predator 420 non hemi valve size

[Trevinator]

i have a predator 420 non hemi in my go kart and i think i may have a bent valve. when i was installing a set of ratio rockers, the push rod came off the rocker and i think it may have bent a valve in the process. the engine still runs, but i have to choke it to start it every time and it backfires on deceleration down hill. i was wondering if anyone knows the stock valve size of the non hemi 420 engine so i can order some new valves for it when i install the new springs and cam, and where i might be able to order them from. most places show the valves for the hemi version of the engine.

 

[Rat]

It depends on WHICH version of the NON-Hemi head it is (model/age)

There are 3 different types of valves in the Predator 212cc engines:

The 1st generation Predator 212cc is a non-hemi engine with a 25mm intake valve, and a 24mm exhaust valve. These valves have 5.5mm stems, which is common to the GX200 and 196cc Clone engines.

The 2nd generation Predator 212cc is the hemi engine with a 27mm intake valve and a 25mm exhaust valve. These valves have 5.5mm stems

The 3rd generation Predator 212cc is a non-hemi engine with 25mm intake valve, 24mm exhaust valve. These valves have 5mm stems. The aftermarket does not support this size stem.

 

[Trevinator]

It depends on WHICH version of the NON-Hemi head it is (model/age)

There are 3 different types of valves in the Predator 212cc engines:

The 1st generation Predator 212cc is a non-hemi engine with a 25mm intake valve, and a 24mm exhaust valve. These valves have 5.5mm stems, which is common to the GX200 and 196cc Clone engines.

The 2nd generation Predator 212cc is the hemi engine with a 27mm intake valve and a 25mm exhaust valve. These valves have 5.5mm stems

The 3rd generation Predator 212cc is a non-hemi engine with 25mm intake valve, 24mm exhaust valve. These valves have 5mm stems. The aftermarket does not support this size stem.

this is a predator 420cc engine. part number 60340.

 

[Rat]

this is a predator 420cc engine. part number 60340.

Oops... so used to seeing 212 that I totally missed the 420 .

Seems to be 38mm intake 34mm exhaust for Hemi/ NonHemi both... someone around here who actually knows 100% for sure is bound to chime in soon

 

[panchothedog]

At O.M.B. Warehouse their 38-34 mm valve package says for Hemi only.
They also sell 31.5 and 35 mm valves for 420 with no designation. Those might be the ones you need.

 

[Trevinator]

pulled the head tonight and looks like a 35mm and 32mm valve set. im guessing the 31.5mm valve will work for it? the batteries in the caliper were dead, so i was going by eye on the scale. there is a couple weird things with the head though. the exhaust does not have a valve seal and only the exhaust has a removable steel spring seat. i would think there should be one on the intake side as well to help protect the aluminum head from damage? im putting heavy duty valve springs in, so should i order a spring seat for it? what about the valve seal for the exhaust? im guessing they must want the oil to lubricate the exhaust valve shaft to keep soot from building up on it?

 

[panchothedog]

Have never seen a seal on the exhaust valve on any of these small engines. I think it gets so hot it would burn it up. I guess I don't know what a removable
spring seat is. I think I would try putting in the new springs just like stock ones were.

 

[Rat]

pulled the head tonight and looks like a 35mm and 32mm valve set. im guessing the 31.5mm valve will work for it? the batteries in the caliper were dead, so i was going by eye on the scale. there is a couple weird things with the head though. the exhaust does not have a valve seal and only the exhaust has a removable steel spring seat. i would think there should be one on the intake side as well to help protect the aluminum head from damage? im putting heavy duty valve springs in, so should i order a spring seat for it? what about the valve seal for the exhaust? im guessing they must want the oil to lubricate the exhaust valve shaft to keep soot from building up on it?

I'd call that normal simply for the following comparison:

My Husqvarna 208 has:
18# springs factory stock,
no stem seals over the valve guides,
and a lash cap only on the exhaust.

