MS460 cold start trouble

[chronicstihl]

This saw runs and idles great once I get it started. However, starting is a problem. It will "putt" and or run for 1-3 seconds, then quit. This sequence will last for 5-10 min. or until I get tired of pulling the cord. This continues until the saw gets warmer then it runs great! I follow the manuals starting procedure.

Things I have done:

New plug
Fresh gas
carb disassembly
- removed bottom plate, inspected screen, "blew out" exposed port.
- replaced fuel hoses
- adjusted idle screw

Chronic

 

[046]

check to see if your choke plate is fully closed.

 

[thompson1600]

Did you replace the fuel filter?
Have you checked the choke arm on the switch to make sure it's engaging the choke on the carb?
Replaced or cleaned the air filter?

Tom

 

[smcowboy1974]

Try turning out the low speed mixture screw, counterclockwise 1/4 to 1/2 turn and see if that helps.

 

[Simonizer]

Make sure cylinder capscrews are tight. Do pressure/vacuum test on crankcase. These saws are normally bullet-proof.

 

[West Texas]

Had that problem on an 044 and it turned out obe the 'inlet' lever in the carb was bent out of shape, flooding the engine. But, it sounds like yours it may need fuel, either by adjusting the L jet as smcowboy1974 suggests above or by increasing the idle speed with a 1/2 turn clockwise of the LA jet.

Now how I would resolve this delimma, is make a few pulls with full choke on. Pull the plug, if its wet, then I'd suspect the carb lever is off adjustment. On the other hand if its not wet, then I'd think it needs more fuel and the L and LA need adjustment.

How I'd approach this is to 'get it started and warmed up' first. Then I'd adjust the L jet for best rpm, in combination with the LA until the chain began to move on the bar. Then I'd back the LA off a 1/4 or 1/2 until the chain stopped moving. This should put you in the ball park for a better start next time.

Tom

 

[046]

Make sure cylinder capscrews are tight. Do pressure/vacuum test on crankcase. These saws are normally bullet-proof.

how many PSI do you pressure up to and how long does it need to hold?

how many inches of vacum is needed and how long should it hold for?

thanks,

 

[Fish]

If it was the choke not fully closing, you would be hard pressed to get the initial
"putt putt'. Give us a little more detail in the history of this saw. I.E., did you
just buy it, it ran great last March, etc.
What exactly did you mean by replaced fuel hoses?
You only pulled the fuel pump side of the carb? How about doing it up right?
If the screen was clogged, then yu need to remove the needle and give it a good
blow out, yu thought I was going to say job, didn't you all? But one thing is for certain
I have never had a "bad" one.

 

[chronicstihl]

saw history

Thanks everyone for the quick responses and new ideas on things to check.

I purchased the saw used late last fall. I was in the local saw shop drooling over the saws. I was looking for a used bigger saw. The sales guy had none. However, he suggested I talk to the customer at the counter with the box and saw.

The box contained the MS460 in many broken pieces. The owner had recently dropped a tree on the saw. The saw had maybe 20 hours on it (confirmed by the shop). Most of the plastic on the saw was broken beyond repair. Anything metal was untouched or not bent. They were able to start the saw to prove it ran for 2-3 seconds. The saw shop wanted $500 plus to repair. I figure half labor half parts. I offered the guy $150 and he accepted.

I used ebay and the local shop and spent $400 total (including purchase price), which includes new bar and chains, lots of plastic parts. The saw looks new.

Stuff I replaced:

fuel filter
fuel hoses
rubber boot on intake
air filter
filter plate
gas tank/handle
safety trigger
throttle linkage
Plus a few things I have forgotten.

Also, I just checked the compression release and it was stuck in the down position. I cleaned it, but it seems bent. Time to replace?

Perhaps I had my carb adjustments all set with the compression release on?

I have not had time to test the saw again. Perhaps Tuesday.

Thanks again for all your help!

Chronic

 

[West Texas]

That was one hellashish endeavor Chronic. Good luck with it. Keep us posted.

Tom

 

[thompson1600]

If the decomp valve is stuck in the open position, you are going to have real problems. That will burn your saw up real fast if you run it very long. Yes it's time to replace it.

 

[chronicstihl]

saw is fixed

Repaired the decomp valve (WD40 shot) and the saw runs great. Starts on the second pull 3 days straight, cold engine. Thanks to everyone for your input. I Stihl need to replace the decomp with a new one. The original is bent but working.

Does it require a special socket? My deep well socket would not work. Hangs up on the decomp valve head.

Chronic