valve clearance question (again!)

[scottyboy2203]

Hi all, Just check my valve clearances (its bloody freezing out!) and exhaust are all at 0.2mm whilst intake varies from 0.076-0.1mm. From memory Intake should be 0.11-0.2mm and exhaust 0.21-0.3mm, so what affect will my clearances have if left unchanged (it's a real ballache)?


On a side note, whilst the cam cover was off I noticed that the cam chain is continuously held tight against the chain guide on the top of the engine (between intake and exhaust sprockets), is this normal?


Thanks!

[darrsi]

That'll be the cam chain tensioner!

[scottyboy2203]

sorry Darrsi, what is the cct?

[darrsi]

As it says on the tin really, it basically stops the cam chain from loosely flapping about, it'll just push against it to keep it reasonably firm in movement.
The tensioner has notches on it, and as the chain wears over time the tensioner will click in a notch to keep the same firmness.
When they've used up all the notches it's normally a sign that you need a new cam chain, and you'll get a warning by the chain making a rattling sound, similar to a sewing machine.
The majority of people will sort it out, simply 'cos the noise drives you barmy, but there are others who live with the noise!


http://www.yamahamotorcyclespares.co.uk/spares/epc2.asp?modelID=9657&PageiD=5&m=YAMAHA+FZS600SP+Fazer+CAMSHAFT%2E+CHAIN&uID=0

[scottyboy2203]

sorry, i meant 'what problem are you suggesting is caused by the cct?' I know what it does but my query was about valve clearances and whether the cam chain should be tight against the upper guide (found between the intake/exhaust sprockets on the head). Not sure what you are suggesting is caused by cct :S

[darrsi]

Bit of crossed wires here, when you asked "what is cct?" i answered. It was just me waffling on, sorry fella.


Not sure about your clearance question, i was kind of answering the 2nd part, i think?   


Just ignore me and i'll go away 

[scottyboy2203]

roger that Darrsi, thanks for the input!

[His Dudeness]

I'm not a mechanic but this is my fisher price understanding of valve clearance

The valve clearance is the gap between the valve and the cam lobe. The cam is shaped in such a way that as it rotates it makes contact with the top of the valve which causes it to be pressed down (ie open) at specific times. Obviously there are times when you need the valves open (ie to get fuel in and exhaust gases out) and there's time when you need the valves closed (ie during compression and firing).

The engine operates at a wide range of temperatures and it is made from different materials which expand at different rates so the valve clearance is a tolerance that's in there to ensure that as everything expands the cam lobe only makes contact with the valve at the precise time that its meant to.

If its too tight (ie the clearance is too small) then you're risking that as everything gets up to temperature the cam lobe might be opening the valve too long and you loose a bit of power. Another problem is that the valves cool themselves by making contact with the head and if they are being held open too long then they don't make contact with the head long enough to cool down and you can burn out the valve and that is the biggest danger of tight clearances. The opposite is when they go loose (ie the gap gets too big). That is less of a problem because they're making enough contact with the head to cool so they're not running the risk of burning out. When they go loose they get noisy and you get that tap tap tap sound. When they go tight they don't make any sound. The reason why they go tight is that the valves wear into the head and so the gap gets smaller.
Thus ends the fisher price lesson on valve clearances

Having said all that you've measured your clearance a bit on the tight side. The bikes not going to explode if you leave them for a while but they're only going to get tighter so its up to you whether you want to do them or not.

[Major Rant]

Tight valves are more of a problem than loose ones...
 
if they're loose then they close early an open late ... It rattles a bit a looses some performance - no harm done.
 
if they're tight then they close late (or not at all) ... The result can be burnt valve seats and even 'blowback' through the carbs.
 
Blowback is highly amusing (and destructive!) and involves smoke and flame emerging from your air-filter 
 
Yours sound tight ... I'd measure them again... They don't usually go tight, apparently.

