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D125 Coil problem?

#1

A

aussietrev

Hi all.
I have a D125 with the 20HP V Twin and it intermittently will only run on one cylinder but then suddenly the other one kicks back in. It might run fine then for a couple of hours or it might play up again within minutes. I'm thinking probably a coil pack, I replaced the plugs even though they both looked okay, and am wondering if there is an aftermarket coil pack available since they want $150 for a genuine one here in OZ. If there is, can anyone tell me the part number please. Anything else that could cause this symptom? The machine has done just over 600 hours.


#2

B

bertsmobile1

Start with the easy bits first
Remove the rocker covers & check the valve lash .
NExt , confirm that the fuel solenoid on the carburettor is working, it should click on & off with the ignition switch.
If so then remove the top cover and remove the kill wires from the coils
Run the mower like this and see if the problem goes away , The kill wire has 2 diodes in it that fail causing random ignition problems
Remember that the mower is more dangerous to use in this condition so it is just for testing , not a cheap fix .
Get back with the results
You should have a Briggs & Stratton 40 series (40?877–0008–G1) which uses the #691060 B & S magneto
Genuine B & S from a JD dealer will be the cheaper than from a B & S dealer by 20% to 30% as JD parts are not subject to the Melbourne Mower Parts Mafia prices
JD part no # MIA12788
The Stens part is # 440-445 which I can do for $ 60 + P&P if you are interested
Do not even think of getting one from Scamazon or Evilpay as the bulk of what is on there are defective parts bought as scrap metal then sold to people who are too cheap for their own good .

​



#3

Tiger Small Engine

Tiger Small Engine

bertsmobile1 said:
Start with the easy bits first
Remove the rocker covers & check the valve lash .
NExt , confirm that the fuel solenoid on the carburettor is working, it should click on & off with the ignition switch.
If so then remove the top cover and remove the kill wires from the coils
Run the mower like this and see if the problem goes away , The kill wire has 2 diodes in it that fail causing random ignition problems
Remember that the mower is more dangerous to use in this condition so it is just for testing , not a cheap fix .
Get back with the results
You should have a Briggs & Stratton 40 series (40?877–0008–G1) which uses the #691060 B & S magneto
Genuine B & S from a JD dealer will be the cheaper than from a B & S dealer by 20% to 30% as JD parts are not subject to the Melbourne Mower Parts Mafia prices
JD part no # MIA12788
The Stens part is # 440-445 which I can do for $ 60 + P&P if you are interested
Do not even think of getting one from Scamazon or Evilpay as the bulk of what is on there are defective parts bought as scrap metal then sold to people who are too cheap for their own good .

​

Click to expand...
Bertsmobile-
Do you just happen to know this particular engine has two diodes in wiring from memory? Just wondering because I see very few mowers or equipment that use diodes.


#4

B

bertsmobile1

The main engine harness # 591392
Google it and you will see the 2 diodes to prevent the coils sending ripples down the kill wires
Honda & Kohler have them inside the magnetos , B & S have them in the wire
I bought a 100 pack from Mouser for about 10¢ each and replace them because down here a loom is just short of $ 100 US
I make up a new set of kill wires then splice it into the old loom as B & S usually crimp them into the wires & there is not enough space to solder a replacement and if the wire breaks then the kill is non functional .


#5

StarTech

StarTech

And you use both splice crimps and heat shrink tubing. Of course I usually replace all the terminals when I make up a new harness. They are not that expensive but the tool is for for use on one project only. When I brought the open barrel I thought $70 was high but have since brought a second one as I had have one of the supplied dies modified and I would definitely buy again if needed.

Splices are Mouser PM 571-42778-2 (22-15ga). These are also use for installing thermal fuses. There is a couple larger sizes available too. These also allow splicing a lead off the main line ie a Y connection without cutting the main line.


#6

B

bertsmobile1

We are getting a bit ahead of ourselves, lets wait for Aussietrev to come back with the test results


#7

A

aussietrev

Sorry haven't gotten to pulling it down yet, it has been horrendously hot here in Oz and not conducive to being in a shed with no AC :cool: Will report on findings once the weather changes for the cooler.


#8

StarTech

StarTech

I trade 50% of you heat for 50% of my cold days lately. That way we both be halfway comfortable. Not laying the cold asphalt in 20-30F temps with the wind blowing just to do electrical wiring.

And the summer months I am a shade tree mechanic for a reason; otherwords, I am not stupid enough to work on 140F asphalt on those days. I rather cook my steaks at 140F+ temps.


#9

B

bertsmobile1

I go native at this time of year
Nov & Dec it is dawn & dusk so siestas in the woods from 12 till 8pm
then from Jan to March it is nite shift for work & sleep during the heat of the day
Was 42 C yesterday, will be 45 today & around the same all next week .


