Reviving 031 spark

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MnSam

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By following Flyboy's directions, I was able to replace my condenser with a capacitor. Instead of a $30-$40+ OE condenser, I spent $3 and restored life to my dad's parts saw.

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My home-made flywheel puller.
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I had to grind a little of the flange off to fit the new capacitor into the old condenser hole. I siliconed it in place and added a little metal retainer to keep it in place.
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That is a very nice right up. You did a better job than I installing the cap. Please tell us what cap you used so when people search, they will have all the data in one thread.

I think there are at least 6 or so AS members with 031s with that cap......instead of a $40+ condenser from the dealer.
 
OK,i see the specs on the replacement cap but what are the specs on the original ??
.22 uf ?? man that aint much..630 volts ??
wish a had an original to put on the tester to see what it is just for the heck of it....NOT going to try to pull the one out of MY 031 either if it's THAT much work..
BTW; they can be checked with a DMM..
 
Did you cut wood with it yet?

Not yet, been cold outside, been quite busy, live in town, need to resupply myself with some cutting material.


OK,i see the specs on the replacement cap but what are the specs on the original ??
.22 uf ?? man that aint much..630 volts ??
wish a had an original to put on the tester to see what it is just for the heck of it....NOT going to try to pull the one out of MY 031 either if it's THAT much work..
BTW; they can be checked with a DMM..

Valid questions, I was wondering myself what exactly the electrical specs where on the original. However, given the fact that I was certain the condenser was bad, it was a "parts" saw, it was a 3 dollar gamble, and the flywheel had to come off regardless of what I put under it I deemed it worthy of a try. And it really didn't take too long. About 10 minutes of dremel work and creating the retainer, the longest part was waiting for the silicone to dry. I certainly wouldn't swap the new capacitor with a known good condenser, and it was a fun project, had to try just to see if it would work.
 
As for the original. I have seen specs from .15uf to .22uf depending on the age of the manual. Capacitor specs are traditionally quite loose. There is capacitance vs. voltage spec for one, and a capacitance vs. temperature curve as well. In addition, there is equivalent series resistance spec and dissipation factor spec. Rarely do I spec a cap for low dissipation factor, but the condensers and Wima caps have very low dissipation factor......Important here.

Also you have the working voltage spec. The Stihl condenser is not spec'd for working voltage but.......

you have to figure the spark plug is seeing 20,000 to 50,000 volts. If the coil has a 100:1 turns ratio then you are seeing 200 - 500 volts on the condenser.....hence the 630V cap. The next lowest cap is 400 some odd volts.
 
As for the original. I have seen specs from .15uf to .22uf depending on the age of the manual. Capacitor specs are traditionally quite loose. There is capacitance vs. voltage spec for one, and a capacitance vs. temperature curve as well. In addition, there is equivalent series resistance spec and dissipation factor spec. Rarely do I spec a cap for low dissipation factor, but the condensers and Wima caps have very low dissipation factor......Important here.

Also you have the working voltage spec. The Stihl condenser is not spec'd for working voltage but.......

you have to figure the spark plug is seeing 20,000 to 50,000 volts. If the coil has a 100:1 turns ratio then you are seeing 200 - 500 volts on the condenser.....hence the 630V cap. The next lowest cap is 400 some odd volts.

WEll hello bedford from barrington nh.
nice to know what close specs are..
yeh,cap specs can be all over the place..i usually go UP on UF after a cap fails and higher voltage dont hurt either..
i have a bunch of super nice mylar hi voltage caps from RF work..dont see why they wouldnt do the job..
 
WEll hello bedford from barrington nh.
nice to know what close specs are..
yeh,cap specs can be all over the place..i usually go UP on UF after a cap fails and higher voltage dont hurt either..
i have a bunch of super nice mylar hi voltage caps from RF work..dont see why they wouldnt do the job..


They just have to be low dissipation factor.....to handle the ripple current i think. Also, there would be too much loss for a cap thermally coupled to the crankcase if it had higher ESR or dissipation factor.

I did a capacitance and dissipation factor vs. frequency sweep on a Ridley Engineering network analyzer. The WIMA caps matched the Stihl Condenser very well.....
 
I finally got to put this into some wood. After the cap replacement and walbro carb kit from Randy's this thing just runs awesome. Absolutely nothing wrong with idle, rev, and top end. My dad bought this used over twenty years ago, and used it every year until 3 years ago to heat his house (he bought another 031 as a replacement). I am half tempted to tell him I couldn't get it running and keep it for myself. Just kidding of course, I will give it to him for his birthday. Thanks again Flyboy for your help.
 
I finally got to put this into some wood. After the cap replacement and walbro carb kit from Randy's this thing just runs awesome. Absolutely nothing wrong with idle, rev, and top end. My dad bought this used over twenty years ago, and used it every year until 3 years ago to heat his house (he bought another 031 as a replacement). I am half tempted to tell him I couldn't get it running and keep it for myself. Just kidding of course, I will give it to him for his birthday. Thanks again Flyboy for your help.

Anytime. I am pleased to hear another success story.
 
Stihl 031 av Capacitor (condenser replacement) no longer availalbe

Sorry to report that the MKP4 .022UF 630V CAP is no longer available. :msp_thumbdn:
Mouser Electronics just replied to my order, saying they had none in stock and that their supplier wante a 1,000 unit order if I wanted one.
I called Mouser and was told that they had no idea where I could get this part if they could not get it without a large order.
Bought a new Stihl Farm Boss 290 - as all the reports indicate this is a very popular and excellent performing saw.
But would still like to find a solution to fix the 031 - it was a terrific saw when it ran!!!!
 
Hey guys. Google found this thread while i was looking for the point gap spec for my 031av. I'm almost certain the condenser is bad so i'm going in for the WIMA cap replacement.

I have a couple questions.

1. Can someone post a direct link to a source the right cap - the 630v one?

2. Can i do this without a Dremel tool?

3. Can i get new points? If so, can someone post a direct link to a source?

4. What are the correct point and coil gap specs?

Thanks from NE Kentucky.
 
Hey guys. Google found this thread while i was looking for the point gap spec for my 031av. I'm almost certain the condenser is bad so i'm going in for the WIMA cap replacement.

I have a couple questions.

1. Can someone post a direct link to a source the right cap - the 630v one?

2. Can i do this without a Dremel tool?

3. Can i get new points? If so, can someone post a direct link to a source?

4. What are the correct point and coil gap specs?

Thanks from NE Kentucky.

Ok, i just bought two for $8 from the link above.
 
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