Author Topic: Running like a dog Part II  (Read 543 times)

Offline Nurse Julie

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Re: Running like a dog Part II
« Reply #15 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 #16 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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Offline Nurse Julie

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Re: Running like a dog Part II
« Reply #17 on: September 10, 2019, 02:18:56 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)
Great, I hope they find the problem for you. It's strange because in the 400/550 Haynes manual they make no mention of pulling the tappets up and securing them (can't remember if it actually says elastic bands or not) before refitting the rocker cover but it definitely shows a picture and explains it in the 500 manual 🤔 I'm not sure if it shows this way in the 750 manual, can't remember at the moment. I know Trig ties them all up with laccy bands on all engines  to prevent damage to the valves whilst bolting the rocker cover down in sequence.
« Last Edit: September 10, 2019, 02:21:09 PM by Nurse Julie »
Im a Nurse, trust me, this won't hurt.....much !!!

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Offline hairygit

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Re: Running like a dog Part II
« Reply #18 on: September 10, 2019, 02:43:59 PM »
Not in the 750 manual Nursey, separate rocker cover, the tappets/rockers are mounted on the cam carriers.
If it's got tits or wheels, it's hassle, if it's got both, RUN!!!

Offline Nurse Julie

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Re: Running like a dog Part II
« Reply #19 on: September 10, 2019, 02:47:17 PM »
Not in the 750 manual Nursey, separate rocker cover, the tappets/rockers are mounted on the cam carriers.
Yep, indeed you are correct Mr Hairy....and thats exactly word for word what Trig has just told me 🙄🙄🙄🙄 Its the Cypriot beer and the sun, I'm brainwashed ....and bloody lovely it is too, being brainwashed that is 🤣🤣🤣🤣
« Last Edit: September 10, 2019, 02:50:54 PM by Nurse Julie »
Im a Nurse, trust me, this won't hurt.....much !!!

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Re: Running like a dog Part II
« Reply #20 on: September 10, 2019, 02:54:30 PM »
The 750 has the rockers etc fully installed prior to cam cover being fitted so the scenario doesn't occur on that, just the smaller capacity fours which are all the same.

Out of interest, what do the rockers catch on if you leave them unelasticated?  I understand the process of fitting them but not the precise layout that would give some sort of interference.

It's highly unlikely that you bend a valve stem like this I'd guess.  They are just very tough to bend at the top end of valve.

But,  if you left the engine at TDC for number one cylinder for example, could you then get a situation in which you pushed the valve down into the top of the piston from "snagging" the rocker arm as you close the rocker cover gasket.  Ie, exactly what you are trying to avoid by using elastic to keep the rockers up.
If you can do that, then it's more likely to bend the valve using the head as leverage against the piston.

If that's a viable scenario,  then it would most likely be #1 cylinder in all probability if you've just checked cam timing is correct before you install cover. And I'd have a guess at exhaust on that cylinder.

Offline paulbaker1954

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Re: Running like a dog Part II
« Reply #21 on: September 10, 2019, 03:03:49 PM »
The 750 has the rockers etc fully installed prior to cam cover being fitted so the scenario doesn't occur on that, just the smaller capacity fours which are all the same.

Out of interest, what do the rockers catch on if you leave them unelasticated?  I understand the process of fitting them but not the precise layout that would give some sort of interference.

It's highly unlikely that you bend a valve stem like this I'd guess.  They are just very tough to bend at the top end of valve.

But,  if you left the engine at TDC for number one cylinder for example, could you then get a situation in which you pushed the valve down into the top of the piston from "snagging" the rocker arm as you close the rocker cover gasket.  Ie, exactly what you are trying to avoid by using elastic to keep the rockers up.
If you can do that, then it's more likely to bend the valve using the head as leverage against the piston.

If that's a viable scenario,  then it would most likely be #1 cylinder in all probability if you've just checked cam timing is correct before you install cover. And I'd have a guess at exhaust on that cylinder.

Here is the picture from the Honda manual, I think I can see that if you end up with a rocker in that sort of position its not hard to bend a valve maybe


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If you think there's light at the end of the tunnel it's usually another train !!

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Offline Nurse Julie

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Re: Running like a dog Part II
« Reply #22 on: September 10, 2019, 03:24:50 PM »
The 750 has the rockers etc fully installed prior to cam cover being fitted so the scenario doesn't occur on that, just the smaller capacity fours which are all the same.

Out of interest, what do the rockers catch on if you leave them unelasticated?  I understand the process of fitting them but not the precise layout that would give some sort of interference.

It's highly unlikely that you bend a valve stem like this I'd guess.  They are just very tough to bend at the top end of valve.

