Predator 212 breaking up at high rpm....too rich?

Baja_brandon96

Baja_brandon96

New Member
#1
#1
I did some basic upgrades to my ungoverned predator 212 doodlebug: an air filter, header, and upjet to a #95 (0.374) main jet, stock emulsion tube. I live in NYC, if that helps in terms of elevation...Running 12x70 gearing, with a Carlisle 15x5x6 snow hog in the back. Was seeing 42mph the other day, although it would hesitate a little bit in the high 30's before pulling the rest of the way. Took it out today and it wouldn't break 37mph, it just stays there....seems to break up. It wants to go faster, but it can't....Am i too rich? (In terms of jetting :) )
 
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Moto Walt

Member
#4
#4
Baja_brandon96 said:
No, stock valve springs. I don't want to raise potential RPMS without a billet rod/flywheel(i assume that would?). I'm just curious as to why it would hit 42 one day, and not the next...
Click to expand...
Valve spring fatigue. You mightve left the engine on a compression stroke where the valve spring was full collapsed the whole time it was sitting. When you collapse a hot valve spring and let it cool down still in a collapsed position, it will lose seat pressure.

Best thing to do is make sure your engine is on the compression release after you get done riding it.

Yea you need a rod, flywheel and valve springs.
 
Baja_brandon96

Baja_brandon96

New Member
#5
#5
Moto Walt said:
Valve spring fatigue. You mightve left the engine on a compression stroke where the valve spring was full collapsed the whole time it was sitting. When you collapse a hot valve spring and let it cool down still in a collapsed position, it will lose seat pressure.

Best thing to do is make sure your engine is on the compression release after you get done riding it.

Yea you need a rod, flywheel and valve springs.
Click to expand...

Thanks for the explanation! Certainly makes sense to me. So basically, make sure the crank is in a position where the pull start rotates freely?
 
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Moto Walt

Member
#6
#6
Baja_brandon96 said:
Thanks for the explanation! Certainly makes sense to me. So basically, make sure the crank is in a position where the pull start rotates freely?
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When you are pulling it over, you'll feel it fall into a "hole" right when it's getting hardest to pull, that should allow the valve springs to be at rest.
 
OND

OND

#8
#8
I would also check the spark plug to see what it looks like....maybe a little rich and these cheap plugs that come stock in these engines aren't much.
 
noseoil

noseoil

Active Member
#10
#10
Agree about the weak valve springs, take a bit of time to look for better ones than the factory ones you have now. It can't hurt.

If you run that Autolite plug, it could be starting to foul out from idling. It's a great plug, but needs a lot of heat to stay clean & run well as designed. If the engine is allowed to idle for a few minutes (cold plug temp), it will begin to foul pretty quickly, especially if it's a bit rich at idle. Take a look at the NGK BR6 plugs. It will stand up to different duty cycles a little better than the X plug you're running & not foul as easily.

Just something else to ponder on your list of ponders. Sounds like you're having fun.
 
ole4

ole4

#11
#11
What RPM are you turning when you went 42MPH? Check plug to see if it is dry black, could be starting to foul. If your rpm is close to 5K it certainly could be valve float.
 
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cheapfun220

New Member
#12
#12
Baja_brandon96 said:
No, stock valve springs. I don't want to raise potential RPMS without a billet rod/flywheel(i assume that would?). I'm just curious as to why it would hit 42 one day, and not the next...
Click to expand...
I did governor removal, air filter, header, jet and emulsion tube, 6* advance timing and autolite 3910x spark plug, and 18 pound valve springs. All on stock flywheel and rod I've been perfectly fine. "Potential rpms" are not a problem as long as you don't drive like a dumb*** and listen to the engine. Some people say they run 8000 rpm on stock rod and flywheel, I try to keep it under 6000.

Sent from my SM-G930V using Tapatalk
 
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