61 with new p&c won't rev

[jettyhouse]

the full story,I cooked my 61 (piston ring fused) cylinder not badly scored.replaced with ebay $100 p&c started with three or four pulls idle adjusted easy,high speed jet adjusts, but it won't rev much over 40 to 50 %.still starts and idles beautifully.The saw is old,but as the story goes it has had so little use "I Havn't even sharpened it!!!"

 

[outdoortype]

When you say "won't rev over 50%, do you mean the saw cuts out or just bogs down? Does the saw have compression? I had a similar experience with a $100 ebay aftermarket p&c. Mine wouldn't generate any rpms or power. IF your compression is low, you could check the ring gap measurement. Maybe the ring is out of spec.

 

[jettyhouse]

plenty of compression if I am not careful it will lift the saw.

 

[Andyshine77]

Is the throttle fully opening?lol

Did you rebuild the carb.

 

[Nicholas]

I've seen ignition modules go stupid causing the condition described in the post. Very difficult to test for. Engine will have spark, but timing won't advance enough to accelerate to wide open throttle. I have also seen where you'll have spark, compression, properly adjusted carb, plenty of fuel, and crankcase with no leaks, and get a no start condition.

Nick

 

[jettyhouse]

the linkage is hitting the stops,but no I didn't touch the carby as the saw as running perfectly when i cooked it

 

[stihl86]

So, it was running fine till you cooked it.

 

[jettyhouse]

yep! sad but true a very relable saw,and why isn't it still??

 

[cjcocn]

So, it was running fine till you cooked it.

yep! sad but true a very relable saw,and why isn't it still??

I think what stihl86 means is that if it was running fine, then it wouldn't have "cooked" the first time and it would be revving normally now.

I would start checking things over. Fuel filter, fuel line, carb rebuild (or at least cleaning), etc.

 

[Nicholas]

If it's a fuel filter blockage/restriction the saw will rev, lean out and quit. If there's a blockage or restriction in the fuel circuits/passages in the carb it will also rev, lean out and quit. If the inlet needle is set too high you'll load the saw up with fuel, it will rev and smoke like a freight train. It also may not rev out to wide open throttle. If you have a fuel line cracked, you'll get a difficult or a no start condition. If the engine can be started, the saw will rev, lean out, and quit. If it's a fuel tank vent the saw will run normal for 1-3 minutes. Then lean out, surge and quit. By cracking the fuel cap open you can test for this. If he saw begins to run normal after cracking the fuel cap you have a tank venting issue. Did you check your spark arrester screen for any blockage? A blocked screen may also cause a saw not to rev out completely.

Nick

 

[Nicholas]

When you rev the saw out, does it sustain itself at 40-50% of wide open throttle? Or does it lean out and quit after reaching 50% of wide open throttle? Is there excessive exhaust smoke present as the saw is reved out?

Nick

 

[litefoot]

I think you should do a pressure/vacuum check before you burn up your saw again.

 

[Nicholas]

You might have to put a new sparkler plug in? You know, if your power equipment don't run right, it's always the spark plug's fault. 7-10 customers that walk in to the shop I work at, believe this. It's the first thing they ask for. I had one wingnut come it ask for a spark plug for his tiller because his tines wouldn't turn. I asked him if his engine started and ran fine. The customer said "Yea, but my tines won't turn, the plug is defective." I told him he my have a broken idler, drive belt, sheared key/pin, or gear case that is out, and all the spark plugs in the world weren't going to solve his trouble. He was still convinced the plug was bad. He took a new plug home, called back 15 minutes later to tell me my new spark plugs were defective too.

Nick

 

[Nicholas]

Doing a pressure and vacuum test is a great idea too. If nothing else, it will eliminate some variables. If you have a severe enough crankcase leak the saw will race and run lean at idle. If you roll the saw from side to side and get wild changes in idle speed and quality you may have a crank case leak too.

Nick

 

[pioneerguy600]

When you changed your P&C was it a matched set or did you get your piston and cylinder separately? Why I am asking this is there has been a rash of cylinders with both open and closed ports getting fitted with the improper piston for the cylinder. Sometimes the saws will start with the improper piston but can`t reach WOT or even enough RPM to properly engage the clutch. Others on here would know more about this but I think that if a open port piston was installed in a closed port cylinder it probably could not get enough air to fuel into the top of the cylinder to reach WOT.Others will correct me if I am wrong.
Pioneerguy600

 

[HiOctane]

First guess,closed port cylinder with a NO window piston like Pioneer600 said.

 

[jettyhouse]

now i think i am getting somewhere,not that i like where i am getting!!How do i tell if they match? but yes they both came as a unit,and can i mod the pair?

 

[jettyhouse]

[none of the above,Nicklas,the saw starts easly.idles fine,no hesitation on pulling the trigger,but stops at maybe have reves,and not enough power to do anything but strugle through a cut.

 

[jettyhouse]

You might have to put a new sparkler plug in? You know, if your power equipment don't run right, it's always the spark plug's fault. 7-10 customers that walk in to the shop I work at, believe this. It's the first thing they ask for. I had one wingnut come it ask for a spark plug for his tiller because his tines wouldn't turn. I asked him if his engine started and ran fine. The customer said "Yea, but my tines won't turn, the plug is defective." I told him he my have a broken idler, drive belt, sheared key/pin, or gear case that is out, and all the spark plugs in the world weren't going to solve his trouble. He was still convinced the plug was bad. He took a new plug home, called back 15 minutes later to tell me my new spark plugs were defective too.

Nick

I like that idea!too easy I think I will put in two!,but seriously the plug is possably 20 years old,I'll go see if my 365 plug will fit? My wife always tells me to check the spark plug, I don't know why she missed this time!

 

[pioneerguy600]

now i think i am getting somewhere,not that i like where i am getting!!How do i tell if they match? but yes they both came as a unit,and can i mod the pair?

You probably don`t have picts of the piston and cylinder so it would be hard for me to say for sure what you have in there. The open port piston is almost a solid design with no openings on either side of the piston pin,[windows] that open through the piston wall to the interior of the piston.
The closed port piston has windows or openings that allow fuel/air mixture to get from the crankcase to the top of the cylinder. You may have to remove the cylinder and check to see which P&C you have.
Pioneerguy600