I think, at last, I am on to something

[Kool_Biker]

Aris:
A friend has a machine shop with a fancy machine that, when you lay the rod horizontally, makes two virtual cylinders of the bearing bores and compares them for perfect parallel. This insures they are not twisted. Length measurements are taken then from a known good rod and compared. But the parallel cylinder measurement to me is most important since I've never seen a hydrolocked rod that was not twisted as well as shortened.

Cool!

Also, and I don't know what this would have to do with the spark plug cap being pulled, but I've seen a valve train that had the 'A' and 'B' shim buckets randomly mixed between the 'A' and 'B' bores and this resulted in valves sticking and a whole bunch of clatter on the top end.

Not sure what you mean by this Dave, in the Honda parts catalogue I only see '14731-422-000 LIFTER B, VALVE' where's 'A'?

Any hydrolocked engine I've seen run had a deep knocking in the bottom end from the piston hitting the crank flyweight at BDC.

My racket is DEFINITELY not deep, it is very 'top end' as also verified by my screwdriver stethoscope.

Good news is that the entire top end is serviceable with the engine still in the frame

So you say perhaps begin by tilting the engine, remove cover, remove camshafts, buckets etc, check everything underneath them, and only then move on to remove head, still engine still on bike. If all these OK, only then remove engine?
Thanks, Aris

[Rick Pope]

Aris,

In all the pictures you have of your work as it progress, do you have pics of the weights at that end of the crank? Just a thought, that perhaps you might have evidence that the piston was touching the crank at bdc.....

[Kool_Biker]

Here you go Rick. Any clues?

DSC07590.jpg

DSC07652.jpg

Thanks, Aris

[Don]

The 'racket', as I have tried to show in the clip, is only there when briskly opening the throttle. Which is not to say the bike is perfect at all other circumstances. But is is most evident when briskly accelerating. And it does go away when plug cap 1 is removed.

What in that description makes you so sure it's not an exhaust leak? All that sounds perfectly compatible to me with an exchaust leak . . . . and the video clip noise sure sounds lots more like an exhaust leak than anything mechanical to me

I would at the very least throw a new gasket under the #1 pipe just to see if it made any difference - So simple to do and costs virtually nothing . . . . those are the kind of 'solutions' you should be hoping for ;)

Don

[Kool_Biker]

Sure Don - Although at this point I would not exclude anything 100% (I am far from professional or experienced) the noise was there when I had my test exhaust as well (an old 6 to 1)and continued after I installed by brand new Deklevic.
Also, 'I feel' an exhaust leak should be audible at all RPM, and there should be a tel tale bit of soot at the exhaust port?
Aris

[daves79x]

Aris:
Every CBX head came from the factory with both 'A' and 'B' buckets and bores. There is an 'A' or 'B' stamped into the head at each bore telling you this. The buckets are identified as 'A' or 'B' by what we call 'grind' marks in the lip of each bucket. Two grind marks top and bottom is an 'A' bucket and one grind mark top and bottom is a 'B'. I think 'A' buckets are the larger of the two, but I'm not sure. Anyway, if you get them mixed during installation, some of the larger ones will end up in the smaller holes and some of them stick, they are that tight. The early shop manual does not make this clear, but page 6-19 of the Pro-Link manual shows this clearly. Again every CBX engine out there has both 'A' and 'B' buckets. I suppose since 'B' is all that is available, then they would be the smaller of the two and work in either 'A' or 'B'.

Yes, you can service the entire top end down to the block easily with the engine still in the frame. Just be sure to remove your front fender as it's easy to scratch it taking off the head. Hopefully it won't come to that.

Dave

[Kool_Biker]

Must confess Dave, this is the first time I hear of this, has escaped me completely ...
The head was revamped by a highly reputable firm in the UK, known to the UK CBX Riders Club, and was returned to me with the valves etc, installed. So never had a chance to check, will do soon enough though ..

BTW, compression, as you asked, with the engine warm and valve clearances set on the loose side (max .011, min .09) as follows:
1. 140
2. 141
3. 144
4. 149
5. 150
6. 144
Ring a bell?
Cheers, Ar

[Don]

It could be a valve not closing all the way as Dave suggests - A compression check should tell the tale there even before you take off the valve cover. A small exhaust gas leak could give you your symptoms . . . . I don't think you've ridden it far enough to see any sooty result - It's not a big leak in any event . . . . those are immediately obvious, BTDT

[Edit] - Your compressions look OK . . . . not as even across the board as you would expect from a nearly brand new engine, but close enough to eliminate the valves not closing all the way theory. Did you take them with all the plugs out and the throttle held wide open?