[scottyboy2203]

Thanks, that was some very comprehensive and informative posts guys! So the exhaust I think is fine as I only have a 0.2mm feeler so can't measure the exact 0.21mm minimum clearance, however 0.2mm went easily with very low drag and 0.25mm wouldn't fit so I'd say exhaust are around the 2.1mm tolerance.


Intake on the other hand, most of them measure 0.004" which is 0.1016mm so that should be fine. Unfortunately one of the intake valves measured 0.003" which is 0.0762mm so that probably does need swapping by the sound of it!


I am not entirely surprised that the clearances would get tighter as you say Major Rant, surely the head would wear faster than the oiled cam/bucket assembly? I think that I will have to stick to the manual on this one and pop in some new shims to be on the safe side!

[His Dudeness]

shims tend to go tight and the older style tappets tend to go loose. you should get a full set of slip gauges and recheck the clearances before you do anything

[Slaninar]

My Fazer (2001) has some 60,000 kilometres. A mate who is a mechanic says those figures are probably lower, like 40,000, judging by the bike's condition (fiddling with those numbers before importing or reselling vehicles is a usual thing here).

Now, Mr. Haynes says something like 40,000 kilometres between checking valve clearences. My mechanical mate says to just leave it until I hear valves rattle. Doesn't want to take my money for just opening and closing the engine back (most local mechanics will charge for checking clearences WITHOUT even opening the bloody engine).

How often do those valves get out of line? What are foccers' experience? Should I just leave it, or check every 20, 40, or 80 thousand kilometres?


Bit of an off topic: about cam chain. It does rattle a bit. The same mechanic mate said to leave it until it rattles a lot louder, this is just OK.

Same for carb balance: leave it until it really gets running really rough.


What do you people do? I've never done any of these things, would go for DIY, but not before it really needs doing.

[limax2]

My mechanical mate says to just leave it until I hear valves rattle. 

That's all very well if the clearance is increasing but, as others have said, it is more likely to get smaller. The first you would know would be when an exhaust valve burns out and one cylinder goes on strike. That said most when checked at 25000 to 30000 miles (40,000 to 48,000 Km) are still within the limits, but not always.   Armed with your manual, a set of feeler gauges and a few basic tools it's a nice little job. Go for it  . Mind you, if they need adjusting that's somewhat more involved.
All this has promted me to check mine, so that maybe answers your question "what do you peaple do".
If the cam chain rattle is not too bad it could just be that the tensioner is getting ready to move onto the next notch. When that happens it should go quite again. If it gets bad I would investigate as a broken cam chain is bad news.
 
If carb balance is the cause of some rough running I would sort it. Why put up with it till it gets really rough  . But then I do have a set of gauges for the job.
 
 

[scottyboy2203]

checking clearances is easy to do and not worth taking to a stealer, 1hrs casual labour (with tea!) had the tank off, cam cover off, clearances checked and bike reassembled. Decided that 2 intake valves were only 1 thou (inches) out of spec on the tighter side so will leave them be for now. Since it's the intake it'll be cooler than exhaust side so burning out due to poor fit against head is less of an issue.


Looks like my rattling is just the bloody cam chain! Poor design Mr Yamaha...

[dickturpin]

Are any new gaskets required for a valve check?

[scottyboy2203]

nope, just be careful with the rubber gasket on the cam cover. It is fairly strong but can be damaged by strong hands!

[unfazed]

I would change that mechanic, an old saying is: "Tight valve clearances annoy the bike and loose valve clearances annoy the rider" still holds true.
Check the valves at the recommended intervals, there is no hard and fast rule with regards to the wear on the valve train.
 

[Slaninar]

I would change that mechanic, an old saying is: "Tight valve clearances annoy the bike and loose valve clearances annoy the rider" still holds true.
Check the valves at the recommended intervals, there is no hard and fast rule with regards to the wear on the valve train.

