1997-2001 Honda CR250 – Top End Rebuild – Part 14: Leak Down Test

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How To Perform A Leak Down Test On Your 97-01 Honda CR250

1997 - 2001 Honda CR250 - Top End Service - Part 14 - Leak Down Test - FeaturedThe Tools You Will Need

  • 48mm Expansion Plug
  • Philips Screwdriver
  • Leak Down Tester
  • Spray Bottle With Soapy Water

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.

Ooh hey, look at these torque specs!

Setting Up Your CR250 For Leak Down Testing

  1. Install your expansion plug tightly in the exhaust port.
  2. Attach your leak down tester to the carburetor boot, and make sure the clamp is tight.
  3. Slowly pressurize your engine.
  4. You DO NOT want to go over 10psi, or you risk blowing a seal.
  5. You want your gauge to sit at 5-6 psi.
  6. If the pressure drops less than one psi in 5 minutes, you are good to go.
  7. If your pressure drops immediately, or more than one psi in 5 minutes, it’s time to go hunting.
Install your expansion plug tightly in the exhaust port.
Install your expansion plug tightly in the exhaust port.
You want your gauge to sit at 5-6 psi.
You want your gauge to sit at 5-6 psi.

Hunting For Gasket And Seal Leaks During The Leak Down Test

  1. 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.
  2. Pressurize your engine and spray the whole engine with soapy water.
  3. Spray the leak down tester itself and then the exhaust plug too, just to be safe.
  4. If there is any leak, you will easily spot the bubbles.
  5. On this engine, the right front base gasket and exhaust valve stopper bolt are leaking.
If there is any leak, you will easily spot the bubbles.
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.
On this engine, the right front base gasket and exhaust valve stopper bolt are leaking.

Related: How does the reed valve work on your dirt bike?

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.

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 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.
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.

Top End Rebuild - Leak Down Test - Re-Torque Cylinder Nuts← Part 13: Cylinder Head Installation

Part 15: Engine Break-In →

 

Keep Your ’97-’01 CR250 Running Right!

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