Timing out???

[RE5Guy]

Hello to all from New Zealand. A new boy here...be kind.

I have recently purchased a US spec '79 CBX that was imported from the US by the previous owner with a view to him restoring it, but he changed his mind (hasn't run since 1990 I understand). Unfortunately moisture has got into the engine through overzealous use of a waterblaster by Biosecurity. Can't have any nasty US bugs in New Zealand now can we! This was about 10 weeks ago. As a result I have been trying to get it going to clean it out.

Now I have got it going on 4,5 & 6, but the other 3 are rather problematical and I would appreciate some advice.

I have had the carbs out (3 times, so I am getting good at it) and they have been disassembled and cleaned out with air. As far as I can tell all jets etc are clear, but I am no expert on these carbs. I have also reset the float levels (isn't the manual as clear as mud about where the 15.5mm should be measured from?). One thing that appears "wrong" about the carbs is that none of the slow jets have the plug in them.

It has 6 new spark plugs in and the coils have been replaced with 3 used units (but not by me)

When I start it, it fights back a bit but will fire up and run ok on 4, 5 & 6 although it runs rather rich. On the other three it bucks and backfires through the exhaust and even back through the carbs. A fine mist of petrol also blows back towards the airfilter box from 1, 2 & 3 (I have the airbox that connects to the carbs out).

The headers on 4, 5 & 6 get hot. The headers on 1, 2 & 3 get warm by comparison. The plugs on 4, 5 & 6 are sooty. The plugs on 1, 2 & 3 are clean. No carbon build up or anything. It looks like they are new plugs that haven't been used after I wipe the small amount of petrol off them.

I can flood all 6 cylanders if I want to.

So because of the plug condition I have gone to thinking this is an electrical issue, not a carb one, which is why I am posting here, but I stand to be corrected.

There is spark at 1, 2 & 3. I can see it if I test them earthed to the rocker cover and I can see the occasional backfire through their carbs.

So after a long pre-amble my question is, is it possible for the timing for 1, 2 & 3 to be out and if so how do I test for it and how can I fix it?

The wiring all appears to be connected up correctly from what I can tell from the Manual.

It is not the cams as I have read about how they can be installed 180 out and checked them.

I would also appreciate if someone could explain to me, or point me in the direction of the information, the firing order and how this is generated through the coils?

Of course any other advice and suggestions gratefully accepted.

cheers

Tony

[Dave Ditner]

Tony, from your decsription, I'll bet it's not electrical. The coils fire cylinders in pairs, #s 1 & 6, 2 & 5, and 3 & 4 every time. It's called a "wasted spark" ignition because one of the cylinders is always on the exhaust stroke.
I"ll bet it's not cams either. If the cams both were 180 out, you'd have a very short lived triple with a propensity to eat cam chains. They won't take double the load.

Now a question or two. Does it ever clean out and run normal, like at higher revs? If so your idle mixture is still screwed up.
Have you ever attempted to drain the float bowls in 4 5 & 6 to see if fuel ever made it there? The early models used a single fuel supply and it might not be making it to the far half, maybe because of a plugged junction tube or something like that.
If I recall correctly there should be rubber plugs in some of the passages in the carb body, but it's been so long since I've had a pair down, I'd have to look at a manual to be sure.

Good luck

[alimey4u2]

To add to Daves excellent advice....

I have also reset the float levels (isn't the manual as clear as mud about where the 15.5mm should be measured from?).

Should be measured from the floatbowl flange to the top of the float on/at the centerline of the main jet....

[EMS]

It must be an issue witht he first three carbs or with the cams. These are the only things that tie 1-2-3 together and separates them from 4-5-6.
The fact that a fine mist of petrol also blows back towards the airfilter box from 1, 2 & 3 would indicate that the inlet valves are open when they shouldn't be.

[alimey4u2]

Could also be a "blocked" (restricted) left side exhaust system....

[sixofsix]

...how about a sheared off Oldham coupling on the cams? Long shot, but that separates 1-2-3 cam(s) from 4-5-6?

Or the linkage between carbs 3-4 is screwed up? So sync is waaay off.

Or burned valves?

I like the exhaust restriction thought.

Try a compression test, that will also eliminate a few things.

Good Luck.

Tony

[RE5Guy]

Thanks gents for all the suggestions. It good to see that the CBX community is so knowledgeable and helpful.

Ok I'll work through your comments....

Davey, thanks for your "wasted spark" explanation. I did wonder if that was the case, but now I know.

When I have had the carbs out I have bench tested them when trying to get the float levels right. As part of this I did drain each bowl seperately so I know there is petrol in them all. I also checked all the linkages and they all are working in sync.

I couldn't figure out where to measure the 15.5mm from so through experimentation I settled on 18mm measured from the far end of the float (end fartherist away from the flange) which probably is about the same as 15.5 half way down.

I had a similar thought about the inlet valves, but how can this be? It runs fine on 3, the cams aren't 180 out, so the cam timing must be ok??? Unless they are all burnt out maybe?

