JD H magneto

[treeman53]

JD H, hand start, starts easily wil a pull, and runs great. Won't start by hand with flywheel. Timing looks good, good snap from impulse spring. I was thinking points, and condenser. Any other areas that would cause this?

 

[Watthour]

A weak magnet and/or coil can also cause those symptoms. My '42 was electric start so it got away with a marginal mag.

 

[treeman53]

Thanks!

 

[John T]

Im with Watthour. The magnet is weak (can be recharged) or the impulse spring is weak (can be replaced)

John T

 

[wore out]

JD H, hand start, starts easily wil a pull, and runs great. Won't start by hand with flywheel. Timing looks good, good snap from impulse spring. I was thinking points, and condenser. Any other areas that would cause this?

Are you saying the impulse snaps "sharply" when the mag is mounted on the tractor, or "on the bench"?

I have seen it happen where there the governor shaft has moved over right a bit (bearing wear or other issues) and the impulse is slightly "pinched" when the mag is installed, slowing down the "snap" of the impulse, making for a weak spark.

Adding a mag mounting gasket or two is a temporary workaround.

 

[treeman53]

Are you saying the impulse snaps "sharply" when the mag is mounted on the tractor, or "on the bench"?

I have seen it happen where there the governor shaft has moved over right a bit (bearing wear or other issues) and the impulse is slightly "pinched" when the mag is installed, slowing down the "snap" of the impulse, making for a weak spark.

Adding a mag mounting gasket or two is a temporary workaround.

Snaps sharply when mounted on the tractor. Pull starts in 5 or 6 feet.

 

[John T]

Snaps sharply when mounted on the tractor. Pull starts in 5 or 6 feet.

That good pull starting but not when hand cranked still makes me suspect the impulse spring is weak or the there’s a problem in the wind and trip assembly. it’s hard on the net to define a hard sharp loud snap versus a soft dull clunk. try removing and inspecting and note any differences in sound and operation on versus off the tractor, even loosen the mounting bolts a bit see if that matters (binding, not enough clearance, etc) ?????????

Of course burned pitted or mis gapped points can make a difference and especially start timing. The mag needs to trip right at tdc not before or after take a look at that also. Again if the magnet is weak so is the spark !!!!!!!

John T

 

[Loosehandle]

JD H, hand start, starts easily wil a pull, and runs great. Won't start by hand with flywheel. Timing looks good, good snap from impulse spring. I was thinking points, and condenser. Any other areas that would cause this?

One other possibility, coolant seep into cylinder. I had this very problem it was crack around center block stud. Check and smell spark plugs, it was worse the longer it sat between starting attempts. It was repaired by machine shop stitching crack.

 

[treeman53]

That good pull starting but not when hand cranked still makes me suspect the impulse spring is weak or the there’s a problem in the wind and trip assembly. it’s hard on the net to define a hard sharp loud snap versus a soft dull clunk. try removing and inspecting and note any differences in sound and operation on versus off the tractor, even loosen the mounting bolts a bit see if that matters (binding, not enough clearance, etc) ?????????

Of course burned pitted or mis gapped points can make a difference and especially start timing. The mag needs to trip right at tdc not before or after take a look at that also. Again if the magnet is weak so is the spark !!!!!!!

John T

I will replace points, and adjust timing. To adjust timing, do I move the plate inside mag, or just loosen mag and adjust until it fires at precisely TDC?

 

[John T]

I will replace points, and adjust timing. To adjust timing, do I move the plate inside mag, or just loosen mag and adjust until it fires at precisely TDC?

Adjusting the inner plate sets the lag angle. Rotating the entire mag outside CCW advances CW retards. It should snap impulse fire right at tdc if too soon she kicks back if too late don’t start as well. After around 250 rpm impulse wind n trip drops out Note I’m rusty on this if wrong please correct me my bad grrrr. Even if timed perfect with good coil and points a weak spring or magnet harms hand crank mag impulse starting.
John T. Not a mag expert no warranty see what the other fine gents have to say also

 

[dan_41jdh]

There are many shortcomings that will contribute to difficult hand-starting, especially those involving the air-fuel mixture (leaky throttle shaft, manifold leaks, incorrect fuel level in the carburetor, stagnant fuel, etc.). Before assuming the magneto is the problem, it would be appropriate to do a simple test to see how strong the spark is – just remove the spark plug wire from the plug and hold the terminal about 5/16” from the block or frame and observe the spark when cranking the engine. If the magneto will produce a spark sufficient to jump that gap during cranking, it is unlikely you have a magneto problem. Deere’s service manual (SM-2029) states that the magneto should produce consistent sparks across a 9 mm gap (that’s just a little less than 3/8”) at 1000 RPM. That’s the only performance criteria that’s necessary outside of timing adjustments.

