UPDATE:
I did a leak down test and found that air was coming out the carb when both valves were closed, I removed the intake valve and saw that it was groved, head looked good. I bought a new intake valve and spring and lapped it all including the exhaust valve, installed everything and pressure test was good. the engine started perfect but again would not go past 50-70 percent RPM under load. under load it idles down with no hesitation so that is fixed
Now I am leaning towards excessive vibration on the engine causing the float to choke off fuel. no load the engine revs up and down perfect. any other advise?? carb maybe needs re cleaned.
thanks
Larry
Hi All
I have a 10 yr old B&S 5hp horizontal shaft industrial engine on a old tamper that tamps dirt by vibrating a heavy steel plate.
The engine works perfect when the tamper belt is not on. starts with 1 pull, idles, revs up. high idle good. just runs perfect.
when I install the tamper belt and put the machine under load it will only rev upto what seems to be half throttle. no surging just half power. plus when I put the throttle back to idle it takes a few sec before it idles again.
here is what I have done.
1. removed muffler, no change
2. removed and completely cleaned carb, fuel tank open/close valve and lines( gravity fed type carb as fuel tank is above it)
3. removed gas cap, no change.
4. inspected lifter gap. .009=exhaust, .005 intake. I did this by removing valve cover as the head has not been removed. rechecked valves when engine was hot and gap was still good.
sprayed WD 40 all around head to check for leaks while engine was running and it does not appear to be leaking.
Anyone have any Ideas as to why this thing is bogging/half throttle only under load?
the rubber bushings that separate the engine from the heavy tamper plate are shot. could the excess vibration under load cause the carb float to bounce and choke of the gas under load?
any suggestions would be great. I posted this hear as you guys seem to know your stuff with these small engines and everything I have tried so far were stuff I found searching old posts on here.