660 dies in cut

[NPKenny]

My 660 is fairly aggressively ported (no pop-up, etc.). I had been running great and only recently began acting up. It will fire fine and run for a minute or two, stumble and die. The saw certainly runs for a shorter time once it gets warmed up.


I pulled it completely down to look at it and the piston looks excellent. I changed fuel lines and cleaned the carb while I was in there. All things looked normal. I put it back together and ran it what I can and the problem still persists. The plug looks perfect and the exhaust side of the piston looks great.

Possible problematic areas that i am thinking to address next include:

Fuel cap is cracked, although it does seem to seal very well. I plan on replacing it.
Grommet to the fuel tank may lose the seal when saw is moved. I noticed this when I pulled the carb back off.
New fuel line may be too small. I will upgrade this.
Impulse line possibly not sealing well on carb. I used threebond on barb when I installed it last just to be safe.


Any recomendations before I order parts? Thanks.

 

[BloodOnTheIce]

If you took the time to port it you should have done a complete
servicing of the saw's fuel system. No point in making a saw fast, if it's not a
reliable runner before hand. Replace the impulse line, fuel hose, carb kit, spark plug
with the correct ones and then do you diagnostics from there.

A friend of mine ports some saws, and everyone of them gets carb kits, or
new carbs, fuel lines, impulse hoses, fuel filters, and spark plugs before
he does any grinding. Because they have to be good running stock saws
before they can be good running fast saws.

 

[NPKenny]

If you took the time to port it you should have done a complete
servicing of the saw's fuel system. No point in making a saw fast, if it's not a
reliable runner before hand. Replace the impulse line, fuel hose, carb kit, spark plug
with the correct ones and then do you diagnostics from there.

A friend of mine ports some saws, and everyone of them gets carb kits, or
new carbs, fuel lines, impulse hoses, fuel filters, and spark plugs before
he does any grinding. Because they have to be good running stock saws
before they can be good running fast saws.

I ported it about 4 years ago and completely rebuilt the saw. Every gasket, seal, etc. It ran perfectly ported for about 4 years.

 

[albert]

If the fuel hoses and impulse don't fit or seal correctly, get the correct hoses, and don't count on sealer to fixthe impulse conection. Pull your carb and go through it again, make sure some of that sealer didn't find it's way in. Test your tank vent too.

 

[BloodOnTheIce]

I ported it about 4 years ago and completely rebuilt the saw. Every gasket, seal, etc. It ran perfectly ported for about 4 years.

Yup definitely go through and replace the impulse hose then.

 

[blsnelling]

Try another coil if you've got one.

 

[corsair4360]

Vent Hose?

Is the vent hose not plugged and free? That is a continual source of irritation for me.

 

[NPKenny]

Try another coil if you've got one.

Afraid of that thought. I don't suppose it uses the same coil as an 044??? That is the only functioning spare I have around.

 

[epicklein22]

44 coil will work, might need a longer spark plug wire.

 

[blsnelling]

44 coil will work, might need a longer spark plug wire.

Which you can thread out of your 066 coil if need be. Hope it works for you.

 

[NPKenny]

Is the vent hose not plugged and free? That is a continual source of irritation for me.

I am sure on this one. I cleaned the vent and replaced the short run of hose.

44 coil will work, might need a longer spark plug wire.

Which you can thread out of your 066 coil if need be. Hope it works for you.

Great. I will report back in a few days when I get a run at it.

 

[NPKenny]

Which you can thread out of your 066 coil if need be. Hope it works for you.

The coil shows very good spark on a spark tester but noticed a few nicks on the plug wire during the inspection. How specific is the coil wire on the 660? The local dealer is having a hard time selling me only a wire as he wants to see the entire coil assembly. I would just assume use a spark plug wire I have in the shop it it is not too unique.

Also, I ordered impulse and fuel lines as well as a new fuel cap and seal. I have to elminate all possibilities.

 

[NORMZILLA44]

This stuff can get frustrating, as any one of the mentione'd item's can present the same syptoms, and trouble. I recently went through it with my 660 that is stock. We checked everything and it took a few headache's keen eyes, and alot of troubleshhoting. Even stumped my shop but they got it. Had to replace the carb, keep at it you our on the right track with good advise my point was you will get frustrated, but keep at it. Walk away for a day or two if it get's to frustrating, and sometimes when you come back to it, new light can shed. Norm............

 

[NPKenny]

This stuff can get frustrating, as any one of the mentione'd item's can present the same syptoms, and trouble. I recently went through it with my 660 that is stock. We checked everything and it took a few headache's keen eyes, and alot of troubleshhoting. Even stumped my shop but they got it. Had to replace the carb, keep at it you our on the right track with good advise my point was you will get frustrated, but keep at it. Walk away for a day or two if it get's to frustrating, and sometimes when you come back to it, new light can shed. Norm............

Point very well received. I've got an 044 in a box that is receiving the rest treatment as well.

 

[NORMZILLA44]

Funny you mentioned the 044, I went through the headaches the first time with my 044, then it was the 660. 2101 in the middle LOL! The first time I learned of the frustrtations was with the 044. I almost gave up got rid of it, and got a new saw. What a mistake I would have made. Funny thing I have learned is alot of the problems are caused by today's gas. Let us know what turns up good luck man!

 

[2dogs]

Try another coil if you've got one.

That is what I would. Warm saw is the key here.

 

[Terry L]

660 dies in cut.

I think corsair4360 got it right. The vent tube is not allowing enough air to replace the gas as it is taken out of the tank, creating a serious vacuum. I modified the vent tube on both of my Stihl 066's and I think the vent on a 660 is the same. What I did was take out the tiny screw in the plastic tube, cleaned everything, then put a tiny wire in the tube, then screwed the tiny screw back in. The problem has never happened again.

 

[NPKenny]

I think corsair4360 got it right. The vent tube is not allowing enough air to replace the gas as it is taken out of the tank, creating a serious vacuum. I modified the vent tube on both of my Stihl 066's and I think the vent on a 660 is the same. What I did was take out the tiny screw in the plastic tube, cleaned everything, then put a tiny wire in the tube, then screwed the tiny screw back in. The problem has never happened again.

I'll try that out too! Seems easy enough.