HH 120 COMPRESSION

Someone please tell me what the compression reading should be on a tec HH120 engine. Thanks

I don't know if you're going to get a number to look for as far as compression is concerned.

A good judge of the internal condition of the engine is to do a leak-down test.

There are home-built testers shown on the web that you can make. They work well.

Here are some links to homemade compression testers:

http://www.motorcycleproject.com/motorcycle/text/leakdown.html

http://www.650motorcycles.com/LeakDownTester.html

Youtube:

https://youtu.be/7UcOn8OEt0Y

I've played around with the leak-down testers before. I made one years ago. Something I found hard to do was get two gauges that gave the same reading. I ended up finding two that were within a couple of lbs of each other and remembered the difference when calculating loss. What I did find very valuable was being able to hear where air was escaping from the engine.

Out the muffler = exhaust valve.
Out the carburetor = intake valve.
Out the oil breather or fill tube = piston rings.

A simple/cheap sparkplug hole COMPRESSION TESTER will show you if the engine has low compression. A LEAKDOWN TESTER is more valuable finding out why the engine has low compression.

One word of warning: The engine will rotate with the application of air pressure. Be sure to have a way to lock it. I see the tester from Harbor Freight tests uses a lower pressure. There are several negative comments about it on their site because of the low pressure.