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Which is better, shims or screw and locknut valve adjustment?

brb

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I remember doing that in the 80s on some of the new Honda scooters. Talk about easy it took longer to remove the plastic covers than to adjust the valves. When the Motocross guys who were used to 2 strokes starting getting 4 strokes with the valve adj. process and saw that external adjustment on those scooters they were pissed at Honda big time. Then again Honda had those 4 strokes singles XR/XL 650 that had 2 rocker arms per valve from the 4V"Radial" head design that had a 5th valve for decompression system at the same time. Leave it to Honda to make a scooter system so easy and a dirt bike so complex. At least with the NC bikes the Auto & Moto engineers worked together.
 

MZ5

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Yes, but Honda cars with screw and locknut valve trains don’t burn valves.

Yes, they do. You just don't have enough experience with them. It's not _common_ at all, but the V6s burn valves sometimes.
 
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MZ5

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With all this development done by many MFGs there is still not a "Keep It Simple Stupid" design that would decrease costs, lighten up valve train weight, lower time and money for maintenance.

Maybe the controlling principle is: Choose any two?
(-;
 

MZ5

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I agree that the adjustment method itself should not necessarily determine check intervals. Now that my NC is well broken in, I’m going to stretch the valve check to 24,000 miles, then based on that, maybe out to 32,000 miles. Has anyone on the forum extended their NC valve checks to run out longer than the maintenance schedule says? 8,000 or 16,000 mile intervals just seem a little silly.

My last valve lash check interval on my '12 was ~15,000 miles. The one before that I went 20,000 miles between checks. The first 2 times I checked on Honda's scheduled interval. At no time has any valve been more than 1/1000 of an inch different from the previous check.

I've adjusted at least one of the valves every time I've opened it, just to put it in the middle of the spec, but I wouldn't have done that if this bike was a shim-under-bucket design. ***EDIT: Most of my fiddling with lash adjustment is due to the fact that tightening the locknuts causes the lash or clearance to change.

Also, it's been more common for the valve lash change to be toward tight than toward loose on my bike, particularly on the exhaust valves.

Based on this, I don't see any reason for me to check the valves more often than every ...25k miles or so? Even that seems likely to be just an exercise.

YMMV
 
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Re: hydraulic lifters, here's an interesting case study/anecdote

Hyundai switched from hydraulic to solid lifters on their beta engine around 2003. The reasons they cited:
-cheaper production costs
-lighter valve train mass

It's an interesting engineering tradeoff, keeping in mind bangernomics and human neglect of maintenance. Hydraulic lifters should be perfect for decades, assuming regular oil changes. Solid lifters are usually due for a check at least every 60-130k miles on a car...

However if it takes 10+ years to accrue that mileage, who is dropping that kind of coin on doing major maintenance (130k mi valve check) on an old Elantra? Probably nobody. But now we have the benefit of hindsight, we know that people arent even bothering with regular oil changes on their old Elantras. So actually, all the pre -03 hydraulic lifter cars missed oil changes, got noisy, rattled for a while, imploded, and got scrapped. Whilst the solid lifter cars are still struggling along even without proper oil changes, because they don't need any oil pressure to keep their valves adjusted properly. So even though the solid lifters aren't perfectly adjusted, they are at least ok enough to keep running, and won't catastrophically fail.
 
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Oldbear

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Interestingly no one mentioned hydraulic tappets as an alternative to valve calibration. Most American car engines from the 60's had them and they never required adjustment. Motorcycles were not as quick to jump in that wagon, apparently due issues at high RPMs, at least that was the standard reply. Yet, I had a Nighthawk 750 in 91-93 with a 10,000 RPM redline and hydraulic lifters. I rode it for ~50,000 miles and never had a problem.

So, why they were not more popular? No sure but probably cost and revenues had something to do with it. Certainly the slow NC engine would be perfect for them.

Most DIY bike owners are ok with changing oil/filters, adjusting chains, changing brake pads and other small maintenance chores. But opening up the engine head to adjust valve clearance is not one of them. I suspect many shops would lose a good chunk in revenues if not valve adjustment was in the cards.
Fully agree. Like ‘em or not HD has ran hydraulic lifters for long time-basically makes maintenance and “change the oil and filter” thing. To me the best thing would be hydraulic lifters and shaft drive. Motorcycle maintenance becomes basically a non issue. I completely fail to see why most bikes wouldn’t be better served by this combination. Car manufacturers have done this for decades, why dont at least some bike manufacturers do the same, at least on lower revving engines. ( yeah I know hydraullic lifters wouldn’t be great on high rev engines, but an NC, almost all V twin cruisers, etc. would be great.)
 

brb

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Hydraulic lifters,fulcrums,rockers do fail and cost more to manufacture than screw adj. Honda chooses the safe and easy for this cost cutting bike. Maybe they knew a lot of the buyers were going to be old Honda riders that enjoy working on there bikes?
 

