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A A A A Author Topic: Valve Timing  (Read 179 times)

nodrog

Valve Timing
« Started on: 26-Nov-18, 20:30 »
Hi all,
  After a long time i finally got around to putting the engine back in my Bike. I have attached a picture. Bike starts instantly and doesn't blow smoke anymore. whackado. I have not run it in yet.
I found coolant weeping from the Head Gasket and when I checked compression it was very Low, 90PSI each side. :boohoo:. The head gasket came in a complete engine kit and seemed very thin. I don't suspect the head gasket as causing the low compression as I had no bubbling from my radiator coolant. I have just replaced the Head gaskets due to the external coolant leak with the ones I got from JHovel.

While the heads were removed I checked my bore diameters again with a bore guage, both are within size limmits 78.02 mm and 78.05 mm  with no more than .02 mm ovalarity. whackado.

I then decided to check my Valve timing, as I fear this is the cause of the low compression. The Manual states the Inlet valve should open at 6Deg BTDC (1mm Lift).
 Can someone please advise if my understanding of this spec is correct? I am guessing that at 6Deg BTDC the valve should have stroked 1mm.

To check this I zeroed a Dial Indicator over the top of my inlet valve while the piston was at TDC on the compression stroke, I then Cranked the motor through the front cover, starting with my socket wrench at verticle. Rotating the motor I did not get 1mm stroke of the valve until I was at about 10Deg ATDC. If my understanding of the Valve timing spec is correct, and my method for checking it adequate? I must assume I have set it incorrectly and will therefore need to reset the Cam Chain.

All opinions welcome, please advise as to weather or not I am approaching these issues correctly.  [ You are not allowed to view attachments ]  

I would also like to advise that Oversize Pistons and rings now seem to be available for our bikes.

CX PHREAK

Re: Valve Timing
« Reply #1 on: 26-Nov-18, 21:28 »
If the bike has a camchain getting toward the end of its life the cam timing will be retarded from the factory figure by about 3.5 degrees.

 They actually like this and make slightly more power. It won't be your problem.

 If you have just replaced the camchain it is probably still correct. I don't have a cam sprocket here inside to count the teeth but one tooth off will put the timing further out than this.

 Do you test the compression with a warm motor? And with the throttle wide open. If not this will give a low figure.

 And I've seen CXs running quite happily with compression down to 110 PSI or so. They generally still go OK but use oil.

nodrog

Re: Valve Timing
« Reply #2 on: 26-Nov-18, 22:06 »
If the bike has a camchain getting toward the end of its life the cam timing will be retarded from the factory figure by about 3.5 degrees.

 They actually like this and make slightly more power. It won't be your problem.

 If you have just replaced the camchain it is probably still correct. I don't have a cam sprocket here inside to count the teeth but one tooth off will put the timing further out than this.

 Do you test the compression with a warm motor? And with the throttle wide open. If not this will give a low figure.

 And I've seen CXs running quite happily with compression down to 110 PSI or so. They generally still go OK but use oil.
Thanks for the reply CX PHREAK, after reading your reply I have just run out and counted the teeth on a old Cam Sprocket, although difficult to count, as i have a lever welded to it, it seems to be 44 teeth.  I calculate 1 tooth to be approx 8.2 deg of cam rotation and therefore about 4 deg of crank rotation. If this is correct I must be out by about 4 teeth. I can't understand for the life of me how this has happened.

During the rebuild I have changed the Main Bearings, Cam Chain and Chain guides, Mechanical Seal, all oil seals, Piston Rings, honed the bores and lapped in the valves. I felt sure I had installed the Cam Chain correctly, remembering to align the cam sprocket with the marks on the case, checking the woodruff key was pointing to the indicator mark and checking 2-1/2 teeth from the Key was directly verticle to engine axis. All the time making sure the chain was taught. This is why I am questioning my understanding of the Valve timing spec's. I have read it is not unheard of for compression to rise considerably during the run-in process, but fear the valve timing is set incorrectly.

Is my understanding of the Valve specs correct?

Cheers

Gordon.

nodrog

Re: Valve Timing
« Reply #3 on: 26-Nov-18, 22:22 »
If the bike has a camchain getting toward the end of its life the cam timing will be retarded from the factory figure by about 3.5 degrees.

 They actually like this and make slightly more power. It won't be your problem.

 If you have just replaced the camchain it is probably still correct. I don't have a cam sprocket here inside to count the teeth but one tooth off will put the timing further out than this.

 Do you test the compression with a warm motor? And with the throttle wide open. If not this will give a low figure.

