CB750 DOHC: Ticking sound
PWBarrett
http://mysite.verizon.net/barrettmanor/EngineTick.mp3
is a link to an mp3 I just recorded of the worrisome ticking sound it's
making.
It doesn't do it until it warms up a bit.
I've done the cam-chain auto-adjustments, although the upper chain is near
its limit.
To me this doesn't sound like what I'd expect from a loose chain though,
which I would think would be more of a continuous grating as each link
rubbed, rather than a tick per revolution.
It coming more from the #1 side, near the top, but it's hard to pin down
more than that. If I had to guess I'd say around the #1 or #2 intake
valves. (I even tried the old trick of listening through a tube placed at
various spots but that was no use at all.)
I've checked/set the valve clearances multiple times, and they're all
between .004 and .006" (.102 - .152mm).
I don't see any broken links in the chains, or any obvious wear marks.
Is there a minimum recommended shim thickness? On the exhaust side I'm down
to a 260 on one valve.
With the engine out, I've turned it over by hand countless times, and
haven't spotted anything. There's no vertical play in the piston rods.
Any suggestions on what to check next would be appreciated.
Anonymous
"PWBarrett" <sp...@barrettmanor.com> wrote in message
news:4ifyl.1834$6%.287@nwrddc01.gnilink.net...
"Ticking" noises can often be traced to exhaust leakage.
However, it's usually the warm up that results in a dec-
rease, rather than the onset. But, I'd cross that off the
suspect list by having a good look there.
The Older Gentleman
> "Ticking" noises can often be traced to exhaust leakage.
<Nods>
--
BMW K1100LT Ducati 750SS Honda CB400F & SH50 Triumph Street Triple
GHPOTHUF#1 chateaudotmurrayatidnetdotcom
Nothing is more dangerous than an ignoramus with a workshop manual,
a 'can-do' attitude and a cheap set of tools
Robert Roland
wrote:
>This is about a 1980 CB750 (DOHC).
>http://mysite.verizon.net/barrettmanor/EngineTick.mp3
>is a link to an mp3 I just recorded of the worrisome ticking sound it's
>making.
Sounds a lot like an exhaust leak near the cylinder head. Probably a
broken exhaust gasket or a crack in the exhaust pipe.
--
RoRo
PWBarrett
re-torqued the exhaust manifolds just before I made that recording. I'll
check again though.
"Robert Roland" <fa...@ddress.no> wrote in message
news:h0tjs4dqr6e8had6f...@4ax.com...
Rkleinsc...@aol.com
> I put in new exhaust gaskets when I put it back together a week ago, and
> re-torqued the exhaust manifolds just before I made that recording. I'll
> check again though.
>
>
> news:h0tjs4dqr6e8had6f...@4ax.com...
>
> > On Wed, 25 Mar 2009 00:55:28 GMT, "PWBarrett" <s...@barrettmanor.com>
> > wrote:
>
> >>This is about a 1980 CB750 (DOHC).
> >>http://mysite.verizon.net/barrettmanor/EngineTick.mp3
> >>is a link to an mp3 I just recorded of the worrisome ticking sound it's
> >>making.
>
> > Sounds a lot like an exhaust leak near the cylinder head. Probably a
> > broken exhaust gasket or a crack in the exhaust pipe.
Did this start suddenly, gradually, or you don't
know ?
If the chain's near its limits anyway, I'd consider
changing it. Made an amazing amount of difference
when I swapped mine out.
Wouldn't hurt to swap it if it's already near its
replacement interval and might get rid of some
extraneous noise even if it's not the noise you're
trying to locate.
?
> Any suggestions on what to check next would be appreciated.
Check the cam chain link by link, looking for a link that is more worn
out than the rest of the links.
The Older Gentleman
I've never had a camchain that suffered like that, and such a fault
would not cause the aforementioned ticking noise anyway.
My own experience of ticking noises is that they have always been down
to one of two things: a slightly blowing manifold or an over-wide valve
adjustment gap on a single valve.
Robert Roland
wrote:
>I put in new exhaust gaskets when I put it back together a week ago, and
>re-torqued the exhaust manifolds just before I made that recording. I'll
>check again though.