Fast forward to cleaning out this Hemi212...
10# maybe 12# valve springs
Stem seals over both guides
Lash caps on both valves

Edit: Pancho chimed in before I was done lol.

I've never seen a removeable springs seat of any kind around the nipple of the guide either

 

[Trevinator]

one other thing that was weird with this engine, is when i went to install the 1.2 ratio billet rockers, the pushrods seemed to be too short instead of too long like the website said. it was to the point that when i pulled the engine over, the pushrod fell off. it seems like it needs longer pushrods, but i dont know. maybe it will work better with the stainless valves im ordering for it? this (link) is the steel valve seat im talking about. just sits around the base of the valve guide.

 

[Rat]

Have never seen a seal on the exhaust valve on any of these small engines. I think it gets so hot it would burn it up. I guess I don't know what a removable
spring seat is. I think I would try putting in the new springs just like stock ones were.

Valve stems and guides shouldn't be getting that hot, even My old Honda SL175 K0 had I/E stem seals. I recall one pair being a brownish orange and the other bein green, can't tell you which was which but I'd figure they were of different compounds to deal with the thermal different.

THEORETICALLY: for there to be enough heat soak up the stem to damage the seal... the stem would have to heat saturated to the point of being weakened.

Keeping in mind the tricks of welding thinner steel sheet without blowing out is to give the oversaturation of heat somewhere else to go.

In that case that extra heat would be transferred into the guide itself such as the two would be at a thermal equilibrium to each other even if not in balance between intake and exhaust.

I'd expect thermal breakdown and flashboiling of the oil preventing any amount of stem lubrication at all and ultimately a stuck valve if there were enough heat to damage the exhaust valve seal.

For that matter the exhaust under my 08 Impala gets plenty hot enough to take the hair off an arm and give a nice sizzling 2nd° burn if you dense enough and the whole system is hung with rubber (2 pre cat, 1 upstream from muffler, 2 post muffler) even before the cat where it's going to be even hotter

 

[Rat]

one other thing that was weird with this engine, is when i went to install the 1.2 ratio billet rockers, the pushrods seemed to be too short instead of too long like the website said. it was to the point that when i pulled the engine over, the pushrod fell off. it seems like it needs longer pushrods, but i dont know. maybe it will work better with the stainless valves im ordering for it? this (link) is the steel valve seat im talking about. just sits around the base of the valve guide.

Only time I've had a rod drop was on the bench, and it was because I just missed the lifter port at the cam, so what felt seated ended up popping out when I hand rotated the crank a few degrees.

Depending on how much actual difference there is you may just need to shim with lash caps. They serve 2 general functions the first is to keep the rocker from shrooming the rod head out, the second is when the rod falls short by 0.5 or so... more cost effective and time efficient to cap it than to grind a longer one to fit

 

[Trevinator]

Only time I've had a rod drop was on the bench, and it was because I just missed the lifter port at the cam, so what felt seated ended up popping out when I hand rotated the crank a few degrees

the first time it happened, it wasnt seated on the adjustment screw at the rocker. i corrected that, readjusted the valve lash pulled the engine over and it still happened. the adjustment screw for the ratio rockers was all the way at the bottom of its travel as well. i did have the pushrod guide plate still installed, so maybe removing that will get the geometry correct or better?

 

[Rat]

the first time it happened, it wasnt seated on the adjustment screw at the rocker. i corrected that, readjusted the valve lash pulled the engine over and it still happened. the adjustment screw for the ratio rockers was all the way at the bottom of its travel as well.

Still seems like something is amiss at the cam to me. The seller could be mistaken or misunderstood something because I have heard the rod length between Hemi and Non Hemi is different... no clue which is which personally though.

i did have the pushrod guide plate still installed, so maybe removing that will get the geometry correct or better?

The only time I've seen this listed as necessary is when using a heftier rod that's just not going to pass through the OE retainer.

 

[Trevinator]

Still seems like something is amiss at the cam to me. The seller could be mistaken or misunderstood something because I have heard the rod length between Hemi and Non Hemi is different... no clue which is which personally though.

