Stihl 064 - possible carb issue?

[mcmoonter]

First post, I've been a long time lurker, thanks for such a great resource

A friend and I took a punt on a ported 064. The saw had been run on neat fuel and had then been bought as a parts saw. The new owner passed it to a U.K. saw porter for a rebuild. He honed the original cylinder and ported it then fitted a new Meteor piston and rings. The owner barely used it afterwards and sold it to fund the purchase of another saw

I think we got about three days use out of the saw. It always was difficult to start from cold, but once running was very powerful and restarted from hot well.

On the fourth day we were milling and it was even harder to start from cold, it produced a ton of smoke from around the clutch cover and it then heated up the clutch cover. We stopped it immediately

Stripping the saw down we found a couple of things. There was a piece of starter cord forced into the gap where the four position choke/half choke/run/stop lever sits. It prevented the choke lever from being fully depressed thus not fully closing the choke butterfly. That may have contributed to the poor cold starting.

Our initial suspicion for the smoke and heat around the clutch cover was a slipping clutch. When I pulled it off there was no evidence of oil contamination or of premature clutch wear.

We did find that there was float at the flywheel. Splitting the crankcase we found the bearing cage on the flywheel side had vanished and the uncaged bearings allowed the crank float.

We rebuilt the bottom end with all ne w OEM bearings, seals and gaskets.

While I was there I checked the inlet boot which was fine. I took the precaution to fit again an OEM impulse hose, fuel hose and filter, tank vent valve and vent hose.

I left the carb alone at this point.

The saw started stubbornly, it didn't respond too well to adjustments at the carb. So I pulled the carb and blew through the jets. Now it just won't start at all.

I've ordered a new OEM Walbro WJ carb kit. I've checked the metering lever with the Walbro tool and it is set correctly.

What else can I do to clean out and service the carb body before I install the new carb kit.

Any advice would be most welcome

 

[mcmoonter]

Dang, I forgot the key part! I'm not getting fuel through to the plug. I'm thinking the carb diaphragm may be past its best or there may be an internal blockage in the carb.

Pulling the fuel line from the tank to the carb releases pressurised fuel.

 

[pioneerguy600]

I find running the carb through a USC the best way to clean them, it has brought many formerly unusable carbs back to life.

 

[CausticUC]

I find running the carb through a USC the best way to clean them, it has brought many formerly unusable carbs back to life.

Take it you mean an Ultrasonic Cleaner? Had to think for a bit on what a USC had to do with a carb, the cleaner was not the first thing to mind.

 

[pioneerguy600]

Take it you mean an Ultrasonic Cleaner? Had to think for a bit on what a USC had to do with a carb, the cleaner was not the first thing to mind.

Yes, they get a carb much cleaner inside small passages than any amount of soaking can do.

 

[CausticUC]

Much less painful than feeding it to someone and waiting for it to be processed I suppose.

Back to the issue, as this is not exactly a young saw and I think that carb has a spring, might be spring fatigue. Your kit should come with a new one.

If you dont have a carb cleaning tool, (looks like a bunch of wires and tiny brishes) you can use a set of welding nozzle cleaning wires.

Get yourself some good carb cleaner, how much work it might need depends on how much varnish is in it from sitting. Running the saw might have lifted some and clogged a needle or passage.

Off hand, if your fuel line is pressuring, your carb pump is likely working and a needle or passage is blocked. I say that under the premise that the saw isnt somewhere fairly warm (expansion lightly pressurizing your tank).

 

[pioneerguy600]

Just about everyone doing carb rebuilds these days has an USC , they can do one or multiple carbs at a time, bigger USC`s can do complete engines or whole saws if required. The tiny carb passages are easily damaged by pushing wires or welding tips through them, it is not a recommended process for cleaning small OPE carbs.

 

[CausticUC]

Always nice to have tools to make things easier, and an ultrasonic cleaner is safer than a heated bath and cheaper than vapor. Though, since he did not clean the carb the first time around.. Hazarding a guess that those options are not conveniently available.

All is good if you do not hurry;
Be gentle, let the cleaner do its work, do not force anything.

Do not know myself if any of the stihl's had pressure fit components, other than the welch plugs. Drilling those out and putting them back in is usually the hardest part.

 

[SEAM]

So I pulled the carb and blew through the jets. Now it just won't start at all.

Did you use compressed air? Compressed air may cause damage (leaky welch plugs, etc.)...

 

[mcmoonter]

Thanks for the tips so far. I don’t have a parts cleaner. I’ll ask around and see if any of my pals have one.

 

[pioneerguy600]

Be cautious about blowing compressed air through the jets, the check valves can be destroyed if hit with high pressure.

 

[mcmoonter]

Be cautious about blowing compressed air through the jets, the check valves can be destroyed if hit with high pressure.

Yikes, maybe too late. Is this the same as the metering valve that will come in the OEM kit?

 

[pioneerguy600]

Yikes, maybe too late. Is this the same as the metering valve that will come in the OEM kit?

No, it looks like a round brass cylinder that protrudes down into the carb throat, inside that cylinder is a round disc that needs to seal, if it does not then erratic behavior will certainly occur. These check valves can be damaged bu compressed air and some carb cleaners. Two stroke carbs don`t stand up to the harsh carb cleaners that was designed to clean 4 stroke carbs. That cleaner will dissolve rubber and plastic.

 

[mcmoonter]

No, it looks like a round brass cylinder that protrudes down into the carb throat, inside that cylinder is a round disc that needs to seal, if it does not then erratic behavior will certainly occur. These check valves can be damaged bu compressed air and some carb cleaners. Two stroke carbs don`t stand up to the harsh carb cleaners that was designed to clean 4 stroke carbs. That cleaner will dissolve rubber and plastic.

Is there a test I can do to verify if the valve is still doing it’s thing?

 

[pioneerguy600]

Not easily, they can be pressed out in either direction. It is quite difficult to get a good seal on one when its in the carb.

 

[CausticUC]

Just to check, which carb do you have? The Walbro WJ is apperently pretty common on the USA version.

https://www.jackssmallengines.com/j...buretor/carburetor-wj-10-1/wj-10-1-parts-list

But the Bing was common on the Australian version, seeing that you are in the UK... and that it was ported.

Or is it some other model?

 

[pioneerguy600]

First post says a Walbro WJ series.

 

[CausticUC]

First post says a Walbro WJ series.

There we go, I missed that the second time around reading it.

Nozzle check valve #20 on Jack's image would be the one we are wondering about?

 

[pioneerguy600]

If that is for a WJ- 65A, then that should be the one.

 

[pioneerguy600]

Stihl part number is, 1115 121 5401