Author Topic: Running like a dog Part II  (Read 4155 times)

Offline paulbaker1954

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Running like a dog Part II
« on: September 09, 2019, 06:13:44 PM »
Starting a new thread as things have changed

Had bike at local mechanic who is convinced the afterfiring on 1 and 2 is being caused by a valve issue.

So I am going to pull the head again but could use some help with steps or procedures I should work through to to check this out

I did do a compression test and this seemed ok but my mechanic said really need to do a leakdown test but problem is I don’t have a compressor. He also said that only sure way to do a leakdown anyway is to take the tapper cover off so nothing is pressing the valves
« Last Edit: September 09, 2019, 06:18:38 PM by paulbaker1954 »
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Re: Running like a dog Part II
« Reply #1 on: September 09, 2019, 09:37:30 PM »
I don't think I understand his reasoning regarding removal of rockers.  T mark on timing will give closed valves on compression stroke for whichever cylinder to be tested. That's assuming your valve clearances verify as ok.

Out of interest what compression psi figures do you have for each cylinder? That should give you a reasonable assessment to proceed with at least.

I'd have thought it's worth checking now to have a record of how it is right before you do any further work on it.
You're looking for 170 psi as ideal two start with.
Did you also test with light oil in each cylinder after taking a dry reading too? So you'll have two figures for each cylinder.

Offline paulbaker1954

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Re: Running like a dog Part II
« Reply #2 on: September 10, 2019, 08:44:45 AM »
I agree about your thoughts that his reasoning is off. AS you say as long as piston is at TDC and there is some slack in the tappet adjusters then that is all you should need for a leak down test.

In any case the mechanic seems very reluctant to take on my bike as he says he is so busy (my thought is he just doesn't want the hassle of taking the project on and he only likes working on more modern injection bikes). That said he is an experienced guy who does a lot of race bike prep and he is clear that he has heard and seen this type of issue associated with valve problems

As to compression test I got a uniform 135 psi across all 4 pots when cold and dry and went up to around 170 with oil in bores. I am not bothered about the 135 reading as there are theories around about why Honda say 170 that are down to using cheaper flexible hose compression testers.

So the compression seems to check out OK so why this damn poor running and after fire.

I decided to go right back to basics and what has changed since it was running well. What has changed is that I changed the Head Gasket and this is when this all started.

So my questions/comments

1) What could I have done (all stupidity included) in the head gasket change that could have damaged/done something to the valves?
2) The afterfire does not happen until the bike gets warm. In fact on first start and off the line seems to be running really well then as the engine gets warmer things just get progressively worse. So the problem is down to something expanding as things get hotter.
3) What is the best attack plan to try and identify a vale issue that gets worse as things warm up?
4) As I am very time limited does anyone know of someone who could fix this for me in the Warrington area?
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Offline hairygit

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Re: Running like a dog Part II
« Reply #3 on: September 10, 2019, 08:54:54 AM »
You may have fractionally bent some valves, probably exhaust ones given the after fire in the pipes, and as the calves heat up the stems expand a fraction, but enough to cause intermittent sticking. That is only a theory, but knowing how easy it is to damage valves fitting the rockers in the 350/400/500 and 550 fours, it certainly warrants further investigation if the head is coming off again. The affected valve seats may show signs of burning as a result, but not much as it has not been ridden much since this started

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Offline paulbaker1954

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Re: Running like a dog Part II
« Reply #4 on: September 10, 2019, 09:00:37 AM »
You may have fractionally bent some valves, probably exhaust ones given the after fire in the pipes, and as the calves heat up the stems expand a fraction, but enough to cause intermittent sticking. That is only a theory, but knowing how easy it is to damage valves fitting the rockers in the 350/400/500 and 550 fours, it certainly warrants further investigation if the head is coming off again. The affected valve seats may show signs of burning as a result, but not much as it has not been ridden much since this started

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Thanks Hairy useful input, one question is you say how easy it is to damage the valves etc. What are the big care points when refitting. May be some clue as to what I have done !!