I just listened to the clip again, this time through a different set
of speakers. I am still almost certain it's an exhaust leak.
I also opened the file in an audio editor and counted the frequency of
the tick. It is around 9 ticks per second, or about 540 per minute. If
your engine is idling at just over 1000 RPM, this means that you get a
tick every *second* revolution of the engine. That is exactly what
you'd expect from a four stroke engine with an exhaust leak.
--
RoRo
The Older Gentleman
> On Wed, 25 Mar 2009 12:24:00 GMT, "PWBarrett" <sp...@barrettmanor.com>
> wrote:
>
> >I put in new exhaust gaskets when I put it back together a week ago, and
> >re-torqued the exhaust manifolds just before I made that recording. I'll
> >check again though.
>
> I just listened to the clip again, this time through a different set
> of speakers. I am still almost certain it's an exhaust leak.
Agreed, agreed, agreed.
>
> I also opened the file in an audio editor and counted the frequency of
> the tick. It is around 9 ticks per second, or about 540 per minute.
Coo. There's smart.
>If
> your engine is idling at just over 1000 RPM, this means that you get a
> tick every *second* revolution of the engine. That is exactly what
> you'd expect from a four stroke engine with an exhaust leak.
But, but, but, all fours idle at 1200-1400rpm, don't they?
<Runs and hides>
Robert Roland
wrote:
>I put in new exhaust gaskets when I put it back together a week ago, and
>re-torqued the exhaust manifolds just before I made that recording. I'll
>check again though.
I just thought of another debugging trick: Pull the ignition cable
from one plug at a time. On one of them, the intensity of the tick
should drop noticeably. Once you know which cylinder the noise is
coming from, it will be easier to locate the leak.
--
RoRo
The Older Gentleman
Who Me?
>> I just thought of another debugging trick: Pull the ignition cable
>> from one plug at a time.
> That's a damn good idea.
Unless......it's a double fire arrangement with 2 plugs in series. If that
is the case, you must ground the plug so the "other" one will still fire.
The Older Gentleman
I don't think I've ever removed a plug cap on a Jap four and had *two*
cylinders die.
Mark Olson
> Who Me? <hitch...@dont.panic> wrote:
>
>> The Older Gentleman wrote:
>>
>>>> I just thought of another debugging trick: Pull the ignition cable
>>>> from one plug at a time.
>>> That's a damn good idea.
>> Unless......it's a double fire arrangement with 2 plugs in series. If that
>> is the case, you must ground the plug so the "other" one will still fire.
>
> I don't think I've ever removed a plug cap on a Jap four and had *two*
> cylinders die.
That's because you're forcing the return current from the secondary
winding of that coil to jump across the next best connection, which
is going to be undesirable, creating carbon tracks on the surface
of the coil, etc. Far better to provide a solid return path to ground
through the removed lead, the easiest way to do it is to put a plug
in the lead and clamp the plug to the engine.
paul c
> Who Me? <hitch...@dont.panic> wrote:
>
>> The Older Gentleman wrote:
>>
>>>> I just thought of another debugging trick: Pull the ignition cable
>>>> from one plug at a time.
>>> That's a damn good idea.
>> Unless......it's a double fire arrangement with 2 plugs in series. If that
>> is the case, you must ground the plug so the "other" one will still fire.
>
> I don't think I've ever removed a plug cap on a Jap four and had *two*
> cylinders die.
>
>
I'll bite - How could any computer-less bike with pickups or ignition
pulse generator(s) on the flywheel rather than camshaft (like the
older inline cb750's) not have a waste spark?
paul c
I've been told that's desireable to avoid the chance of burning a
coil. Is that what you mean by 'carbon tracks'?
Mark Olson
Yes, sort of. You can also get energy directed back into the ignition
module when disconnecting plug leads. Trust me, you don't want to do
that. Just put a plug or a screwdriver or something into the disconnected
lead and ground it.
The Older Gentleman
Yes, they do run on the wasted spark principle. But the plugs aren't
wired in series, AFAIK.
