Would you adjust a valve clearance if it was 0.03 mm LOOSER than max spec?

[CanadaFZ6]

I am thinking I am not going to bother taking the cams out and all the hassle that goes with swapping the shim. Did the first valve check late, 47,000km on the dash. (40k first check)

I have no tight valves (intake 0.13-0.20, ex 0.23-0.30), infact, I have a couple exhaust valves that are around 0.33 mm, 0.03mm looser than what Yamaha states as max spec. Tight valves are dangerous because they can get super hot and end up dropping and destroying a motor blah blah. But what about a tiny bit loose, besides that they are tickier when loose?

What do you say? Adjust down to within spec or not?

This is not my first valve check on a bike, I think I have a decent feel for the drag, and not forcing the feeler to the point it compresses the spring a tiny amount giving a false reading or anything. The only thing I can think of is that they were set a tiny bit on a loose side from the factory, and haven't moved at all since....

 

[Gary in NJ]

Yes, better too be loose than tight. The loose ones will tighten up over time. Also, the clearance gets tighter as the engine comes up to operating temperate. Follow-up and check again in another 10,000 km.

 

[CanadaFZ6]

Yes, better too be loose than tight. The loose ones will tighten up over time. Also, the clearance gets tighter as the engine comes up to operating temperate. Follow-up and check again in another 10,000 km.

Yeah, good point. Thanks. I know the exhaust get even hotter hence they always have a larger spec.

I wish these motors were a little quieter but they have quite an orchestra to them of valve and cam chain noise. I almost went ahead and replaced the cam chain just to see, but decided not to. Tensioner was just replaced too.

 

[Gary in NJ]

The fuel injector servos make quite a racket too. Mechanical music.

 

[TownsendsFJR1300]

I had two exhaust valves .001" too tight on my last check.

I also debated adjusting or just leaving it alone. As I already had a shim kit and was ALREADY
in there, I adjusted it... Good for another 26,600 miles...

As noted, your looser one won't hurt anything, just perhaps a tad noisier.

 

[bigborer]

Loose is better than tight (up to a point) on engines that don't really rev that much. There is a risk of having the valves bounce around and wreak havoc, and the more rpm the higher the risk. At the very least, there will be accelerated wear as the cam lobes will smash into the valve buckets instead of gliding right over them as they would if there was proper clearance - the extra noise with loose valves comes from this hammering action.

I've just done the timing on one of the cars and measured the valve clearance as I was there. A few were 0.01 to 0.02mm over the specified limit. I left them like that, that car has max power at 6k rpm, max torque at 4k rpm, and the limit was at 0.37mm so that was only 2.5-5% looser over the limit.

However, I'd never have piece of mind leaving the valves 0.03mm (10% over the limit!) too loose on a 600cc engine with max power at ~12k rpm and 14k max rpm.