7

One thing I noticed while trying measure cam lobe to lifter clearances on a 98 Mazda 626 GF 2L, was that when I rotate the crankshaft there seems to be one spot where I have to put in a lot more effort to turn it than in the rest of the revolution. Like it was really sticking at one particular spot.

Is that indicative of anything?

EDIT

It felt a little stiff when valves I1+E3 were about to open, when I4+E2 were about to open and really stiff when I3+E4 were about to open.

If I got a good momentum going while turning the crankshaft I didn't feel it so much.

Also measured cam to lifter clearances. Spec is 0.23mm to 0.30mm

+---------+-----+-----+-----+-----+
| Cyl #   |  1  |  2  |  3  |  4  |
+---------+-----+-----+-----+-----+
| Intake  | .24 | .29 | .24 | .24 |
+---------+-----+-----+-----+-----+
| Exhaust | .29 | .24 | .29 | .24 |
+---------+-----+-----+-----+-----+

Not sure what to make of it, maybe some of the spring are just a little stiffer than others?

Zaid
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Robert S. Barnes
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1 Answers1

4

When rotating a 2 or 4 stroke motor there is an illusion of sticking between TDC and BDC. The rings are reaching their maximum friction coefficient at that time do to maximum distance traveled within the bore.

So, it may seem as thought there is a sticking issue, in actuality it is an innate feature of a two or four stroke ICE.

DucatiKiller
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