Adjusting the valves DOES make a difference!

[M640]

So there I was like so many others, I had just cleaned and re-installed the stock carbs back on my bike. 1978 CB400a Hondamatic. All stock including air box. : )
I couldn't for the life of me get this thing to run good if at all. Kick after kick and also used the starter, and if it did start it ran badly and not for long. I adjusted the pilot screw and idle, checked and rechecked fuel, spark, etc and no bueno as far as starting and continuing to run.

Finally I took the advice that I had read and seen on yt so many times before and decided to look at other items on the bike. I started with valve clearance. I was convinced
that "the valves aren't going to matter that much" as I manipulated the feeler gauge, adjusted the screw and locked it all down. But I'm also open minded enuf to try. The next day I through on the tank, pulled the choke and gave the bike a kick. I was sure it wouldn't start......wrong. It started on the first kick and ran, pretty darn good. I left the choke on until I thought the bike was warm enuf to release the choke and wala, the bike still ran. I reved it a number of times and the bike still ran. In fact it ran so good that I took it out on the driveway, shifted it to 1 and rode across the driveway. By the way, the bike was still running. Holy Sh#$% and [email protected]#$, the valves do matter.

I had never paid much attention to valves. I'm owned at least 15 or so bikes in my life and never adjusted the valves on any of them. I somehow believed that they wouldn't matter that much and always dismissed that part of service. I'm here to tell you that today was living proof that the valves do in fact matter and I'm now a very big believer in making sure that I check them from now on.

[ancientdad]

Moved to Tips and Tricks section.

Glad things worked out well. Yes, these engines are sensitive to many things in order to perform at their peak.

[J-T]

It's sometimes surprising how the same symptoms can have a variety of causes. It usually pays to make sure everything is up to snuff.

[ancientdad]

It's sometimes surprising how the same symptoms can have a variety of causes. It usually pays to make sure everything is up to snuff.

Well said J-T, it's kinda like "90% of carb problems are electrical"... or is it the other way around??

[HerrDeacon]

I had never paid much attention to valves. I'm owned at least 15 or so bikes in my life and never adjusted the valves on any of them. I somehow believed that they wouldn't matter that much and always dismissed that part of service. I'm here to tell you that today was living proof that the valves do in fact matter and I'm now a very big believer in making sure that I check them from now on.

I've always been surprised at how many bike owners neglect valves, it was always something I've felt was vitally important and will check them on their recommended schedule. Or if its a 'new-to-me' bike, its one of the things I'll check as part of giving the bike a once-over. I wouldn't be able to rest not knowing if they were set correctly or not. At least on these old bikes its super easy to check and adjust them, my Africa Twin is a royal pain to check.

Glad you did it and the results speak for themselves. Well done!

[M640]

The difference in how well it ran was amazing. I'll never overlook valves again.

[mike in idaho]

Back in My shop days, when doing the 500 mile check up on a customer's new bike, it wasn't uncommon to find one or more tight valves that needed re-adjusted.

[Windmill John]

M640, When I read that line: “I'm owned at least 15 or so bikes in my life and never adjusted the valves on any of them.”

It was like watching a horror film!……

But, still, it’s good of you to admit it.

[ancientdad]

And of course they could have been bikes with shims, or like some of the Honda's 4 cylinders in the '80s, hydraulic "lifters" if that's the right terminology (never touched one myself). But otherwise... yeah, could end up a horror story.

[Windmill John]

It’s a good point. I checked the shims on my 650 two years ago. Inlets close to limit, but being shims, it’ll be a while yet before they’re out.
and, if he’s had 15 bikes with shims…..
Or a new bike that gets sold every two to three years….

[ballbearian]

Back in My shop days, when doing the 500 mile check up on a customer's new bike, it wasn't uncommon to find one or more tight valves that needed re-adjusted.

I'm sure some shops figured they could skate on thorough set ups, since valves are kind of "hidden" adjustments and tight is quiet, also if it gets ridden much it will get done at the check ups (and another retail opportunity to sell accessories, etc.)I saw this a bunch in the bicycle shops I worked.

