proper compress testing (Honda Express)

Matthew Scholtens /

I have searched this forum for some answers on proper compression testing techniques but I have found some inconsistencies or not enough information.

Would some please tell me if the following steps are the correct way to complete an accurate compression test on my NA50 Honda Express?

1. Have the throttle wide open with the choke off.

2. Complete test on a cool (or hot) engine (or it doesn't matter?)

3. Do I have to turn over the engine several times until the compression gauge reaches it's highest value or just turn it over once and use that value?

4. After turning the engine over, leave the gauge on for a few minutes to make sure that the pressure does not continue to drop over time. The compression gauge I am using does not "lock in" on one value, but will decrease if I start to remove it from the spark plug hole.

Please let me know if these statements are true or false or set me on the right path. Thank you for your knowledge and expertise.


Re: proper compression testing (Honda Express)

Matthew Scholtens /

I'm an idiot. I meant to put compression test in the subject line. Those 2-cycle fumes must be getting to my head!


Re: proper compress testing (Honda Express)

Jonas Quimby /

That's more or less it. A hot engine will likely read a little higher then a cold engine due to metal expanding and sealing better.

You kick the bike over a few times to get the highest reading.

Once you've done this the gauge will slowly drop by nature of the imperfect seal of an engine, but it shouldnt hit zero any time soon.

125 PSI or so indicates a rather worn Express. 165-ish indicates an engine with very very little wear. 140 is pretty normal.

The lower you are, the more power is being wasted. On such a small engine, this is important.

Re: proper compress testing (Honda Express)

Matthew Scholtens /

So a test result of 128-130 PSI is on the border of rather worn. I did notice some grooves in the cylinder wall when I was cleaning stuff a while ago. I guess the question because, is it worth honing (sp?) and getting a new set of rings or pick up a big bore kit? Which would you recommend and if you recommend the kit, where is a good place to get them from?


Matthew "lost in compression space" Scholtens

Re: proper compress testing (Honda Express)

Jonas Quimby /

An Express engine with no real scoring of the piston wall or cylender can show a bit of a boost from the lightest of hones and new rings.

If your bike is really high miles or badly scored though, this way probably isnt for you.

There are a few kits for the Express, but I've never used any of them.

Things to remember about them though is that you WILL need more oil then the oil injector provides, and you will very likely need to re-jet your carb. Most Express carbs dont have swappable jets, so this may be difficult.

The direction I'm going is a somewhat modified Urban Express engine bolted up to an Express frame. Do a search on this forum for my username or urban express or some such thing and you should find all my posts on the topic.

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account