Also what do you mean by valve "calves"???
« Last Edit: September 10, 2019, 09:11:08 AM by paulbaker1954 »
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Re: Running like a dog Part II
« Reply #5 on: September 10, 2019, 09:28:32 AM »
Agree with HG regarding potential of valve damage and your mechanic guy.

As said above,  if you are taking the head off anyway it'll obviate the need to complete leak down testing.  Just support head upside down and fill each combustion chamber with choice of petrol / Paraffin / isopropyl alcohol and it'll leak out down through the port if it's not sealing properly.

Are those compression values after this build or prior to it? Raising psi with oil is usually considered to improve piston ring sealing generally and not valves which logic is used to seperate the two fault areas. As you indicate,  your stated figures don't initially point to a valve problem.

Warm up has different combustion mix than hot which is generally much easier to burn,  coming off richer running to optimum is more likely to show error as it's less tolerant of combustion inaccuracies.  This is potentially a change that you see rather than a mechanical shift due to heat.

If we make a statement of fault "it's burning something in the exhaust post combustion chamber" then work up potential from there it shows options to consider.

If you switch off while running down hill in gear,  open throttle and the switch back on again,  the exhaust will backfire.  That's one way of producing the effect by way of demonstration of principle as you've actively passed unburnt combustible mixture through the cylinders into exhaust.

So,  with a bent valve,  it could have reduced compression and pass partly burnt mixture (incomplete burn will change depending on mixture)  down exhaust port.  Not much in volume but accumulating until it reaches critical condition to explode,  giving you the symptoms you get.
Hotter combustion temp will just set off backfire more easily than choke running,  which could give you the change you see from engine temperature.

Offline hairygit

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Re: Running like a dog Part II
« Reply #6 on: September 10, 2019, 09:59:30 AM »
You may have fractionally bent some valves, probably exhaust ones given the after fire in the pipes, and as the calves heat up the stems expand a fraction, but enough to cause intermittent sticking. That is only a theory, but knowing how easy it is to damage valves fitting the rockers in the 350/400/500 and 550 fours, it certainly warrants further investigation if the head is coming off again. The affected valve seats may show signs of burning as a result, but not much as it has not been ridden much since this started

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Thanks Hairy useful input, one question is you say how easy it is to damage the valves etc. What are the big care points when refitting. May be some clue as to what I have done !!

Also what do you mean by valve "calves"???
Sorry, bloody auto correct crap that I can't turn off in Tapatalk, it should have said as the VALVES get warm and expand, the stems start sticking in the guides.

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Offline paulbaker1954

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Re: Running like a dog Part II
« Reply #7 on: September 10, 2019, 10:02:34 AM »
You may have fractionally bent some valves, probably exhaust ones given the after fire in the pipes, and as the calves heat up the stems expand a fraction, but enough to cause intermittent sticking. That is only a theory, but knowing how easy it is to damage valves fitting the rockers in the 350/400/500 and 550 fours, it certainly warrants further investigation if the head is coming off again. The affected valve seats may show signs of burning as a result, but not much as it has not been ridden much since this started

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Thanks Hairy useful input, one question is you say how easy it is to damage the valves etc. What are the big care points when refitting. May be some clue as to what I have done !!

Also what do you mean by valve "calves"???
Sorry, bloody auto correct crap that I can't turn off in Tapatalk, it should have said as the VALVES get warm and expand, the stems start sticking in the guides.

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HA HA I get some really crazy auto corrects

Anyway what is the the correct/safe procedure for putting tappet cover back on. I know about the elastic band trick but anything else to watch for
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Offline hairygit

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Re: Running like a dog Part II
« Reply #8 on: September 10, 2019, 10:21:50 AM »
Ensure ALL tappets are slacked off and wound out as far as they will go, the problems occur when a tappet depresses a valve as the rocker cover is tightened down, and the pressure results in bending the valve stem.