 And I've seen CXs running quite happily with compression down to 110 PSI or so. They generally still go OK but use oil.
Thanks for the reply CX PHREAK, after reading your reply I have just run out and counted the teeth on a old Cam Sprocket, although difficult to count, as i have a lever welded to it, it seems to be 44 teeth.  I calculate 1 tooth to be approx 8.2 deg of cam rotation and therefore about 4 deg of crank rotation. If this is correct I must be out by about 4 teeth. I can't understand for the life of me how this has happened.

During the rebuild I have changed the Main Bearings, Cam Chain and Chain guides, Mechanical Seal, all oil seals, Piston Rings, honed the bores and lapped in the valves. I felt sure I had installed the Cam Chain correctly, remembering to align the cam sprocket with the marks on the case, checking the woodruff key was pointing to the indicator mark and checking 2-1/2 teeth from the Key was directly verticle to engine axis. All the time making sure the chain was taught. This is why I am questioning my understanding of the Valve timing spec's. I have read it is not unheard of for compression to rise considerably during the run-in process, but fear the valve timing is set incorrectly.

Is my understanding of the Valve specs correct?

Cheers

Gordon.
Whoops  NoNo.

Silly me the Crank Gear must be Half the number of teeth as the Cam Gear, HMMMM I'm about 16 Deg on the Crank past where the spec say's I should be. Looking like I must pull the motor again, as I must be 1 tooth out.

CX PHREAK

Re: Valve Timing
« Reply #4 on: 26-Nov-18, 22:50 »
I think your calculation to arrive at 4 teeth must be incorrect. Using your own figures 4 teeth gives me 32.8 degrees. These are an interference engine and this likely would cause valve clash.

 Back to your late cam timing. Your bike likely has wear in the upper rockers and shafts and this would likely have a delaying effect on the action at the valve head.

Cam timing is also checked with valve lash reduced to zero in most cases. If you've not done this this will also have an effect.



Your bike has likely already used up camchain adjustment on assembly. The reason : wear on the sprockets, then they stretch rapidly to about the 1/3 mark when in a running engine. Make your adjustments often.

Your piston rings will not be bedded so compression is likely naturally low at this point.

 Do multiple retorques on Joes gaskets as they are quite compressible. They are good gaskets. Just help them settle in. When retorquing immediately reset the valve clearances. They close as the gasket compresses. If you have already performed a retorque ....

 Is the bike running?

 I feel you may have developed the post assembly paranoia....

nodrog

Re: Valve Timing
« Reply #5 on: 27-Nov-18, 00:06 »
I think your calculation to arrive at 4 teeth must be incorrect. Using your own figures 4 teeth gives me 32.8 degrees. These are an interference engine and this likely would cause valve clash.

 Back to your late cam timing. Your bike likely has wear in the upper rockers and shafts and this would likely have a delaying effect on the action at the valve head.

Cam timing is also checked with valve lash reduced to zero in most cases. If you've not done this this will also have an effect.



Your bike has likely already used up camchain adjustment on assembly. The reason : wear on the sprockets, then they stretch rapidly to about the 1/3 mark when in a running engine. Make your adjustments often.

Your piston rings will not be bedded so compression is likely naturally low at this point.

 Do multiple retorques on Joes gaskets as they are quite compressible. They are good gaskets. Just help them settle in. When retorquing immediately reset the valve clearances. They close as the gasket compresses. If you have already performed a retorque ....

 Is the bike running?

 I feel you may have developed the post assembly paranoia....
Yes I definately have Post Assembly Paranoia  happy0194.

Yes the bike is running very nicely.

I did mess the calc up though, 1 Tooth is about 8.2 deg's of the cam shaft, therefore 16 deg out on the crank. My results for the inlet valve opening (1mm Lift) were 10 deg ATDC when the spec says 6 deg BTDC.  Strangely coincidental ?



CX PHREAK

Re: Valve Timing
« Reply #6 on: 27-Nov-18, 00:26 »
I doubt it would be running well if the timing was one tooth off at the cam.... though I've never actually seen it. I think it would run like abag of cr@p though, if it didn't eat itself.

 The crank pointer is vague being so far distant but a misalignment at the cam is obvious. If you flip the cam sprocket one tooth either way the misalignment is obvious.

 Check your valve clearances, if overtight you will lose compression.

 Other than that, doing regular retorques with valve clearance checks and camchain adjustments I'd just short change the oil and filter and enjoy and evaluate it for a while.

nodrog

Re: Valve Timing
« Reply #7 on: 28-Nov-18, 17:39 »
I doubt it would be running well if the timing was one tooth off at the cam.... though I've never actually seen it. I think it would run like abag of cr@p though, if it didn't eat itself.

