valve spring question

T

theguy2024

Member
Quick question: I have a 208cc powerfist small engine I changed out the stock valve springs and installed 18 pound springs. The thing is, one of the springs went on nicely, snapped in and is compressed. The other spring isn’t compressed at all with the retainer snapped on. it’s loose and has a bit of play. Is this okay? Do I need a bigger valve?
 
theguy2024 said:
Quick question: I have a 208cc powerfist small engine I changed out the stock valve springs and installed 18 pound springs. The thing is, one of the springs went on nicely, snapped in and is compressed. The other spring isn’t compressed at all with the retainer snapped on. it’s loose and has a bit of play. Is this okay? Do I need a bigger valve?
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No that is not okay. Measure the uninstalled height of old and new and let us know.
 
It's very odd that one spring would fit normally & the other didn't!
On every engine like that (that I know of), both intake & exhaust springs are exactly the same!

I would take it all back apart & compare the new springs to the old ones.
Keep in mind that the intake spring is supposed to have an oil seal underneath it.
 
Maybe one set of retainers is not fully seated I've had something like that happen with valves that had 2 groves and only caught the top one but looks right
 
Venice Motor Bikes said:
It's very odd that one spring would fit normally & the other didn't!
On every engine like that (that I know of), both intake & exhaust springs are exactly the same!

I would take it all back apart & compare the new springs to the old ones.
Keep in mind that the intake spring is supposed to have an oil seal underneath it.
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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
 
Your going to want a billet flywheel the factory one will blow up on you
 

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theguy2024 said:
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
Click to expand...

I already forgot this stuff. With stock springs you need to measure your installed height then buy springs that give you the desired pressure at install height. Ie springs will say something like 18lbs @ .850”. Longer than stock springs may bind at full lift.

It looks like that motor is a predator clone. I would call ARC Racing and find out for sure. I ran 18lbs on stock fw and rod for years. 5800rpm.
 
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theguy2024 said:
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
Click to expand...

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
 
"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"
If the stock valve springs were 30mm. the 18lb springs should also measure 30mm. A 7mm shortage of the 18lb springs is wrong. You need to reach out AGK Affordable Go Karts

Tom
 
Billet flywheel guys.... ARC / AGK before you get into governor's and valves... Wouldn't hurt to balance it also...
 
Tom from Rubicon said:
"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"
If the stock valve springs were 30mm. the 18lb springs should also measure 30mm. A 7mm shortage of the 18lb springs is wrong. You need to reach out AGK Affordable Go Karts

Tom
Click to expand...
This is so important or you will bend push rods and there's metal guide plates instead of plastic when you get some RPM out of a stock 4 stroke of any cc/cubic inch and don't forget the cam lube with molly on everything... When you get ready to start it for break-in put the oil in through the valve cover and check the lash every 10 minutes of initial run time... Over 10 hours of break in you should loose .002- .004 seating in... So setting the lash on the tight side won't hurt you... Lap your valves good and clean out the abrasive... A little swirl in the guides while washing up... No seals if you're going to rev it to the moon and no 2nd ring so it will drink some oil maxed out... A sight glass to know your oil level bunged in... Just like the early days which these single cylinder engines resemble they were oily pigs burning and leaking everywhere... I'm going to try a pulse fuel pump from an outboard omc... And pump oil to the head with a breather... And add however many tablespoons of oil the system uses... Shoot it at the top of the valve cover with a 90° fitting with a v noch in the end... Another one pointing at the crank pin and you can grind off the splasher arm... Or a rod with out one... Semi dry sump with windage and scrapers... Polish everything inside so the oil doesn't cling to anything... Little money but a lot of time fussing ;)
 
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