minimum piston to valve clearence

[damann33]

what is the minimum clearence I should have on my 140cc lifan? I have bought a head with 28/24 valves and will be running a domed piston, the valves will probably hit the piston and I juss needa to know how much clearence the valves need. Thanks

[themountain]

http://www.miniriders.com.au/forum/tech-talk/15939-valve-cam.html#post148849<--- have a look at this before you do ANOTHER post on this matter!!

[damann33]

lol, again its not that big of a deal, I am just making sure of the specs so I dont mess up, this extra post could save my 1000 dollar engine but thanks for the link

[no_crf50_here]

1000 dolla motor? is it hand built by midgets?

[damann33]

lets work it out to figure out how much it cost

motor 500 shipped

head ported/polished 178 shipped

cylinder/pistons/gaskets/spacers $160.00

mikuni carb $70

exhaust $80.00

cam sprocket $ 15.00

17t sprocket $25.00

cam, rockers, springs $120.00

full engine gasket kit $15.00

dremel tool to cut piston dome $10.00

oil cooler $60.00

total just over $1200.00 bucks

hand built by me

[no_crf50_here]

are you a midget? Jokes..hehe

Sounds like you got some ok deals..

if you really want to find out if it will bind, build motor and put some play dough on top of the piston doesn’t have to be a thick layer, very slowly hand turn motor one rev and pull apart again, the valve will leave an impression in play dough you'll know how far away it is from piston, OR motor won't turn over and you'll have a good idea that there is some thing wrong, pull apart again and check if play dough has been squashed to the piston. A bit of work but for a newbie it's a save way to go.

[damann33]

yea I am familiar with that and am looking at every little thing to get this engine done right. most likely the larger valves will hit the piston dome since it will be sticking out about 4.3mm from the cylinder top, I will juss need to figure out exactly how much I have to remove off the piston dome. I am trying to find a show that uses those Isky products to make it easier and done right

[Cactus Jack]

Do the clay check on a STOCK 140 first to find out the stock piston to valve clearance .... then use that as a MINIMUM clearance distance for your new modded engine after you do another clay check with the hi comp piston , bigger valves , race cam , different cylinder and gaskets etc plus add a bit extra on top of the stock clearance as a safety margin in case you miss a gear , peak rev the engine , and float or bounce the valves ........

Do NOT confuse piston to valve clearance with valve lash (rocker to stem clearance adjustment ie .003/.004 ) Piston to valve clearance is much larger than that ...

[damann33]

yea I will use the clay method on my stock setup before proceeding. I have to admit I was confused with those two measurments, now I know the proper terms I will go maybe 1 or 2 tho more for the saftey margin, thanks man

[cass38a]

You wont stuff a grand. I fail to see how your carby or half your other parts would be broken if you had the valves hit the piston.

Why dont you start another couple of threads so you can spread the info out.

The reason people get the S#@* about new threads being starded is if in 6 months another member is looking for a similar answer they cant find it in one spot.