#10

StarTech

StarTech

Please Bert I didn't want that thought in my head this early in the morning. That would be as bad as the Shawn pants that were posted on the ODK forum a few years ago,


#11

B

bertsmobile1

Native, not naked
The black fellas do the same as native animals in the heat of summer during the day
Find a cool shady spot & stay there
I have a pine forest near by from an abandoned christmas tree farm
In the forest it can get as much as 15 C lower than the air temperature and 25 C lower than the ground temperature.
Just come back in from turning the wartering system off 54 C on the grass so that will be near 70 C on the black bitumen road


#12

StarTech

StarTech

Bert I knew what you meant...But even some look really bad. Wearing heavy white loose fitting clothes do work except there is no way to keep them that white unless you don't work.

Now that is hot as the top black driveway here in the peak Summer here. Hot enough to melt the soles of some foot wear. I think my drive hit 152F this at one time. In some place the new paving just slide off the old surfaces. They are now repaving those areas.

Yes I switch to working under the shade trees during that time. That's why I don't mind being called a shade tree mechanic.

Now it wa 40F here and I just got my shearing and boy was my head cold with the wind blowing.


#13

B

bertsmobile1

StarTech said:
Bert I knew what you meant...But even some look really bad. Wearing heavy white loose fitting clothes do work except there is no way to keep them that white unless you don't work.

Now that is hot as the top black driveway here in the peak Summer here. Hot enough to melt the soles of some foot wear. I think my drive hit 152F this at one time. In some place the new paving just slide off the old surfaces. They are now repaving those areas.

Yes I switch to working under the shade trees during that time. That's why I don't mind being called a shade tree mechanic.

Now it wa 40F here and I just got my shearing and boy was my head cold with the wind blowing.
Click to expand...
people forget that the temperatures you see & hear are the air temperatures measured inside a white painted box
sunlight heats up everything it strikes and the rate of cooling by the air is proportional to the difference in the temperature between the surface & the air
so when the air is 48 ( yesterdays max ) you don't get much cooling


#14

StarTech

StarTech

That why they paint heat sinks black as it absorbs more heat. Different materials heat differently too due color and material used.

And 118+F is hot no matter where you are just like -10 F is damn cold.

Strange yesterday it was 70+ F and the day before was only 35F max. Now of we had storms last night with 6 people getting killed in Tennessee. I have learned this time of year when the temps are at 70F be ready for severe storms and tornadoes. It is what I call the magic temperature.


#15

A

aussietrev

Well guys, the heat finally stopped, then the rain started. At last it is a sunny cool day up here so all fired up with all new filters, spark plugs, even a new fuel pump and tools in hand I go to try and track down the problem. I have a home made lift and put the old girl up all keen and was set to take the panel out to replace the fuel filter and oil filter and I think I may have found the problem. I'm not certain but I'm thinking the big hole smashed out of the side of the crankcase may have something to do with it running really rough on one cylinder.:mad:
So advice please, is it worth throwing a new engine in her and if so, what would people recommend? The machine only has around 600 hours on it.


#16

StarTech

StarTech

aussietrev said:
Well guys, the heat finally stopped, then the rain started. At last it is a sunny cool day up here so all fired up with all new filters, spark plugs, even a new fuel pump and tools in hand I go to try and track down the problem. I have a home made lift and put the old girl up all keen and was set to take the panel out to replace the fuel filter and oil filter and I think I may have found the problem. I'm not certain but I'm thinking the big hole smashed out of the side of the crankcase may have something to do with it running really rough on one cylinder.:mad:
So advice please, is it worth throwing a new engine in her and if so, what would people recommend? The machine only has around 600 hours on it.
Click to expand...
So you think that a broken rod might be the problem? Lucky for it to be even to running at all.


#17

A

aussietrev

StarTech said:
So you think that a broken rod might be the problem? Lucky for it to be even to running at all.
Click to expand...
Yes, I'm thinking so. Even if it is something else that caused the hole though it means replacing the engine doesn't it? Due to cost though I am wondering if it is worth it to go with a new V twin or maybe drop down to a single cylinder job around 18-19 HP for less than half the cost. Thoughts?


#18

Tiger Small Engine

Tiger Small Engine

aussietrev said:
Yes, I'm thinking so. Even if it is something else that caused the hole though it means replacing the engine doesn't it? Due to cost though I am wondering if it is worth it to go with a new V twin or maybe drop down to a single cylinder job around 18-19 HP for less than half the cost. Thoughts?
Click to expand...
How is this engine running if the connecting rod smashed a hole through the engine case? You could TIG weld the case and see how long it runs I guess. Whether you go single or twin cylinder engine, a new engine is costly to put on an old mower. Never an ideal situation to decrease horsepower with a repower.