How difficult is it to DIY. Would I need those spacers, what do you call it, if valves are out of spec?

[scottyboy2203]

Get yourself a Haynes manual first and it is easy enough for someone with basic spanner skills. Checking the clearance involves tank removal for access, cam cover and alternator cover off and then spin the engine round by hand so its at TDC for each cylinder as you check it with feeler gauges. Once you know how out of size they are you need to work out what shims need replacing. Unfortunately the actual replacing of the shims is a lot harder as you need to remove cam chain/sprockets in order to get under the buckets and replace shims...Haynes will walk you through but only attempt if you're competent

[Major Rant]

there is no hard and fast rule with regards to the wear on the valve train.

He's right .... not all of the movement is caused by wear.
 
Its a huge stack of dissimilar metals (steel and aluminium) that gets repeatedly heated, cooled and vibrated.
Steel and Ally both have a habit of 'creeping'.
Leave them 10 years: its surprising that the engine is still underneath the tank  .

[Dave48]

IMO  checking the clearances @ the recommended intervals is a worthwhile exercise since as others have said the results of  running clearances too tight can have expensive & entertaining effects! . Although new engines are more or less "built by robots" there is a specified RANGE of clearance that is acceptable-this allows for small differences in rates of expansion due to heat,chemical composition of metals involved,etc.etc. If measured clearances found to be near or at minimum acceptable limit then extra work is needed to replace shims on valves concerned. Haynes explains the procedure clearly including the shim thickness calculation.
Similarly cam chains have a finite life & eventually need replacing-I would do it on a high mileage bike simply for peace of mind-imagine the consequences of the chain giving up the ghost when giving it some stick -bye bye engine!   Its like the cage drivers who "forget" to change the cambelt @ recommended mileage & blow their motors up when thepistons start kissing the valves.
Prevention better than cure?

[scottyboy2203]

Major Rant, as an engineer that last bit had me laughing more than I should admit!


Consensus seems to be checking that they are within tolerance at the required mileage is worth doing as it is really rather easy to do. If you find they are out of the specified range (~0.1mm range, which is quite large as motorbike engines go!) then decide if you can sort it or instead use a mechanic. This shouldn't cost an arm and a leg, most expensive bit will mostly likely be shims and a couple of hours labour. Most mechanics will suggest full service at same time since he has to take everything off to do the job!


Happy riding!

[Slaninar]

Major Rant, as an engineer that last bit had me laughing more than I should admit!


Consensus seems to be checking that they are within tolerance at the required mileage is worth doing as it is really rather easy to do. If you find they are out of the specified range (~0.1mm range, which is quite large as motorbike engines go!) then decide if you can sort it or instead use a mechanic. This shouldn't cost an arm and a leg, most expensive bit will mostly likely be shims and a couple of hours labour. Most mechanics will suggest full service at same time since he has to take everything off to do the job!


Happy riding!

Full service meaning cam chain, carb balance, or what?

[scottyboy2203]

Well last time I took it to a dealer he suggested doing carb balance, replace all fluids/filters/spark plugs etc but that does send the bill sky high and isn't always necessary.


If you are just checking clearance and everything is fine then just pop it back together and ride it!

[Slaninar]

Well last time I took it to a dealer he suggested doing carb balance, replace all fluids/filters/spark plugs etc but that does send the bill sky high and isn't always necessary.


If you are just checking clearance and everything is fine then just pop it back together and ride it!

My carbs are a bit out of ballance. If checking filters involves a lot of work needed for carb balance as well, that makes sense. If not, then no need.

Same goes for cam chain replacement. It's probably near the end, but still works. So I'm between minds whether to do it or not.

Sparsk, fluid, brakes, coolant - all piece of cake and regularly DIY. Air filter as well.

The only thing I'm scared of doing is this "inside" the engine.

Yes, rear suspension linkage needs lube as well per Haynes, but no play and I'd rather leave that as is.