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broken champion rockers

M

minibikedude

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I built a predator 212 motor with a .40 rod ,hemi flat top piston, billet lifters, 1/4 in cm pushrods ,black mamba cam, arc flywheel, champion rockers and a 24 mm mikuni carb. I have the motor in a mini bike and have ridden it about five times when it stopped running. I took off the valve cover and saw that the champion rockers were broken. This is my second set of champion rockers because the first ones broke from crooked studs. Can I get away with using the stock rockers and push rods? I'm using 26 lb springs and don't know why my champion rockers broke I thought they were supposed to not break?
 
What block are you using? If the Hemi block and a .040 Rod you might have piston to head clearance issues also...
Billet lifters from who? Isky I believe are longer which uses shorter push rods...
Has the head been milled?

Been pushing Champion Rockers to 8500rpm for a few years now on the same set...
I run a Hemi block with a .040 Rod, flat top, gx160 lifters, 2.175 rods, gx200 head milled .090 and a .045 gasket and a .350 cam dual springs...in one build with no issues...
 
Im using a non hemi predator block, the lifters are from isky and the pushrods are also they are shorter to work with the lifters stock height. The head is stock right now with no milling . Thanks for the responses
 
Broken or just falling off to one side ? like said in the other post some thing is not
right if your breaking them.I turn them 8500-9000 for 4 years now maybe longer and have not had either style break.
I am some what lost as to why you would go shorter push rod and lifters with a head that's not milled.
 
Coil Binding the springs????
Its either that or interference with valve hitting piston..
Which would be easy to see once head is removed..
 
I looked at the piston , head and valves and they look ok no marks on them. The rockers broke on the shaft ends and also on the bottom casting . The first time they broke was because I tightened them down too much and had crooked studs . This time I screwed in the studs by hand and the slid the rockers on and put some flat nuts that are smooth on the bottom. Thanks for the help this is my first high rpm build. Can I use the stock rockers or should I get another set of champion rockers.
 
Almost has to be the springs binding up like Jerry D. said. At max lift check to see if the end of a large paper clip will fit between the springs. Kinda of a cheesy way of checking but it works. If it does go in then check if the retainer is hitting the stem or something along those lines.
 
OK I will try this tomorrow with the stock rockers if the paper clip doesn't fit and its binding do I need stronger springs?
 
With a Mamba cam and 26lbs springs there should not be coil bind...
The stock rockers will work but I wouldn't push it very hard at all...

Are the valves floating at higher rpms? This would be more of a valve issue though...
I could never run the 26lbs springs with the Champion rockers they would float at 6700-7000rpm every time...

Are you running lash caps? How is the tip of the rocker riding on the valve/lash cap?
 
Ive searched this forum and omb and cant find a thread where anyone is getting coil bind with the mamba cam and 26 pound springs. I have gotten valve float a few times and had it pinned down hill with the clutch slipping. Could I have spun it more than the rockers can handle? I don't have any lash caps and the tip is on the valve stem thanks for the responses
 
How much clearance do you have between the rocker arm and your retainer?
Floating valves can cause issues... But it would have to be some severe floating for a good amount of time and abuse... I would think...

Still can't see them breaking...though...I could see the stud breaking before a rocker arm... The push rods aren't going to bend because you got 1/4" rods... Did you measure them ? Also when checking you rocker tip on the valve tip is it sitting mostly centre of the valve tip? Why aren't ya running lash caps?
 
I don't know the clearance between the rocker arm and retainer but there are no marks on the retainer. The push rods are 5.07 in long, the rockers tip was on the center of the valve stem. The rocker arms did not break just the shaft that they move on and the cast part on the bottom of the rocker set up. I am not running lash caps because I have a rtc 8 head with 5 mm valves . The valves do stick out a good bit out of the keepers.This head never had lash caps I have read it does not need them ?
 
Yes that makes sense, you dont use lash caps with the stock rtc-8 valves and retainers. They are hardened valves anyways and don't need lash caps. Must have been a weak batch of parts if you broke the shaft the rocker mounts on, and not the rocker itself
 
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