Valve Clearances...how can you tell they're out?

[Tex 36,816]

7 minutes ago, baben said:

Could this be an issue with injectors on a twin? I ask in utter ignorance.

 

Yes. Or a triple or a four. Or any number of cylinders that have a separate throttle body for each cylinder. Thankfully many modern engines now come with a single throttle body to feed all the cylinders. ‘Performance’ engines still tend towards individual TBs, so while the NC and my 900 Triumph have a single body the T120 and Thruxton have two.

 

Andy has just replied which confirms that the more modern incarnations of ‘cooking’ engines are being simplified. 

 

Tigger has 3..  

[Tex 36,816]

48 minutes ago, Trev said:

 I thought odd that the Guzzi manual only has one specific measurement for each. I checked the manual for the last bike I did valve clearnaces on, SUzuki GSXR1100, and that tolerances as expected. I need to do the Griso somewhen so will try to make sure I have correct info on tolerances for that before I start.

 

It doesn’t surprise me that Guzzi simply give a clearance with no tolerance. The old Brit factories did the same. This ‘new fangled’ + or - stuff came in with the Japanese and shim type adjustments (because, with the best will in the world, sometimes the correct shim is just not possible). 

[Scootabout 2,247]

On 29/07/2018 at 00:02, alhendo1 said:

 

If the vibration thing cant/won't be sorted I'll take mitigating action and make it bearable. ...bar brace etc...I really like the CB....

 

A long shot, but you haven't fitted a top box recently. have you? My NC700X vibrated more after I did that, at least when the box wasn't attached (but the rack was, IYSWIM). 

[embee 7,288]

Tolerances are fundamental to process control. Dimensions of any part or clearance need to be measured and monitored, and designs specify the appropriate values. Manufacturing will record measurements and feedback into the control of the process, monitoring the scatter or drift to determine the degree of control and identify any inherent issues which may need attention. The run charts shown below as examples are typical of how processes are monitored. All the measurements are within +/-2 but clearly things are going on which are influencing the process.

"Go/no-go" gauges of any type are of no value to informing the manufacturing engineers of what the process is doing, whether it is under control or not. This gauging philosophy used to be common but as far as I'm aware is non-existent nowadays in any self-respecting manufacturing process. You have no indication of whether the process is drifting one way or is exhibiting random variation etc. Using 2 different feeler gauges may well be a perfectly acceptable way to set the clearances in a real-world service environment.

Things are specified the way they are for good reason, even though it might not be immediately apparent. Valve clearances are specified to provide a satisfactory running condition for all operating circumstances, from a cold start at -30C to sustained max power at 40C ambient for example. Tolerances are there to allow for practical aspects of assembly and setting etc., but that's different to saying it's ideal at either end.

[SteveThackery 3,090]

6 hours ago, baben said:

Could this be an issue with injectors on a twin? I ask in utter ignorance.

 

Nowadays injectors are made with such precision that they are pretty well guaranteed to be matched closely enough to make no difference.  Might well have been different back in the day, though.

[SteveThackery 3,090]

6 hours ago, Tex said:

 

It doesn’t surprise me that Guzzi simply give a clearance with no tolerance. The old Brit factories did the same. This ‘new fangled’ + or - stuff came in with the Japanese and shim type adjustments (because, with the best will in the world, sometimes the correct shim is just not possible). 

 

No, I cannot agree!  Or rather, this isn't a new fangled thing, at least not in engineering in general.  No dimension can be achieved exactly, so every dimension must have a tolerance.   It isn't possible to set a clearance to a precision of 0.0000000 (recurring) millimetres, nor is it possible to measure with infinite precision.  The Brit factories, and Guzzi, were wrong to give a dimension with no tolerance.  It is meaningless.  A points gap might be specified as 15 thou.  So would 15.001 thou be acceptable?  15.1 thou?  Who's to say?

 

In any case, I can remember cars and bikes from the 50s and 60s had a points gap specified as 15 +/- 1 thou, or sometimes 14 - 16 thou.  So they were certainly using tolerances sixty or seventy years ago for some of the measurements.

 

[fj_stuart 4,739]

22 minutes ago, SteveThackery said:

 

No, I cannot agree!  Or rather, this isn't a new fangled thing, at least not in engineering in general.  No dimension can be achieved exactly, so every dimension must have a tolerance.   It isn't possible to set a clearance to a precision of 0.0000000 (recurring) millimetres, nor is it possible to measure with infinite precision.  The Brit factories, and Guzzi, were wrong to give a dimension with no tolerance.  It is meaningless.  A points gap might be specified as 15 thou.  So would 15.001 thou be acceptable?  15.1 thou?  Who's to say?

