Hi I've seen older threads but don't seem to relate closely to my problem. Mower is 5 years old. Recently (few months) began running slower than normal and lumpy or slightly erratic. Speeds up to correct speed and no lumpiness, just before fuel runs out. This and the fact that the plug is sooty suggest rich running. As I've replaced the plug and checked the gap, cleaned the foam filter and recharged with oil there is only one thing left I guess & that's the carb. I notice that the two springs that possibly help adjust the fuel mixture are very "soft" ie little tension. There is a good deal of movement from them while the engine is running lumpy but I think that is from the semi automated way the carb is set up. I've read that the diaphragm on this carb can be affected by holes hair line cracks etc and that there is a kit around that replaces this. Can anyone confirm I'm on the right or wrong track here? Any other ideas are welcome.
Briggs & Stratton Classic 35 (3.5bhp) runs rich...
Oct 01, 2006
4 Replies
You say you checked the foam filter - what about the actual air filter. Mine occasionally clogs up with fine grass/pollen and oil mist which you can clean out/change filter if particularly bad.
Slurp
Not quite the same problem as you've got - My mower was running rich, lumpy performance and eventually stalling after a few minutes mowing. I removed the carburettor and gave it a clean which seemed to fix it but the problem re-occurred 15 minutes later....
I investigated carb service kits and found that a new one (including pump spring, diaphragm and seals) was only £12 whereas the 'service' kit was £14. I also bought replacement governor springs while I was at it.
New carb fitted (didn't bother with changing the springs in the end)and the mower runs fine again...
Peter
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