Compression test with only only a kickstarter? 74 KZ400D.

I have been getting large amounts of what I assume to be blow by lately (white smoke coming from crank case vent tube and exhaust. Also I can't get my idle down once I start riding. ) I am trying to do a compression test but I only have a kick starter.

if it is in fact blow by, could that have anything to do with my wonky ass idle? It just stays at whatever RPM I'm at when I clutch in. It sounds like a stuck throttle cable but when I look in my carbs, the slides are down. I'm at a loss. Any help is appreciated.

Also, I am completely new to bikes. My whole life has been cars so this is all new to me.

You can do a compression test with the kick starter. No doubt your leg will be tired, but just keep kicking it over until the number no longer increases. The highest number you reach is your compression reading.

Also, if you have wildly different compression readings between cylinders, it would be very hard or impossible to get your carbs synced and working properly, since you essentially have two cylinders fighting each other. Smoke is a good indicator that you have probably got at least one of the cylinders in a condition of being past the allowed clearance OR stuck piston rings, thus the engine is consuming oil via combustion. Sounds like the first order of business is to determine what's going on INSIDE the engine.

Be sure to bring the engine up to full operating temperature before doing the compression test, and remove all spark plugs during the test. Ed

Compression test abc's

1. Run the bike to running temperature, if you can't the compression test will be inconclusive but still worth doing
2. Kill switch and ignition off, no key in ignition
3. Remove all the plugs
4. Insert compression test into #1
5. Open throttle wide open
6. Kick it, kick, kick it until the compression stops climbing (5-25 kicks)
7. Record your compression
8. Repeat for other cylinders

If the test is done with a warm engine the psi for each cylinder should be 100 or more. 130-140 is somewhat common for a stock old bike that has not seen the road or a ton of engine wrenching.

If you get a read below 100 you have a leak. Next step is to run a wet compression test. Add a cap full of engine oil down the spark plug hole of the cylinder in question and repeat the compression test. If the psi goes up it means your rings are worn or locked up, because the oil is filling in the gap that causes the leak. If the number stays the same then your piston/rings are most likely fine and your issue is valve related. Proceed to check your valve clearances and inspect for worn valves that are not closing correctly.

Sometimes when bringing an old bike back to life rings and valves can free up just by running the bike and heating up the parts. Make sure the oil is new and don't let the engine overheat. Point a fan to the front of the engine block, run the engine between 1000-2000 rpm at a steady idle.

Repeat the compression test again and compare your notes. No change means you will have to get in there and make sone changes.

Don't worry too much about smoke, sometimes rings/valves need a hot engine to seat after a long time. Reference a service manual and make sure all the head bolts are torqued correctly.

...just my 79 cents

Idle could be throttle cable is not closing or stuck. Or something choke related, like the choke valves on the carbs are not closing. Could be an air leak on carb boots from the air box, or clamps on the engine side.

Are you running the stock airbox?

And then there are my favorites; points and timing and carb syncing. These 3 in my opinion are the cause of most mysterious idle problems.

Damn that's a lot of responses all at once lol. Now if I roll the bike down a hill in gear with the spark plugs out and a compression tester hooked to each cylinder? And I'm not on the stock airbox. I'm running dual mikunis on it right now.

What, no air box!?!?!? :whistle:

LineArtist wrote: What, no air box!?!?!? :whistle:

air cleaners, no air box.