#19

StarTech

StarTech

Tiger if you had bother to look-up the D125 you would had seen the JD used a V-twin on the mower. I have had v-twin even with a fuel pump still run somewhat with a hole in the crankcase.

https://partscatalog.deere.com/jdrc/sidebyside/equipment/68105/referrer/navigation/pgId/1100914


#20

A

aussietrev

StarTech said:
Tiger if you had bother to look-up the D125 you would had seen the JD used a V-twin on the mower. I have had v-twin even with a fuel pump still run somewhat with a hole in the crankcase.

https://partscatalog.deere.com/jdrc/sidebyside/equipment/68105/referrer/navigation/pgId/1100914
Click to expand...
I obviously knew it was a V Twin, otherwise it would have been pretty bizarre for me to be posting about it running rough on one cylinder. What I was asking was what people thought about dropping it back to a single cylinder engine given that a no name 20HP twin is about $1400 whereas a single 18HP is only around $600. I rarely mow on full throttle anyway and there are plenty of 42 inch cut mowers on the market that run 18 or 19HP singles.


#21

A

aussietrev

It is barely running, will start eventually but rough as. If it did break a conrod, depending where it broke, e.g., close to the big end bearing, it would be possible to still run if the piston was up at TDC I guess. I guess there wouldn't be that much of a problem of power down size for a new 18HP against a tired 20HP. Plenty of 42 inch cuts run similar engine sizes.


#22

Tiger Small Engine

Tiger Small Engine

StarTech said:
Tiger if you had bother to look-up the D125 you would had seen the JD used a V-twin on the mower. I have had v-twin even with a fuel pump still run somewhat with a hole in the crankcase.

https://partscatalog.deere.com/jdrc/sidebyside/equipment/68105/referrer/navigation/pgId/1100914
Click to expand...


I am pretty familiar with John Deere riding and zero turn mowers. Whether the D125 is a 2 cylinder or not, with a hole in the crankcase, we call that a clue that things ain’t good. Maybe a little less pointing fingers and a little more teamwork would be in order.


#23

A

aussietrev

StarTech said:
So you think that a broken rod might be the problem? Lucky for it to be even to running at all.
Click to expand...
Took out the plugs and run a compression test, 120PSI on one, Zero on the other. Using a very bright torch peered through the hole in the crankcase, there is only one con rod attached to the crankshaft, just a shiny spot above it where the other one should be. So I guess either the big end bolts weren't done up properly or it snapped them and threw something through the case.


#24

B

bertsmobile1

Well Trev it is dead so you have to make up your mind if it is worth putting a new engine in it
A new B & S will set you back around $ 2,000 ( Aus ) a Kawasaki around $ 1,500 for Kohler you will need to auction of one of your children
A Loncin will be a little under $ 1,000
A B & S short block is not a viable option in Aust as B & S are unlikely to have one & if they do it will cost near the same as a new engine
As for engines, anything with a 1" PTO will go in but you will have to do some wiring modifications
In NSW , Dave in Charmhaven & Johnno & Johnno both direct import Loncins and their retail is only 10% above my wholesale .
Unless you are bagging +/- 4 Hp will make no difference apart from the bigger engines using more fuel


#25

A

aussietrev

bertsmobile1 said:
Well Trev it is dead so you have to make up your mind if it is worth putting a new engine in it
A new B & S will set you back around $ 2,000 ( Aus ) a Kawasaki around $ 1,500 for Kohler you will need to auction of one of your children
A Loncin will be a little under $ 1,000
A B & S short block is not a viable option in Aust as B & S are unlikely to have one & if they do it will cost near the same as a new engine
As for engines, anything with a 1" PTO will go in but you will have to do some wiring modifications
In NSW , Dave in Charmhaven & Johnno & Johnno both direct import Loncins and their retail is only 10% above my wholesale .
Unless you are bagging +/- 4 Hp will make no difference apart from the bigger engines using more fuel
Click to expand...
Final update. Pulled the twin out and removed the sump. The conrod remains were in about ten pieces. Went with the 18HP from Dave in Charmhaven. After tapping the mounting holes it bolted right in as luckily the chassis is double drilled for the V twin or a single B&S/Honda pattern. The plug on the engine was the same so the wiring was simple, the throttle cable being longer for the twin barrel carby had to be run in an S pattern but it works fine now. There seems to be very little difference in the cutting performance although it does seem to be a little slower across the ground when travelling from area to area. With the side exhaust it is a lot louder than the twin was. Thanks for your help and advice, much appreciated.


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