How To Perform A Leak Down Test On Your 97-01 Honda CR250
The Tools You Will Need
- 48mm Expansion Plug
- Philips Screwdriver
- Leak Down Tester
- Spray Bottle With Soapy Water
- (Master Tools & Parts List Below)
The leak-down test is a critical step in your CR250 rebuild because it’s an easy way to check your work. If you have a bad seal or something isn’t torqued correctly, this will tell you.
Setting Up Your CR250 For Leak Down Testing
- Install your expansion plug tightly in the exhaust port.
- Attach your leak-down tester to the carburetor boot, and make sure the clamp is tight.
- Slowly pressurize your engine.
- You DO NOT want to go over 10psi, or you risk blowing a seal.
- You want your gauge to sit at 5-6 psi.
- If the pressure drops less than one psi in 5 minutes, you are good to go.
- If your pressure drops immediately, or more than one psi in 5 minutes, it’s time to go hunting.
Hunting For Gasket And Seal Leaks During The Leak Down Test
- Place a towel over your crankcase to protect the crankcase interior from overspray. The right crank seal is the last thing to test if you can’t find the leak anywhere else.
- Pressurize your engine and spray the whole engine with soapy water.
- Spray the leak down tester itself and then the exhaust plug too, just to be safe.
- If there is any leak, you will easily spot the bubbles.
- On this engine, the right front base gasket and exhaust valve stopper bolt are leaking.
Fixing Gasket And Seal Leaks
The exhaust valve stopper bolt does not have a gasket or o-ring, so I wrapped the threads in Teflon tape and re-torqued, which did the trick.
The base gasket and mating surfaces where in good shape, so all I had to do was loosen the bolts and gradually re-torque, which evened out the pressure and fixed the leak.
After you fix any leaks, repeat the leak down test, and if everything looks good, we can move on to the break-in process.
Top End Rebuild Tools List: (Links to Amazon)
- Piston Pin Puller
- Piston Holder
- Machinists Straight Edge
- Feeler Gauges
- Telescoping Bore Gauges
- Digital Calipers
- Plastic Scraper
- Spark Plug Thread Follower
- Motion Pro Torque Wrench Adapter
- Molybdenum Grease
- Lithium Grease
Top End Rebuild Parts List: (Links to Amazon)
Keep Your ’97-’01 CR250 Running Right!
- Service Specification
- Clutch Replacement
- Carburetor Service
- Engine Top End
- Engine Bottom End
- Front Suspension
- Rear Suspension
- Wheels & Tires
- Kickstarter Inspection
- External Shift Linkage