May need to adjust valve lash. Those 390’s are notorious for needing adjustment. Could also be bad gas, clogged fuel filter, dirty carb, or fouled plug.
Alright cool, so basic maintenance stuff.
Appreciate the advice.
Yeah I probably should do routine maintenance on it, I haven’t looked over everything in a couple months… been busy late season!
I was thinking it may be a unique problem because it runs fine when under high pressure load, like surface cleaning. But when I put on my low pressure nozzle and it’s under maybe half load, its gets to missin.
Ok the spring is still there… I checked valve clearance and they were only .01 off. Did my best to get them perfect… I adjusted the throttle stop screw, that sets the max throttle, to stop the throttle a little sooner. That got it sounding alot better, but not like it use to.
Checked oil, checked air filter, and sediment cup. All Is well…
Theres 1 more throttle adjustment screw that faces the exhaust side that I might mess with a little… i think it adjusts the actuation of the throttle under load If I’m not mistaken…
Belts are also In decent condition.
So far it seems to be a engine speed problem based on throttle.
My tach is broken sadly… but I know it likes to run around 3600rpm… any more or less and its not as smooth.
I will update more once I try adjusting the throttle screw and check the spark plug(its only 3 months old though, so probably fine)
Its almost a year old and ALOT of hours. I full time pressure wash and, and iv been running though jobs recently.
Ok I looked with a flash light into the tank and wow… it has sediment all over the bottom… possibly problem found? Getting late but first thing tomorrow I’m cleaning that tank out…
Any tips or tricks? And I had no idea there was a fuel filter other than the sediment cup… do I replace that or just clean it?
The carb bowl/sediment cup is the same thing and it’s after this problem, so I wouldn’t worry about it right now.
Pour some out, then blow backwards through that fuel line. See if you can feel/hear anything.
You can always take the filter off and check with a deep socket, but be careful as they are easy to strip or misalign and then they leak. I wouldn’t bother unless replacing.
It’s a hard nylon mesh that can’t get internally blocked (like foam etc) just externally.
Alright I checked the sediment bowl and it was totally clean… so I assumed the filter was clogged… poured some lucas carb injector cleaner and gas into the tankn, screwed the lid on and shook(the mix of the 2 creates pressure) the tank hard… I had the tube plugged and it blew out SHOT OUT EVERYWHERE … lol… now covered in gas I feel like a real mechanic…
I tried blowing through it before that and It was tough but I did hear air and got some through…
After the cleaning I can now blow through a little better.