I think any gas leak anywhere is going to be louder with more throttle applied, greatly reduce with steady throttle and go away completely when you eliminate combustion by pulling the plug wire . . . . and those are the symptoms you have. If it's a valve, I suspect an exhaust valve . . . . and intake should cause some popping I would think

Personally from listening to it, I don't think it's related to the connecting rods in any way - If that turns out to be correct, the cure (whatever it is) will certainly be much less painful

Don

[Kool_Biker]

Thanks Don, yes, engine warm, all plugs out, kill switch off, choke off, throttle wide open and a fully charged battery.
Re the conrods theory, I had a look at the old pistons (had kept them) and there is nothing wrong with no 1, or any other one for that matter and from what we can all see in the supplied pics, the crank plates (not sure what u call them) do not seem scuffed which I guess would give away a bent rod.

Re the exhaust gas theory, I can't fault your logic but not sure what else to do other than tighten the exhaust port nuts well .. And don't forget, I had the exact same symptom with my previous test 6:1 exhaust . Still conceivably it could be that both exhausts were a bit short on no 1? BTW I am using new copper, crushable gaskets.

Tomorrow, even before the engine cover comes off I will remove the LHS exhaust manifold and examine gasket and seat, and throw a big - big party if this theory proves to be correct.

[Don]

I'll cross my fingers for you Aris! I'm assuming you changed those copper gaskets between the old exhaust system and installing the new one . . . . and that your collar doesn't bottom out against the head when you tighten it down? I use the white fiber ones since they seem to be good for 3 or 4 remove/reinstalls of the pipes and it seems like I'm always removing my stainless headers to sand and polish them . . . . 2 or 3X a year at least

BTW - I like your self-portrait in the clutch cover on your avatar . . . . bet you selected that one just for that reason ;)

Don

[Kool_Biker]

Bike on the bench and dismantling has just began ..
The copper gaskets were brand new but as I see in the pics below, not sure they were 100% the correct diameter.
Other than this, can you see that elusive exhaust leak?

BTW what is the correct outer diameter of the crushable gasket?

P1060959.jpg

P1060977.jpg

Cheers, Aris

[Jeff Bennetts]

Aris, once you put the exhaust back on, If you still have the noise (God forbid) pull the # 2 plug and see if the noise goes away like before when you pulled the # 1 plug. Just curious if reducing the load on the motor makes the noise go away regardless of the cylinder you kill.

[Don]

On the bottom picture on the far right pipe (which I assume is #1) there appears to be a small area which isn't sealing at about 1 o'clock. In the upper picture (of the head) there appears to be a matching black spot on #1 at about 5 o'clock - Would those two spots line up when the pipes were on the bike??

There are several spots on all 3 of those gaskets that look suspect to me . . . . and #3 has a very thin ring of contact area, much like the suspected area of #1 - #2 looks like a much better fit, no doubt because it's a seperate pipe and can be moved around a little for a better fit. I think we may be looking at a significant difference between the original pipes and the remanufactured ones

I would try a set of the white fiber exhaust gaskets and see if they don't give you a much better seal all around

Don

[Kool_Biker]

Aris, once you put the exhaust back on, If you still have the noise (God forbid) pull the # 2 plug and see if the noise goes away like before when you pulled the # 1 plug. Just curious if reducing the load on the motor makes the noise go away regardless of the cylinder you kill.

Jeff, good point and yes, I have done this. The noise goes away only when no 1 is disconnected.
Thanks, Aris

[Kool_Biker]

On the bottom picture on the far right pipe (which I assume is #1) there appears to be a small area which isn't sealing at about 1 o'clock. In the upper picture (of the head) there appears to be a matching black spot on #1 at about 5 o'clock - Would those two spots line up when the pipes were on the bike??

This is correct. Could it explain the 'racket'? Looks tiny to me, and doesn't seem unique to no 1.

I would try a set of the white fiber exhaust gaskets and see if they don't give you a much better seal all around

Do you know where I can get these?
Also, anyone knows the correct dimeter of the crushable ones. I cannot help thinking these are a bit oversize.

Cheers, Aris