 

In any case, I can remember cars and bikes from the 50s and 60s had a points gap specified as 15 +/- 1 thou, or sometimes 14 - 16 thou.  So they were certainly using tolerances sixty or seventy years ago for some of the measurements.

 

 

Steve, I wouldn't get too upset about it. My CBF250's clearances are specified without any range (0.12mm inlet, 0.15mm exhaust) and the gap is controlled by shims. These come in 0.025mm increments. So if I measure an inlet gap of 0.11mm what do I do? Well, I'd re-shim to get it on the high side ie 0.135mm which seems sensible (to me, anyway)

[SteveThackery 3,090]

2 hours ago, fj_stuart said:

 

Steve, I wouldn't get too upset about it. My CBF250's clearances are specified without any range (0.12mm inlet, 0.15mm exhaust) and the gap is controlled by shims. These come in 0.025mm increments. So if I measure an inlet gap of 0.11mm what do I do? Well, I'd re-shim to get it on the high side ie 0.135mm which seems sensible (to me, anyway)

 

It's cool - I'm not upset about it.  I just like criticising the rubbish practices and products we Brits made and which led to the downfall of the industry.

[alhendo1 3,031]

9 hours ago, Scootabout said:

 

A long shot, but you haven't fitted a top box recently. have you? My NC700X vibrated more after I did that, at least when the box wasn't attached (but the rack was, IYSWIM). 

I have a Givi box and rack fitted but it's not that....I got that fitted a while ago and it was fine....been touring with it no problems....it's in the dealership for them to have a look today....but I'm not holding out much hope...I've already had the pre emptive get outs like...."it's a small twin..they do vibrate a bit" and "we don't sell that many of these...I'm not sure if that's normal or not...."...I will report back....so long as they don't make it any worse I can always get a second opinion at my leisure.

[Andy m 23,468]

Valve clearances aren't an engineering/manufacturing tolerance, the process is out of control regardless of what you do. Mechanics will be trained to get it to the point where an undefined stack of feelers with a nominal value of 0.12mm is some undefined sliding fit. The engineers will have worked out that at 40 degrees using  twelve Soviet made 0.01 blades (which double as rat files) and considering "running" to mean able-to-rattle, you'll have 0.14 at the 80th percentile. At minus 5 using a single Chinese 0.12 blade and tightening the adjuster onto it with a 12 foot bar will give 0.10 at the 80th percentile. You have your tolerance and if it works at that the machine will function. Give the service monkey a choice between fourteen 0.1 blades and one 0.1 and you actually get greater variation. Adding small print with temperatures and calibration requirements will simply be ignored.

 

Andy

[Trev 18,563]

20 hours ago, Trev said:

Did the right hand side of my Guzzi V7 last night.

 

Started by trying to make sense of the fair bit of conflicting info out there (as usual) on what the gaps might be, I just went with the manual in the end although, apparently that's not always best with Guzzis? Propped bike on side stand and piece of wood and clicked it into top gear and removed spark plugs so I could find top of compression stroke with a paper straw. Rocker cover came off nae problem, both inlet and exhaust felt a wee bit tight, exhaust a bit more so than the inlet. After twenty minutes of loosening and retightening the buggers I've ended up with both a tiny bit less tight I think, maybe, just about, not blinkin worth it!

 

All back to together, both plugs in, out of gear and it fired up fine and sounded the same as it did before, no surpise. Tonight I'll check the left hand side but, unless significantly out, I won't faff about adjsutung but will leave as is.

 

Unlike me, please remember the manual states 'valve clearance check' not 'valve clearance adjust' for a reason, they very likely won't need adjusting so don't waste time and effort trying to improve the tolerance by half a gnats wotsit 

 

Checked left side last night, inlet was fine, eensy wincy bit tight (an engineering term to annoy the heck out Murray Steve & Andy ) so  I left it alone, exhaust was a little too open so I did tweek this one up a little but didn't go mad trying to get it to the enth degree (another of those engineering terms). Popped the lot back toegether, ran it up, sounded fine, ready for a jaunt to Devon/Dorset/wherever on Friday.  Despite ordering a new pair of rocker gaskets I have left the old ones in place as both were firnly seated to the head and I didn't want to faff about removing them. If arrive at the Devon meet with oily troos then that will have been the wrong decision 

[embee 7,288]

I guess the clue is in the word "tolerance". Much of the challenge in engineering of sophisticated machinery is in determining the "tolerance" of the product to variation. The term "robust" is often used to describe things which will operate at or near the optimum while various aspects may vary according to the weather, what was on telly last night or whether the user has had a curry. Sensitivity to variation is critical, the more sensitive the tighter the required control, the less sensitive the better from an engineering point of view. Two examples of extremely robust products are the old Honda Cub engine, and the Briggs & Stratton lawnmower engine, both of which will survive abominable neglect and abuse. Did those engineers know what they were doing or was it just luck?

