Question about valves

Xav

Xav

Hero member
Location
France
Hi all

Before changing shims, I like to have opinions on the valve clearances I found today

To recap, my bike is equipped with the famous 180 engine series 2, with camshafts 4C - 91 067 km

inlet cylinder 1 -  0.20 very loose - 0.25 does not pass
inlet cylinder 2 -  0.15 very loose - 0.20 does not pass
inlet cylinder 3 -  0.15 very loose - 0.20 does not pass

exhaust cylinder 1 -  0.20 very loose - 0.25 does not pass
exhaust cylinder 2 -  0.15 very loose - 0.20 does not pass
exhaust cylinder 3 -  0.15 very loose - 0.20 does not pass

Surprised that the number one is in these values and that the hold of 0,20 (or 0,25 on cylindre 1) passes in no way. But then in no way!

I already control at 89 000 km. There was already the difference between the cylinder 1 and its neighbors. Except the exhaust, the values were 0.25 (cylinder 1) and 0.20 and that the inlet, 0.20 passed by forcing

Preliminary control also at 86 000 km. (in fact, I like to put hands inside my engine!... :D) 0,20 everywhere, except ECH roll 1 - 0,25

You get to follow me?


I intend to check the tightening of the cylinder head. I shall take back the values after the dynamometric share

But in the meantime, I takes any advice

Regards

Xavier
 
Hi Xavier

Firstly, I would be running 0.20 for inlets and 0.25 for exhausts.  Secondly, I would recommend finding some feeler gauges that will let you measure more accurately than to the  nearest 0.05.  The small differences that you are showing are hard to assess with such a wide tolerance on measurement, but don't look like a real problem.  If you changed shims recently some bedding in could easily have happened.  If I understand correctly that you are going to put the bike on a dynamometer, careful setting up of the valve clearances to be identical between cylinders (within 0.02, for example) may make a significant difference.  For road use this is not so important, though.  It is easy to end up chasing your tail with this job, as others will tell you, and I am sure there is an old thread with various views on this subject.

Cheers

Nick
 
Thank you Nick for your answer

You are completely right. I have just bought today feeler gauges with more tolerances

I shall redo a more precise control this weekend

Before opening this topic, I looked for by the search engine a subject which dealt with my question. My technical vocabulary is not very vast, and except some terms which managed me towards various subjects, I did not know how to find of answer to the questions that I settle

In your opinion, with the cam shafts 4C, what would be the acceptable mini tolerance before a change of shims?

Xavier
 
Xavier,

I would be inclined to err on the side of loose. The exhaust clearances being the most important. In the '80s/'90s I would always re-shim if I saw any exhaust clearance get close to 0.20....and this was when fuel was better (my local garage still sold 5 star petrol  :o 

Fuel quality will have s significant effect on valve wear - It is worth remembering that modern fuels are pretty crap, with lots of benzene being left in the keep the octane rating up. Benzene evaporates VERY quickly, so old petrol is to be avoided (drain it out and use it in the lawnmower). 

Pete
 
Hi Xavier, the figures of 0.20 and 0.25 are what I use with 4C cams.  Setting up I would aim for just a little slack, maybe up to 0.22 inlets and 0.27 exhaust.  If the figure is within the range 0.18 to 0.24 inlet, 0.23 to 0.28 exhaust I would not adjust it unless one valve has small clearance and the other two are at the larger end of the scale.  Pete is right about not letting the exhausts in particular close up too much.

To put it more simply, I always aim to have the clearances slightly large, and all cylinders identical (but practically this means within about 0.02 of each other) to start with.  There are many variables at play when measuring the clearances, such as clearance in the cam bearings and how the shims and buckets are sitting.  So the final result is not always exactly what you expect based on your measurements and shim choice, but the tolerance is wide enough.  I will do some searches and see if I can find more information for you, there are comments on things like pushing down on the cams when measuring clearances, etc.

Cheers

Nick
 
Xavier,

Always check clearances with cam chain in position and correctly tensioned.  Clearance within the cam bearings can influence valve measurements to quite a degree. 

Can also push down firmly with one hand on the cam while measuring, has the same effect...

piet
 
The weekend is approaching its end, and I rechecked everything, with a more appropriate set of gauges, after having had control of cylinder head tightening and control of the cam chain

Inlet cylinder 1 - 0.22 (tight)
Inlet cylinder 2 - 0.22 (0.23 tight)
Inlet cylinder 3 - 0.22 (tight)

exhaust cylinder 1 - 0.24 (0.25 tight)
exhaust cylinder 2 - 0.22 (0.23 tight)
exhaust cylinder 3 - 0.21 (0.22 tight)

I think I'm being in acceptable values. I put back the valve cover in position, looking forward to buying a new cam chain

I think that when I'll exchanged the cam chaine, I shall take advantage of it for r?gler valves with bit more then 0,20 / 0,25 (0,20 and 0,25 slack)

Thank you guys having put me in the right direction and work adjustment (setting ?)

Xavier
 
Hi Xav,
#2 and 3 exhaust  are too tight and outside the tolerences I'd normally go for. My acceptable tolerances are in. 0.19-0.22 and ex. 0.24-0.27. anything out side that and the cams are removed and reshimmed. That's my tolerences, other views may be different. I'll let the experts comment.
 
After thirty years and 200 odd thousand kilometers of ownership you should probably consider yourself to be one of them experts Rob.


              Keith.
 
laverdakeith said:
After thirty years and 200 odd thousand kilometers of ownership you should probably consider yourself to be one of them experts Rob.


              Keith.
Click to expand...

Thank you sirs for your complements of answer

Keith, be reassured, Rob's answer suits me perfectly, and I am going to follow his good advice.

It is necessary for me to change the cam chain before doing anything about my shims

Thank you all for all this valuable information. My engine also thank you  :D

Xavier


PS : Moreover Keith, I have just sent you an e-mail...
 
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