Why no gas to carb? MS260

[roccus]

Stupid questions...

1. What is the history of this saw? Why did you tear into the carburetor? Was the saw running ? If not, how did it become non-running?

2. What was the result of Alex's thumb over the carb test? Was there fuel on the spark plug or was it still dry?

Hello Steve this was a parts saw that came with another ms260 running saw I bought it looked to be a complete saw but when you pulled the startr it had a clanking noise so I took the jug off and found the wrist pin was missing and it had a badly scored piston and gouged cylinder so I got a NWP big bore top end kit and decided to just do the carb the carb on this saw is a WTE with 3 adjustments while I was at it I ordered an OEM kit for that when I took the bottom cover off the carb I found there is a pocket in there and it was filled with saw dust so I cleaned it out everything else in it looked good so I just put the new gaskets and diaphragm in it. While I had it all part to clean it up I did look at the impulse line and looked ok I did not look at the bearing seals.

The running saw is a nice saw it has an issue though it starts idles and runs real well but when you make a cut at the end of the cut when you let off the throttle it stalls out like for some reason it does not get enough gas so I have to feather the throttle to keep it running it seems feathering the throttle on it helps it recover to get the gas pumping in again and it then idles fine till next cut. That saw has the 2 adjustment carb on it I want to do the muffler mod on it and read here you really should have the 3 adjustment carb to richen the mixture to accommodate the muffler mod so I picked up an OEM WT 194-1 for it thinking it may kill 2 birds with 1 stone give me the 3rd adjustment and maybe solve the stalling problem it has when you let up off the throttle after a cut.

So back to the parts saw when I saw I was not getting gas into the carb I decided to try the new OEM carb I got for the running saw on it but still no gas getting into the carb I did try putting my thumb over the carb opening thinking it would increase vacuum and maybe suck the gas in but it did not carb and plug still bone dry. I have polished the ports a bit on the new NWP jug I did not enlarge or modify the ports at all just smoothed them up a bit and I have shaved the tab off the limiter on the WTE carb to do a muffler mod on it as well... so this is where I am at with it

I have another thread here on this saw of the build... http://www.arboristsite.com/community/threads/top-end-kit-ms260.303874/

This is the parts saw with the new top end kit on it

 

[merc_man]

Your saw that runs but stumbles upon idle return spuds like it needs a low side adjustment. Mabe a little lean or rich.

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[roccus]

Your saw that runs but stumbles upon idle return spuds like it needs a low side adjustment. Mabe a little lean or rich.

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Thanks merc I figure it is fuel related and I plan to put a fully adjustable carb on it with the muffler mod that saw has a like brand new ES 20" bar with 3/8 .05 chain on it for from what I have read here the 260 will need that little more boost for that chain and bar set up

 

[merc_man]

If you muf modded it and dont have the fully adjustable carb i would stop useing it. Cant properly tune it

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[HarleyT]

What about my post? Have you tried that simple test?

 

[Bedford T]

Go buy a pressure tester I was just like you a man with multiple problems. Clear it up. The fuel system is a real critter. And you can have an air leak that effects your pulse. Take a dab of grease and put it in the mouth of the impulse line and gently turn the engine and watch that grease. It should breath. If it does not you know you have an engine air leak. Then you can move on to your fuel lines, filter, carb. Top of fuel line can leak and bottom portion can suck air if it leaks. Lots to check

 

[roccus]

What about my post? Have you tried that simple test?

Yes I did I think that may be another problem with this saw... these 2 stroke motors is not my forte so all this is new to me I have spark at the plug but it is not a nice bright blue spark it looks a bit weak to me yellow in color it did not fire at all when I put some gas down the carb but as someone else pointed out if it is not getting gas it will not run period even is it has good spark si I am going to take first things first get it so gas is going into it then if needed replace the coil and this being a brand new top end not broken in yet I really don't want to start dumping a whole lot of raw gas down into it

 

[Bedford T]

Do you have a pulse

 

[roccus]

Do you have a pulse

Not sure I will try your grease tip for now thanks for that tip it's a good one

 

[HarleyT]

"but as someone else pointed out if it is not getting gas it will not run period even is it has good spark"

The act of squirting gas into the intake is to make sure that it is in fact, getting gas.

