Dolmar 117 hoisting middle finger!

[arbor accoster]

Friend of mine has a Sachs Dolmar 117, said it quit while in the cut. I checked it out and has great spark but only about 75#compression. Before I get to carried away it does have fuel and is getting fuel. Pulled jug off and cyl looks as good as new and piston looks ok. rings are not stuck either. lightly honed cyl and put back together now has 100# comp but still wont hit. Put a new plug in and same result even with ether. wont even try to hit. I then pulled flywheel off to see if it sheared the key. It is fine. Pulling on the thing is like trying to drag a dead sow. Seems to have more compression than it is registering. I know this isnt perfect comp but why did it quit in the cut and why wont it even try to hit. Any thoughts or is it just a boat anchor?

 

[doc874]

I don't pretend to know alot about this brand but, what they all have in common is fuel and fuel mix, how old is the fuel? Is it possible it got contaminated say with water? How is the ratio of oil to gas mixture? You say it's pulling "like a dead sow", is it possible it may have overheated and the piston swelled also check crank seals for damage. If it has good spark at the plug and getting fuel but won't ignite or even threaten to do so then try changing the fuel and get good synthetic oil to mix, it doesn;t break-down as easily at high rev's and high temp and lubes better. This is the easiest to do and least expensive.

 

[BigUglySquirrel]

Check out the crank bearings. I've heard of similar problems (hard to pull) with Stihls. The extra friction can prevent the saw from being able to overpower the rotating assemblies mass. Think of stalling out a manual tranny truck...

 

[Lawn Masters]

Possibly a leaking crank seal? check the base gasket on the cylinder and probably replace it. that might fix it, though a flywheel key would cause this, but I dont really know since you mentioned its not sheared. I'd replace it anyhow, just to be sure.

 

[TonyM]

I have had three different saws now that I could not get to even fire upon cranking. Changed the gas and they started right up. I go that route first. Fresh fuel, quality mix oil.

Next, dump a teaspoon of mix into the either the spark plug hole or the carb throat. Make sure the ignition is on, choke is off, throttle set to fast idle, and give a dozen or two worth of pulls, and see if it fires, or maybe even runs a little.

If it runs a little and dies, you probably have a fuel delivery problem. If it never even fires, yet has spark, change the spark plug and try again. If it still doesn't fire, I'm betting weak spark. It takes more voltage to jump a gap when under higher pressure, so you may get spark on the plug at atmospheric pressure, but not under the compression pressure while in the saw. I have had old John Deeres that refuse to start, with spark. Then you clean the points, and they fire right up.

You only need fuel, compression, and spark, and it should at least fire.

 

[arbor accoster]

I did change the base gasket and put in a new plug. I dont think it is crank bearings because without spark plug it wheels right over. I also put fresh mix in carb. Finger still flies. Im willing to bet now it is weak spark but it looks like solid state, dont know for sure but I didnt see any points.

 

[TonyM]

I think it is solid state. Usually they either work or don't. What was your friend doing when the saw originally quit? Did you try putting fuel directly in the spark plug hole? Maybe you've got a bad enough crankcase air leak, that even fuel dumped in the carb is not finding it's way to the combustion chamber via the transfers. I'd try some fuel right in the plug hole. Other than that, it has to be spark timing or voltage.

What about the coil air gap. Has the coil moved away from the flywheel. The strength of magnetisum is proportional to the inverse of distance to the forth power, so a small change in distance affects the field strength a lot. If you could get your hands on an inline spark tester, then you could test the spark under compression pressures.

 

[cbfarmall]

Possibly a leaking crank seal? check the base gasket on the cylinder and probably replace it. that might fix it, though a flywheel key would cause this, but I dont really know since you mentioned its not sheared. I'd replace it anyhow, just to be sure.

Why would he replace a perfectly good flywheel key that he verified wasn't sheared?

Chris B.

 

[Dan Forsh]

Now let me start by saying that I don't know an ounce of what these other guys do, and anything I do know I've learned here, but it sounds like you could be straying in to my specialist subject.