Next?
The Older Gentleman
> Far better to provide a solid return path to ground
> through the removed lead, the easiest way to do it is to put a plug
> in the lead and clamp the plug to the engine.
That's what I generally do anyway. Because when I pull a plug, it's
almost always because I want to make sure it's sparking, IYSWIM.
Mark Olson
> paul c <toledob...@oohay.ac> wrote:
>
>> The Older Gentleman wrote:
>>> Who Me? <hitch...@dont.panic> wrote:
>>>
>>>> The Older Gentleman wrote:
>>>>
>>>>>> I just thought of another debugging trick: Pull the ignition cable
>>>>>> from one plug at a time.
>>>>> That's a damn good idea.
>>>> Unless......it's a double fire arrangement with 2 plugs in series. If that
>>>> is the case, you must ground the plug so the "other" one will still fire.
>>> I don't think I've ever removed a plug cap on a Jap four and had *two*
>>> cylinders die.
>>>
>>>
>> I'll bite - How could any computer-less bike with pickups or ignition
>> pulse generator(s) on the flywheel rather than camshaft (like the
>> older inline cb750's) not have a waste spark?
>
> Yes, they do run on the wasted spark principle. But the plugs aren't
> wired in series, AFAIK.
Plugs *are* wired in series on your typical inline four bike engine
with two coils. One end of the secondary winding goes to each plug,
the circuit is completed through the spark gap of each plug and then
through the plug shells and the cylinder head.
Newer stuff with a single coil per plug obviously does not have the
plugs wired in series.
Bob Scott
>The Older Gentleman wrote:
>> Yes, they do run on the wasted spark principle. But the plugs aren't
>> wired in series, AFAIK.
>
>Plugs *are* wired in series on your typical inline four bike engine
>with two coils. One end of the secondary winding goes to each plug,
>the circuit is completed through the spark gap of each plug and then
>through the plug shells and the cylinder head.
>
cylinders that coil fires?
It doesn't sound right to me - surely then a 400/4 wouldn't drop onto 3
in the rain but straight onto 2?
Other thing that springs to mind is that some of the Laverda 180 triples
use ND coils, one single output and the other twin output. I'm told
suitable single output ND coils are rare secondhand and the common dodge
is to buy a pair of coils from a 4 and just tuck the surplus lead out of
the way. I could be wrong here as I've never run a 180 triple myself.
--
Bob Scott
Mark Olson
> Mark Olson <ols...@tiny.invalid> writes
>> The Older Gentleman wrote:
>>> Yes, they do run on the wasted spark principle. But the plugs aren't
>>> wired in series, AFAIK.
>> Plugs *are* wired in series on your typical inline four bike engine
>> with two coils. One end of the secondary winding goes to each plug,
>> the circuit is completed through the spark gap of each plug and then
>> through the plug shells and the cylinder head.
>>
> Hmm, are you sure about that? So if one plug dies you lose both
> cylinders that coil fires?
Yes, I am 100% sure how a dual-output bike coil (most auto coil packs
also work this way) works. The secondary winding isn't connected
to earth- the two HT terminals that connect to the plug wires go
straight to the secondary winding and nowhere else, there is no
internal connection (such as a center tap) of the secondary winding
to earth.
> It doesn't sound right to me - surely then a 400/4 wouldn't drop onto 3
> in the rain but straight onto 2?
Just because there isn't a spark in the gap of one of the plugs doesn't
mean the coil terminal that that plug is connected to isn't somehow getting
the return current back to the other coil terminal. Kirchoff's Law.
Rkleinsc...@aol.com
> The Older Gentleman wrote:
I made up some plug extenders which run between the
plug top and cable and allow shorting plugs to ground
with a screwdriver. Useful for setting idle adjustments
and cable slack.
Mine were made of 1/8" diameter aluminum standoff
spacers tapped to 4mm with a 4mm bolt extending
out one end to connect to the cable and the 4mm
hole at the other end threading onto the spark plug.
Using an insulated screwdriver, you can now short
between the exposed part of the extender and the
cylinder head to cut out one cylinder at a time.
