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#92318 - 05/16/06 4:23 am bench testing a magneto?  
Joined: May 2004
Posts: 181
zgears Offline
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zgears  Offline
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Portland OR
ive got my bike together, and its timed right. but, i cant get it to fire. any one know anything about bench testing a magneto. how do i know if its hot enough? im geting a orange spark not a blue one.


53 thunderbird
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#92319 - 05/16/06 7:57 am Re: bench testing a magneto?  
Joined: Oct 2003
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dave jones Offline
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dave jones  Offline
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Emsworth, sunny south of Engla...
My B31's magneto would make a blue spark if I spun it with my fingers when off the bike. I would try checking the condenser, the pickup and copper slip ring (clean with methylated spirits)and clean/ gap the points. Make sure you have the right kind of plug cap for a mag. Try removing it and check the spark from the end of the wire. Also try changing the wire. You may find that some simple things will make a big difference.

#92320 - 05/16/06 10:14 am Re: bench testing a magneto?  
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gs750 Offline
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gs750  Offline
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New York
Quote:
......I would try checking the condenser, the pickup and copper slip ring (clean with methylated spirits)
That would be denatured alcohol over here.


1971 Triumph T100C
1974 Honda XL350
1982 Suzuki GS750T
2000 Honda VFR800FI
#92321 - 05/16/06 12:24 pm Re: bench testing a magneto?  
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RF Whatley Online content
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RF Whatley  Online Content
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North Georgia, USA
Take a good sparkplug and rip off the "strap" over to the center, so that you have a center electrode with a 3/16" spark gap in any direction. Your mag should be able to jump that gap with only a quick 1/4 turn by hand. And the spark should be bright blue.

bigt


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA

"Shop Boy" at Rodi British Bikes
#92322 - 05/16/06 4:50 pm Re: bench testing a magneto?  
Joined: Mar 2005
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John Healy Online content
John Healy  Online Content



Joined: Mar 2005
Posts: 9,964
Boston, Massachusetts
Bench testing a magneto, without proper equipment, is typically anecdotal.

Although Richard's test is sort of reassuring it is not a fair test. It will not tell you about the condition of the condensor or the condition of the insullation of the armature's secondary windings. It will also not tell you about the condition of the magnet.

That said, it will give you a good idea if the bike will start or not. It will not tell you what will happen after the bike warms up and you are miles from home.
;2c:
john


#92323 - 05/16/06 5:01 pm Re: bench testing a magneto?  
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RF Whatley Online content
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RF Whatley  Online Content
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Joined: Oct 2003
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North Georgia, USA
Quote:
Originally posted by John Healy:
Bench testing a magneto, without proper equipment, is typically anecdotal.
John, although I respect your knowledge, experience and great wisdom, this time, however, I have to respectfully disagree. Bench testing a magneto is really more like urinating into the wind. You get this nice warm feeling all over, but in the end you've probably not even done so much as to impress your friends.

laughing


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA

"Shop Boy" at Rodi British Bikes
#92324 - 05/17/06 1:10 am Re: bench testing a magneto?  
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beagleplex Offline
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Well, let's say we DO have the right equipment. What temperature would the mag have to be to perform the "Heat Soak Test".

#92325 - 05/17/06 11:05 pm Re: bench testing a magneto?  
Joined: Mar 2005
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John Healy Online content
John Healy  Online Content



Joined: Mar 2005
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Boston, Massachusetts
www.srm-engineering.com/MagDynoElectrical.pdf?img

Although SRM uses typical engine operating temperature, I would suggest operating temperature, plus 50% as a safety factor. There are days in August where the temperature of the motor will get at least 50% higher in traffic than it typically runs the rest of the year


#92326 - 05/18/06 5:46 am Re: bench testing a magneto?  
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beagleplex Offline
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beagleplex  Offline
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Thanks John, SRM really have a slick site these days! Those magmaster machines must be thin on the ground even in the UK....

#92327 - 05/18/06 1:07 pm Re: bench testing a magneto?  
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RF Whatley Online content
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RF Whatley  Online Content
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North Georgia, USA
Gosh, I feel so inadequate! Maybe I should come out with a full-color brochure on our shop's Lucas mag tester. laughing


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA

"Shop Boy" at Rodi British Bikes
#92328 - 05/18/06 7:29 pm Re: bench testing a magneto?  
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beagleplex Offline
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beagleplex  Offline
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It would be great to see a photo of a Lucas brand mag tester. Do you think they actually built it or relabelled a third-party machine? Some photos of your workplace are far overdue!

