Difficulty starting (almost new) 661

[Howard Justice]

Spending more time on this site i now understand CAD.
We have a MS661 that’s about 2 YO. Prolly run 3-5 tanks. Most recently run at Newnan GA tornado response last year. Recently went to help remove a 42 in poplar and it never popped. Checked plug and was dry. Certainly welcome thoughts on diagnostics or starting options. Obviously I’m not a saw mechanic. Pulling the cord on that saw a continuous 25-30 times at 66 is a bit different than at 56 … even w compression release. TIA

 

[ErnieG]

Ethanol may be your problem
Ernie

 

[Howard Justice]

Thank you Ernie. All our saws have only seen cans of pre-mix. We have been fortunate to have gallons of Tru fuel and similar donated. We don’t allow any of our saws to be fueled w “gas station”mix. Too many volunteers may mix incorrectly. After Hurricane Michael we had two pallets donated of a Jonsered 2-Cycle 50:1 Pre-Mixed Fuel otherwise we buy Tru Fuel or it is donated.

 

[irhunter]

With a dry plug, sometime very early in the diagnose phase, I pour a bit of mixed gas down the plug hole (say, 1/4 teaspoon), reinstall plug and boot, try to start.

 

[trains]

Spending more time on this site i now understand CAD.
We have a MS661 that’s about 2 YO. Prolly run 3-5 tanks. Most recently run at Newnan GA tornado response last year. Recently went to help remove a 42 in poplar and it never popped. Checked plug and was dry. Certainly welcome thoughts on diagnostics or starting options. Obviously I’m not a saw mechanic. Pulling the cord on that saw a continuous 25-30 times at 66 is a bit different than at 56 … even w compression release. TIA

If that was the case on any saw, I would first check that the fuel metering needle is not stuck down inside the carb, sometimes, when all the mix dries out, the oil can stick things closed, inc some of the drillings/ passages inside the carb.
The fuel metering lever is what is attached to the fuel metering diaphragm, and regulates how much fuel is kept on that side of the carb, think fuel bowl and floats on a car carby (sorry I dont know your level of experience here, so sorry if its a bit basic).
Needle is part no1 on page 23 of the IPL attached.

The 661 carb is pretty much like a normal carb, but instead of a main jet/ mixture screws setup, its just electronically controlled by the fuel solenoid.

I would first look ahead of the solenoid to make sure the fuel filter is ok, but my gut would be to look inside the carb, and check the needle is not stuck.

simple clean with some fresh mix, and away you go.

Some fuel down the plug hole, and when it fires up, might be enough to lift the needle up and free it too.
But then expect it to possibly flood out, as the needle/ seat area wont be clean and provide a tight seal, leaving it for a few hrs might let the fuel mix dissolve the dried up oil, and it may come good, but I would give the carb a clean if it fires up with some fuel down the plug/ or intake.

hope these help too, there is a fault finding flow chart in the service manual too.

edited for clarity, morning coffee still to activate brain.

 

[Howard Justice]

With a dry plug, sometime very early in the diagnose phase, I pour a bit of mixed gas down the plug hole (say, 1/4 teaspoon), reinstall plug and boot, try to start.

Thank irhunter! I’ll try that tomorrow!

With a dry plug, sometime very early in the diagnose phase, I pour a bit of mixed gas down the plug hole (say, 1/4 teaspoon), reinstall plug and boot, try to start.

Thank you!

 

[Howard Justice]

If that was the case on any saw, I would first check that the fuel metering needle is not stuck down inside the carb, sometimes, when all the mix dries out, the oil can stick things closed, inc some of the drillings/ passages inside the carb.
The fuel metering lever is what is attached to the fuel metering diaphragm, and regulates how much fuel is kept on that side of the carb, think fuel bowl and floats on a car carby (sorry I dont know your level of experience here, so sorry if its a bit basic).
Needle is part no1 on page 23 of the IPL attached.

The 661 carb is pretty much like a normal carb, but instead of a main jet/ mixture screws setup, its just electronically controlled by the fuel solenoid.

I would first look ahead of the solenoid to make sure the fuel filter is ok, but my gut would be to look inside the carb, and check the needle is not stuck.

simple clean with some fresh mix, and away you go.

Some fuel down the plug hole, and when it fires up, might be enough to lift the needle up and free it too.
But then expect it to possibly flood out, as the needle/ seat area wont be clean and provide a tight seal, leaving it for a few hrs might let the fuel mix dissolve the dried up oil, and it may come good, but I would give the carb a clean if it fires up with some fuel down the plug/ or intake.

hope these help too, there is a fault finding flow chart in the service manual too.

edited for clarity, morning coffee still to activate brain.

Thank you Trains!
Most helpful!
Dumb question: would a shot of carb spray possibly help loosen needle? I’ve seen others do this in the field occ and seemed to work? Some years ago I put oil in wrong tank in my 261. Should’ve been an indicator I was tired and probably should’ve put the saw away sooner. I did my research and one of the required items to fix this mess was carb spray… Much carb spray and pouring and dumping fuel in. Eventually after quite a while I was able to crank it … hopefully I won’t make that mistake again. I guess that goof once every 30 years is OK?

