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Old 09-29-2012, 08:27 AM   #1
rightone1974 OP
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Location: Saint Maries, Idaho
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Question spark issue with my 76 dt250c

I am having a issue with spark on my 76 dt250 if i pull the plug it gets spark after a few times kicking it over and takes like 30 mins to start if it starts. what would cause this problem? I get the case cover off and it looks clean and dry in there but how do i get off the cover to the points and condenser there is one bolt in the middle of the basket and there are several screws around the side of it? can someone please help me get this thing running. It was running great before this problem. My battery was draining over night i filled the battery up with water now it stay charged could there be an electrical issue on it?
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Old 09-30-2012, 01:10 AM   #2
Gray_Rider
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Nothing to do with the battery.

The spark comes from the coil in the magneto on a DT. Assuming the wiring is all OK. The points may be dirty or burned. You might clean them up with a points file through the slot in the rotor, otherwise you need a special puller to take the rotor off and replace the points. First check the spark plug cap on the HT lead is OK.
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Old 09-30-2012, 11:05 AM   #3
rightone1974 OP
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what kind of puller would i need like one for pulling a steering wheel off a car? is there a place i can get a free wire diagram and the output of each wire to test and make sure all the wiring is ok? It gets spark after sever kicks but still wont fire up the day before it was running good I put a new plug in and got it started up then the next day it would not even try to start up i think it is weak spark how would i trouble shoot my wiring the points look good on it i think there is 2 sets of points but i may be wrong.
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Old 09-30-2012, 12:33 PM   #4
Tim McKittrick
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Amazon has a puller for about $15:

http://www.amazon.com/Motion-Pro-08-...ype=motorcycle

You need to remove the flywheel to access the points and condenser. As you eventually get spark I would start by replacing the condenser and points- how old are they anyway? It make sense to begin with new. While you have the bike apart make sure all the connections are good to the coil and plug.

The next issue is timing- these machines were timed by measuring the point at which the points opened before top dead center (BTDC) by piston height- in other words, instead of crank angle you had to measure how far the piston was from TDC with a dial indicator. A timing light won't do you any good as there are no timing marks. Fine tuning the timing is by slightly altering the point gap: you can get close but setting the points to their factory stated clearance but it won't be spot on- but it should be close enough to determine if you have spark. The advance mechanism is attached to the flywheel and you have to remove the flywheel to get to the points- so its a bit of a juggle. Install the points and then set the gap once the flywheel is reinstalled.

Here is the tool you need to accurately set the timing:

http://www.startinglineproducts.com/...&productID=582

I have made similar tools using a standard dial indicator and a hollowed out spark plug, but it's probably far easier just to purchase a tool and get the job done. Oh- a word of warning: your local Yamaha dealer will look at you in utter confusion if you ask them how to do this unless their lead repairman is over 50 and has been working on bikes all his life.

You will also need a way to accurately access the moment the points open- I have always just used a multi-meter and disconnected the points- then I use the meter's continuity function (mine has a buzzer) to turn off just as the points open. I set the gap, remove the flywheel, reattach the points, and reinstall the flywheel. It's a pain the first time you do it but once you have the method down it goes pretty fast.

Lastly- I believe the spec for your motor is 3.2mm BTDC


A general tutorial on the technique:

http://www.youtube.com/watch?v=Iqardto3Kbs

Once you've mastered this you will be a part of a dwindling club of arcane knowledge.
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Old 09-30-2012, 08:03 PM   #5
rightone1974 OP
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Wicked

Quote:
Originally Posted by Tim McKittrick View Post
Amazon has a puller for about $15:

http://www.amazon.com/Motion-Pro-08-...ype=motorcycle

You need to remove the flywheel to access the points and condenser. As you eventually get spark I would start by replacing the condenser and points- how old are they anyway? It make sense to begin with new. While you have the bike apart make sure all the connections are good to the coil and plug.

The next issue is timing- these machines were timed by measuring the point at which the points opened before top dead center (BTDC) by piston height- in other words, instead of crank angle you had to measure how far the piston was from TDC with a dial indicator. A timing light won't do you any good as there are no timing marks. Fine tuning the timing is by slightly altering the point gap: you can get close but setting the points to their factory stated clearance but it won't be spot on- but it should be close enough to determine if you have spark. The advance mechanism is attached to the flywheel and you have to remove the flywheel to get to the points- so its a bit of a juggle. Install the points and then set the gap once the flywheel is reinstalled.

Here is the tool you need to accurately set the timing:

http://www.startinglineproducts.com/...&productID=582

I have made similar tools using a standard dial indicator and a hollowed out spark plug, but it's probably far easier just to purchase a tool and get the job done. Oh- a word of warning: your local Yamaha dealer will look at you in utter confusion if you ask them how to do this unless their lead repairman is over 50 and has been working on bikes all his life.

You will also need a way to accurately access the moment the points open- I have always just used a multi-meter and disconnected the points- then I use the meter's continuity function (mine has a buzzer) to turn off just as the points open. I set the gap, remove the flywheel, reattach the points, and reinstall the flywheel. It's a pain the first time you do it but once you have the method down it goes pretty fast.

Lastly- I believe the spec for your motor is 3.2mm BTDC


A general tutorial on the technique:

http://www.youtube.com/watch?v=Iqardto3Kbs

Once you've mastered this you will be a part of a dwindling club of arcane knowledge.
Thank you for the info, I believe they are the original points and condenser from 1976 it only has just over 5000 miles on it, im thinking about just replacing all the guts inside of the flywheel just to be sure it is all new.
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Old 10-01-2012, 04:08 PM   #6
rightone1974 OP
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I cleaned my points and it runs now i think i am going to get all new electrical components for the bike this winter and put them in is spring. Thank you for all the info guys I really do appreciate it.
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