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Discussion Starter · #1 ·
The main thing I can't wrap my head around is why some valves so much longer than others between valve checks and what stops the other manufacturers from following suit. For instance... yamaha has 26,000 mile valve checks on many of their bikes (I don't have all the data, hunting down service intervals is a pain) while many other bikes recommend half that or less. Are yamahas valve trains made of unobtanium? or do the other manufacturers just have much more conservative service interval estimations?
what about some of the hotter supermotos that require valve checks every oil change (1000 miles)? and dirt bikes that need them every few hours, are theirs made of butter? - Note, yamahas dirt bikes are typically known for having the most solid valve trains so they must be unobtanium too.
 

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A guy on a scruffy bike
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The main thing I can't wrap my head around is why some valves so much longer than others between valve checks and what stops the other manufacturers from following suit. For instance... yamaha has 26,000 mile valve checks on many of their bikes (I don't have all the data, hunting down service intervals is a pain) while many other bikes recommend half that or less. Are yamahas valve trains made of unobtanium? or do the other manufacturers just have much more conservative service interval estimations?
what about some of the hotter supermotos that require valve checks every oil change (1000 miles)? and dirt bikes that need them every few hours, are theirs made of butter? - Note, yamahas dirt bikes are typically known for having the most solid valve trains so they must be unobtanium too.
It's a design choice, a compromise like most things. The finer you tune something, the closer the tolerances, the more it needs to be looked after. Yamaha simply designs theirs with more of an emphasis on ease of maintenance than on fineness of tune.

At one end of the spectrum, you have something like Ducati's desmo system, that runs tolerances ten times tighter than normal, and thus requires a check interval between 5K and 7.5K depending on year and model (some of the newer models are 15K now, due to customer demand). At the other end, most Harleys have hydraulic lifters in the pushrods, and *never* need to be checked or adjusted.

Dirtbikes are a whole 'nother thing. I don't know why they are so maintenance intensive; I haven't had much experience with those.

This all pre-supposes modern technology; older machines need more maintenance simply because they are more primitive. My 1960 Heinkel scooter isn't a highly tuned engine, but it needs the valves to be checked and adjusted every 1000 miles. Fortunately, that's literally a less than 10-minute job.

PhilB
 
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Discussion Starter · #3 ·
But if the yamahas aren't giving up a noticeable amount of power for the looser tolerances, what is the downside? (ignoring the 09 and later R1s with ecu imposed throttle stops).
 

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IMO, manufacture intervals are a suggestion at best. My old monster never needed a valve adjustment (just timing belt adjustments) and it was supposed to be done every 6k or so. It had 9k on it when I sold it. My R6 started making valve noise at about 8,000 miles. I believe valves are supposed to be checked at 26k on that bike. I don't know if Buells have hydraulic lifters or not, but I just had valves put in mine last year.

It seems to me that checking valves in a street bike is rare at best. I just listen for a tick and then I adjust them. On streetbikes; super rare.
 

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I might add that one should not complain about the cost of a valve shim job on a modern sport-bike. A lot of stuff has to be removed just to get at the valves and checking clearances and calculating shim thicknesses required is time-consuming. Also everything must be carefully torqued in sequence and care taken that seals, dowels, gaskets, cams etc are properly placed. I did my Triumph STR myself and it took 3 days being extra careful and taking my time as it was my first time doing this job. I can do it again in half the time but it is still a 12 hr job, so don't complain if a dealer charges $600-$800.
 

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But if the yamahas aren't giving up a noticeable amount of power for the looser tolerances, what is the downside? (ignoring the 09 and later R1s with ecu imposed throttle stops).
If they aren't, then it sounds like maybe they are making better choices in their design.

OTOH, I haven't seen them having a lot of success in racing stock-based bikes recently, so maybe their design doesn't hurt anything on the street but has limitations in racing; it's not uncommon for sportbike design to be skewed to homologate something for racing even if it doesn't make the street version any better or faster -- maybe the other manufacturers are doing that with their valve designs.

OTOOH, not all that many bikes even ever get to 26K, and the average sportbike owner doesn't keep his bike that long, so maybe the others are figuring that the difference between a 26K valve check interval, and whatever intervals they have, doesn't matter in real life to much of anyone.

PhilB
 

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The last bike that I needed to actually check that valves at interval was a 1996 ZX-9R

...since then nothing I've owned has needed shimming at below 24,000.

The Speed Triple was at 65,000 miles when I finally had to shim something. I bought it and "the valves were close, but in tolerance" it took it probably another 40,000 miles and a couple years to get it out. It also inherited a few new parts in that time.
 

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It is also true that manufacturers are aware of and supportive of their dealers, and that valve adjustment intervals are rarely purchase decision points. It does them absolutely no harm to spec them at extremely conservative intervals to help generate dealer maintenance revenue.

KeS
 

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my R6 has been nothing but bullet proof and I've rode it as hard as I could for years.
I did the valves last winter with 40k on the clock.
3 of them were on the tight side just under the min.
 

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If you talk to most mechanics, by nature suzuki and Kawasakis valves tend to move more than Honda and Yamaha, quality in material and engine design?

But its been this way for as long as I can remember.

Street bikes( atleast ones that turn Rpm), tend to wear more on the exhaust side, dirt bikes tend to wear more on the intake side, this can be via more dirt injestion.

But once a valve has needed shimming about 3 times, that valve is pretty much toast.
 

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Keep in mind also that the check intervals are just check intervals, meaning that's how often you should check them but not necessarily how often they need adjustment.

Just like tire pressure, valves should be checked more often than they need to actually be adjusted.
 
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