Hi guys, I have a Jetfast edger with a 2hp Briggs motor on it. The engine will kick initially when pulled over but will not start. Things I have done are as follows: Originally when I got this it had no spark so I replaced the points ignition setup with a later model ignition. Has plenty of spark now and I have tried several spark plugs, all with the same outcome when attempting to start it. I have replaced the gasket between the carburettor and tank, I have replaced ther 2 gaskets between the carburettor assembly and the engine, the fuel intake tube and mesh filter are clear, the fuel jet is clear and the 2 holes in the carby inside the jet housing are clear, the fuel needle valve is undamaged, it has excellent compression and the valve clearance is ok, the choke mechanism is working properly and the mixture jet is set to approx. one and a half to two turns out, although I have tried different settings with no result. When fuel or carb cleaner is put directly into the carby it will fire and run very slowly for about 10 seconds, then stops and will not start again. Frustrated to say the least. Appreciate any input. I have attached a diagram of the model carburettor that is fitted to this edger.
Did you measure the compression, pull it over a few times? I'm wondering if their isn't a leak somewhere or if something is physically stopping the engine from turning over properly? These engines left one of the valves ever so slightly open to help it make it easier to pull start, did they not? Perhaps something is not quite right there? Other than that, I can't think of anything else right now, seems like a tricky one.
I don't collect mowers. I just require Multiple Mowing Solutions™.
Thanks for the input guys, the exhaust is fine, however I did do a compression test using a tester and the highest reading was 60psi, can anyone confirm if that's too low, I did the oil in the cylinder trick to build it up and it fired up easily but still didn't run, after smoke dissipated it would not fire again. I think that indicates rings more so than valves if i'm correct.
As Mystyler has said, the 'Easy Spin Starting' decompression system used on these older Briggs, means that compression test gauges are of no real use as a diagnostic tool.
The excerpt which follows is taken from the 1981 edition of B&S' 'Service And Repair Instructions'.
Quote
The intake lobe on the camshaft is ground with a small ramp which holds the intake valve open 1/100 of an inch for a tiny fraction of the compression stroke. At slow starting speed the interval of time that the valve is open is relatively long and therefore enough air escapes to noticeably reduce the compression. However, at operating speeds the interval of time is so short that there is practically no escape and therefore horsepower is unimpaired. Actually at 3600rpm the valve is opened for a mere 1/200 of a second. In all other respects the valves operate as in any other four stroke cycle engine.
The force required to start an engine is reduced by 50% with 'Easy Spin' and would be noticed most by a person who has difficulty starting the ordinary engine.
The test that the Briggs manual recommends, is to spin the flywheel in reverse to normal rotation, and see if it 'bounces back' when it approaches TDC.
This one, filename 'Briggs & Stratton Service and Repair Instructions 1984.pdf' is actually better than the later CE8069-1 version, I find, for the older engines.
Cheers, Gadge
"ODK Mods can explain it to you, but they can't understand it for you..."
"Crazy can be medicated, ignorance can be educated - but there is no cure for stupid..."
