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MR50 no spark http://vintagedirtbikeforums.alp-sys.com/viewtopic.php?f=21&t=4614	Page 1 of 1

Author:	Hammerlane [ Sun Mar 27, 2016 12:37 pm ]
Post subject:	MR50 no spark
74 MR 50 Elsinore, have installed a new CDI, bypassed the OEM rectifier with the one in the CDI kit. (also tried with the OEM rectifier) double and triple checked wiring and still no spark.. its drivin me nuts here.. prior to installing the CDI I was getting some spark, it was weak and inconsistent. at the Magneto wire (black w/yellow stripe), I get 3 to 3.2 A/C volts max.. was only getting 280 millivolts max w/ points installed. magneto/stator coil Ohms are 1.5 measured between the points contact wire and the mounting screw on the coil. new spark plug gap is .024.. and nothing. I believe I read somewhere ohms should be .08 ? and volts should be somewhere around 60v+ A/C ? should I assume the magneto/stator is bad? almost have this bike done, this is the last thing I need to complete.

Author:	rayivers [ Sun Mar 27, 2016 3:31 pm ]
Post subject:	Re: MR50 no spark
So you now have an aftermarket CDI (electronic) ignition replacing the OEM points/magneto ignition, is that correct? Ray

Author:	Hammerlane [ Mon Mar 28, 2016 4:39 am ]
Post subject:	Re: MR50 no spark
Attachment: IMG_4211.JPG [ 49.27 KiB \| Viewed 7691 times ] Yes, my understanding is the CDI replaced the points and I have both the original rectifier and the one provided with the CDI. the magnet and stator (on the crank shaft) are still in use (see photo).. this is where I can only create 3 volts. I also have a new ignition coil without a capacitor, plug wire and spark plug. It is pretty much all new except the magnet and Stator. handle bar switch has been bypassed and there is no corrosion on any of the connectors.

Author:	rayivers [ Mon Mar 28, 2016 2:48 pm ]
Post subject:	Re: MR50 no spark
Is this the unit you installed? http://re-mx.com/mr50-cdi-electronic-ignition If so, I'd recommend returning to the OEM points ignition. This isn't really a capacitor-discharge ignition; it's just an electronic switch & sensor replacing the point contacts. I think these were initially used on lawnmower-type engines, and I don''t believe the timing can be adjusted, although you should be able to check it with a timing light. Hee's a wiring diagram, which you may already have: http://carwiringdiagram.net/diagrams/14 ... iagram.png The stator output is a very short 100 - 200VAC pulse, which most meters won't read accurately (they'll read something, but it'll be way low). If you have a meter like a Fluke 87 or similar, these have a setting for reading pulses like these. Also, some meters really do not like reading coil resistances. I believe my MR175's stator-coil resistance was 270 ohms or close to that (you need to unplug the stator cable to read this, making sure the points are open). 1.5 ohms is about what you should read at the ignition-coil input, and possibly correct if the cable was plugged in during the reading. Ray

Author:	Hammerlane [ Mon Mar 28, 2016 9:55 pm ]
Post subject:	Re: MR50 no spark
1. yes that is the CDI unit I installed. 2. I still have the manual for my meter, I'll check on its capabilities. I removed the stator mounting plate and measured resistance on the bench with the point set removed. I also checked with it installed in the bike. no change. with stock set up (points installed, condenser and coil) I had a very weak (and I mean barely there) intermittent spark w/ a new spark plug gapped at .024 I cleaned the points w/600 grit and set the gap to .008 with brass feeler gauges. they open when the "F" aligns with the mark on the case as they should. I also set them at .006 and .012 with no change. I'll pick up a new set of points and reinstall the OEM components and try again.