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Offline hairygit

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Re: Running like a dog Part II
« Reply #9 on: September 10, 2019, 01:03:58 PM »
I find it much easier when trying to source a valve seat leak to fill the tract up with petrol rather than the combustion chamber, you get more in and it's far easier to see the leakage as you can look directly at the valve seat whilst it's trying to leak past. This was how I lapped valves in, I'd just hold the stem with a tap wrench and see if any petrol leaked past, if the seals good it wouldn't leak past even with lower pressure exerted on the valve seat. I liked using petrol as it was easy to obtain and it was very easy to spot as it leaked past.
   In most situations I would 100% agree on that one Oddjob, but if the stem is fractionally bent, so little that it only gets sticky when the stem is at running temperature, it may not have damaged the seat enough to see any leakage. Also, if the bend is so minor it probably wouldn't show lapping valves in if there is any clearance in the guides.
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Offline paulbaker1954

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Re: Running like a dog Part II
« Reply #10 on: September 10, 2019, 01:18:02 PM »
I find it much easier when trying to source a valve seat leak to fill the tract up with petrol rather than the combustion chamber, you get more in and it's far easier to see the leakage as you can look directly at the valve seat whilst it's trying to leak past. This was how I lapped valves in, I'd just hold the stem with a tap wrench and see if any petrol leaked past, if the seals good it wouldn't leak past even with lower pressure exerted on the valve seat. I liked using petrol as it was easy to obtain and it was very easy to spot as it leaked past.
   In most situations I would 100% agree on that one Oddjob, but if the stem is fractionally bent, so little that it only gets sticky when the stem is at running temperature, it may not have damaged the seat enough to see any leakage. Also, if the bend is so minor it probably wouldn't show lapping valves in if there is any clearance in the guides.

Hairy i tend to agree on this point. I think this is why a compression test is fine because the valves are sticking when they warm up a bit.

I am going to pull the head and take whole head complete with valves to my local machine shop who are really good and have them check clearance, straightness etc. They are very good and have all the right measuring kit

We will see !! I have exhausted pretty much all other possibilities and looking back all this started when I replaced the head gasket. Given that valve timing is right for sure and tappet clearances are OK.................
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Offline Rob62

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Re: Running like a dog Part II
« Reply #11 on: September 10, 2019, 01:25:24 PM »
For what its worth, my advice would be to strip the head and barrels, start with new gaskets / seals and thoroughly inspect all the components, valves, pistons, rings etc as they are refitted, get the head checked for cracks / warpage etc.

Since you don't have a specific diagnosis there is no specific cure, so stripping and rebuilding is probably the only way forward and provides an opportunity to check everything is within spec when refitting... you will hopefully find something and cure the issue. And if you are mechanically competent you can do it yourself and save money as these engines are not high tech...

Good luck with it.. hopefully you will solve it soon.

Offline paulbaker1954

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Re: Running like a dog Part II
« Reply #12 on: September 10, 2019, 01:45:34 PM »
Paul, by any chance did you take the bike to Hammer and Tongs in Warrington?

For some reason I'm not convinced the valves are the problem, not sure why, just a gut feeling, something in my head keeps saying it's a gasket problem, again, I'm not sure why but I can't shut the damned voice in my head up.

I'll be happy if it is a valve problem, at least then I can tell the voice to shut the hell up and stop bothering me.

Am I going mad? it's a possibility.  ;D ;D

No -- I went to IFS engineering in Lymm (Iain Sutton) bit grumpy but seems pretty on the ball. He is convinced it's valves
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Offline Nurse Julie

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Re: Running like a dog Part II
« Reply #13 on: September 10, 2019, 01:50:50 PM »
Oh dear Paul....you have done well so far retaining your sanity over this problem 😀 Did you back off the tappets fully and hold the tappets up with elastic bands when you fitted the rocker cover?
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Offline paulbaker1954

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Re: Running like a dog Part II
« Reply #14 on: September 10, 2019, 02:02:14 PM »
Oh dear Paul....you have done well so far retaining your sanity over this problem 😀 Did you back off the tappets fully and hold the tappets up with elastic bands when you fitted the rocker cover?

Hi Julie
Yes this is doing my head in !!!

Thinking back when I put the cover back on it was a struggle to get on, I backed off the tappets but no lazzy bands. Cover seemed to be offering some "push" resistance. I am now thinking this is what caused the problem but I guess will only know when I get the head off AGAIN and get the valves checked out. Head is off to my local machine shop with valves in for them to check it all out (they are very good)
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