Frustrated, trying to get Weedeater to run.

Phototone

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I've got a few older weedeaters I'm trying to get running, and I am having some difficulty. Take for example, a couple of featherlite models of different vintages. Both have 120lbs compression, as measured via a compression tester replacing the spark-plug, both have good spark, as indicated by a visual in-line spark tester. One has brand new carb, the other has a rebuilt carb. New fuel lines and in-tank fuel filter. Both will pump up gas into the primer bulb. Neither one will go. Very frustrated at what should be solvable. I have had great success with Lawnboy 2-cycle lawnmowers. What am I missing here?
 

bertsmobile1

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Crank case Vacuum.
120 lbs is good but not if 50% of it came past the crankcase seals and not the carb.
Check the carbs are functioning by removing them , leaving fuel lines attached, and blowing through the air passage with low pressure air.
I use one of those old reverse vacuum cleaner type spray painting kits for this ( saved it from the tip ) .
Blowing through the carb you should see the air fuel mix coming out the end of the carb, Dont smoke while doing this and be wary where you are bowing the explosive air/fuel mix.

Next step is to check the crankcase seals.
This is a PIA job as you will need to bank off the carb and muffler and then do a leak down test with the piston at BDC to open the inlet port.
 

Phototone

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Well, on these 2-cycle engines the only place that would have a crankcase seal is where the crankshaft exits to the flywheel. Only one seal. Behind the flywheel. Are these readily available and replaceable, as they are on Lawnboy 2-cycle mowers? The crankshaft is not supported with a bearing front and back, only the flywheel side. The back is sealed off with a piece that also includes the back shroud and gas tank on some models.
 

bertsmobile1

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I do not do seals on Weedeaters because the owners can buy a new one for the cost of the repair.
And yes same deal as on the lawn boy.
Usually there are two, one under the flywheel and one behind the clutch.
Easy to replace, parts are listed in my suppliers catalogue, not expensive, just 3 billable hours @ $ 60.00 /hr.
Usual sign of seals is difficulty of starting from cold ( seals dry & leaking bad ) revs a bit high but runs OK when hot ( seals wet & sort of working but allowing air in ).
I would check the crank case vacuum first, new seal won't hurt , but still might not be the problem.

Is the exhaust port clean and not blocked, choking the engine ?
 

Phototone

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I realize that most weedeaters are cheap enough that it is not economically feasable to figure shop labor rates for extensive repair. However I am a hobbiest, and I enjoy working on small engines just for the satisfaction of making them run. Parts are certainly cheap enough, and if I sell them for more dollars than I put into them in parts and acquisition of the broken weedeater, I'm fairly happy. I am finding these very tiny 2-cycle engines and carbs are more difficult to get running than the Lawnboy lawnmower engines I am much more familiar with.
 

motoman

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Do the vacuum test and let us know.
 

bertsmobile1

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I realize that most weedeaters are cheap enough that it is not economically feasable to figure shop labor rates for extensive repair. However I am a hobbiest, and I enjoy working on small engines just for the satisfaction of making them run. Parts are certainly cheap enough, and if I sell them for more dollars than I put into them in parts and acquisition of the broken weedeater, I'm fairly happy. I am finding these very tiny 2-cycle engines and carbs are more difficult to get running than the Lawnboy lawnmower engines I am much more familiar with.

You are not alone on that one.
There is a reason why there are no more bottles left in the wine cabinet.
And it is small cubic shaped & made of alloy
 

primerbulb120

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Have you tried spraying starting fluid in the air intake and attempting to start it? If so, what were the results?

I have worked on a lot of trimmers (20 or so) including two Weed Eater Featherlites, and not one of them had problems with its crankcase vacuum. I don't have a way to do a valid vacuum test either, and I can usually get them running.
 

bertsmobile1

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And I do have the equipment which is quite cheap.
Well you can get a cheap pump for around $ 20 or so called a vaccum brake bleeding pump.
You then need to make a few bits & pieces.
There are hundreds of U-Tube videos of how to make on one the cheap and cheap ones work just as well as $ 3000 snap on ones.
You can not properly access any two stroke engine without having some means of checking the primary compression and the primary compression is highly dependant upon the condition of the crankcase seals.

You also should test cube carbs both under pressure and vacuum.

Oh and I have replaced crankcase seals, generally on high end chainsaws.
And I do around 6 two stroke engines, each & every week.
About 1 in 10 will have faulty seals.
 
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