Author:	rayivers [ Tue Mar 29, 2016 3:43 am ]
Post subject:	Re: MR50 no spark
Another thing worth trying is to examine the entire stator with a magnifying glass, especially the spacers / washers on the points connections and the coil winding and wires. If it's easy to do, you might want to unscrew the coil and isolate it from the stator plate, then try reading its resistance again (just in case there's a short from the winding to the center laminations). The winding on the MR50 coil looks kind of strange to me. Ray

Author:	Hammerlane [ Tue Mar 29, 2016 6:10 pm ]
Post subject:	Re: MR50 no spark
Soooo.. decided to take another lap around the barn so to say.. reinstalled complete OEM ignition system found the points are considered obsolete from my sources. so I ran some 600 grit thru them again, tested to be sure the points were not grounded and reinstalled the old set gapped at .014 only one good avenue for a replacement stator out of Calif. so I reinstalled the original that I thought was bad. took another A/C voltage test before the rectifier, came up with 3 volts max.. and Resistance again at 1.1 to 1.5 ohms according to my meter. The old plug wire had made contact with the exhaust in the past and a twisted wire repair was how it came to me.. I broke the connection and clamped the wire directly to the plug, wouldn't you know.. spark.. nice hot white one. just for giggles I did a continuity test on the spark plug boot end and nothing.. I tested the new one I had and sure enough found my problem.. soldered the new section of wire on, installed new boot, plug and some fresh gas and 2nd kick.. puttputtputt putt puttputt is there something inside that boot that could disconnect ? I removed the wire from the end of the boot and tested just the boot. will post some pix when I get them loaded up.. nice little bike.

Author:

Hammerlane [ Tue Mar 29, 2016 6:30 pm ]

Post subject:

Re: MR50 no spark

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Finished running bike..

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Author:	rayivers [ Tue Mar 29, 2016 8:05 pm ]
Post subject:	Re: MR50 no spark
The bike looks great! and runs now too! It's funny - when I saw the MR50 wiring diagram for the first time a few days ago, the first thing that jumped out at me was 'Noise Suppressor' (i.e., a resistor plug cap). Inside your bad plug cap is surely a burnt-black 1,000 to 5,000 ohm high-voltage resistor; I'm amazed they last as long as they do. I should've mentioned it - I always replace any resistor cap on my bikes with a non-resistor one ASAP - but all's well that ends well, I guess. Even when they work fine they also reduce spark intensity, especially when combined with modern resistor plugs (which have one built in) for a double-whammy effect. They're discontinued and hard to find, but if you can get your hands on an NGK B6HV plug, it should work really well in that motor for a very long time. The Champion L-9G-MC is an equivalent (it's funny how discontinued plugs are often so expensive individually, yet so cheap in bulk): http://www.ebay.com/itm/NOS-Champion-Sp ... 0538129492 The points used to be available from Sudco (P/N 616-851), but I don't know about now. The NGK LZFH non-resistor cap is the one I use: https://www.denniskirk.com/ngk/lzfh-spa ... 200279.sku Ray

Author:

Hammerlane [ Thu Mar 31, 2016 10:05 am ]

Post subject:

Re: MR50 no spark

So, have a video of it but can't seem to post it anywhere.. (damn computers)
bike fires first kick and carries my 225 lbs around thru all gears
and Yes I was able to find the spark plug NGK B6HS for it..

I went thru almost all 60 pages of information on here looking for a solution and do recall seeing something pertaining to the
resistor cap, that's where the idea to check it came from..
Total build consisted of:
front fork assy. both sides.
carb rebuild, had to make new gasket for float bowl. O ring on the seat was bad, replaced needle/seat.
throttle grip assy. rebuild, cable and housing, new grips
Electrical system
brakes front and rear
bearing inspect - all in good condition
gave the whole thing a good scrubbing

Thanks to the web site and you Ray for all your help.. been a cool little build
Hope this information helps someone else someday.

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Author:	Rick [ Tue Apr 12, 2016 4:53 pm ]
Post subject:	Re: MR50 no spark
Man. I am so lucky to live in AZ where corrosion is mostly non-existant. That carb was toast. Glad you recovered it. Rick

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