[mike in idaho]

Skate? We never sent a new one out the door without a proper check of all the settings, valve lash included. They tend to tighten up as the first few hundred miles are run up. Tight valves equal hard starting and poor idling when hot, customers don't like that.

[ballbearian]

Skate? We never sent a new one out the door without a proper check of all the settings, valve lash included. They tend to tighten up as the first few hundred miles are run up. Tight valves equal hard starting and poor idling when hot, customers don't like that.

Yeah and they burn too, right? I said "some" shops, obviously not you or your shop, you got a conscience, or you wouldn't have brought it up. I was just talking philosophies, our shop had the best rep in town but still my boss would kind of half gripe that he wouldn't see my customers the rest of the season so he could sell them more goodies.

I've heard, "slappy valves are happy valves", is that kind of right? You got oodles more experience than me, like forever.

[ancientdad]

I've heard, "slappy valves are happy valves", is that kind of right? You got oodles more experience than me, like forever.

I've always disagreed with that term and philosophy, it might be fine for the short term but too loose does damage eventually.

The first Honda shop I worked at, where I did most of my new bike assembly prior to becoming a mechanic at the next stop, did not have us do pre-delivery checks on anything. He wanted the bikes on the showroom floor as soon as possible, they waited until their first service to get that done. Though I'm sure at least some came back with issues as a result, I never saw any of it the short time I was there.

[ballbearian]

I've always disagreed with that term and philosophy, it might be fine for the short term but too loose does damage eventually.

The first Honda shop I worked at, where I did most of my new bike assembly prior to becoming a mechanic at the next stop, did not have us do pre-delivery checks on anything. He wanted the bikes on the showroom floor as soon as possible, they waited until their first service to get that done. Though I'm sure at least some came back with issues as a result, I never saw any of it the short time I was there.

I remember you mentioning that the hammering effect from too loose valves could hasten the mushrooming effect on adjusters and valve stems. I suppose it's just a saying that helps me remember that they wear tighter as time goes, or that's what I was taught by an experienced friend mechanic.

[RockReef]

Is there a tips and tricks section on this site for actually how to use feeler gauges? I’m probably on the younger side here (early 30’s, no offense), and had no clue how to use them when I started wrenching 10-15 years ago. Self taught, out of poor necessity; I didn’t have anyone teaching me much about mechanical work when I grew up.

I taught myself with a lockable micrometer, so I could develop a “feel” for how it should feel. Because when I started the small increments really threw me.


Sent from my iPhone using Tapatalk

[teebo]

Is there a tips and tricks section on this site for actually how to use feeler gauges? I’m probably on the younger side here (early 30’s, no offense), and had no clue how to use them when I started wrenching 10-15 years ago. Self taught, out of poor necessity; I didn’t have anyone teaching me much about mechanical work when I grew up.

I taught myself with a lockable micrometer, so I could develop a “feel” for how it should feel. Because when I started the small increments really threw me.


Sent from my iPhone using Tapatalk

Samsies. Except I'm well past early 30's.

I did the same with a micrometer. I feel I'm a lot better now after that.

69 CB350K1/68 CB450K0

[Windmill John]

I always felt that dealers would definitely not check clearances on Transalps and Africa Twins. Great bikes, but it took me over five hours to to check the tappets, having to remove all the paraphernalia.

[Richard Pitman]

I'd be amazed if Honda didn't set the valve clearances accurately on the production line, but the dealer certainly ought to check them at first service. Bet they don't these days, engines being buried under all that extra modern junk, and if they did check them it'd be a major job to adjust them when it's shims inside cam buckets. I've done this a couple of times on my CB600, not a trivial task with 16 valves and two camshafts to remove and refit without breaking the cam carriers etc.

I learnt to adjust valves on my C100 50cc, followed by the 175 and 250, not an issue on the other two stroke tiddlers. Good practice for my first two car engines, simple pushrod in line fours. If anything, I'm guilty of setting the clearances too tight because I can't stand tappet rattle. Loose 2 thou on the exhaust, tight 2 thou on the inlets.

