Calling all Points experts - Need Dirt Bike help

[Guest]

Hey everyone - so I picked up a 1985 Honda XR80 dirt bike for my son for $200. It has no spark. It's a points ignition which I know very little about. The gasket for the side case wasn't in the best shape so I suspected some dirt got in there and I was right. Last night I pulled the flywheel and this is what I'm looking at right now.

VQ7vJnwl.jpg

So where should I start? I'm thinking use some really fine grit sand paper to clean the points and reset the gap. Other than that I'm not sure what else I should be doing. Also I heard a rumor that you can get a really accurate points gap using a multimeter....anyone know how to do that?

Thanks for the help, I posted over at the Thumpertalk forums but not getting much response over there....this isn't that popular of a bike I guess.

[Jeepfreak81]

Oh and here's a shot of the flywheel itself

ztzh9y1l.jpg

[rustybronco]

Don't know anything about the model you are working on. Does this bike use a battery? The reason I ask is because of the exciter coil in your first picture. It could be used to generate voltage for recharging the battery, or to generate voltage to power electrical loads only.

Also, you might want to check a parts diagram to see if the bike uses a condenser.

Yes you can set the points gap with a VOM.

[Jeepfreak81]

No battery or lights on the bike but it does have a condenser.

[rustybronco]

You file points contacts not sand them. A point file is the proper tool, lacking one of those a small regular file will do. Just set the point gap with the proper feeler gauge and it will be fine. No need to use a dvom or self powered test lamp to tell you when they are just opening.

[jabcb]

You can get a points file for around $5 at an auto parts store.


Need to clean the points after you file them.
Just take a clean 3 by 5 index card & drag it through the points a few times till it stays clean.

[Jeepfreak81]

Ok cool, thanks for the tips. Hopefully that'll get this bike going. My son is super excited to ride it.

[derwood]

remove the points to file them, if they need it, make sure they close squarely. Gap the points to spec with a feeler gauge, (flat type) then set ignition timing. If you put a rolling paper between the points it makes it a little easier to tell when they open (that is when the coil fires) If the condenser is bad you will have no spark.

AND BTY... NO you cannot check or set the points gap with a VOM, be handy if you could but you can't. that would require a dwell meter or you might able to use a frequency counter but you would have to convert degrees to percent, and the bike has to be running anyway. a feeler gauge will work fine.
ign timing can be set with the help of a vom, but the rolling paper trick works. some folks don't have VOM's, but every body has papers.

[Geo]

Make sure the cam that the points ride on is clean and extremely smooth and lightly GREASED. If not, the cam follower on the points will wear prematurity and close the point gap.

[rustybronco]

AND BTY... NO you cannot check or set the points gap with a VOM,

I should have been more specific. You can set the point gap opening point with a VOM. Dwell angle cannot be set with it.

[Gorminrider]

It's worthwhile to change the points condenser as well, if the bike has been sitting around and you don't know it's maintenance level previous.
The "points condenser" is the little can with a single wire pigtail you'll see nearby.
They are cheap.

[koolaid_kid]

I should have been more specific. You can set the point gap opening point with a VOM. Dwell angle cannot be set with it.

I agree. Does not appear to be anyway to adjust timing.
Analyzing the two photos, here is my thoughts:
In the first photo, there are 4 rotating parts, 90 degrees apart. In the second photo, there are 4 fixed parts. When the rotating parts pass the fixed parts, they generate voltage (one or both appear to be magnets). This would energize the exciter coil. When the points open, the exciter coil sends its collected voltage to the plug, which then fires. Being cleaned might make for a stronger spark.
Always replace points and condensers in pairs; one being bad or weak would still cause a no spark condition.

[Big T]

I'd just go ahead and replace both points and condenser, otherwise, you're chasing your tail

There's a reason points burn, it's because the condensor is bad

[Jeepfreak81]

Thanks for all the tips guys. I did get the gap set and am getting good spark now. Fired the engine a few times. Had some trouble because the gap would close or open after adjusting it. Finally I gave it a good tight turn to lock it down and it seems to be staying. Now I just need to figure why it smokes more than Cheech & Chong