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Stihl 088 carb problem

Raj

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My 088 was acting up. kicking back when cold. Then it would loose power and die in a cut. It would idle no problem. When reving no load it would sound great, no sputter or hesitation. Spark plug is a nice brown ashy colour with some light black oil around the threads, I do run 40:1 oil.

I put in a carb kit but there was one small brass plug I didn't change and a screw in nozzle that I didn't touch.
Ran good for a few heavy cuts.

Now today it seems to over rev, the speed doesn't match the throttle and when you release the throttle it will drop RPMs to a higher idle, then within seconds rev down to idle. Saw will idle and rev no problem, no cutting.

Whole carb is not available in my area.

Any idea what I missed when i put the carb kit?
 

pete mctree

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Almost sounds like an air leak or split impulse pipe. I presume you have pressure tested the machine?
The 200t carbs used to develop a similar problem - welch plug was often the cause (that and the accelerator pump, which I don't think the 088 has). It may be the issue allowing air in. Simple way is to use something like nail varnish to seal it & then test again.
 

Raj

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No pressure test yet.

I did discover the new diaphragm was bent up. Hope that's the issue. Dealer has a new kit coming tomorrow, otherwise I'll try to bend it back.
 

Nutball

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Does it make a pulsing sound too after you let off the throttle? We have saw like that. I keep forgetting to richen it. It doesn't kick, but can be hard to start and keep going at times as it leans out and dies at idle.
 

Raj

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No, just a smooth engine bog. Idles fine and throttles great no load.

Thanks all. Going to make plates for pressure testing tomorrow. Dealer has some replacement parts for me. Hope I solve this. Damn milling is backlogged.
 

Raj

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Pressure test. Held 6psi for more than 5 minutes. Pressurized through impulse line.

Metering diaphragm was bent up bad in the carb kit. It didn't push the meter arm down far enough?

Edit. Saw held a vacuum no problem.


20181109_125029.jpg
 

Raj

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Dealer got a whole new kit for me, sold at cost because of the other new kit had the bent diaphragm.


Edit: cylinder compression easily reached 150psi.
 

Raj

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A Facebook page mentioned that cracks tend to develope in the plastic angle fuel inlet, sucking air. Seems it's not a separate part. Mine has a small crack. What can be done? Rubber extension?

20181111165535322d0c32d7d0dd68.jpg
 

Raj

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I'll put a dap on, wrap some metal around it.

New fuel filter just came in, hope it's all solved. Did a couple passes, one on some white oak and a spruce board for a custy.

20181112_161741.jpg
 

Raj

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I have not epoxyed the crack yet. I hate to say I think my fuel filter was a big issue that I over looked. Carb did have some crud in it, and damaged carb kit didn't help, nor the long delivery time for parts. I hope I have it fixed. Milled a 9ft long white oak no problems today, RPMs matched the throttle.

Going to look into a tach to mount on the saw when milling.

I tend to stay away from cheap filters, any good sources for decent aftermarket fuel filters?
 

Raj

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Now it seems my second 088 has carb problems. Took the carb apart to find little plastic like pieces. Looks like someone used epoxy on a welch plug! Hope to fix it Monday.
 
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