You and I can tolerate a fairly wide temperature range, but some climates are more suited to our well being than others. Peoples' sensitivity varies.

 

Politicians generally have the affliction of doing the same thing over and over yet expect different outcomes, and are usually disappointed. The converse is folk who do different things every time yet expect the same outcome, and are usually disappointed. Process control will show them what's going on if they care to look, which usually they don't.

 

I always find it interesting to read folk's views of engineering. The guy on the barstool in the local pub can state something quite categorically and it is circulated around the internet as gospel writ in stone. The engineers who produce the machine clearly have absolutely no idea what they are doing, bunch of oily rag knuckle dragging wastrels. Don't start me on break-in procedures, the guy in the USA who puts together bits off the shelf to make bike engines for club racing has the final word and all the engine manufacturers are simply ignorant cheating robbing charlatans hell bent on spoiling your life. Such is the way.

 

I usually end with one observation on such things; it's your engine, you bought it, do what you want.

[baben 11,696]

1 hour ago, embee said:

I guess the clue is in the word "tolerance". Much of the challenge in engineering of sophisticated machinery is in determining the "tolerance" of the product to variation. The term "robust" is often used to describe things which will operate at or near the optimum while various aspects may vary according to the weather, what was on telly last night or whether the user has had a curry. Sensitivity to variation is critical, the more sensitive the tighter the required control, the less sensitive the better from an engineering point of view. Two examples of extremely robust products are the old Honda Cub engine, and the Briggs & Stratton lawnmower engine, both of which will survive abominable neglect and abuse. Did those engineers know what they were doing or was it just luck?

You and I can tolerate a fairly wide temperature range, but some climates are more suited to our well being than others. Peoples' sensitivity varies.

 

Politicians generally have the affliction of doing the same thing over and over yet expect different outcomes, and are usually disappointed. The converse is folk who do different things every time yet expect the same outcome, and are usually disappointed. Process control will show them what's going on if they care to look, which usually they don't.

 

I always find it interesting to read folk's views of engineering. The guy on the barstool in the local pub can state something quite categorically and it is circulated around the internet as gospel writ in stone. The engineers who produce the machine clearly have absolutely no idea what they are doing, bunch of oily rag knuckle dragging wastrels. Don't start me on break-in procedures, the guy in the USA who puts together bits off the shelf to make bike engines for club racing has the final word and all the engine manufacturers are simply ignorant cheating robbing charlatans hell bent on spoiling your life. Such is the way.

 

I usually end with one observation on such things; it's your engine, you bought it, do what you want.

AK47 was a very robust design. Everything was very loosely fitted so it did not matter what you did to it - it still worked. Unlike the American M16 which was beautifully engineered with very fine fittings - that jammed up as soon as you showed it a muddy puddle....

[Trev 18,563]

2 hours ago, embee said:

I usually end with one observation on such things; it's your engine, you bought it, do what you want.

 

Love this, hope you don't mind if I 'steal it with pride' for my owen use? 

[Tex 36,816]

10 hours ago, SteveThackery said:

 

It's cool - I'm not upset about it.  I just like criticising the rubbish practices and products we Brits made and which led to the downfall of the industry.

 

Aye, that’s hindsight for you. If only you had been born 50 years earlier (with the knowledge you gained from your university course ‘pre-loaded’) you could have saved the industry ..  

[SteveThackery 3,090]

4 hours ago, embee said:

Two examples of extremely robust products are the old Honda Cub engine, and the Briggs & Stratton lawnmower engine, both of which will survive abominable neglect and abuse. Did those engineers know what they were doing or was it just luck?

 

In the case of Honda - exceptional engineering throughout.  As for Briggs and Stratton and that hideous lawnmower engine (hideous because it makes more mechanical noise than a 15,000hp ship engine) then any durability must, surely, be dumb luck.