When you say it's hard to pull do you think that it could be the difficulty to pull fast enough that's stopping it from firing?

If so, check the starter rope's pulley for cracks. I had the same problem with one a while back, take the plug out and it pulls no problem, put it back in and the resistance is enough to cause the rope to bind on itself if the pulley is cracked. I've since seen a few cracked pulleys, so could be one worth checking for.

 

[Lawn Masters]

Why would he replace a perfectly good flywheel key that he verified wasn't sheared?

Chris B.

It was only a thought. probably, its a weak coil, or, it might be something relating to the pulley too, but I cant say if I'm not looking right at it in front of me.

Could be worse, could be like Manges 346XP mystery he had awhile back, where the piston was probably wrong.

 

[rupedoggy]

You guys are barking up the wrong tree. Why did the compression go from 75 to 100 pounds with a hone and no other parts replacement? There is something wrong. 100 pounds is not enough in most saws. Get off the spark and fuel delivery. This saw is in need of a new piston and rings and maybe a cylinder. A good Sachs has 160 pounds of compression. Mike

 

[jokers]

Mike,

You`re right that 100# is a little weak, but it should fire on that in my experience.

Did anyone else consider that the muffler may be plugged since it pulls over "like a dead sow" but is only registering 100psi? If he can`t crank it fast enough, normal leakdown could be skewing his compression numbers(I know, seems contradictory), especially on a saw with a worn ring and a freshly honed cylinder.

Could also be that he`s using a four cycle gauge. LOL!

Russ

 

[cuttinscott]

Sachs Dolmar 117 is a 3.7 c.i. breaker point ignition saw the points and condensor went obsolete a long time ago the whole ignition system may be upgraded to the SEM type from a newer 120 super. which made the saw run alot nicer and actually lighter via the alum flywheel vs. the steel wheel. also avg comp is between 100 - 125 psi to run fine make sure you have a crisp blue spark and not a mellow yellow spark. the carb on that saw was a till hk series that is also discontinued the whole carb can be replaced with a walboro ill have to check part #'s if you need. clean fresh fuel is a must.

scott

 

[Lawn Masters]

The compression is a good bit on the low side, I'd focus on a new piston, and rings, then see how much better things work. if that doesnt fix it, I dont know what will. The average Dolmar saw should be running about 130-160psi in the cylinder. anything less, it MIGHT run, but not too well if at all.

 

[TonyM]

I wasn't putting a lot of faith in the compression readings due to the difference between the two readings. Plus he said the piston and cylinder look good. Plus he said it cranks over hard. I suggested in a PM that he mesaure the ring end gap in the bore while he had it apart. Didn't hear what the result was. I would think a saw with 100psi would fire. It may not idle real well, and obviously won't have as good of power. Saws I've seen with low compression seem to start hard, idle poorly, they may cut okay, but as soon as they warm up, if they stall you'll never start it again 'til it cools.

If the 117 is points and condenser ignition, I'd look there, unless you can verify that the compression is truly low.

 

[arbor accoster]

Im pretty sure it is not a fuel or spark problem, the spark is a blue color and you can hear it. I would not want to be touching plug when cranking over. I can put mix or ether in spark plug hole and same result, no response. I am cranking it over pretty fast, way fast enough to start it. I can start an 084 and a 394xp without decomp valve easily. You just get tired of pulling on it,ha ha ha. All kidding aside it just has to be low enough on comp it wont volitize to burn. Anybody have a piston and rings for sale?

 

[arbor accoster]

Oh I almost forgot, I did try it without muffler, Finger is still high

 

[Dan Forsh]

Okay, I might be coming at this a little left of field, but it's worth a try....

Take a hammer, at least 8lbs, may be more. Take a good long swing and hit the B*****D as square as you can.

Does it still have that finger raised?

 

[TonyM]

Okay, how much you want for it? Tell your friend to trade her in on a nice shiny new Dolmar!

 

[Dan Forsh]

Do it, trade it now.

Tony will give you top dollar, anything to cover up the "Dolmargate" scandal!