I replaced a condenser in my Goldie years ago that had a Mica condenser in its KNR1 racing mag. Lucas actually made a conversion kit that had the paper and tinfoil condenser , two little brass posts and all the other little bits to fit the smaller competition (KNC1) style cond. into the racing armature. I tested that mag clamped in a bench vise spun with a 3/8" butterfly impact and one of those Briggs and Stratton clamp on spark testers. Snap snap snap and good to go...maybe it took a few tries though, smile come to think of it. I bought that kit from a guy named Jim Hunter in Los Angeles who was selling out his bike shop. What a great guy! Oops, talking beezers on the Triumph board!

#92329 - 05/19/06 2:13 am Re: bench testing a magneto?  
Joined: May 2004
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zgears Offline
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Portland OR
Thanks for the info. i just had my mag rebuilt by Waren Wheeler in Ont. Canada. ive had good results from him in the past, but it looks like this mag is still weak. i dont think he has SRM's Wonder Mag Tester 9000 . maybe ill send it back. or, is there some one in the states that restores mags?


53 thunderbird
#92330 - 05/19/06 2:49 am Re: bench testing a magneto?  
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RF Whatley Online content
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RF Whatley  Online Content
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North Georgia, USA
The shop I work at does. Call 770-867-1676, 9-9EST, 7 days a week. Can't beat those hours!


bigt


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA

"Shop Boy" at Rodi British Bikes
#92331 - 05/23/06 2:38 am Re: bench testing a magneto?  
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zgears Offline
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zgears  Offline
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Portland OR
i just got some more mags, there missing some parts. do you think i should send them too? or should i try to locate the parts?


53 thunderbird
#92332 - 05/23/06 3:13 am Re: bench testing a magneto?  
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RF Whatley Online content
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RF Whatley  Online Content
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North Georgia, USA
Send the armatures. You can keep the busted bodies.

bigt


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA

"Shop Boy" at Rodi British Bikes
#92333 - 02/28/07 8:17 am Re: bench testing a magneto?  
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magmark Offline
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Carlsbad, California
If you want to bench test a magneto - say the common K2F - all you need is a drill motor, a small engine spark gap tester - set at "S/E" (small engine or about 1/4" gap) from a lawnmower shop, a piece of rubber tubing, a short piece of metal rod and two small hose clamps. Use the rubber tubing to connect the metal rod to the threaded end of the mag drive shaft, clamped to each with a hose clamp. Turn it with your drill motor, counter-clockwise unless it is a Vincent mag, then turn it clockwise. Ground the other spark lead to the body of the mag when testing. Don't hold onto the mag with your bare hands. Clamp it in a padded vise. This wider gap simulates firing in a dirty combustion chamber and is really only showing you that the mag is capable of putting out a spark - cold, not under operating temperature. It is a fair start and easily done. More of an insulation check than anything else!

magmark

#92334 - 02/28/07 12:59 pm Re: bench testing a magneto?  
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AussieOn81Bonne Offline
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Sydney
Hey Z,

Try Benchtesting it with a sledgehammer (or even a murderer) i could not wait to ct the maggie off of my baby - nothing but hassle.

Seriously - i have heard of testing with a drill before and i think that Mark might be right on the mark so to speak.

Parko


Once was blind but now can see
81 T140E
50's T'Bird
#92335 - 02/28/07 5:34 pm Re: bench testing a magneto?  
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RF Whatley Online content
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RF Whatley  Online Content
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Posts: 11,108
North Georgia, USA
Quote:
Originally posted by beagleplex:
It would be great to see a photo of a LUCAS brand mag tester. Some photos of your workplace are far overdue!
I actually considered posting a couple of photos every week of what happens at the shop where I play on weekends. A couple of weeks ago I walked in on "Mr Bones" himself, Dave Aldana busily rebuilding a B50 flat track engine. One week we had 2 Vincents in for electrical service. Two weeks ago the boss was building up 3 Tiger Cubs for AHRMA trials. Last week he was preping his 2 Manx Nortons and his roadracing 650cc Norton for Daytona. It just seems like there's always something going on there.

And, so as not to steal the thread, on the "off days" we build mags and generators. laughing


Don't hide 'em, Ride 'em !!

RF Whatley
Cornelia, GA

"Shop Boy" at Rodi British Bikes
#92336 - 03/05/07 4:26 am Re: bench testing a magneto?  
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Posts: 544
joe a. Offline
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joe a.  Offline
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minnesota
bench testing by spinning with your hand is as good as spinning with a drill maybe even better as it should spark fine if quickly spun by hand with it's drive gear...neither is a proper test as previously stated it just shows it sparking but can't detect faults at temp,under actual cyl press,vibration,etc. it will spark with a bad secondary or bad condensor with these tests but you need to put the mag under adverse conditions to see if it is truely working properly.i usually do several static tests and then heat soak and run it on my test stand at speed for a sufficent time...but as i had said before if you are questioning your mag it probably is due for an overhaul as most are quite old and in need of help.cotact me if you want it tested properly....joe @ v-cycle


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