OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Trimmers and Brushcutters Two Stroke Trimmers & Brushcutters stihl w/snipper

Hi everyone, I have been given a stihl /snipper a mate got at a garage sale for $5. It dosent have any identification except it says pro series and stihl so I was hoping someone could tell what it is. I did get it running but it keeps loosing it's spark so I assume it is the coil ,I have tried a known good spark plug and I took the coil off overnight and put it out in the sun for half a day and then reinstalled it . It started sraight away and ran for about three minutes and died . While I had it going I reved it high and I could feel it cutting in and out so I gave it more throttle and got through the cutting out bit then tuned it and ran on idle for about a minute and died , try to start it again and once again no spark . Im uploading photos but the selection only gives me one choice HTML


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Here is a fs74 which has a very similar powerhead, this one has been cooked and seized to death, everything ls on it should be okay, but somone ran it without oil....




If you can measure the distace between the mounting hoels the coil may fit, the coil on yours may be fine, maybe try it with the kill switch disconnected near the coil quickly to rule out any wiring issues.

Thanks Joe carroll, the distance between the centre of each hole is 40 mm
The number on the coil is 4137/1304/A/AD/4137/FS/and the last three digits I think are 512 and the numbers on the inside of the plastic cowl are 4137 084 0902. Idid pull the trigger apart and found that it had a switch in it ,so I cleaned it out and tomorrow will try it again. Also tomrw I will take one of the wires off the coil if still have problem. I will get back to you in the morning thanks again,Rob

Sorry I tkink the measurement between the poles, the iside edge of one pole to the inside of the other is 17 mm and I used a tape measure so it could be out by a fraction.

Ill check the one I have here out tomorrow, cant make any promises, but m only goping to part it shortly anyway as the actuan engines junk...

I have tried with the kill wires off and it idled beutifully until it got hot and then just shut down , it wouldn't start again untill it cooled down. I also tried with kill wires on and exactly the same thing happened . So once it cooled down again I took the kill wires of again it ran till it got hot,so I'm pretty sure it would be the coil as after it ran I had taken the spark plug out and tested iton the engine and no spark at all when it was hot. Tried with several spark plugs with the same result. Coil =$ cheers and I hope your coil is the same

roebuck, if you are sure it always has no spark when it's hot and it usually has spark when it's cool, and this doesn't change when the kill wires are removed, it does sound like a temperature-dependent ignition module failure. If Joe can help you with a module that fits, trying it with the other module seems like the first thing to do.

Unfortunately it wont be a fit, 10 points for trying though heres a pic

Thanks heaps Joe for all your trouble .I do need an air cleaner and cover if you would$.
I'll start looking for one at the tip. This machine has me stumped. Today I have had running but still the same thing, just dies and when I do get it going it won't idle now . This one is beating me up

The one in the background of your photo looks more like the one I have lol. The tip is open tmrw so maybe with a bit of luck . Thanks again .

Could someone tell me if it is possible to change the welsh plugs in a small carby without any specail tools and the process would help greatly,thanks

The manual says you remove the plugs by driving a special punch through them, then levering them out with the punch. You could grind up a punch like theirs rather than buy one.

To install new plugs, lay a bead of nail polish around them, put them in convex side up (hollow side down) and tap them flat with a pin punch.

Hi Grumpy, thanks for that information ,I will practice on a dudd carby first to get it right. Today I found out why the coil kept losing spark ,in the beginning it had a join in it so I cut that bit off . I don't know why someone had added extra as there was enough lead there anyway and messy too. So then I grabbed my spark tester and started the engine it fired up and I kept an eye on the tester as it looked pretty good but every now and then the glow in the tester went out very briefly but the engine kept on running and then it would stop,it would start again and do much the same thing. This when I noticed a little slight kink in it so I took the spark boot and clamp then slid the protection sheath off and there it was another joint and very neat too, but it was a little bit more I had to cut off. The join had yellow sticky stuff in it . Putting the boot and clamp back on ,used the tester again and it works really well. Know the lead is only just long enough to attach to the spark plug ,it works good but I would like to make it longer so as it not to be to tight. Can I replace the HT wire or do I have to add more or is there something else . Any ideas. Hope this makes sense and I also still don't know what series fs it is cheers.

Ignition modules usually have the high tension lead permanently attached at the coil, so the whole lead can't be replaced. I had the same problem you have a month ago with a Honda GXV120 module: the previous tenant had cut off the lead near the coil, for some reason only he could understand. I didn't have any high tension lead, so I visited a mower repair shop and bought a bit of lead and a spark plug end fitting (for a truly unbelievable price: $14.50, for a dollar's worth of stuff). I joined it to the stump of the original lead by cutting the head off a self-tapping screw, and screwing it into the cores of both the old and new wires, filled the join with epoxy, and shrank a piece of heat-shrink tubing across the join. It has been on my weekly-mow mower ever since, and has operated perfectly.

Thanks Grumpy,that's what I'll do.great stuff.

The type of stihl is a sf 85 , that is the engine but the bent shaft belongs to another machine alltogether says the guy from our local stihl shop and he also said that the engine was a comercial motor the first of the pro-series.

Grumpy, I don't know what has happened ,I have cleaned the carby and I didn't touch the welch plugs . My only problem is when I prime the carby it's not filling up the primer like it did before. When I prime the carby it gets a tiniest bit of fuel and then crank it and it will start straight away and only go for a few seconds and then it won't start, prime it again and same all over again. The primer bulb dosen't seem to fill like before so could you please help me on this . Cheers Rob.

Hi Rob, diaphragm carburetors are a source of a fair amount of frustration to me as well as many other people. However we seem to be stuck with them on machines that have to operate upside-down and on various extreme angles.

Here is the Owner Manual for your machine:
http://www.stihlusa.com/WebContent/CMSFileLibrary/instructionmanuals/FS80_85_Manual.pdf

Here is the workshop manual:
http://www.worldoftrainz.com/Downlo...4137%20Components%20Service%20Manual.pdf

If you focus on the service manual, starting on page 44, hopefully the solution is in there somewhere.

I'm having issues at the moment with a Walbro WA74 carburetor, and finding it is a long process, mainly because they seem to have a large number of design variants and haven't documented them individually. However with a bit of luck you'll do better, just because Stihl have that detailed manual on your specific machine.

Please come back after checking through the manual - if you haven't found it by checking for an assembly error, we can start a bit-by-bit process.

Hi Grumpy, frustration is an under statement, I've pressed on both addresses as above but nothing happened and I will try again later as my computer is having a fit witch I think my stihl has got to close to it and may of given it a virus. I don't mined the challenge and I'm not giving up on this one. The shop has told me to throw it and buy another at the cost of aprox $100 and I've been told this many times before . With the help of people like you and all of outdoorking and some patients I will work this out no matter how long it takes. Will keep you posted on this one. Thanks heaps ,rob. :cheers2:

Ok got the manuals and will read thoroughly soon as I get the chance thanks heaps again Grumpy.