I measured everything, both valves are the same length, the stock springs are 30mm uncompressed and the 18LB springs are 23mm uncompressed. I just saw on amazon they have 22LB springs that are 35ish mm. Would you advise installing these on a pretty much stock (governer deleted) engine or do I need a beefier cam
It looks like you opened a little bit of a 'can of worms' here.... You need to proceed with caution, so you don't destroy your new engine!
First of all... I would use the 18-lbs springs with a stock cam... (cams, bearings & all connected valve train parts can be damaged if you use springs that are too heavy).
Next... All valve springs are designed to have a certain amount of preload to get the desired spring tension.
You can use some shims underneath the 18-lbs springs that you have, to get the proper preload... (if you don't have enough spring tension; you can get 'valve float' at high RPMs).
The last thing you need to check it that the springs don't have any 'coil bind' when fully compressed by the cam lobe.
These are all things you can find on YouTube... Good luck & keep us posted!
Also... just so you know that I know what I'm talking about... Here's some links to see a minibike that I built with a 212cc Predator that I punched out to 250cc ; It hits 9000-RPMs & made 19-HP on a dyno at a recent minibike show.
Venice Motor Bikes (@venicemotorbikes) • Instagram photos and videos
Venice Motor Bikes (@venicemotorbikes) • Instagram photos and videos