 

4 hours ago, embee said:

I always find it interesting to read folk's views of engineering. The guy on the barstool in the local pub can state something quite categorically and it is circulated around the internet as gospel writ in stone. The engineers who produce the machine clearly have absolutely no idea what they are doing, bunch of oily rag knuckle dragging wastrels. Don't start me on break-in procedures, the guy in the USA who puts together bits off the shelf to make bike engines for club racing has the final word and all the engine manufacturers are simply ignorant cheating robbing charlatans hell bent on spoiling your life. Such is the way.

 

God, yes, isn't it amazing!  I'm astonished by the number of people who consider themselves experts and are only too keen to slag off everyone in their chosen area of expertise.  Also, they assign all kinds of dark motives to others (I've actually heard all of the following said): 

 

"They want it to wear out so you'll buy another one."

 

"It's designed to fail just after the warranty has run out."

 

"Of course every manufacturer cheats on their emissions, it's just VW who got found out."

 

"They are deliberately starving the NHS of funds so that it collapses completely; then they can start again with a fully privatised, insurance-based system."

 

"Nobody in government give a f**k about the rest of us, they just want power.  They're all the same."

 

"The people in charge know how to make free energy, but they're keeping it secret because it would collapse the world economy."

 

"Suzuki obviously have no idea how to design a decent combustion chamber, which is why they had to use two spark plugs."

 

"Basically, nobody has honourable intentions - everybody is in it for themselves."

 

How depressing it all is!

 

 

[Trev 18,563]

Another ridiculous claim I've heard:

 

'Mourinho is a great manager, he's only pretending not to know what to do at Man Utd to get out of his contract' 

[embee 7,288]

1 hour ago, SteveThackery said:

 

….. As for Briggs and Stratton and that hideous lawnmower engine (hideous because it makes more mechanical noise than a 15,000hp ship engine) then any durability must, surely, be dumb luck.

 

Have to agree to disagree on that one. Usually the engines aren't that noisy, it's the blade and the rest of the machine which make most of the noise. The B&S (and Tecumseh etc) will go on for ever if it has even the slightest bit of oil in it. The only ones I've seen with a rod through the side were run dry. They are so simple and tolerant of abuse I admire the engineering. Interestingly if you compare a modern one with an ancient (50yrs old) one you find there are about half the number of separate components, even though they actually look quite similar in many ways. More modern production engineering.

[SteveThackery 3,090]

48 minutes ago, embee said:

Have to agree to disagree on that one. Usually the engines aren't that noisy, it's the blade and the rest of the machine which make most of the noise. The B&S (and Tecumseh etc) will go on for ever if it has even the slightest bit of oil in it. The only ones I've seen with a rod through the side were run dry. They are so simple and tolerant of abuse I admire the engineering. Interestingly if you compare a modern one with an ancient (50yrs old) one you find there are about half the number of separate components, even though they actually look quite similar in many ways. More modern production engineering.

 

Well, I am absolutely happy to change my mind in the light of your experience with them.  My only experience was about 45 years ago, with one in a lawnmower, and although it started and ran fine, the noise was terrible.

 

I honestly thought it was valve noise, piston slap, ringing of the cooling fins, and loose bearings.  However, I was only a teenager back then and I've never had chance to update my impression in the light of greater experience and knowledge.

 

For what it's worth, I, too, admire engineering like that, - engineering which appears crude but in fact is masterfully simple - low cost, does the job, durable.  That is fine engineering, in my book.

[Scootabout 2,247]

6 hours ago, SteveThackery said:

 

In the case of Honda - exceptional engineering throughout.  As for Briggs and Stratton and that hideous lawnmower engine (hideous because it makes more mechanical noise than a 15,000hp ship engine) then any durability must, surely, be dumb luck.

 

 

God, yes, isn't it amazing!  I'm astonished by the number of people who consider themselves experts and are only too keen to slag off everyone in their chosen area of expertise.  Also, they assign all kinds of dark motives to others (I've actually heard all of the following said): 

 

"They want it to wear out so you'll buy another one."

 

"It's designed to fail just after the warranty has run out."

 

"Of course every manufacturer cheats on their emissions, it's just VW who got found out."

 

"They are deliberately starving the NHS of funds so that it collapses completely; then they can start again with a fully privatised, insurance-based system."

 

"Nobody in government give a f**k about the rest of us, they just want power.  They're all the same."

 

"The people in charge know how to make free energy, but they're keeping it secret because it would collapse the world economy."

 

"Suzuki obviously have no idea how to design a decent combustion chamber, which is why they had to use two spark plugs."

 

"Basically, nobody has honourable intentions - everybody is in it for themselves."

 

How depressing it all is!

 

 

 

First five don't seem far off the mark. Last four, maybe not