Author Topic: chainsaw carbs--what is the function of the "membrane"? (NGC)  (Read 2000 times)

Offline yackee

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I just pulled the carb for the first time on my chain saw to clean the carbs, while trouble-shooting some hard-starting and after letting it sit with gas over winter (FWIW a Husqvarna 435 16").

I watched a bunch of YouTube videos, and got the basic run-down of how chain saws are set up, what the various carbs look like, etc., and I managed to successfully pull, clean, and replace the carb, and now the saw runs fine, though only after I squired myself in the eye with carb cleaner. Thankfully the hose was nearby.

But after all of this, I find myself still not really understanding the mechanics of a chain saw carb. In particular, what exactly does the "membrane" do? I have only worked on guzzi and vespa carbs (various dell'ortos) and the chain saw carbs seem so different. Is the membrane essentially the float chamber and fuel filter?

 Anyway, just curious if any guzzi folks can explain the very basic of how these things work (especially given how different they look/seem than what I am used to). Sorry if this is too off-topic!

oldbike54

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Re: chainsaw carbs--what is the function of the "membrane"? (NGC)
« Reply #1 on: June 10, 2015, 07:39:09 PM »
 Doesn't the membrane function as a diaphragm .

  Dusty

Offline acogoff

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Re: chainsaw carbs--what is the function of the "membrane"? (NGC)
« Reply #2 on: June 10, 2015, 08:18:08 PM »
     Fuel pump
'77850t3FB Owned since it was new
Marshall County Minnesota USA

dilligaf

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Wildguzzi.com

Re: chainsaw carbs--what is the function of the "membrane"? (NGC)
« Reply #3 on: June 10, 2015, 08:22:02 PM »

Offline charlie b

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Re: chainsaw carbs--what is the function of the "membrane"? (NGC)
« Reply #4 on: June 10, 2015, 09:23:48 PM »
Yep.  Pumper carbs.  Work really well....until they don't :)  Rebuild kits available and cheap.
1984 850 T5 (sold)
2009 Dodge Cummins 2500

Offline Muzz

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Re: chainsaw carbs--what is the function of the "membrane"? (NGC)
« Reply #5 on: June 10, 2015, 11:07:40 PM »
     Fuel pump

A wee hole from the crankcase to the carb compresses the diaphragm and works the fuel regulating needle.
Muzz. Cristchurch, New Zealand
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