Who Me?
> Yes, they do run on the wasted spark principle. But the plugs aren't
> wired in series, AFAIK.
>
Well, we finally found something you DON'T know. ;-)
I had a Kawasaki I4 from the mid to late 80's that I quite assure you WAS
equipped with 2 plugs in series......with the block as an intermediate
conductor. Since that was a fairly common engine in the Ninja and other
models at the time, I assumed it was a common arrangement in other engines
too. Maybe not.
That fact alone doesn't also make it a double fire but I'm pretty sure the
plugs were paired so that the 2nd one was indeed firing at the end of the
exhaust stroke (wasted).
Who Me?
> Hmm, are you sure about that? So if one plug dies you lose both
> cylinders that coil fires?
>
Yes.....IF the plug fails in such a manner that it goes wide OPEN and the
spark also can't jump to the block. A relatively rare occurance, I would
think.
The Older Gentleman
> > Yes, they do run on the wasted spark principle. But the plugs aren't
> > wired in series, AFAIK.
> >
>
> Well, we finally found something you DON'T know. ;-)
It happens :-)
Which is why I added AFAIK....
But I've still not had (AFAIK) a four drop onto two pots on the rare
occasions when I've removed a plug. I'll have to test this again when I
get home.
Mark Olson
> Who Me? <hitch...@dont.panic> wrote:
>
>>> Yes, they do run on the wasted spark principle. But the plugs aren't
>>> wired in series, AFAIK.
>>>
>> Well, we finally found something you DON'T know. ;-)
>
> It happens :-)
>
> Which is why I added AFAIK....
>
> But I've still not had (AFAIK) a four drop onto two pots on the rare
> occasions when I've removed a plug. I'll have to test this again when I
> get home.
That really won't prove anything one way or another. Go back and
re-read what I wrote about the return current jumping to an
alternate point.
Take a look at any electrical schematic for an inline four or twin
with dual-ended coils.
The Older Gentleman
> That really won't prove anything one way or another. Go back and
> re-read what I wrote about the return current jumping to an
> alternate point.
>
> Take a look at any electrical schematic for an inline four or twin
> with dual-ended coils.
Oh, I'm crap with electrics. Really. It's just something I've never
'got'.
So why does a four keep running on three if you pull off a plug cap,
then?
Who Me?
> Oh, I'm crap with electrics. Really. It's just something I've never
> 'got'.
Yet you somehow feel that you MUST comment on something that you admittedly
"never got".
> So why does a four keep running on three if you pull off a plug cap,
> then?
Maybe someone else will waste their time trying to explain but since you
probably still won't "get it", I certainly am not.
Go back and re-read the previous 6 posts or so.
paul c
> Mark Olson <ols...@tiny.invalid> wrote:
>
>> That really won't prove anything one way or another. Go back and
>> re-read what I wrote about the return current jumping to an
>> alternate point.
>>
>> Take a look at any electrical schematic for an inline four or twin
>> with dual-ended coils.
>
> Oh, I'm crap with electrics. Really. It's just something I've never
> 'got'.
>
> So why does a four keep running on three if you pull off a plug cap,
> then?
>
>
You must've forgotten - that was your old Vauxhall, the one with the
distributor.
The Older Gentleman
> The Older Gentleman wrote:
>
> > Oh, I'm crap with electrics. Really. It's just something I've never
> > 'got'.
>
> Yet you somehow feel that you MUST comment on something that you admittedly
> "never got".
>
Oh dear, oh dear, you really are being objectionable.
Right through this bit of the thread, I have made it plain that I'm not
particularly good on electrics
I've used 'AFAIK'.
I've admitted I'm not good on this, and I admit it again. I'm interested
in learning new stuff. On other stuff, a lot of stuff, I know a great
deal. Electrics has always been my blind spot.
I've read Olson's posting, and I still don't really understand it
because... well, read the above again.
Mark Olson
> Mark Olson <ols...@tiny.invalid> wrote:
>
>> That really won't prove anything one way or another. Go back and
>> re-read what I wrote about the return current jumping to an
>> alternate point.
