Mr flint and others have a look at this guy's clip, my advice; spend the time to block any openings with pieces of cloth stuck into them before removing any buckets.
https://www.youtube.com/watch?v=sL-siybQWco
Nothing to be scared off but learning from someone else's mistakes is the best way
As for which way the clearance shifts, it seems that over time the manufacturers have balanced valve seating and camlobe wear so they balance each other out by selecting hardness etc. just a wild guess...all we do is a fine adjustment check.
There are engines without shims but different size buckets and they are good for the life of the engine according to the manufacturer.
Here is a quote from the toyota yaris forum;
" I have had motorcycles for 15 years that use the same adjustment set up as on the ECHO and Yaris. Once set properly they tend to last a long time. My 92 ST1100 had 109k on it and was never adjusted. On the other hand, a 2001 BMW I bought new had ZERO clearance on both exhaust valves from the factory. Lucky for me I checked it at 600 miles.
Almost no cars use this system. Frankly I would not trust a Toyota mechanic to do an adjustment. The good news is a CHECK is easy, well within a home mechanics capacity. More good news....very few ECHOs or Yaris's have ever had their valves checked much less adjusted. The origional setting last perhaps the life of the car.
Bad news.
An adjustment is difficult and rarely done by mechanices at Toyota. Also, as the valves wear they receed into the head causing the clearance of the exhust valves to lessn over time. You wind up with tight exhaust valves which burn and cause a valve job.
Good news. You seldom if ever hear of this problem (valve job) I never have.
Recommendation.
Check your adjustment yourself at 60,000 miles. I wtote a proceedure at Edumunds at the ECHO forum. Theres like 6000 posts in it now."
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