The only time I've seen this listed as necessary is when using a heftier rod that's just not going to pass through the OE retainer.

the cam is still stock and i have not yet removed the side cover on the engine. not sure what could be wrong at the cam side. the rockers are specific to the non hemi 420. my pushrods are 6.5", like they should be and a hemi 420 is 7" which would be way too long. these (link) are the rockers and where it says the pushrods should be shorter. but looking at the listing, its showing 5.6" pushrod length. if it was 6.5, it would be longer like i suspect it needs to be, but saying 5.6 makes me think its a typo and it should be 6.6" and therefore longer.

 

[Rat]

Just a thought did you get the engine new, or was it on the cart with some hours on it?

The deceleration backfire is ABSOLUTELY 100% a lean carb. I know because I had the same issue on my 208 in the initial set up phase after making a longish exhaust for it but was still running a stock type carb.
I did some looking into it and it comes down to being lean enough to run great but also super heat the exhaust, where any sudden off throttle deceleration spits a little unspent fuel down the exhaust, the heat alone ends up igniting it.
My 208 was bad enough it would backfire post shut down just after the engine stopped turning.

 

[Rat]

the cam is still stock and i have not yet removed the side cover on the engine. not sure what could be wrong at the cam side. the rockers are specific to the non hemi 420. my pushrods are 6.5", like they should be and a hemi 420 is 7" which would be way too long. these (link) are the rockers and where it says the pushrods should be shorter. but looking at the listing, its showing 5.6" pushrod length. if it was 6.5, it would be longer like i suspect it needs to be, but saying 5.6 makes me think its a typo and it should be 6.6" and therefore longer.

Gotcha, seems very much likely be a typo, and the seller needs to correct the issue too short of rods are definitely going to hop out from a lack of lifter tension holding then down

 

[Trevinator]

Just a thought did you get the engine new, or was it on the cart with some hours on it?

The deceleration backfire is ABSOLUTELY 100% a lean carb. I know because I had the same issue on my 208 in the initial set up phase after making a longish exhaust for it but was still running a stock type carb.
I did some looking into it and it comes down to being lean enough to run great but also super heat the exhaust, where any sudden off throttle deceleration spits a little unspent fuel down the exhaust, the heat alone ends up igniting it.
My 208 was bad enough it would backfire post shut down just after the engine stopped turning.

i got the engine new. i think the backfire might be a slight exhaust leak at the gasket. there is evidence of a leak there at the head. i tried a larger jet and it didnt seem to run as good when i tried a 41-42 jet size.

 

[Rat]

i got the engine new. i think the backfire might be a slight exhaust leak at the gasket. there is evidence of a leak there at the head. i tried a larger jet and it didnt seem to run as good when i tried a 41-42 jet size.

Exhaust leak can definitely do it to... my 208 got some sort of moody when the header cracked a weld

 

[Trevinator]

just ordered a bunch of parts. stainless valves, titanium retainers,lash caps and a flat top piston for some extra compression. also ordered another valve spring seat. with the extra spring strength, i would rather it be on steel vs directly on the aluminum head. i also have a set of champion 1.1:1 rockers on the way, so i might be able to use them until i can get the longer pushrods. i figure if im going to have it apart, lets go all in. and do it once.

 

[Rat]

i figure if im going to have it apart, lets go all in. and do it once.

Exactly why I haven't done anything too serious with the 212Hemi beyond mild porting and governor delete, it needed opened because of the sitting condition it was in (came with house purchase, and a dead B&S powered Kart)

The Briggs got a gov delete, recoil repaired, some porting, a custom intake made and a PZ19 carb... it sits until I decide what to do with it.

I only did what little I did because they needed inspected and cleaned.

Both it and the Briggs were half full of oil, half full of water, thankfully neither was seized and both cleaned up beautifully minus the Briggs fuel tank which was completely full of rust and water. Once the rust was cleared from the B&S tank it didn't hold anything due to being so perforated.