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Question: How do valves tighten over time?


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I understand how cam lobe wear and shim wear can combine to make an intake valve go loose over time.

But how can an exhaust valve get tighter over time given the wear factor.

Motor heads please explain!!

1968 Triumph Bonneville 650
1971 Norton Commando Roadster
2002 Harley 1200 Sportster
2003 Honda ST 1300
2016 FJ 09
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Yamaha must use fantastic materials in their valves and valve seats.  A 26k mile interval?  Wow.

I've had Kawasakis and Suzukis that had 4k intervals, and you'd better not wait much longer...

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Ignore that 26k miles interval.  Wait that long and you will have zero exhaust valve clearance and may have already burned a valve.

Adjust at 16k miles, maybe earlier, definitely not later. 

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I agree, and recently checked/adjusted mine at 12k.  However, I think it is Ok for a valve to get down to minimal clearance.  As you say, that is what you will find at 26k.  Many riders go way past 26k without trouble.  Yamaha knows this.  Otherwise, they would call for the 16k interval, no?

Anyways, all of my valves were fine at 12k, except the two exhausts on cylinder #3.  Those were down to around .25mm with spec being minimum of .28.  The other two cylinders were right around .30 with max being .32.  I went the extra effort to replace those two shims to make #3 exhausts be .30.  But really, would it matter?  I seriously doubt it.

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I wouldn't minimize this problem.  For the future of anyone who reads this there have been far too many blown exhaust valves here, FZ-09 forum, and on YouTube if the valves aren't looked at till 26500 miles.  You are then looking at an over $1000 bill.

I stand by my 16000 mile inspection.

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I'll say 16,000 is a good check.  Checked mine at 18,000 and the exhaust valves were all out of spec.  I put the miles on the bike in a year!  80 percent of the miles were highway miles and long distance miles with not a lot of high rpms and not that many cold starts.  Many 400+ mile days where I would ride from gas stop to gas stop.  Pretty easy miles in my opinion.  

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14 hours ago, enx said:

Valves on my tracer 900 was first inspected on 60.000km. They were all in spec.

What kind of interval is 60k k.?? That's 37200 some miles. That's way too long. Did they change it?

Did you do the work?

Do you trust who did it?

VERY unusual that all are fine.

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4 hours ago, peteinpa said:

What kind of interval is 60k k.?? That's 37200 some miles. That's way too long. Did they change it?

Did you do the work?

Do you trust who did it?

VERY unusual that all are fine.

Plenty of records of MANY bikes doing more than 60K km without the valve clearance moving beyond spec?
Not saying i'd advice anyone with a tracer to wait that long, but not even close to being unheard of on many other bikes, probably stating the obvious, but worth mentioning i feel like...
I had my old VFR 800 checked at 28.000 kilometers and it was dead on spec :)
Letting a bike warm up (correctly) and treating it with a degree of mechanical sympathy obviously goes a long way. But obviously people also value different things in a bike, and not everyone wants to "baby" it around most of the time.

Case and point the above youtuber, the way he changes gears when he tries to "get at it" to follow his friend onto the highway is EVERY reason i'd never let anyone but my dad ride my bike lol. I would not be shocked if he just guns it while its cold also... Mega cringe (in my opinion) 

Edited by Sunde
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5 hours ago, peteinpa said:

What kind of interval is 60k k.?? That's 37200 some miles. That's way too long. Did they change it?

Did you do the work?

Do you trust who did it?

VERY unusual that all are fine.

My trustworthy mechanic said that is no need to check them until 80.000km. He checked a few cp3 engines at 40.000km and none of them needed adjustment.

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I'm strictly talking the CP3 engine only.

I owned 2 Hondas previously that I checked but never adjusted for 85k miles on one and 65k miles the other. Barely moved .005-.001 inch. the entire time.

Did I expect the same from Yamaha?  Yes.  Didn't pan out.

Are the early years of the CP3 somehow down in quality or factory set-up?  IDK. The initial results haven't been optimistic.

Once you break in the engine, it's supposed to be capable of hard running till 26500 miles per the maint. schedule.

A lot of bikes in the past had a 600 mile valve check.  Public Didn't like that.

Now we have a 26500 mile first check, public is happy, buys it, and it's conveniently out of warranty when the valve burns.

 

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