>>
>> Take a look at any electrical schematic for an inline four or twin
>> with dual-ended coils.
>
> Oh, I'm crap with electrics. Really. It's just something I've never
> 'got'.
>
> So why does a four keep running on three if you pull off a plug cap,
> then?
>
<emailed>
The Older Gentleman
Ah. Thanks. Understood now.
Bob Scott
>Bob Scott wrote:
>
>> It doesn't sound right to me - surely then a 400/4 wouldn't drop onto 3
>> in the rain but straight onto 2?
>
>Just because there isn't a spark in the gap of one of the plugs doesn't
>mean the coil terminal that that plug is connected to isn't somehow getting
>the return current back to the other coil terminal. Kirchoff's Law.
>
Now I'd best go and google Kirchoff's law. One of these days I'll
actually understand electrical stuff but I'm not going to hold my
breath.
--
Bob Scott
ian field
"The Older Gentleman" <totallyde...@yahoo.co.uk> wrote in message
news:1ix9dnf.b7tpw6coqmjoN%totallyde...@yahoo.co.uk...
> Mark Olson <ols...@tiny.invalid> wrote:
>
>> That really won't prove anything one way or another. Go back and
>> re-read what I wrote about the return current jumping to an
>> alternate point.
>>
>> Take a look at any electrical schematic for an inline four or twin
>> with dual-ended coils.
>
> Oh, I'm crap with electrics. Really. It's just something I've never
> 'got'.
>
> So why does a four keep running on three if you pull off a plug cap,
> then?
>
The coil is effectively strung between 2 plugs, so the voltage has to jump
the spark gap at a plug at each end to complete the circuit.
If you only lose one cylinder with a plug cap off then the spark is
completing the circuit by some other means, like dodgy insulation on the
floating lead or where it joins into the moulded coil body.
A point raised earlier in the thread, if the leakage spark is allowed to
continue any length of time will burn a carbon track in the insulation, the
leakage track will eventually become permanent - so no spark at the plug gap
when the plug cap is put back on.
PWBarrett
closely at everything, and I don't see any cracks or uneven surfaces. I
replaced the gaskets on that side, put it back together, and it still sounds
the same.
It also doesn't change if I push on the pipes.
I tried running with one plug at a time unhooked (I put an old plug in the
disconnected cap and wedged it against the block just in case there's
something to that). It still ticks no matter what.
So... I pulled the valve cover again. The only thing I can see is maybe the
upper cam chain slapping against the top chain-guide a little at one point
in the rotation. But that would make a sound in the center, and the one
thing I can tell is that the sound is closer to #1 or maybe #2.
I checked the valve clearances again for the umteenth time. What would you
consider a clearance excessive enough to cause noise?
I guess I'll order a cam chain, but just put it back together and ride it in
the meantime.
"The Older Gentleman" <totallyde...@yahoo.co.uk> wrote in message
news:1ix6scc.qi98ry1dtgrpsN%totallyde...@yahoo.co.uk...
> ? <macm...@gmail.com> wrote:
>
>> On Mar 24, 5:55?pm, "PWBarrett" <s...@barrettmanor.com> wrote:
>>
>> > Any suggestions on what to check next would be appreciated.
>>
>> Check the cam chain link by link, looking for a link that is more worn
>> out than the rest of the links.
>
> I've never had a camchain that suffered like that, and such a fault
> would not cause the aforementioned ticking noise anyway.
>
> My own experience of ticking noises is that they have always been down
> to one of two things: a slightly blowing manifold or an over-wide valve
> adjustment gap on a single valve.
Who Me?
> I checked the valve clearances again for the umteenth time. What
> would you consider a clearance excessive enough to cause noise?
>
That depends on what the recommended clearances are.
Does this sound go away ......or change much when the engine is thoroughly
warmed up?
In addition to a valve clearance problem, it could be a weak (or maybe even
cracked) valve spring, a sticky valve guide or a burnt and leaking exhaust
valve.........but the cam chain would still be a good place to start.
paul c
...
