What are the symptoms of a bad valve adjustment?

Once your valves start to lose their proper clearance, they’ll be easy to notice. This rough idling is caused by the valve opening late, choking off fuel. Stalling after a cold start is common. In other cases, you may hear a loud rattling noise as the valve knocks against the side of the shaft.

How do I know if my scooter needs a valve adjustment?

The symptoms of engine-valves that are too tight, are as follows:

Bad fuel economy.
Difficult to start.
Stalling idle.

What happens when valves are out of adjustment?

Too much or too little valve clearance can result in poor performance or a rough idle because the engine can’t “breathe” normally and operate at peak efficiency. Too much clearance means the valves will likely clatter and, over the long term, cause damage to the valves, camshaft lobes or rocker arms.

How do you know if you need a valve job?

A valve job is simply a re-cutting or “re-facing” of the valve seats, and sometimes the valves. Valve jobs are necessary when the seats are worn to the point that there is no longer a proper seal between the seat and the valve. By re-facing the seats and/or valves, the proper seal is re-established.

Can valve adjustment affect idle?

Unless they’re adjusted so wrong and are to tight, the valve adjustment won’t affect the idling. That will keep them from closing all the way. Either you have a vacuum leak from an unhooked hose or your valves were not adjusted correctly.

Will valves out of adjustment cause smoke?

NO. Oil can get into the combustion chamber two ways: Past the rings or the valve stem seals. If the smoke is visible during acceleration it is getting past the rings.

Does valve adjustment affect compression?

Yes, valve lash can affect compression results. Too tight = valve potentially open all the time. However over time it is VERY unlikely that lash would become too tight.

How do you know when to replace valves?

If you’re tearing down a race engine, therefore, some clues to look for that would indicate it’s time to replace the valves would be loss of valve lash (due to valve stretch), unusual or uneven seat wear, scuffing on the valve stems, or wear or chatter marks in the keeper grooves.

How do you diagnose a bad valve?

Here are some symptoms of a bad valve seal that may need to be replaced:

Performing the Cold Engine Test. One sure-fire way to tell if you have a faulty valve seal is to perform a cold engine test.
Idling.
High Levels of Oil Consumption.
High Levels of Smoke.
Engine Braking Test.
Acceleration Power is Compromised.

What should the valve clearance be on a 150cc scooter?

For most 150cc GY6 engines the clearance should be around .004″, but check your manual. For 50cc engines I’ve seen .002″ recommended.

How many valves does a single cylinder scooter have?

On single cylinder engines there are two valves (one exhaust, one inlet). Then follow the instructions in your manual if you’re lucky enough to have one that gives them. If not then you can try this. Put the scooter on the center stand and/or a jack so that the back wheel is off the floor.

What happens if the valve is too big on a scooter?

If it is too large, the valve won’t open all the way (and you’ll get a loud “clattering” noise) and if it is too small (or non-existent), the valve may not properly close. Either way is a problem. You either won’t get fuel/air into the cylinder properly or you won’t get good compression and/or exhaust and the valve may overheat and suffer damage.