BG56 primer bulb.

[Gerbutt]

Hello folks

 

I’ve got a BG56 blower that not pulling fuel up with the primer bulb. I’ve fitted a new carb kit and primer bulb but it still wont. I noticed I could hear it when I took the fuel cap off and assumed there must be a hole in the filter line, but got a new one and it still doesn’t work. I’ve also fitted new lines from that to the carb. Any ideas?

[Paddy1000111]

Did you replace flange under the bulb too? This part-

Flange for Stihl BG86, BG86C Leaf Blowers - 4241 120 2200 | L&S Engineers

WWW.LSENGINEERS.CO.UK

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Flange Genuine Stihl Part OEM Part No. 4241 120 2200 Suitable for the following Stihl Machines: BG 86, BG 86 C, BG 66, BG 66 C, SH 56, SH 56 C, SH 86, SH 86 C, BG 86, BG 86 C...

 The one that has the one way valve in it? If you take the fuel line off and put your finger over the inlet and pump the bulb does it suck onto your finger and the bulb stay depressed or can you pump away and there's no vacuum? 

[Gerbutt]

No not that part. I did have one go years ago but the spring fell out so I knew it was knackered. Would that cause the sound of air going in and out in the fuel tank even though the filter is in the fuel?

[Paddy1000111]

Well it will stop it sucking through the fuel pipe. I should be right in saying there's two pipes out of the carburettor that go into the valve on the top of the tank? Part 8&9 in the image below? If that one way valve is shagged then it will just be pushing air in and out of the easiest part which will be the return line not the fuel vacuum line hence why you can hear pumping in the tank. Otherwise you could have the pipes hooked up to valve 7 back to front? 

Edited November 16, 2020 by Paddy1000111

[Lowestoft Firewood]

Mine has had a split primer bulb for ages. It starts ok but for some reason now it only runs flat out. not sure if the issue is linked or not ?

[Gerbutt]

Just put a new flange on and it’s still doing it. So far it’s had a new carb kit, new lines into the tank and to the carb and the new flange. Any other ideas?

[Paddy1000111]

It sounds like parts 7/8/9 are incorrectly assembled? If you pull the filter out and take it off. Do you feel suction on the hose when you pump the bulb? 

 

Just thinking, part 7 could be cracked/split and that would give you the same issue. if you take off 8/9 do you get vacuum on one of them when the bulb is pumped?

Edited December 6, 2020 by Paddy1000111

[Gerbutt]

Hello paddy. I’ve just put a known good carb on and it’s all fine. The original carb has had new kit, flange and a good clean. Do carbs just break over time?

[Paddy1000111]

It's C1M carb on that if I'm right? It should say on the side. IIRC there's a jet valve in them that can cause air to be dragged in if it fails. Part 62/6. Or you have a leak somewhere else in the carb, have you pressure/vac tested it?

[bmp01]

One way valve in the main jet - true story, and they do fail. Especially if compressed air has been blown through the carb without some sympathy. Some carbs have one way valves in other places that can get displaced by compressed air too.

You can test the main jet one way valve - remove the hi screw, use a bit of soft hose to seal over the hole.... blow / suck on hose, if the valves working you'll know. Or try the same on the new carb for comparison. Drifting the main jet out is not too hard if you want to test it out of the carb, refitting is easy too.