The Yamaha XT500 TT500 Forum

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 Post subject: Electrical problem after 10 minutes of riding.
PostPosted: Tue Apr 18, 2017 4:24 pm 
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Kickback

Joined: Tue Apr 28, 2015 12:39 am
Posts: 62
Location: Toronto Canada
This is the third time this has happened. After about 10 minutes of riding the bike suddenly dies and there is no spark. I push the bike home and wait a bit and about 30 minutes to 1 hour later the spark comes back without me doing anything. Initially I thought it was the lack of gasket around the points cover and the condenser somehow grounding out the the cover. But, I installed a new gasket and also have a new coil and condenser. It seems to me that something is overheating because of corrosion and therefore increased resistance. Not sure where to start.


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 Post subject: Re: Electrical problem after 10 minutes of riding.
PostPosted: Tue Apr 18, 2017 5:58 pm 
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Viking Member
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Joined: Sat Nov 20, 2010 5:50 pm
Posts: 1485
Location: Cannock, Staffordshire, England
For what they cost, I'd eliminate the condenser first by replacing it. Are you losing the spark when checking with the capon and a plug, or just the HT lead?

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Honda SL70 1971
Suzuki RV90 1974
Suzuki B105P Bearcat 1967
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 Post subject: Re: Electrical problem after 10 minutes of riding.
PostPosted: Tue Apr 18, 2017 6:10 pm 
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Kickback

Joined: Tue Apr 28, 2015 12:39 am
Posts: 62
Location: Toronto Canada
Bill Badger wrote:
For what they cost, I'd eliminate the condenser first by replacing it. Are you losing the spark when checking with the capon and a plug, or just the HT lead?


I've got another condenser on order. I take the spark plug cap off and kick over with another spark plug to see if I see a spark. I don't take the spark plug that's in there out because I don't like to take them out too often to prevent cross threading or wear of the threads.


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 Post subject: Re: Electrical problem after 10 minutes of riding.
PostPosted: Tue Apr 18, 2017 7:55 pm 
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Thumper Pilot
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Joined: Tue Feb 19, 2013 12:21 am
Posts: 487
Location: SE BC Canada
If you've already replaced the points and condensor and the wiring and switches are good then the problem might be the ignition magneto coil. They typically fail with an intermittant loss of contact or short in the windings when hot. When the bike is in the failure mode, check the coil resistance.

patuca


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 Post subject: Re: Electrical problem after 10 minutes of riding.
PostPosted: Wed Apr 19, 2017 3:26 pm 
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Viking Member
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Joined: Fri Feb 25, 2011 8:47 am
Posts: 643
Location: Robertsbridge UK
Classic magneto winding breakdown. Ok when cold. Messes about hot


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 Post subject: Re: Electrical problem after 10 minutes of riding.
PostPosted: Fri Apr 21, 2017 2:01 am 
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Kickback

Joined: Tue Apr 28, 2015 12:39 am
Posts: 62
Location: Toronto Canada
Not what I wanted to hear. I'll replace the stator or have it rewound.


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 Post subject: Re: Electrical problem after 10 minutes of riding.
PostPosted: Fri Apr 21, 2017 6:16 am 
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Kickback

Joined: Mon Apr 17, 2017 8:03 am
Posts: 20
Worth replacing that stator if haven't replaced in long time.


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 Post subject: Re: Electrical problem after 10 minutes of riding.
PostPosted: Fri Apr 21, 2017 9:08 am 
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Thumper Pilot
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Joined: Thu Sep 29, 2011 10:11 am
Posts: 337
Location: Graz, Austria
It is a bit funny that the engine dies instantly, with no stuttering and backfiring.

Some more possible explanations would come to mind then:

Jamming breaker point axle when hot
Some shorting to ground of one of the cables/breaker point/condenser

Other stuff to check:
Spark plug electrode gap
Breaker point gap

It is relatively easy to convert the XT ignition system from magneto to battery type ignition, just for testing.

> post70131.html#p70131

Also, we have seen brand new though failing condensers or spark plugs as well.

For a spare condenser, you can test with a cheapo replacement from the electronic department. This one is known to be working for years in a mates XT:
http://www.motorang.com/motorrad/xt_tips.htm#kondi2

OTOH you can use ANY ignition condensor found on any battery ignition car or motorcycle with breaker points, like old 2CV, beetle, FIAT126, FIAT600, MZ, JAWA, Dnepr/Ural, Mini Cooper, Ford Falcon etc etc.
Electrically they are all the same. The only problem is to fit them in the original place, but for testing you may just fit them somewhere else nearby and leave the ignition cover open.
My XT500 had a FIAT 126 condenser for a long time (which is small enough to make it work there).

Andy

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for XT500 oil filling >
post63900.html#p63900


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 Post subject: Re: Electrical problem after 10 minutes of riding.
PostPosted: Fri Apr 21, 2017 4:14 pm 
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Kickback

Joined: Tue Apr 28, 2015 12:39 am
Posts: 62
Location: Toronto Canada
So it look like I've completely lost the spark. I started it for about 30 seconds today and then I the bike died. It looks like I've completely lost the spark now and not just after riding. Tried different condensers and checked and cleaned many connections. I then measured the resistance across the white and yellow wires coming from the stator. I had about 0.5 ohms and 0.6 ohms which is too high according to the manual. I'm waiting for a flywheel puller to arrive so I can take the stator out and have the coil rewound.

I'll post a picture once I have the flywheel off.


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 Post subject: Re: Electrical problem after 10 minutes of riding.
PostPosted: Fri Apr 21, 2017 7:19 pm 
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Thumper Pilot
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Joined: Tue Feb 19, 2013 12:21 am
Posts: 487
Location: SE BC Canada
Hi Prospect:

It sounds like you're measuring the wrong wires. The white and yellow wires are for the headlight and battery charging coil and they have nothing to do with the ignition.

Normally the ignition generator coil line is the black (or black/white) wire and this is a totally different coil.

patuca


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