A restricted exhaust, now that is a good idea! It isn't blocked because I can see vapour coming out the end as it cleans itself out. But last night when I was looking at it again, searching for inspiration (as you do) I noticed that the chrome changes colour about half way up the left muffler and thought that was strange.

I found an old wasps nest in the instruments, so who knows what may have found a home in the exhaust.

It still has the original exhausts on it. Can anyone point me in the direction of a schematic of what these things look like inside. Has anyone got any suggestions on how to tackle checking this possibility out? I'm guessing pushing a stick down the exhaust hole ain't going to get me far. There is bound to be many twists and turns in there.

Hey Tony, pardon my ignorance, but what is an Oldham coupling?

cheers guys

Tony

[EMS]

, but what is an Oldham coupling?

cheers guys

Tony

It's the small disc that sits between the cam halves. It is a special design coupling that transmits torque and compensates for a radial offset between two rotating pieces, usually shafts. It has two rectangular ridges, one on each side, turned by 90 degrees relative to each other that slide in matching grooves in the shafts (here cams) that it connects.

[alimey4u2]

I was wondering how to check to see if an exhaust system was restricted ?
"Guessing" your problem would be common to 3 cylinders.
I would tape off two of the pipes & a shop vac on "blow" would supply the motive force.
How would you measure the difference ?
Tap in on the delivery side with a long clear plastic tube, fill with water to make a crude U tube manometer.
The level will be displaced due to the "back pressure" & can be measured in inches.
Both levels of displacement should be about the same ??

Worth a try....

[Rick Pope]

Wouldn't that measure pressure, not flow? A partially plugged exhaust would still let enough air pass to have even pressure across all three pipes.

My guess is that if the exhaust is restricted, it would be in the muffler itself, unless there is something wrong with the inner wall of the header pipes....

[Dave Hansen]

Mice can pack an impressive amount of stuff in an exhaust. Could be enough that you see some exhaust come out but not flow enough to let it run.

[alimey4u2]

Wouldn't that measure pressure, not flow? A partially plugged exhaust would still let enough air pass to have even pressure across all three pipes.

My guess is that if the exhaust is restricted, it would be in the muffler itself, unless there is something wrong with the inner wall of the header pipes....

Exactly ...If flow is restricted, pressure increases.....If it were bad enough to cause the symptoms I would think that the higher "relative" pressure would be significant.

[RE5Guy]

Gents,

I have had the left hand exhaust off and had a real good poke around in it with a length of #8 fencing wire and got a good idea of how the internals are constructed but I could find no evidence of any blockage. I didn't set up a manometer but I did tape off the two "attached" headers and stuck my shop vac into the middle header hole after removing it. On suck there is enough air being sucked through the pipe that if I put my hand over the exhaust end the suction is enough for me to be able to lift the assembly off the workbench.

Using this test I would think it is highly unlikely that it is blocked. Anyone disagree?

I've got the carbs off again and have set the floats at 15.5 but haven't put them back in again yet. Is there anything else in the carbs that people would suggest I check?

As I have mentioned before there are no plugs covering any of the slow jets. Is this a potential cause of my problem? What would people expect to happen if the plugs are missing?

I am also planning to check the cam timing for each pot, mainly because I am running out of ideas. I believe the firing order is 153624. Is this correct?

I haven't done a compression test yet. Although I have 2 compression testers, neither has the right size screw in attachment. Might have to do something about that.

thanks

Tony

[daves79x]

Tony:
If your carbs are stamped 'VB60', then they absolutely need the rubber plugs in the idle jet orifice. It will be extremely rich without them. If your carbs are VB62 or VB64, then they don't use them. Also, the VB60 carbs have 2 main jets. You can't do any evaluation without the rubber plugs in place, but it sounds like you still have some plugged idle circuits.

You just need to start from scratch electrically and make sure all wiring and connectors are correct and clean. Make sure all coil wires go to the correct plugs and the low side of the coils are wired correctly. I doubt if you have any top end problems unless the bike has been apart and not run since. The Honda shop manual is a necessity for sorting all this stuff out. Lots of good help on-line for cleaning carbs also.

Dave

[RE5Guy]

Thanks Dave

they are VB60s, looks like I'll need to make up some plugs from something and try that. The plugs on 1,2 and three are very sooty so that all make sense. The other 3 are brand new clean.

All I want to do is get it running properly to make sure I have got all the moisture out of it. I am then going to strip it down for a frame up rebuild. As part of that I will rebuild and refurbish the carbs - including putting the proper plugs in. (someone has painted the carbs black - it looks horrible)

I do have a workshop manual and I have already gone through the wiring circuit. I do have a good spark on all 6 plugs.

I have no idea about the bike's history. I was told it hadn't run since 1990 but who knows if it has been apart or not. The cams have been out because I can see that some incorrect bolts (different head shape) have been used in putting it back together.