Have a Hayter Harrier 56 BBC in at the moment. I don't normally deal with mowers so this is a bit new for me. With the engine running the governor linkage is constantly pulsing. It's clear that the springs that act on this linkage have been messed with however I can't figure out what the arrangement should be and I can't find any illustrations on line anywhere. The parts diagrams are only in exploded form and don't show a complete assembly.
Can anyone give me a clue please or ideally a picture of what the arrangement should be. Would be very grateful. Thanks. Alan
The pulsing I assume is what we call hunting where the engine rpm constantly surges up and down. This is a common issue especially noticeable on machines fitted with BBC fitted as blade isn't acting as a flywheel.
The hunting is normally cause by fuel issues, either bad fuel (old not fresh fuel), or a slight blockage in the carburettor. I'm betting it would be more likely the carb needs cleaning to resolve this one. Depending on what carb you have it coulld also be related to float level, take a look here for that info, Check Your Float Level (https://thegardenmachineryforum.co.uk/index.php?topic=20.0)
OK, I wondered about the lack of flywheel effect initially until I saw how much the governor linkage was moving and the fact that one of the two springs does not seem to be connected at both ends.
The big problem is I can't engage the blades as the machine is in to have the lever that activates the blades replaced as the original is broken.
I think I might just sit on it until I resolve that issue and see how we go from there. Thanks for the advice.
Should also add that if I manually restrain the governor linkage the engine will run smoothly.
The flywheel effect from the blade helps to disguise the problem is what I was getting at. ;) The engine shouldn't hunt if fuel system is set up working properly, regardless of the blade engaged or not.
Maybe a couple of photos of carb and throttle linkage would help to determine exactly what series engine we're talking about.
OK Problem sorted now thanks. Gave the carb a good clean, not particularly dirty but there were globules of water in the fuel bowl. Also having the carburettor in bits made it easier to figure out what the springs should be doing and where they attach to. All running well now.
The water droplets issue is very common nowadays with ethanol in the fuel it grabs moisture out of the air and it ends up in the bowl.
Glad you got it sorted. :tup:
OK, story continues!
The handle that activates the blades drive had been broken and the replacement was installed this morning. Having done this of course I started the machine to test it out and we were back to the surging and hunting we had previously.
So Mick, I should have looked a little harder at your link to float level problems because of course that is exactly what's going on! However in my defence I did check this previously and following cleaning and being allowed to dry out the float level looked spot on. I think re-immersion in petrol has swelled the rubber seat back up and of course back to the original problems. Carb rebuild kit is on it's way.
Thanks again Mick.
Hi Alan. The introduction of fresh fuel can do this to the rubber parts especially if it's been sitting with old dead fuel in it for a while.
If he float level is way out then hopefully it will help if not cure the problem, there's no guarantee. Fingers crossed.
I ordered carb overhaul kit 792383. Annoyingly it did not contain the rubber seat!! I had seen a You Tube video where the guy said sometimes these kits have the seat missing. Is this the case?
Anyway, as I had the carb in bits I've turned up a brass seat, fitted it and the machine appears to be running OK now. Let's hope this is the last of it.
Out of interest Mick, where do you get the seats from? Are they a separate item or in a kit?
Quote from: Renardiere on March 03, 2021, 05:26:25 PMOut of interest Mick, where do you get the seats from? Are they a separate item or in a kit?
They are a stock item at any Briggs and Stratton dealer. It comes as just a needle and seat kit. You'll probably find it for sale on various other places on the internet, search for, Needle / Seat Kit part number 398188
Hope this helps. ;)