4 stroke engine works with too much noise and vibration. how to make it queter? when adjusting valve clearances, should i err toward big or small and how would that affect sound and vibration in each case?
Which 4-stroke engine do you have? As a general ballpark figure, if you set valves to .005" intake and .007" exhaust cold, you should be okay. You can always run a bit tighter or loose if you live in hot climes, but I've found those to work well. My HS49's intake valve was 0.022 the first time I checked it!
All single-cylinder engines have some NVH, that is just because they are inherently imbalanced. For example there is a roughly 800RPM (4200-5000) range in my 4G+SBP setup where there is a harmonic imbalance and it causes a lot of vibration which goes away if I pedal, easy because that's 60-72 pedal RPM for me.
If your setup is always shaking, there may be a problem somewhere that needs addressing.
Can you take pictures of your setup? It would help a lot for all experienced eyes to spot potential issues.
Honestly, an HS49 with ~30" of 3/4" ID flexpipe, no muffler, is quite loud IMO.
Mine is much, much louder than all 6 of the chinagirls even with modded non-cat kit pipes I've had.
The "5-7HP" Briggs cigar muffler keeps the same snarly and popping tone, but greatly reduces the amount of sound that bounces off of buildings. These little engines can be crazy loud! I have my straightpipe pointed towards traffic LOL
I think he took his apart or was going to. Remember asking about how to take the flywheel nut off. Might be why. Vibration can be a lot of things but if it’s still going normal speed I wouldn’t worry about it. If it sounds like it’s running weird maybe. They shouldn’t vibrate nearly as much as the crappy girls though. Maybe you need to tighten the mounting bolts. My 79cc vibrated because I used rubber and the whole thing would shake.