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Owned, ridden, and worked on motorcycles since I was a kid. Couldn't afford to take my bikes to the shop for maintenance, so if I wanted to ride I learned to wrench on them myself. Same train of thought carried over to my trucks, and also to my lawn equipment.

I am completely stumped with my FS 55 and HS 45 though.

I drained the fuel and pulled the carbs. All diaphragms and gaskets were delicately and carefully removed and inspected, no tears or pinholes.

Pulled the main jet, float jet, and high and low speed needle jets, checked their condition followed by full sprays with Berryman Chemtool and then compressed air in all orifices. Primer bulb is good and works, even tried with gas cap loose just in case the cap is plugged.

New spark plug properly gapped and strong spark is present. Good compression on the FS 55.

Pull, pull, pull, pull. Cuss, swear, stomp. Repeat.

Tool won't start.

What did I do?

:welcome:

Slip the carb off and blow air through the venturi.
Low pressure , high volume is best.
You are looking for fuel being atomised and blown out the engine end.
This will confirm that the carb is working properly.

The fuel filers block & clog and the fuel lines crack & leak.

Secondary ( top of piston ) compression is good but you need primary compression as well and you can only test that with a vacuum pressure gauge.

If they have not been used for a while, remove the muffler and give it a try.

bertsmobile1 said:

:welcome:

Slip the carb off and blow air through the venturi.
Low pressure , high volume is best.
You are looking for fuel being atomised and blown out the engine end.
This will confirm that the carb is working properly.

Click to expand...

So low pressure air through the venturi and look for atomized fuel misting through the pilot circuit (low speed) orifice. Okay, hopefully these old eyes can pick it up.

bertsmobile1 said:

Secondary ( top of piston ) compression is good but you need primary compression as well and you can only test that with a vacuum pressure gauge.

Click to expand...

So are you suggesting a leak down test? Guess I'll have to strip the plastic shrouds off and look for possible leak areas at the case halves, intake, and exhaust port. Going to have to find some expanding rubber plugs to put in the suck and blow holes first though.

bertsmobile1 said:

If they have not been used for a while, remove the muffler and give it a try.

Click to expand...

I removed the screen from the muffler and cranked it. Seems to be plenty of air coming out.

I'm thinking about ordering some carb rebuild kits from Amazon just in case the diaphragms are damaged in some way.

Thanks for the advice.

These carbs are cheap and so are the parts that go in them.
When ever they are dissasembled all the gaskets should be replaced.
The gasket kit wil be about 60% of the price of a new carb so that makes it a no brainer to go for the carb.

As for the blow through test, I use an old vacuum cleaner spray painting set up and just hold the air tube to the filter end of the carb with some tape,
That means you have one finger free to move the throttle and can put the other hand at the outlet thus you can feel the fuel comming out. just a little with the throttle closed and a lot with the throttle open.
You can use a dust blower but you need to be carefull as it will pick up form the main jet hole, not the idle jet hole.

desertrider said:

So low pressure air through the venturi and look for atomized fuel misting through the pilot circuit (low speed) orifice. Okay, hopefully these old eyes can pick it up.

I removed the screen from the muffler and cranked it. Seems to be plenty of air coming out.

I'm thinking about ordering some carb rebuild kits from Amazon just in case the diaphragms are damaged in some way.

Thanks for the advice.

Click to expand...

Can you see through the screen on the muffler?

I wouldn't rebuild the carb unless I *really* liked doing such things. A new OEM carb for the FS can be had for ~$30 on Amazon. Aftermarket for a lot less. Be sure to get both gaskets for the carb, to the block and to the choke assembly. There are two types of carbs out there for the FS, The old one has brass nipples, the newer are plastic.

I ended up using an old style. It works. Don't assume that the carb that you buy has been tuned.

You might want to replace the fuel line assembly. I built one.

Picked up a carb for the fs 55 yesterday from the dealer. Cost $30. For that money can't afford to even open it up, especially when there is a good chance the check valves will stick.

I got a new carb for my Stihl for $9. Chinese carb, but it works perfect! :thumbsup:

primerbulb120 said:

I got a new carb for my Stihl for $9. Chinese carb, but it works perfect! :thumbsup:

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Zama, the OEM, are made in China... :laughing:

With ethanol gas I'm beginning to think that maybe carbs should be considered consumable.

jm123 said:

Zama, the OEM, are made in China... :laughing:

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Exactly!