Powerfab 125 with G300 Honda engine problems
Lee Ganley
My dad has the above digger bought second hand, all was well with everything working if a wee bit smokey but ran well enough. All of a sudden it packs up and will not start, not even with starter fluid.
On checking the spark at the plug it was intermittent, so I've stripped it down and ended up changing the coil and condenser, along with the plug, clean d up inside the fly wheel around the magnets and still no spark. The points weren't changed as they look new and clean.
I've tried everything I can think of and can not get a spark at the plug, I've even checked the oil level on the engine as I read about anoil level cut off?
Anyway I've even thought of pulling the engine out and either replacing it or working with on a bench while I sort it, which brings me to my second problem, it's clearly four bolts that secure the actual engine to the base of the frame, then there is what looks like some kind of impeller block secured on onto a plate where the drive shaft comes out of the engine into a rubber coupler, similar to a prop shaft uni joint on a car. How do you separate the engine from the hydraulics? Can this shaft be split without having to drop the hydraulic fluid ?
Thanks in advance for any help, because something that's is clealy relatively simple has got me flummoxed.
Cheers Lee.
peter
Hi Lee,
Have you checked to see if the points are actually going open circuit. If you have a multi meter disconnect the coil wire from the points, turn the engine until the points are open and measure the conductivity to make sure you have an open 9 high resistance between the points gap. Then with the coil still disconnected turn the engine until the points are closed and check continuity to make sure you have a short circuit between points contacts.
Sorry if this seems very simplistic but I hope it helps in some way as it may be the points insulation has broken down. I have seen this before.
Peter Ling
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Tom Carty
Lee Ganley
Thanks for the reply, I haven't checked this and will do it. Can you clarify what you mean by "9 high resistance when open". I think I follow you with checking the points, but the only ones I've worked with were on old mini's and MG's not used to this no battery lark.
Cheers Lee.
peter
Sorry its just my poor typing it should have read (high resistance) If you find the points are not going high resistance when open it could be in insulation breaking down on the points or and stop switch that is connect. If when you remove the coil wire from the points you will also remove the stop wire so if the points are going open just check any stop wires connected and remove that wire and try again.
Very simply the point and coil works as follows the points are closed and the flywheel magnet goes by the coil this magnetic flux is stored in the coils iron core. Once the energy is stored in the iron core at the correct time just after top dead centre of the piston the points open causing the flux stored in the core to collapse thus generating a very high voltage in the secondary winding that connects to the spark plug. Or at least that how I understand it. You say you have changed the coils so there should be no problem there although I’ve seen new parts fail before.
Peter
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Lee Ganley
Lee.
Lee Ganley
The kill switch wire is not connected to a switch at the moment as it's on a bench Noe so there is no switch that can be faulty.
On a Hail Mary pass I stuck the multi meter probe in the plug cap and the negative to the casing and gave it a pull, the meter was set to 20V dc and gave a fleeting reading of 14-17V. I've changed the plugs about but still can't get any spark at the the plug when ground to the engine block.
Is there any other tests or ideas I can try.
Cheers Lee.
David Chandler
HTH
Dave C
Chesterfield
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peter
Hi Lee,
Be very carful about trying to measure the high voltage side of the coil with a multi meter as you will blow the meter.
So yes to recap
You have changed the coils an the condenser?
You have continuity with wires removed when closed between the point wire and the case?
Under the above test conditions you have an open circuit when points are open?
One last electrical test I can think of is to make sure both primary and secondary coil wires (if both presented externally) are connected to the casting and have a good contact, may want to take them of and clean connection.
If the above are correct you may need to look at the magnet. As I said in my previous email the magnet going past the coil has to generate magnetic flus in the iron core that is then turned into voltage when the points open. If the electrics are testing out OK you may need to check that the magnetic has not lost some of its magnetism should be strong attraction if you hold a screw driver near it. If this is ok check the gap between the magnet and the coil iron core. This should be very close and the nearer it is within reason the higher the level of magnetic flux stored and consequently the more spark voltage.
If these are all ok You may be looking at a faulty coil or condenser ( Some time new products do fail as we don’t do 100% QA testing they can get through and on the market)
Peter Ling
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Lee Ganley
Cheers Lee
Lee Ganley
I'll take the advice on the multi meter, just a bit of desperation as all my experience is on cars where I've got the battery to work with, although more complex a system it's feeling like cars are bloody easier.
To recap,
The coil with plug lead,cap and plug have been changed for new, this came with attached condenser. I've tested the condenser both new and old with a multi meter and they charge and discharge.
The points with all coil/condenser wires removed have continuity when closed but not when open, there is also continuity between the case and the static arm of the points, there is no points wire. Theses points just have the open and closing jaws and a bolt which accepts the condensor wire and a wire direct from a post on the coil, also attracted the this coil post is a wire for the kill switch which I presume just grounds the coil to kill all spark, at the moment this is not attached to anything and is insulated so not grounding.
The coil itself has now wires to ground, it looks like primary and secondary coils ground actually at the bolt on positions, here the casing has been filed with sand paper to ensure good contact.
The flywheel, if that's the correct term has been cleaned out with wire brush and dust removed, the internal raised sections checked for burrs etc and seem fine, I'm no expert as you may have guessed, but the magnet seems strong enough and certainly hold the woodruff key and pulls a screwdriver to it.
You mention the coil to flywheel gap, on this motor the coil attaches to the case by two bolts which pass through the coil in machined holes, this holds the coil in one fixed position and so I can't move the coil closer or further away from the flywheels internal surface? Am I missing something?
This thing should run on a bench with a coke can as a fuel tank! Can't believe I can't sus it out!
Beginning to think the new coil must be bad, from the net I've seen different coils tested with a meter to read resistance through primary and secondary coils, not found a vid for this coil or its specs yet but I'm thinking that's something that needs doing.
One the up side at least it's on a bench now and I'm not kneeling at the side of a digger.
Cheers Lee.
Lee Ganley
The secondary shows 1400k ohms and the primary 0.7 ohms.
I can’t find the specs for a g300 but a g160 should be 5.9 to 7.1 k ohms on the secondary. So I’m thinking my nice shiny new coil is duff.
Cheers Lee.
peter.ling
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Lee Ganley
For the sake of sanity it’s worth springing for another one.
Cheers Lee.
Lee Ganley
So far I've changed the coil, the condenser (twice, as it's had two different new sets), the points changed and replaced for a CDI unit, plug and plug cap, all earth points cleaned, the flywheel cleaned and magnet cleaned and still strong.
Still no spark!
In the end I bought a new litany engine to get the digger going, however this is driving me nuts not being able to solve it.
If anyone can come up with anything I'd love to hear it, if nothing else to cure my moribund curiosity.
Cheers Lee.
Jon
Could it be as stupid as the HT lead needs replacement?
Good luck
Jon