 The crank pointer is vague being so far distant but a misalignment at the cam is obvious. If you flip the cam sprocket one tooth either way the misalignment is obvious.

 Check your valve clearances, if overtight you will lose compression.

 Other than that, doing regular retorques with valve clearance checks and camchain adjustments I'd just short change the oil and filter and enjoy and evaluate it for a while.
I think you are correct about the Valve timing.
I have now checked both the open and closed angles. Doing so has allowed me to calculate the center-line.
I have attached a file comparing my Valve measurements against Spec.
The first thing I noticed is that the valves are not only opening late, they are also closing early.
Using these figures I can see that the Center-lines of my cam are close enough to spec. Leaving me to the conclusion that my cams and lower rocker arms are worn.

Not sure where to go from here, Engine is out again. It was starting and Idling Ok.

What would others do in this situation.  [ You are not allowed to view attachments ]  



Seagrass

Re: Valve Timing
« Reply #8 on: 28-Nov-18, 18:08 »
You are totally overthinking this and I have doubts that your diagnosis is correct 

CX Phreak has rebuilt more than one of these motors and continues to be one of the most respected guru’s for the CX500.

I agree with him that I suspect your low compression figures are due to the new rings and honing of the bore and the compression will rise once the engine is properly run in.

If you must do something, remove the rear cover and check the camshaft/valve alignment.

If it is OK as suggested, put it back together and go out riding. If it needs adjusting, make the adjustments and then put it back together and go out riding.

Seagrass

nodrog

Re: Valve Timing
« Reply #9 on: 28-Nov-18, 19:56 »
Thanks Seagrass I may have a tendancy to overthink everything.

I appreciate CX Phreaks input, as I do yours,  infact I am hoping he checks out the file I posted.

A little bit about me.

 I like repairing things, I am a Fitter and Turner with 40 years experience, and trying to understand my bike and how it works  inside and out. I have never repaired a Motorbike before and know very little about them. This process is a learning experience for me.  When I do ride the Bike I want the satisfaction of understanding what makes it tick and the knowledge necessary to keep it ticking.
 
For me it is as much about the repairing as it is about the riding.

I have now learnt that the center-line specs are a much better indicator as to whether or not the valve timing is correct.




CX PHREAK

Re: Valve Timing
« Reply #10 on: 28-Nov-18, 22:10 »
I actually don't get how duration can be lost.

 In the pics your bike appears to be an 81 shadow which will have a CDI spec cam and I assume this is the chart you are using.

 But, I think the TI cam actually has a shorter duration for better mid range. If I remember right, roughly 35 {+180} degrees as opposed to about 52 {+180}. Can you verify your ignition type or possible cam replacement at some time?

nodrog

Re: Valve Timing
« Reply #11 on: 29-Nov-18, 00:40 »
Iactually don't get how duration can be lost.

 In the pics your bike appears to be an 81 shadow which will have a CDI spec cam and I assume this is the chart you are using.

 But, I think the TI cam actually has a shorter duration for better mid range. If I remember right, roughly 35 {+180} degrees as opposed to about 52 {+180}. Can you verify your ignition type or possible cam replacement at some time?
Thanks for the info mate,

I will contact the previous owner tomorrow, I got the bike from a mate, it was in bits but the cam was in the motor. It is possible that the cam was changed at some time, i will look into it.'I was definately of the opinion that the bike was a CX500 (b) (1981 Australian) The engine number and frame number confirm this.
It is a CDI.
Do you think it would hurt to run it with this cam. Did i mention that the Chain setup seems correct? I have checked it again today.

Seagrass

Re: Valve Timing
« Reply #12 on: 29-Nov-18, 08:02 »
Gordon thanks for the info. I also have a background as a fitter turner as I did the trade course in the 1970's as part of my apprenticeship in weighing equipment. I have never actually been employed as a fitter and turner BUT the disciplines of that trade were certainly practiced while I was working for Avery Scales and I have continued to use some of those disciplines throughout my life.

I think the main problem you are having with the valve timing is that your assessment of the valve timing and Honda's documented values do not and possibly cannot, ever match up. Cam/valve timing can be measured in many different ways and if you have ever had a camshaft re-ground you begin to understand that it is a bit of a "black art". I cannot remember the exact details but some times measurements are given based on a reference point of so much lift and others do it from baseline. It really can be very confusing.

I suspect the only way you are going to be able to be 100% assured everything is OK, is if you are able to do the same measurements on another "known to be good" engine. This is probably not likely to happen unless you can find another forum member close to you that currently has an engine out of their bike.