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Hydraulic lifters,fulcrums,rockers do fail and cost more to manufacture than screw adj. Honda chooses the safe and easy for this cost cutting bike. Maybe they knew a lot of the buyers were going to be old Honda riders that enjoy working on there bikes?
Guess I’m getting old, but the “charm” of having to fettle with a bike has disappeared for me. Too many years with old Brit bikes I guess. (One has not truly lived until one has lived with a late 60’s BSA or Norton as dailytransportation). Valve adjustments every 3 k miles and tube tires are THE reason I don’t have an RE Interceptor sitting in the garage today. Love the look-hate the maintenance. The NC’s “not bad” maintenance wise, but I miss shaft drive and 26k valve adjustments on my old Yamaha.
 

itsmenc700

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WHAT?
Here in the states I have in 42 plus years NOT had a car engine I had to adjust the valves on.
I thought all cars here were hydraulic valves, unless you had some exotic one or some high performance type engine.
Yes it does seem like the NC and other lower revving bikes could go the hydraulic valve way.
 

bigbird

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I thought all cars here were hydraulic valves, unless you had some exotic one or some high performance type engine.
Yes it does seem like the NC and other lower revving bikes could go the hydraulic valve way.
Not so much anymore.
All Subarus use shims (nothing mentioned in the owner's manual about inspection or adjustment) and Honda still uses screw and locknut on their SOHC engines.
I don't know about Nissan, and Mazda.
I believe Toyota uses hydraulics.
 
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brb

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Having been a Auto/Moto mechanic in my past I have seen hydraulics that would not hold adjustment indicating replacement needed soon with maybe a bent pushrod to go along with, to mechanical that keep running no matter the clearance. American vehicle owners were never big on maintaining the autos they drove, its more important how cheap and fast to get it back after it breaks down. While the Moto owners where a bit better at maintaining and wanting there "baby" perfect when they picked it up. Nowadays I do not go crazy maintaining any of my equipment but there is a certain bit of satisfaction when I work on the NC be it valve adj,chain, fluid checks, nut&bolt checks. I still remember learning about "torque stripe" after a motor mount fell out on the old 77 CB750F, been checking ever since. It has always been a therapy session for me to work on my bikes but when you start looking at paying someone or having to remove cams to adjust valve clearances you can not ignore it. They say you never see a motorcycle outside a Psychologist office and if you do its the psychologist ride. Got to go now the bike is in the garage for the winter break and I can do without the copay to the psychologist so off to the garage with a cup of coffee I go.
 

MZ5

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Not so much anymore.
All Subarus use shims (nothing mentioned in the owner's manual about inspection or adjustment) and Honda still uses screw and locknut on their SOHC engines.
I don't know about Nissan, and Mazda.
I believe Toyota uses hydraulics.

When did Subie ditch the HLAs (hydraulic lash adjusters) and go to shims? All my Subarus over the years have had HLAs, possibly excepting the BRAT, which we never checked or adjusted.

Mazda uses HLAs, and at least some Nissan engines do.
 

Rabbit

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Fully agree. Like ‘em or not HD has ran hydraulic lifters for long time-basically makes maintenance and “change the oil and filter” thing. To me the best thing would be hydraulic lifters and shaft drive. Motorcycle maintenance becomes basically a non issue. I completely fail to see why most bikes wouldn’t be better served by this combination. Car manufacturers have done this for decades, why dont at least some bike manufacturers do the same, at least on lower revving engines. ( yeah I know hydraullic lifters wouldn’t be great on high rev engines, but an NC, almost all V twin cruisers, etc. would be great.)
Nc750x new cost 9500$. New Harley cost 17000$ or so. Many bikes are built to a price point (more so than cars today). Adding those items would drive up the price and limit the audience.
 

Oldbear

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Nc750x new cost 9500$. New Harley cost 17000$ or so. Many bikes are built to a price point (more so than cars today). Adding those items would drive up the price and limit the audience.
True, but even the lowly Sportster has hydraulic lifters. Not a deal breaker by any means but you gotta wonder why. Oh well,at least we don’t have Amal carbs with “ticklers” anymore
 

670cc

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Nc750x new cost 9500$. New Harley cost 17000$ or so. Many bikes are built to a price point (more so than cars today). Adding those items would drive up the price and limit the audience.
Crazy. They cost $9500 now? Back in July, 2012, new, fresh stock NC700X manual models were selling for $6300 plus TTL at a couple Powerhouse dealers. I paid $6500 for mine in July, 2012, brand new, no freight or setup charge, a week from when the NC first became available in the USA.
 

bigbird

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When did Subie ditch the HLAs (hydraulic lash adjusters) and go to shims? All my Subarus over the years have had HLAs, possibly excepting the BRAT, which we never checked or adjusted.

Mazda uses HLAs, and at least some Nissan engines do.
My engine is the FB25 series, 2.5L DOHC.
It was introduced in 2011, so shim adjustment has been around over 10 years now.
 
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