But,  if you left the engine at TDC for number one cylinder for example, could you then get a situation in which you pushed the valve down into the top of the piston from "snagging" the rocker arm as you close the rocker cover gasket.  Ie, exactly what you are trying to avoid by using elastic to keep the rockers up.
If you can do that, then it's more likely to bend the valve using the head as leverage against the piston.

If that's a viable scenario,  then it would most likely be #1 cylinder in all probability if you've just checked cam timing is correct before you install cover. And I'd have a guess at exhaust on that cylinder.

Here is the picture from the Honda manual, I think I can see that if you end up with a rocker in that sort of position its not hard to bend a valve maybe


(Attachment Link)
That is exactly the position, with the tappet touching just the very side of the top of the valve stem when tightening down the rocker cover, that causes bent valves. That's why the manual puts huge importance on making sure they are not touching so as to prevent bent valves.
Edit...sometimes you are given a warning that things are not right by the threads stripping when trying to do up the bolts as there is too much resistance and either the thread will strip first or if not, then the valve bend. Something has got to give if the tappet is touching the valve in the wrong place.
« Last Edit: September 10, 2019, 03:32:14 PM by Nurse Julie »
Im a Nurse, trust me, this won't hurt.....much !!!

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Offline matthewmosse

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Re: Running like a dog Part II
« Reply #23 on: September 10, 2019, 07:47:22 PM »
One of mine gave a clear sighn this was the issue, the tappet and top of valve both went blue with heat discoloration. To ride it was ok for maybe a mile, then rough as a badgers rear end. Was mostly ok again if allowed to cool.  That engine still sat in a corner someplace. If that's the problem I geuus the effected valve and guide need replacement. Should be easy enough to spot by rolling the valve stem along glass and testing if a feeler gauge can slip under it at various points as its rolled. Is it viable to ream a valve stem rather than replace and then ream the new one? Probably not.

Guy I bought my first 550/4 from said he had on some bikes stereightened valves that had bent when camchains had let go and got the bikes going again, but given the dammage a dropped valve can do it's a step too far even for me.
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Re: Running like a dog Part II
« Reply #24 on: September 10, 2019, 08:43:18 PM »
This has made me laugh,  I clipped it to remind me of what some do inside engines.

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Looks like it's been running a while too  ;D


Offline Erny

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Re: Running like a dog Part II
« Reply #25 on: September 10, 2019, 09:23:15 PM »
 ;D ;D ;D ;D
never seen such "repair"
But can imagine, somewhere in the middle of nowhere in the past (no spares avail) that can fix issue ;)

I still remember in communist times in Czechoslovakia, some guys fixing rod's bearings with layers of aluminium foil - and it was working quite well for some time
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Offline matthewmosse

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Re: Running like a dog Part II
« Reply #26 on: September 11, 2019, 02:15:03 PM »
Is that what I think it is? A plate screwed to the top of a piston? I have seen it before but what a bodge. Kind of thing some of my mates used to attempt. Amazing how long an engines will last with sutch ' repairs' I had a dumper engine once that had obviously run some considerable time with a piston top knocking around in the combustion chamber, long enough for the exhaust port to be chocked with carbon build up til the ports were pencil sized holes. Other cylinder was fine, it would probably still have run.....
Got a 500/4 with rust and a sidecar and loadsa bits. nice and original and been round the clock

Offline paulbaker1954

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Re: Running like a dog Part II
« Reply #27 on: September 11, 2019, 03:20:49 PM »
Is that what I think it is? A plate screwed to the top of a piston? I have seen it before but what a bodge. Kind of thing some of my mates used to attempt. Amazing how long an engines will last with sutch ' repairs' I had a dumper engine once that had obviously run some considerable time with a piston top knocking around in the combustion chamber, long enough for the exhaust port to be chocked with carbon build up til the ports were pencil sized holes. Other cylinder was fine, it would probably still have run.....

I was trying to work out what it was - unbelievable !!!
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Re: Running like a dog Part II
« Reply #28 on: September 11, 2019, 03:34:50 PM »
Yes,  top of piston #3 watercooled 750 Suzuki triple.

You'd have to say it's inventive  ;D at a guess.

Offline paulbaker1954

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Re: Running like a dog Part II
« Reply #29 on: September 13, 2019, 10:44:48 PM »
Ok head off AGAIN and checked valve leakage by putting petrol in combustion space-no leakage but I am guessing that if it was top of stem that got bent putting cover back on that would be expected as the bend would be above the guide (opinions please).

Taking head to local machine shop for valve check and overhaul next week so will know more then
If you think there's light at the end of the tunnel it's usually another train !!

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