 

[trains]

I would not use carb spray on it, unless it was apart, and the fresh fuel mix did not dissolve the dried up fuel mix, (if that is indeed your problem).

Try fuel down its throat/ plug hole, that does 2 things, proves you have spark, as it will run for a bit, and also may pull enough vac on the fuel pump due to the pulse of higher rpm (way higher than hand cranking with the pull cord), and may free the needle, and flow fuel.

Try that first, its good advice from IRHunter, then get back to us and we can methodically step thru it so you dont leap frog over the problem.

Stick to a plan, dont get distracted, and try too many things at once, you will leap frog over the issue, only stupid question is the one you dont ask.

 

[Howard Justice]

I would not use carb spray on it, unless it was apart, and the fresh fuel mix did not dissolve the dried up fuel mix, (if that is indeed your problem).

Try fuel down its throat/ plug hole, that does 2 things, proves you have spark, as it will run for a bit, and also may pull enough vac on the fuel pump due to the pulse of higher rpm (way higher than hand cranking with the pull cord), and may free the needle, and flow fuel.

Try that first, its good advice from IRHunter, then get back to us and we can methodically step thru it so you dont leap frog over the problem.

Stick to a plan, dont get distracted, and try too many things at once, you will leap frog over the issue, only stupid question is the one you dont ask.

Thank you. That’s what I’ll do.

 

[user 122190]

For such an infrequently used saw there is bound to be some fuel issues lurking somewhere. I would get it started as best as you can, and run that saw hard. Line up a few big logs, and once the saw is running, attack the logs, and don't let up til you run it out of gas.

 

[Howard Justice]

For such an infrequently used saw there is bound to be some fuel issues lurking somewhere. I would get it started as best as you can, and run that saw hard. Line up a few big logs, and once the saw is running, attack the logs, and don't let up til you run it out of gas.

Thank you Montana Resident! Agreed.

 

[Howard Justice]

Thank you Montana Resident! Agreed.

And will post a pic!

 

[trains]

Thank you Montana Resident! Agreed.

Just be careful, if you have fuel delivery issues, and they are not sorted, you run the risk of running lean and causing damage.

I would find the issue, fix it, and then run it knowing it will be both reliable, and not damaging the saw.

 

[user 122190]

Thank you Montana Resident! Agreed.

And if that doesn't work, pull the carb off and apart and spray the hell out of it with carb cleaner and compressed air.

 

[user 122190]

Just be careful, if you have fuel delivery issues, and they are not sorted, you run the risk of running lean and causing damage.

I would find the issue, fix it, and then run it knowing it will be both reliable, and not damaging the saw.

I guess I read this wrong. If he running issues, then I agree. I thought it was only starting issues.

 

[trains]

I guess I read this wrong. If he running issues, then I agree. I thought it was only starting issues.

Well since were not sure what the issue is yet, but from what has been described, its no fuel flow, better to err on the side of caution.

Agree, if its just a stuck needle, then running it hard will help with the flow of fuel/ and or flooding issues whilst the fuel dissolves the dried up oil mix, but if its something else, and its running lean, then giving it some work could harm it.

if it was a little 180 or cheapie, not much to loose, but its a bigger toy and a bit more expensive, so would prefer to help him find the fault and fix it, a lot more $$$ is at stake.

 

[PV Hiker]

I stopped using carb cleaner sprayed until I separated the carb apart and physically removed the metering needle. Once I left a needle in that had a rubber cone seal and it deformed it unusable. So I never know what carb is going to have a rubber cone to help seal or not.

Just thought of something, I do have a can that I can fill and air pressurize it with mix and using a straw can spray out a carb. Hummm.

 

[Howard Justice]

I guess I read this wrong. If he running issues, then I agree. I thought it was only starting issues.

Correct. Starting issues. When we ran it last year …. It was much more capable than our 461!

 

[Howard Justice]

Well since were not sure what the issue is yet, but from what has been described, its no fuel flow, better to err on the side of caution.

Agree, if its just a stuck needle, then running it hard will help with the flow of fuel/ and or flooding issues whilst the fuel dissolves the dried up oil mix, but if its something else, and its running lean, then giving it some work could harm it.

if it was a little 180 or cheapie, not much to loose, but its a bigger toy and a bit more expensive, so would prefer to help him find the fault and fix it, a lot more $$$ is at stake.

Ran perfect. Won’t start. Thanks for all the insight here!

 

[trains]

Ran perfect. Won’t start. Thanks for all the insight here!

Let us know what you find, rekon the stuck needle is the best place to start, dont be tempted to remove the fuel filter and blow back thru the fuel hose to try and unseat it, most likely will pop off a fuel line.

So get back to us, did putting some fuel down its throat, or in via the plug make it try to run, but then die off as the fuel was consumed ?

Edited to add,

take off the air filter cover and have a good look at the wiring etc, make sure no critter has been in there eating/ nibbling and causing any obvious damage too the fuel solenoid side of things.