 

[John T]

There are many shortcomings that will contribute to difficult hand-starting, especially those involving the air-fuel mixture (leaky throttle shaft, manifold leaks, incorrect fuel level in the carburetor, stagnant fuel, etc.). Before assuming the magneto is the problem, it would be appropriate to do a simple test to see how strong the spark is – just remove the spark plug wire from the plug and hold the terminal about 5/16” from the block or frame and observe the spark when cranking the engine. If the magneto will produce a spark sufficient to jump that gap during cranking, it is unlikely you have a magneto problem. Deere’s service manual (SM-2029) states that the magneto should produce consistent sparks across a 9 mm gap (that’s just a little less than 3/8”) at 1000 RPM. That’s the only performance criteria that’s necessary outside of timing adjustments.

Yo Dan, long time no see. I agree, VERY GOOD INFO ! Regarding vacuum leaks and how they hamper hand starting for the others here, if the carbs throttle shaft bushings are worn at slow hand start speed that allows a lot of air to get sucked in which leans the fuel/air mixture so she dont start HOWEVER if shes cranking fast like an electric start tractor or being pull started the mixture is less leaned out so she starts. Similar to an earlier post if at idle you spray starting fluid or carb cleaner or propane in an area (manifold gasket etc etc) and that makes her speed up or smooth out YOU FOUND A VACUUM LEAK. Its hard to describe over the net but a good high visible blue spark is needed versus a thin wimpy hard to see yellow spark HOWS THAT FOR A SCIENTIFIC EXPLANATION LOL

Im more rusty on all this versus back in the day when I was giving a few seminars at shows but still enjoy the topic. Ever get to Florida Flywheelers?? If so come visit.

John T

 

[dan_41jdh]

Yo Dan, long time no see. I agree, VERY GOOD INFO ! Regarding vacuum leaks and how they hamper hand starting for the others here, if the carbs throttle shaft bushings are worn at slow hand start speed that allows a lot of air to get sucked in which leans the fuel/air mixture so she dont start HOWEVER if shes cranking fast like an electric start tractor or being pull started the mixture is less leaned out so she starts. Similar to an earlier post if at idle you spray starting fluid or carb cleaner or propane in an area (manifold gasket etc etc) and that makes her speed up or smooth out YOU FOUND A VACUUM LEAK. Its hard to describe over the net but a good high visible blue spark is needed versus a thin wimpy hard to see yellow spark HOWS THAT FOR A SCIENTIFIC EXPLANATION LOL

Im more rusty on all this versus back in the day when I was giving a few seminars at shows but still enjoy the topic. Ever get to Florida Flywheelers?? If so come visit.

John T

Hey John T – the one and only time I attended the Flywheelers was back in 2015, and I about froze to death! I was so glad to get back to the upper Midwest where the weather was warmer! Who would have thought that you had to scrape frost off your windshield in middle Florida?? So don’t expect to see me there again for a while! (But it was an amazing show despite the temperature and strong breezes.)

By the way, your information is always good – it doesn’t need to be “scientific” if it is based on fact and proof and not on speculation and belief. And I wouldn’t say you’re “rusty”; I think “well-seasoned and experienced” is more appropriate.

 

[John T]

Hey John T – the one and only time I attended the Flywheelers was back in 2015, and I about froze to death! I was so glad to get back to the upper Midwest where the weather was warmer! Who would have thought that you had to scrape frost off your windshield in middle Florida?? So don’t expect to see me there again for a while! (But it was an amazing show despite the temperature and strong breezes.)

By the way, your information is always good – it doesn’t need to be “scientific” if it is based on fact and proof and not on speculation and belief. And I wouldn’t say you’re “rusty”; I think “well-seasoned and experienced” is more appropriate.

Yep I was there that colddddd year like to froze. Of course that years weather was the exception instead of the rule. Usually the February show is warmer than January. Lord willing I will be there next year

John T

 

[treeman53]

Yo Dan, long time no see. I agree, VERY GOOD INFO ! Regarding vacuum leaks and how they hamper hand starting for the others here, if the carbs throttle shaft bushings are worn at slow hand start speed that allows a lot of air to get sucked in which leans the fuel/air mixture so she dont start HOWEVER if shes cranking fast like an electric start tractor or being pull started the mixture is less leaned out so she starts. Similar to an earlier post if at idle you spray starting fluid or carb cleaner or propane in an area (manifold gasket etc etc) and that makes her speed up or smooth out YOU FOUND A VACUUM LEAK. Its hard to describe over the net but a good high visible blue spark is needed versus a thin wimpy hard to see yellow spark HOWS THAT FOR A SCIENTIFIC EXPLANATION LOL

Im more rusty on all this versus back in the day when I was giving a few seminars at shows but still enjoy the topic. Ever get to Florida Flywheelers?? If so come visit.

John T

You certainly aren't this rusty!

 

[teddy52food]

If the magnet needs charging, I can do it. Weak magnet = weak spark. I also have the proper testers to take the guess work out.

 

[Mike(NEOhio)]

I will replace points, and adjust timing. To adjust timing, do I move the plate inside mag, or just loosen mag and adjust until it fires at precisely TDC?

Pretty simple. Turn the flywheel to left cylinder to its compression stroke and line up the LH IMPULSE mark which is TDC. The coupling slot should be horizontal. Set the mag to fire the top terminal, put in on and roll it all the way forward. Then roll it backward slowly till the impulse just trips and tighten it.