Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Hello, and thank you for choosing Just Answer. My name is***** will be happy to assist you.
How long will your engine run, before your rocker arm breaks? Does it break off near the rocker arm stud?
Are you saying two or three times, or two or three days?
Thanks for your reply. Have you checked to see if your valve is sticking?
Keep in mind that if you are using the correct push rod, this means that our problem has to be valve related.
Let's go back. How many rocker arms have you replace already?
Are they OEM rocker arms?
Are you having this problem on your intake side or your exhaust side? These are troubleshooting questions.
Are you using a stock cam gear in your engine?
Have this problem existed since you first started racing this engine?
Can you give me a minute, to pull up your engine?
Looking over your engine, here are some things I would like for you to check.
First check your flywheel key. Pre-detonation could cause our problem. Keep in mind that ignition timing is very critical, when you are racing and revving your engine at high rpms.
The next thing to check, will be your valve springs.
When you are checking your valve springs, rotating your crankshaft until your piston is at Bottom Dead Center. Press each valve in, and feel the pressure on each spring.
Thanks for this information. Can I get you to check something for me?
I would like for you to remove your spark plug. Shine a flashlight into your spark plug. Take a look at the top of your piston. Check to see if you see any ping marks in the top of your piston.
Valve guides was going to be my next suggestion for you to check. You and I have basically covered everything else.
First, remove your valve cover, and shine a flashlight in between your valve springs, to check for obvious movement.
Check to see if your intake valve guide protrudes higher that your exhaust valve guide ...
Before removing your springs, remove your spark plug, and rotate your flywheel, check to see if both rocker arms travel the same distance.
If your valve guides are at fault, I would consider replacing the head ...
If you measure the distance, after your rocker arms fully opens your valves, is the distance the same on both valves. Measure from the bottom of your cylinder head, to the top of your valve keeper.
Thank you for checking.
Are you saying your intake valve is longer than your exhaust valve??
No problem. I would like to make a suggestion to you ...
Ok. You stated that your ignition timing is good, so we can eliminate pre-detonation as a possible cause. This leads me to say, that you and I can reasonably suspect, that our problem is very likely caused by a problem within your cylinder head. I suggest that you remove your cylinder head, and give it a really close inspection.
I will agree, because I strongly believe that another cylinder head will resolve our problem.
You are very welcome! Find a good used one, and carry it to your local machine shop, to get it rebuilt.
My suggestions are based upon the fact that your engine ran great for the first 5 or 6 races. Since then, something have worn, or moved within your existing head.
Check eBay for a cylinder head, if you do not find one locally. You may save yourself some money ...
You are welcome!
I hope you also have a good night. I do hope all goes well for you.