What I am trying to say is that as you have now double checked that the cam chain is installed correctly, I suspect that everything is actually OK even though your measurements tell you there is something wrong. The other reason I say this is because you have already told us that "Yes the bike is running very nicely"

Hope this helps.

Seagrass

nodrog

Re: Valve Timing
« Reply #13 on: 29-Nov-18, 10:20 »
Gordon thanks for the info. I also have a background as a fitter turner as I did the trade course in the 1970's as part of my apprenticeship in weighing equipment. I have never actually been employed as a fitter and turner BUT the disciplines of that trade were certainly practiced while I was working for Avery scales and I have continued to use some of those disciplines throughout my life.

I think the main problem you are having with the valve timing is that your assessment of the valve timing and Honda's documented values do not and possibly cannot, ever match up. Cam/valve timing can be measured in many different ways and if you have ever had a camshaft re-ground you begin to understand that it is a bit of a "black art". I cannot remember the exact details but some times measurements are given based on a reference point of so much lift and others do it from baseline. It really can be very confusing.

I suspect the only way you are going to be able to 100% assured everything is OK, is if you are able to do the same measurements on another "known to be good" engine. This is probably not likely to happen unless you can find another forum member close to you that currently has an engine out of their bike.

What I am trying to say is that as you have now double checked that the cam chain is installed correctly, I suspect that everything is actually OK even though your measurements tell you there is something wrong. The other reason I say this is because you have already told us that "Yes the bike is running very nicely"

Hope this helps.

Seagrass
I like this idea mate, helps a lot.

I do know where there is another engine nearby. I will contact the owner (A good friend) and see about checking it today.

will let you know how i go.

Mins Man

Re: Valve Timing
« Reply #14 on: 29-Nov-18, 17:29 »
I have continued to use some of those disciplines throughout my life.


Very interesting Cephas.......please tell us how your fitter and turner skills apply to your current employment. :tease:

Seagrass

Re: Valve Timing
« Reply #15 on: 29-Nov-18, 18:47 »
I have continued to use some of those disciplines throughout my life.


Very interesting Cephas.......please tell us how your fitter and turner skills apply to your current employment. :tease:

I often have fits and I can turn nasty if pushed too far rolleye0012

Seagrass

82 Turbo & 2000 Valkyrie

Re: Valve Timing
« Reply #16 on: 29-Nov-18, 18:57 »
 I know if I were a fitter and turner - I would definitely fit something somewhere for you Harry and then turn it for you as well - an aptly placed rough ended pineapple would be my weapon of choice.


 lmao

nodrog

Re: Valve Timing
« Reply #17 on: 29-Nov-18, 22:02 »
Gordon thanks for the info. I also have a background as a fitter turner as I did the trade course in the 1970's as part of my apprenticeship in weighing equipment. I have never actually been employed as a fitter and turner BUT the disciplines of that trade were certainly practiced while I was working for Avery scales and I have continued to use some of those disciplines throughout my life.

I think the main problem you are having with the valve timing is that your assessment of the valve timing and Honda's documented values do not and possibly cannot, ever match up. Cam/valve timing can be measured in many different ways and if you have ever had a camshaft re-ground you begin to understand that it is a bit of a "black art". I cannot remember the exact details but some times measurements are given based on a reference point of so much lift and others do it from baseline. It really can be very confusing.

I suspect the only way you are going to be able to 100% assured everything is OK, is if you are able to do the same measurements on another "known to be good" engine. This is probably not likely to happen unless you can find another forum member close to you that currently has an engine out of their bike.

What I am trying to say is that as you have now double checked that the cam chain is installed correctly, I suspect that everything is actually OK even though your measurements tell you there is something wrong. The other reason I say this is because you have already told us that "Yes the bike is running very nicely"

Hope this helps.

Seagrass
I like this idea mate, helps a lot.

I do know where there is another engine nearby. I will contact the owner (A good friend) and see about checking it today.

will let you know how i go.

Well Seagrass,

I checked my mates motor today using the same procedure I applied to my own motor. I got exactly the same results on his motor. I don't think this is coincidence, obviously I have miss interpreted the spec's. Now I will put it back together, run it in and get over my (to quote CX Phreak ) "Post Assembly Paranoia"

Cheers.

rooray

Re: Valve Timing
« Reply #18 on: 08-Dec-18, 08:03 »
Just use water in the radiator, without coolant too. Add coolant about 300+k after retorquing the head bolts.
Coolant is slippery and will find any weak point.
The gaskets need to be fully “at home”

 


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