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Hi. I havent used my blower for about 9 months. Im sure I didnt store it properly. I tried to start it today and it wont start. I pumped the bulb 5 times as instructed and turned the choke to cold start (switch pointing up), changed the sparkplug (the old one was dark and oily) and poured out the old gas and put in fresh new high octane gas and oil mix (50 to 1). Its making a spark (pulled the plug and grounded it and it sparks when the cord is pulled). I tried squirting carb cleaner into the carb air intake and also tried pouring a teaspoon of gas into the combustion chamber. Nothing works. I am guessing my carb is gummed up from old gas. There is a youtube video of a guy rebuilding this carb but it looks really involved and meticulous. are there any other tricks I can try to get this thing going? The best ive gotten out of it is the tiniest bit of sputter and white smoke after pulling the cord like a crazy person for ten minutes.

On a side note, I pulled off the rip cord and tried turning the crank with a power drill but when the pull cord assy is removed the plug wont spark at all as if the pull cord trips some interlock or something but theres noting there I can find. Was hoping that turning it over and over with a drill it would eventually clear the clogs and start.

Any small engine techs out there that can spare me from taking this thing into a shop?

Thanks!

Bad news.
The carb has to come off for cleaning.
You accomplish nothing by spraying carb cleaner down the throat on any carb.
Not as daunting as it looks.
get some butches paper, fine art paper anything that is glossy.
Lay it out as you take the bits off.
Put the bits off the top on one side and the bits from the bottom on the other side.
It is a lot easier than it looks
You just have to take your time, most bits will only go on one way.
The big problem is dust so do it inside and cover the whole lot with some glad wrap if you need to leave bits to soak.
Do not shove your 200psi air compressor down any holes, if you can not blow low pressure air through the holes then clean them.
Walbro has the best service manual on their web site.
All cube carbs work the same so, there are only 2 types so walbro / zama / tillosen all work the same.

bertsmobile1 said:

Bad news.
The carb has to come off for cleaning.
You accomplish nothing by spraying carb cleaner down the throat on any carb.
Not as daunting as it looks.
get some butches paper, fine art paper anything that is glossy.
Lay it out as you take the bits off.
Put the bits off the top on one side and the bits from the bottom on the other side.
It is a lot easier than it looks
You just have to take your time, most bits will only go on one way.
The big problem is dust so do it inside and cover the whole lot with some glad wrap if you need to leave bits to soak.
Do not shove your 200psi air compressor down any holes, if you can not blow low pressure air through the holes then clean them.
Walbro has the best service manual on their web site.
All cube carbs work the same so, there are only 2 types so walbro / zama / tillosen all work the same.

Click to expand...

DONE. Stihl no worky. I actually found a good deal on a brand new carb. Replaced it today, no change in symptoms. I also changed both fuel filters for good measure. No change.

In review: I get a spark but put in a new sparkplug. I get an occaisional backfire with slightly white smoke puffing out of the carburator *not the exhaust). New carb. New fuel filters. Brand new high octane gas and stihl oil in 1/50 ratio. Its not in cutout. Choke is on cold. Unit is about 2 years old with light usage overall and no use the last 9 months.

So, what can I try next besides taking it in?

Thank you!

Just curious but does it have a spark arrestor in the exhaust?

Mikel1 said:

Just curious but does it have a spark arrestor in the exhaust?

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Honestly don't know. I can tell you if it comes w one in the factory then it's still there. I am the orig owner and haven't removed any parts. Why do you ask?

Only thing I can think of since it's probably getting air and fire it must not be getting fuel. A clog in the lines maybe? I tried squirting a few drops of fuel I to the combustion chamber to see if it would sputter but that failed to. Was I thinking correctly in doing this? Any other way to diagnose if it's not getting fuel?

Sometimes they clog up and will not let you startup.

Mikel1 said:

Sometimes they clog up and will not let you startup.

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How do I check? Maybe a wasp built a nest in it.

The screen in the exhaust is problematic. It will cause an abnormal amount of carbon buildup in the combustion chamber and exhaust port on the engine. This will happen even with using Stihl synthetic engine oil.
The screen is there for the machine to be 50 states emissions compliant. It is removable and many have removed it to improve the performance.
What is the compression of this engine?
Although this engine is a 4 stroke with operating intake and exhaust valves, it is a dry sump engine and needs to have mixed fuel, and you know this.
Alternate spark plugs don't work well in these engines, what spark plug do you have in this engine and what is the gap?

jasonblu said:

Only thing I can think of since it's probably getting air and fire it must not be getting fuel. A clog in the lines maybe? I tried squirting a few drops of fuel I to the combustion chamber to see if it would sputter but that failed to. Was I thinking correctly in doing this? Any other way to diagnose if it's not getting fuel?

Click to expand...

The primer bulb draws fuel thru the supply hose, the hose with the filter in the end, thru the carb and back to the fuel tank thru the 2nd hose. If you have spark at the correct time and compression, but engine will not run, then it is likely an internal carb problem.

Mad Mackie said:

The screen in the exhaust is problematic. It will cause an abnormal amount of carbon buildup in the combustion chamber and exhaust port on the engine. This will happen even with using Stihl synthetic engine oil.
The screen is there for the machine to be 50 states emissions compliant. It is removable and many have removed it to improve the performance.
What is the compression of this engine?
Although this engine is a 4 stroke with operating intake and exhaust valves, it is a dry sump engine and needs to have mixed fuel, and you know this.
Alternate spark plugs don't work well in these engines, what spark plug do you have in this engine and what is the gap?

Click to expand...

I removed the spark arrestor. No change. I removed the exhaust tank. No change. I have a brand new NGK 3365 CMR6H spark plug installed which is what the br600 manual calls for. (Also what came out of it from the factory) the gap is factory set at, I believe, .20 but I could be wrong there.

Mad Mackie said:

The primer bulb draws fuel thru the supply hose, the hose with the filter in the end, thru the carb and back to the fuel tank thru the 2nd hose. If you have spark at the correct time and compression, but engine will not run, then it is likely an internal carb problem.

Click to expand...

Ok. So maybe I got a bad carburetor from the dealership today?

Take the coil off and check it.

EngineMan said:

Take the coil off and check it.

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Thanks for the tip. can you tell me how to do that or refer me to where I can read up on that procedure?

Does the coil make the spark? Because I get a nice blue spark when I pull the plug out, ground it to the block and pull the cord.

Check to see if there is continuity between the low tension terminal (which is used to switch off the engine) and earth.

EngineMan said:

Check to see if there is continuity between the low tension terminal (which is used to switch off the engine) and earth.

Click to expand...

Wait, I have a nice blue spark. How could it be the coil?

Not getting any more ideas here I Took it to a small engine guy. He noticed there was no resistance when spinning the starter armature indicating no compression (why did no experienced engine guys on here tell me to check this?). He popped the valve cover off. A rocker arm had slipped off the valve piston. He rotated the arm back and said it would start now. He noted the area was very dry so he squirted some oil over the valve rockers.

Now the big question is why did the arm slip off. Is this indicative of another problem?

Mad mackie, You did mention compression btw or rather it was assumed it to be good though I never said it was. Until now I didn't know how to know if it was good or not without using a compression tester. Now I know. Spin it and feel for resistance.