototone

beg said:
what kind of spark?:is it snappy or just sparking a weak blue?you done replaced everything so I assume it has great compression.Is the plug wet?I would pop for a new coil if you can find one otherwise you have to use the newer one with is ***** backwards on the on off switch wiring Is it the cool looking International with the cub cadet style shroud?
Click to expand...

This coil on this mower is NOT LIKE any other later lawnboy coils. It has three pole ends, and 3 magnets on flywheel. In other words, on all later coils, there are 2 end pieces that you gap with flywheel, this has 3. The later coil would not work, nor mount. Yes, it is the one with the cub cadet style shroud. This has a mechanical governor also, like the older models with points. Not the vane-style later carb. The spark appears to be the same quality as my later Lawnboys which run. It doesn't take much speed when hand-turning the flywheel to make spark.


#5

dewguy1999

dewguy1999

This may be a stupid idea but I'm going to throw it out there anyway in case it does have merit. Is it possible it's not sparking after the plug is installed?


#6

M

motoman

Photo, Visible spark may still be weak under compression and not fire. Try using a spare or discarded plug as a test . Open the gap up to 1/8" or so and try. (Cut off the side electrode even with the top of the center one). I tried this on a trimmer which was failing. A new trimmer would fire the 1/8", not the failing one.


#7

L

LB8210

Did you have the mower running before the rebuild?

What was wrong with the mower before the rebuild? Just because the rings are new doesn't mean that the compression is good. How many lbs compression does it have? Too low and it will not start or run. The rings may not be seating well and or how much taper in the cyl?. Is the cyl round ? Is there any scoring on the cyl wall? Did you deglaze the cyl? Low compression will also cause poor fuel delivery to the combustion chamber. First things first. What did you get for your compression test reading?


#8

Two-Stroke

Two-Stroke

I tend to trust a solid-state coil if it sparks at all. I've heard of ones that will spark visibly but not spark good enough to fire -- but I've never seen that personally.

Here's another possibility that nobody has mentioned:

Is the crankcase sealing properly? If not, the cause could be crankshaft seals or the gasket between the reed plate and the crankcase.

Don't forget that a two-cycle engine must have a good sealing crankcase so that, on the downstroke, the fuel-air mixture will compress and at the right moment, shoot up into the combustion chamber.

Good luck.


#9

P

Phototone

Two-Stroke said:
I tend to trust a solid-state coil if it sparks at all. I've heard of ones that will spark visibly but not spark good enough to fire -- but I've never seen that personally.

Here's another possibility that nobody has mentioned:

Is the crankcase sealing properly? If not, the cause could be crankshaft seals or the gasket between the reed plate and the crankcase.

Don't forget that a two-cycle engine must have a good sealing crankcase so that, on the downstroke, the fuel-air mixture will compress and at the right moment, shoot up into the combustion chamber.

Good luck.
Click to expand...

I have new crankcase seals
I have new gasket between reedplate and crankcase
I have new reeds, adjusted correctly
I have new gaskets for top and bottom plates.
I have new gasket between cylinder and crankcase


#10

P

Phototone

LB8210 said:
Did you have the mower running before the rebuild?

What was wrong with the mower before the rebuild? Just because the rings are new doesn't mean that the compression is good. How many lbs compression does it have? Too low and it will not start or run. The rings may not be seating well and or how much taper in the cyl?. Is the cyl round ? Is there any scoring on the cyl wall? Did you deglaze the cyl? Low compression will also cause poor fuel delivery to the combustion chamber. First things first. What did you get for your compression test reading?
Click to expand...

Last spring (2013) after a clean-up and carb rebuilding it ran quite good, with easy starting, until one day it just wouldn't start. I put it away until this week, to do refurbishment.


#11

L

LB8210

Compression reading?


#12

P

Phototone

LB8210 said:
Compression reading?
Click to expand...

Thats next. Stand by


#13

L

LB8210

Test it this way. Use no oil or any lube just dry with only the oil left over from the last time it was run. Note reading on the first pull, then pull 3 more times note this reading , then pull until needle stops rising and note the last reading. I should have asked this first, What is the model and serial numbers?


#14

P

Phototone

IT WORKS!

Compression reading was 70lbs According to book, thats good! (that with new rings that may not be seated yet)

I put new spark plug in, poured some raw gas down carb, and it fired up just fine.

Now to mow a yard....the real test.


#15

P

Phototone

LB8210 said:
Test it this way. Use no oil or any lube just dry with only the oil left over from the last time it was run. Note reading on the first pull, then pull 3 more times note this reading , then pull until needle stops rising and note the last reading. I should have asked this first, What is the model and serial numbers?
Click to expand...

