1980 YZ250 Lots of new parts - still no spark

[Vankaye]

Hi, I am trying to source the electical specs for a 1980 Yamaha YZ250.

I've scoured the interwebs and couldn't find fuck-all... so I thought I would ask you guys.

I'm specifically looking for the testing specs for the stator and coil.

I have restored this bike and it ran great for quite a while but suddenly started losing spark intermittently.
I bought a new coil (brandnew) and plug and cap. Didn't help.
I replaced the stator with a really pretty specimen I found on Ebay but I suddenly have no spark at all.

I am looking for test specs so I can test the used stator I got and of course I should probably also see what kind of resistance the new coil is showing.

Here are some before and after of the restoration:

[k-moe]

Shop manuals are worth every penny spent. http://www.servicerepairmanualonline...stroke-manual/

[Vankaye]

Originally Posted by k-moe

Shop manuals are worth every penny spent. http://www.servicerepairmanualonline...stroke-manual/

I agree. I have the Clymer manual for the bike but there doesn't seem to be any resistance specs.

The whole bike is rebuilt. I would never attempt that without a manual. Not trying to be a wise-guy, just trying to pre-qualify myself.

[Scootern29]

From experience, I would bet it is the CDI box.

[pvangel]

I agree with the black or CDI box, that is the most common failure on these vintage bikes, I went through a bunch on my 1980 rm 125 until I couldn't find them any more...PVL ignitions is the only way to go but it's about $500 for the setup. The biggest forum on these bikes is www.vintagemx.us that I know of, ask away and you will get answers right away!

[pvangel]

PVL does make one for your bike, http://www.pentonracingproducts.com/pvl.htm

Didn't see pricing there but $519.00 on another site.

[kbasa]

Moved to 2 smokers.

[wfopete]

Hmmm. Fresh resto? Might want to check your grounds.

[Scootern29]

He has already had the bike running and it progressivly lost spark. I doubt it is the grounds.

[Grreatdog]

Have you checked the kill switch? Back in 79 we spent a couple of hours working on my friend's DT175 because it suddenly lost spark and died on the trail. We finally either jumped or disconnected the kill switch and it fired right up.

[Foot dragger]

looks like a fun bike once its sorted,I just lucked into one the other day.
Its a 1976 Montesa 250 enduro,saw it on craigslist,called the guy,loaded the dog and loading ramp and zipped up and got it quick like.

The guy said it ran,turns out the engine is rebuilt and sounds like new,frame has fresh powder coat,new SS spokes,new square Amal carb all dialed in,new oem fenders,cad plated bolts,pretty much all stock except the carb,even stock bars from 76.
Ive been doing wheelies around the back yard,the thing starts quick and runs clean. It runs like a crisp Bultaco but shifts on the left side and kicks on the right.
I hate to say what I paid but it was way too cheap,way.

[D.T.]

Nice job!

I'd like to find an old YZ or IT to fix up.

[dentvet]

fun bike. try playing with the cdi, freeze it or try a heat gun. i had a tw200 that missed badly until i squeezed the box with my hand

[Twin-shocker]

Most AC ignitions will work fine using AC pit bike CDI units, which can be found for less than $20 on Ebay. You need to sort out the correct pins of the PB CDI to connect to your OE wiring, but this is pretty easy, and a new Chinese CDI is better than taking a chance on a used part which might not work anyway.