> A point raised earlier in the thread, if the leakage spark is allowed to
> continue any length of time will burn a carbon track in the insulation, the
> leakage track will eventually become permanent - so no spark at the plug gap
> when the plug cap is put back on.
>
Thanks, when I queried that I had compression tests in mind. I
believe a number of bikes won't crank with the kill switch on,
certainly I've had a couple of single-cylinder ones like that. I've
no idea what 'any length of time' could be but I imagine it could vary
depending on other conditions. When I've watched people taking
(lengthy) compression tests, I've wondered once or twice why they
didn't ground the plugs, for safety's sake.
PWBarrett
I was using .09 +.05 -.02 just to avoid excessive tightness when hot.
Now I've brought that max back down to the book max of .13, and tightened up
a couple of valves that were on the high side of the range, to bring them
more to the center.
Still ticking. (Maybe it's actually a Timex.)
The sound doesn't go away after a 5 mile ride.
But it does go away sometimes under load, then come back when I let off the
throttle.
Which leads me back to the worn cam chain theory.
I don't think it's a sticky valve guide or a burned valve, because I just
re-worked the head. All the valves travelled freely, and I lapped them and
made sure they didn't leak.
Oh well, when my new chain arrives, I'll see what that does.
'anybody managed to swap an upper cam chain with the engine still in the
frame? Seems like it would be doable. I'm not looking forward to pulling
the engine again.
"Who Me?" <hitch...@dont.panic> wrote in message
news:Cswzl.14573$8_3....@flpi147.ffdc.sbc.com...
paul c
> The book-recommended clearance is .08 mm +.05 -.02
> I was using .09 +.05 -.02 just to avoid excessive tightness when hot.
> Now I've brought that max back down to the book max of .13, and
> tightened up a couple of valves that were on the high side of the range,
> to bring them more to the center.
> Still ticking. (Maybe it's actually a Timex.)
>
> The sound doesn't go away after a 5 mile ride.
> But it does go away sometimes under load, then come back when I let off
> the throttle.
> Which leads me back to the worn cam chain theory.
>
> I don't think it's a sticky valve guide or a burned valve, because I
> just re-worked the head. All the valves travelled freely, and I lapped
> them and made sure they didn't leak.
>
> Oh well, when my new chain arrives, I'll see what that does.
> 'anybody managed to swap an upper cam chain with the engine still in the
> frame? Seems like it would be doable. I'm not looking forward to
> pulling the engine again.
>
>
There are many people here who know more about engines than I do, but
if I'm not mistaken, nobody asked if the four headers heat up equally,
say thirty seconds after starting from cold. One guess I have would
be that if they do, that might eliminate a valve as a possible
culprit. Also, a couple of times, I was able to figure out which
cylinder by putting a heavy screwdriver on each port and laying my ear
on the handle. Just a couple of easy suggestions from an admitted
aamateur...;
The Older Gentleman
> >
> Fair enough, learn something new every day.
>
> Now I'd best go and google Kirchoff's law. One of these days I'll
> actually understand electrical stuff but I'm not going to hold my
> breath.
My reactions precisely :-)
The Older Gentleman
> What would you
> consider a clearance excessive enough to cause noise?
Um, in the case of my old air-cooled Kwak four, about two or three times
the recommended max clearance.
It's an odd'un and no mistake.
Who Me?
> The book-recommended clearance is .08 mm +.05 -.02
> I was using .09 +.05 -.02 just to avoid excessive tightness when
> hot.
Hot/cold is figured into the published specs. Don't try to out-smart the
engineers; you will end up out-smarting yourself !! ;-)
PWBarrett
any of the range of the tensioner so it's fine.)
Still ticks.
I'm hoping it's some shim bucket or other such part that I swapped into this
head, with a clearance on the tight side, that sticks when it heats up, but
might wear in.
OTOH it occurs to me it could be a clogged oil passage, and something's not
getting oil.
At this point I'm inclined to ride it till it seizes up, then push it off a
cliff.
"The Older Gentleman" <totallyde...@yahoo.co.uk> wrote in message
news:1ixbymk.o50q2y14rwc29N%totallyde...@yahoo.co.uk...