Well, I had to use some assembly lube, to insert the piston back into the cylinder. So the assembly is oily.

See above, the mower works now.

I get a maximum compression reading (this was before it ran first time) of 70 lbs, according to Lawnboy Service manual this is OK.
The Mower is an International Harvester (made by Lawnboy)...has a D-600 series engine.


#16

L

LB8210

The compression reading at the time of assembly prior to being run may be a false reading. Only after running and washing out the assembly lube and testing on a cold motor will you get a true reading. The actual reading after having run the motor may be border line and is lower than 70lbs. If you have been using starting fluid to get it running you may have washed the oil off of the rings and lowered your compression below the minimum 65lbs required to run. And then by adding fuel / oil mix you then relubed the rings and cyl walls restoring the compression high enough to run. Wait until tomorrow with a cold motor and retest the compression. What is your spark plug gap and spark plug number and brand?


#17

P

Phototone

LB8210 said:
The compression reading at the time of assembly prior to being run may be a false reading. Only after running and washing out the assembly lube and testing on a cold motor will you get a true reading. The actual reading after having run the motor may be border line and is lower than 70lbs. If you have been using starting fluid to get it running you may have washed the oil off of the rings and lowered your compression below the minimum 65lbs required to run. And then by adding fuel / oil mix you then relubed the rings and cyl walls restoring the compression high enough to run. Wait until tomorrow with a cold motor and retest the compression. What is your spark plug gap and spark plug number and brand?
Click to expand...

Its running now, very strong, and starts on first pull every time when warm. I have an issue with the primer not priming, but I have the parts to fix that. I did not use "starting fluid" when I was testing yesterday, rather, I used WD-40-which I generically called "starting fluid", which works quite well as starting fluid generally, and is oily, so it doesn't wash the cylinder walls down. MY problem was (I think) an old spark plug that got oily from the assembly lube (which I replaced with a fresh plug), and primer not working. Poured a little gas down the carb after putting in fresh spark plug, and it started right up, and ran. I just mowed a big yard. excellent performance.


#18

M

motoman

Photo, Glad your'e running. Two stroke did mention an important topic-crankcase pressure. Maybe he will say more for 2 strokers watching, like the test gear used to test crankcase pressure.


Two stroke. Weak sparks get weaker at hot as the transistors miss there and improve a little at cold. But they cannot heal themselves like a semi-gummed carb. :smile:


#19

Two-Stroke

Two-Stroke

motoman said:
Photo, Glad your'e running. Two stroke did mention an important topic-crankcase pressure. Maybe he will say more for 2 strokers watching, like the test gear used to test crankcase pressure.


Two stroke. Weak sparks get weaker at hot as the transistors miss there and improve a little at cold. But they cannot heal themselves like a semi-gummed carb. :smile:
Click to expand...

I know those insturments exist but I don't have one. :ashamed:

Here's what I do: Disconnect the sparkplug wire (for safety) but leave the plug in. Lift the mower up on its side and rotate the crankshaft by hand -- and observe carefully the feel of both the upstroke and the downstroke (relevant to crankcase pressure). If I'm familiar with what a good-running engine of the same series feels like I can tell if the suspect engine is OK -- within a reasonable margin of error. I've worked on quite a few D-series and F-series LBs so I know what they should feel like.


#20

robinb66

robinb66

Phototone said:
I have new crankcase seals
I have new gasket between reedplate and crankcase
I have new reeds, adjusted correctly
I have new gaskets for top and bottom plates.
I have new gasket between cylinder and crankcase
Click to expand...

how bout the gasket between the carb and reedplate?


#21

P

Phototone

robinb66 said:
how bout the gasket between the carb and reedplate?
Click to expand...

Brand new gasket there also.


#22

M

motoman

I once use a hardware pressure gauge rigged up for a Husky chainsaw motor that was acting up. I think the drill is like a compression reading . Take the reading and see if it holds.
Wish I had bought a Yamaha 350 and kept it. (trivia)


#23

J

jp1961

Another thing to check is if you installed the reeds correctly. The reed must be installed with the rough edge away from the machined surface on the reed plate. It also has to have a .015" gap when installed. The reed evidently has a rough edge and a smooth edge.

Jeff


#24

P

Phototone

Its all fixed now.

After all the rebuilding, the "MAIN" issue was the carb primer was not working, thus it wouldn't start. I put in a "kit" of primer parts, it primes well now, and it starts easy when cold. I did take another compression reading after the mower had been setting for four days, and I got about 68 lbs max, after several pulls, so I am within spec. (D-400 engines are supposed to have min. of 65 lbs).


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