Built predator only hits 7500rpm

Dollatee123

New member
Hey I have a predator that’s fully decked but it only has one issue. I have 32-28 valves ported and polished 14cc chamber with a 26mm mikuni and 36lb springs with all billet parts flywheel side cover valve cover flattop piston and a .308 grind cam with champion rocker arms fully vented with oil catch can but it only hits 7500rpm no load and sounds like it’s hitting a rev limiter and is just maxing out won’t go higher it’s build to go 10k only thing that is stock on this is the spark coil which I heard some of them have rev limiters
 
Hey I have a predator that’s fully decked but it only has one issue. I have 32-28 valves ported and polished 14cc chamber with a 26mm mikuni and 36lb springs with all billet parts flywheel side cover valve cover flattop piston and a .308 grind cam with champion rocker arms fully vented with oil catch can but it only hits 7500rpm no load and sounds like it’s hitting a rev limiter and is just maxing out won’t go higher it’s build to go 10k only thing that is stock on this is the spark coil which I heard some of them have rev limiters
Should I install 1.3 ratio roller rocker would that solve the problem or will my valves hit my piston
 
First, dry revving an engine is a good way to disassemble with no tools.

Also, the engine goes rich with no load.
Bolt to kart or dyno, give a little load with brake, and see where revs go before getting too excited about not revving.

1:3 rockers won't change rev potential, at least not for higher. You'll need more valve spring seat pressure to get any gains. Also need to check coil bind, and retainer to guide clearances to allow extra lift. Worth noting, piston to valve clearances get closer as well.
Not just a drop in conversion.
 
Dyno Cams description of their 308 cam says its targeted for less RPM's, mid 8000's. Thats what I run in everything but box stock and yeah it hits a wall past 8650. And by the way we are fast at 8600. Whats the point of hitting 10,000?
 
How
First, dry revving an engine is a good way to disassemble with no tools.

Also, the engine goes rich with no load.
Bolt to kart or dyno, give a little load with brake, and see where revs go before getting too excited about not revving.

1:3 rockers won't change rev potential, at least not for higher. You'll need more valve spring seat pressure to get any gains. Also need to check coil bind, and retainer to guide clearances to allow extra lift. Worth noting, piston to valve clearances get closer as well.
Not just a drop in conversio
Dyno Cams description of their 308 cam says its targeted for less RPM's, mid 8000's. Thats what I run in everything but box stock and yeah it hits a wall past 8650. And by the way we are fast at 8600. Whats the point of hitting 10,000?
How would I check for the coil bind? That could be limiting me to 7500rpm when It’s bolted on my mini bike with my juggernaut I barley can hit 7k rpm
 
Checking for coil bind involves removing valve cover, turning engine to max lift on one or the other valves, and measuring distance between coils of valve spring with a feeler gauge.

Did you try with shut off switch disconnected? Those can sometimes ground out ignition.

If carb is too rich, it will flood out the spark at higher rpm.

Also, check if coil is hitting flywheel at rpm due to crankshaft flex. Aftermarket flywheels also have stronger magnets, which can damage stock coils if too close.
 
It doesn’t look like I have coil bind. At first I ran my spark coil pretty tight from the arc flywheel but I moved it back and it didn’t touch anywhere btw, I took my head off and my exhaust valve looks white for some reason. The spark is light brownish so it’s not running to rich 130 main jet mikuni 26mm I but my spring on max lift and the coil seems like it has a lot room to go
 
Also there’s some white milky stuff in my oil catch can it
 

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Wait in your picture I saw a fuel tank. Is there a stock fuel tank on your motor? Because it may not be flowing the fuel to carb very well when you have that many mods and turning that high rpm the fuel might not be getting gravity fed fast enough. Just a thought
It has a vent hole in it already but I tired putting in 135 main jet and it started bogging around 5500 and won’t go higher cuz of the bog I went back down to a 130 and it barley bogs top end. You think it could be that I need a fuel pump huh? It still doesn’t go more than 7k rpm for some reason
 
This could have an effect .
If 130 is better then 135 .
Try a 125 .
Rod clearance ?
125 is too small bogs on top end like the 135 130 seems to be the sweet spot right now with no bogging but it can barley go past 6800rpm under load. And my rod clearance is fine doesn’t hit anywhere. I’m just mind boggled trying to figure out why it hits a wall at 7k
 
I use royal purple oil and this is what is dripping out of my valve cover to oil catch can line some white milky stuff
 

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