 

[Bedford T]

Check the pulse

 

[HarleyT]

If you did this, it is either flooded, compression problem, or ignition.

 

[HarleyT]

If you have spark, and considering the history of this saw, I would look for a sheered flywheel key first.

 

[Bedford T]

Because you just did your top.
Check pulse
Check the fuel delivery system
Check the key
Test your carb

 

[HarleyT]

Whether or not the "pulse" circuit was blocked, it would still fire on a prime...

 

[HarleyT]

The "squirt down the hole" test is the first, simple test.... It did not fire/run/vroom. So it is either flooded, compression, or ignition.

 

[HarleyT]

And if it is ignition, then it is either no spark, or timing is off.

Since you have spark, then I would consider timing....

 

[HarleyT]

But I would seriously rule out flooded first, and check the flywheel key for being sheared due to insufficient torque......

 

[SteveSr]

Hello Steve this was a parts saw that came with another ms260 running saw I bought it looked to be a complete saw but when you pulled the startr it had a clanking noise so I took the jug off and found the wrist pin was missing and it had a badly scored piston and gouged cylinder so I got a NWP big bore top end kit and decided to just do the carb the carb on this saw is a WTE with 3 adjustments while I was at it I ordered an OEM kit for that when I took the bottom cover off the carb I found there is a pocket in there and it was filled with saw dust so I cleaned it out everything else in it looked good so I just put the new gaskets and diaphragm in it. While I had it all part to clean it up I did look at the impulse line and looked ok I did not look at the bearing seals.

Scored piston - ran lean and seized. Sawdust in the carburetor - more bad news. I am assuming that the sawdust in the carb was NOT in the same chamber with the wire mesh fuel screen. This means that it was in the impulse chamber. The only way it can get there is through a leaking impulse line or bearing seal. It is a good thing that this saw didn't run as you would have likely roached the new top end in short order... just like the original!

I also see that you have done a muffler mod on this saw. It is unknown (by me) if the WTE carb has enough adjustment range to handle this modification without being too lean on the top end. Someone with more experience can chime in here. The WTE with limiter caps also has a certain turn offset built into the base setting as the caps only allow for 3/4 turn of adjustment. The adjustment in the manual and printed on the AF cover only applies if the cap is installed with the correct offset. The WT-194 will have enough range but you'll have to trade the compensating snorkel lid from the old carb.

These saws seem to have a history of seal leaks especially on the flywheel side. Pressure testing is strongly advised. Special tools are recommended to remove the crank seals especially the flywheel side to avoid scratching the crankshaft or boogering the housing. Once you get it torn down check the bearings for any radial play - which can ruin seals in short order. If you can feel any radial play in the bearings they are toast and must be replaced.

The running saw is a nice saw it has an issue though it starts idles and runs real well but when you make a cut at the end of the cut when you let off the throttle it stalls out like for some reason it does not get enough gas so I have to feather the throttle to keep it running it seems feathering the throttle on it helps it recover to get the gas pumping in again and it then idles fine till next cut. That saw has the 2 adjustment carb on it I want to do the muffler mod on it and read here you really should have the 3 adjustment carb to richen the mixture to accommodate the muffler mod so I picked up an OEM WT 194-1 for it thinking it may kill 2 birds with 1 stone give me the 3rd adjustment and maybe solve the stalling problem it has when you let up off the throttle after a cut.

Poor / no / or inconsistent idle can also be a symptom of an air leak. Looks like you may have gotten a 2-for-1 deal! It needs to be checked and fixed before you burn up this saw. I see a Mity-vac in your future! They aren't that expensive and will save you a lot of guesswork... which you are doing now.

Good luck,

Steve

 

[HarleyT]

Huh?