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Author Topic: Two Stroke Carb Flooding and starter failure.  (Read 1903 times)

Offline Mick

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Two Stroke Carb Flooding and starter failure.
« on: May 13, 2017, 07:45:34 AM »
Here's a tip for those that have been caught out by a flooding carb. 

This example is based on a Stihl BG56C Blower carb, but it can apply to loads of different machines with similar carbs.  Also two parts to this post, the second part is related, but is to do with starter failure, (ERGO Start) Failure.

So you discover the carb is flooding, and give it a strip down and clean, perhaps sonic clean it.  Reassemble and stick your pressure gauge on it to find it dropping like no tomorrow.  First thing most people think of is the metering needle is leaking, which in a lot of cases it is.  Metering needle (indicated by Blue arrow in attached image).

But you also need to make sure the pump diaphragm and gasket is good too otherwise it will give you the same symptoms as with a leaking metering needle.  If this diaphragm has a tiny hole in it, or the gasket isn't sealing correctly the fuel will get pushed through the pulse hole, and straight into the crankcase.  Pulse hole, (indicated by green arrow in attached image)

So when you're pressure testing a carb and find the pressure dropping, just put your finger over the pulse hole on the front face of the carb and see if the pressure drop stops, if it does then its a fair indication that something wrong with the pump diaphragm or gasket.  Replace them and test again.  Pump Diaphragm (indicated by red arrow in attached image)

Part Two, the Ergo start failure on these machines can often be due to a flooding carb, so if you get one of these crappy starters with that extra coil spring constantly failing then make sure the carb is good.  If it floods then it wets up the engine too much causing the engine to partial (or fully) hydraulic which will wreck the starter when the operator goes for it on first pull.

Hope someone finds this useful.  I'll attach a couple of pics of the offending items below.
« Last Edit: March 02, 2020, 12:40:33 AM by Mick »