[ballbearian]

I'd be amazed if Honda didn't set the valve clearances accurately on the production line, but the dealer certainly ought to check them at first service. Bet they don't these days, engines being buried under all that extra modern junk, and if they did check them it'd be a major job to adjust them when it's shims inside cam buckets. I've done this a couple of times on my CB600, not a trivial task with 16 valves and two camshafts to remove and refit without breaking the cam carriers etc.

I learnt to adjust valves on my C100 50cc, followed by the 175 and 250, not an issue on the other two stroke tiddlers. Good practice for my first two car engines, simple pushrod in line fours. If anything, I'm guilty of setting the clearances too tight because I can't stand tappet rattle. Loose 2 thou on the exhaust, tight 2 thou on the inlets.

Yikes, remove the camshafts! We had a special tool to depress the buckets when the piston was down, then a small magnet lifted the shims out for replacements. This was on FIAT's and VW Schirocco's too I guess. I'm glad my Suzi GS750L, 16 valve is not like that and has adjusters directly on the forked rockers.

[Richard Pitman]

Yes, shim over bucket would make life somewhat easier. I think some Kawasakis and Ducatis are like that. The CBR/CB 600 shims are tucked away inside the cam buckets, ( where they can't fly out at high rpms ) hence cam removal to get the buckets out, then messing around with a magnet to get the shim out of the bucket, a right palaver. Get the cam timing right on both cams, then torque down the cam carriers, even slight variations there alters the valve clearances. A job that I doubt I'll be bothering to do again in this lifetime ...

[ballbearian]

Wow, Richard, what an ordeal. Hats off to you for doing it once.

[ancientdad]

Yikes, remove the camshafts! We had a special tool to depress the buckets when the piston was down, then a small magnet lifted the shims out for replacements. This was on FIAT's and VW Schirocco's too I guess. I'm glad my Suzi GS750L, 16 valve is not like that and has adjusters directly on the forked rockers.

As Richard mentioned, some had/have shims on top of the buckets and others beneath. My CBXs had shims on top and though I never did them personally, my longtime friend still working for the Honda dealership when I rebuilt my first CBX (due to wearing out the #5 rod bearing) did the shims for me at the dealership during his lunch hour. I took the engine to him in the back of my '66 Ford station wagon and he did them right on the tailgate, swapping in one for one right out of the parts boxes with zero cost for the shims. I did the Kawasakis while at the City garage with a little ball-ended tool Kawasaki sold (and I still have the damn thing) to depress the buckets as ballbearian described above. Glad I never encountered any of the buckets with shims underneath like Richard's Hornet.

[ancientdad]

Is there a tips and tricks section on this site for actually how to use feeler gauges?

There is a Tips and Tricks section, surprised you hadn't seen it yet. I don't think anyone has done a thread on feeler gauge usage though

[Richard Pitman]

You can just about make out the cam lobe sitting on top of the bucket in this picture, stripped down this far just to check the clearances. The cam carriers are the most fragile looking castings you can imagine, and have to have the bolts loosened and tightened very carefully, otherwise pressure of valve springs might be enough to snap them if bolts not done in sequence, like a cylinder head.

[ancientdad]

Ah, the price of high-performance design.

[deckeda]

Glad this turned out well. I'm no expert with feeler gauges but understand the concept. A few months ago I figured my Coleman minibike was just maybe past its 10-hr mark, where the first valve adjustment is due.

It's got one of the Honda GX200 clones. Someone online said, "These get a little loose when hot, so adjust them a little on the closer end of the range." I did that, and deleted all the compression ... the pull cord nearly flew out of hand it pulled so easily. And of course would not start. I set them again -- to the middle number -- and it was fine. Yeah, just a little adjustment makes a big difference!

[wentwest]

I've only done valve adjustments on a couple of things. The CB450 has those eccentric adjustment shafts so it was pretty straight-forward. On my Miata I was able to loosen the camshaft bearing caps enough to get the old shims out and the new in without any serious problems. On my daughter's Toyota Tacoma I had to use the Kawasaki ball end lever to pry down the cap and get to the shim, and then blast compressed air into the notch to get the shim to finally pop out. It's definitely a fussy job and deep research into internet forums pays off.

[M640]

Lol, the thing is if it was running good I didn't mess with it.