Mildly Built Predator 212 Non Hemi Surging at WOT

[JSleez]

Hello everyone,
Been trying to get this mildly built predator 212 running.
Build list:
Predator 212 Non Hemi
Billet Rod
Cast Alum Flywheel (12 degree key)
26 pound springs
26mm Amazon Mikuni Carb (140 jet)
Hot 265 cam
Header pipe
Oil sensor and governor removed

Engine idles fine, and is good up until WOT. I don’t have any load on the engine but at WOT in the higher RPM range it surges, it doesn’t die but just keeps surging. Is this valve float? Spark plug seems fine.

any help would be appreciated!

 

[Denny]

What does it do under load? You got to do that first.

 

[BrownStainRacing]

Hello everyone,
Been trying to get this mildly built predator 212 running.
Build list:
Predator 212 Non Hemi
Billet Rod
Cast Alum Flywheel (12 degree key)
26 pound springs
26mm Amazon Mikuni Carb (140 jet)
Hot 265 cam
Header pipe
Oil sensor and governor removed

Engine idles fine, and is good up until WOT. I don’t have any load on the engine but at WOT in the higher RPM range it surges, it doesn’t die but just keeps surging. Is this valve float? Spark plug seems fine.

any help would be appreciated!

26# springs needs .850" installed height to get 26# seat pressure.

Let's say, you didn't measure install height, jus put em in, and they are at .9" installed height.

Well, they are not 26# seat pressure at .9", they are probably closer to 10# springs at .9" installed height.

26# valve springs can easily handle 7000 rpm, if installed at .850" install height.

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[panchothedog]

Don't rev your engine wide open throttle without a load on it. You will screw stuff up. You may have already. The engine will react differently when it is working.
Put it on your kart or on your bike ( whatever you intend to use it on ) and ride it.
Draw your evaluation and begin tuning based on how it performs while hauling you around. Based on what you listed for parts, you should have a fairly potent engine. Revving the crap out of it on the bench ain't helping a bit.

 

[JSleez]

Tested under load. It rides fine until I go WOT. Then it cuts out. Almost feels like the engine shuts off. It’s intermittent. checked the spark plug and it looked decent. I dropped down to a 125 jet. Clip is in the 3rd position.

 

[BrownStainRacing]

Tested under load. It rides fine until I go WOT. Then it cuts out. Almost feels like the engine shuts off. It’s intermittent. checked the spark plug and it looked decent. I dropped down to a 125 jet. Clip is in the 3rd position.

Plug looks too shiny to me.

Is that oil?????

 

[JSleez]

No oil. I just put a new plug and a new coil on to see if it was spark related, still the same issue. Coil gap is set at .30.

 

[Master Hack]

Looks lean to me.

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[JSleez]

Some photos of the top of the piston. Seems normal. I’ll twist the air fuel nut in a little to see if that helps.

 

[Master Hack]

Have you changed the pilot jet?
you sure its a genuine mikuini?

 

[JSleez]

Went back out. Had the air fuel screw just under a full turn out from fully in. Plug looks better, however still getting the cutting under WOT

 

[JSleez]

Have you changed the pilot jet?
you sure its a genuine mikuini?

It’s not. I said Amazon Mikuni. Pilot jet is stock.

 

[BrownStainRacing]

Went back out. Had the air fuel screw just under a full turn out from fully in. Plug looks better, however still getting the cutting under WOT

Its too lean on the high side.

The air/fuel mix screw is for the low side, that looks fine.

Add more jet to the high side til you see more color on the porcelain, then adjust needle up/down til you get quickest acceleration.

When you get it tuned, run some seafoam in gas to help clean the combustion chamber. That's a mess, I've seen engines with over 100 hrs on them that don't look that bad.

 

[Master Hack]

l don’t know if amazon sells real stuff or chinese s**t..
l ask, cuz l went through a similar problem.
solution was to throw away the knock off away, get the real deal, install a smaller pilot and a bigger main.

not saying that works for everyone, but my guess is yer lean on top.
jetting? fuel delivery?
take it for what its worth - nothing.

 

[BrownStainRacing]

I missed that part.
l ask, cuz l went through a similar problem.
solution was to throw away the knock off away, get the real deal, install a smaller pilot and a bigger main.

not saying that works for everyone, but my guess is yer lean on top.
jetting? fuel delivery?
take it for what its worth - nothing.

I see the same around here. It's hit and miss for a good 1.
Get 1 in and it's fine with a main jet change, then the next 1 you have to change every thing and it still don't work right.
I gave up on em and gave all my spare parts away.

 

[JSleez]

I missed that part.
l ask, cuz l went through a similar problem.
solution was to throw away the knock off away, get the real deal, install a smaller pilot and a bigger main.

not saying that works for everyone, but my guess is yer lean on top.
jetting? fuel delivery?
take it for what its worth - nothing.

Just swapped to a 130 jet. Fuel delivery is just a tank feed.
Plug looks better but the cutting is even worse now. So odd.

also attached a picture of the bike

 

[BrownStainRacing]

Just swapped to a 130 jet. Fuel delivery is just a tank feed.
Plug looks better but the cutting is even worse now. So odd.

also attached a picture of the bike

Looks better. Go up 1 more jet size and see how it acts. It maybe worse, but at least you will know where you need to stop.

Get pics of the side of the ground strap too.

 

[JSleez]

Looks better. Go up 1 more jet size and see how it acts. It maybe worse, but at least you will know where you need to stop.

Get pics of the side of the ground strap too.

Gonna do that tomorrow here’s a photo of the grounding.

 

[Master Hack]

Bigger jet bigger problem only at WOT…..
hints of fuel delivery problems.
float level?
fuel line size?
debris in needle/seat?
pinched fuel line?
vacuum leak?
crap carb?

 

[BrownStainRacing]

Gonna do that tomorrow here’s a photo of the grounding.

No, no,......ground strap on plug is what I need to see.