Dropped a cylinder

[Ingah]

On the way into work today the CB500, against my express wishes, went into single-cylinder mode. Seemed to restrict it to 90mph, so i suspect that's what riding an CB250RS is like

I suspect it's the spark plug as i realised a week ago that i hadn't actually replaced the spark plugs on this bike (i thought i had, but then i found the new spark plugs still in their box...), and it had been a little more reluctant to start, slower etc, for a little while.

However, if i'm wrong, could there be a cause that makes this a dangerous fault? Am currently 30 miles from home at work, and don't want to take a risky ride back when i can just call my breakdown company when i finish working later today.

[Fozzie]

Take the plug out on the non-firing cylinder and have a look, tell us what you see

If anything disastrous had happened you would damn well know about it

[Ingah]

Take the plug out on the non-firing cylinder and have a look, tell us what you see

If anything disastrous had happened you would damn well know about it

Unfortunately i don't have the tools with me to remove the spark plug, so it's either AA, or ride it back..

So, is riding it on a single cylinder going to flood petrol into places where it shouldn't? - because i've got everything i need to check it out and fix it, including new spark plugs, at home. But i'm not at home!

[JellyBelly12345]

Similar thing happened to me on the way to work a few weeks ago. I'd changed the spark plugs end of last year and all was running fine but a few weeks back one of the plugs came out of the cylinder somehow (I think when I tightened it the thread must have been crossed or else the torque wrench was playing silly buggers and lying to me).

Anyway, there was a lot of noise getting the rest of the way to work and the bike wasn;t too happy but I managed to limp to work and back home again afterwards, about 20 miles, without any damage to the bike. Not sure if it was a wise decision but seemed safer than phoning the missus and asking her to stop watching Jeremy Kyle and bring my tools to work.

[Stu]

check connections to the coil and plug also wiring to the coil if you can before you try to get it home

was it wet outside? could just be damp if it was so may start ok when its time to go home

personally i would just get the AA to drag you home and save pratting about and sort it at home

[Fozzie]

Take the plug out on the non-firing cylinder and have a look, tell us what you see

If anything disastrous had happened you would damn well know about it

Unfortunately i don't have the tools with me to remove the spark plug, so it's either AA, or ride it back..

So, is riding it on a single cylinder going to flood petrol into places where it shouldn't? - because i've got everything i need to check it out and fix it, including new spark plugs, at home. But i'm not at home!

 

Id just get it recovered home and get a nice warm van to take you there instead.

Unless the rings on the piston have gone on the cylinder that dropped I wouldnt worry as the fuel will just get kicked out in with the exhaust. In my bike i get pops and rumbles as it slightly over fuels so it should do the same with yours.

Obv if it shed itself of the piston rings then petrol will get down into the engine and contaminate the oil. But like I said earlier you would really know about it if that happened

[cyberwolf]

i had a prob with zzr600 where it was only running on 3 cylinders it turn out too be the carb, something had come off the carb and no fuel was getting to the cylinder, could be something along same lines for you?

[Ingah]

Well the AA man came and guess what.. The problem had gone. Most amusing and embarressing

Then again, my exhaust was definitely blowing, so i had the chance to 'fix' that when i got home (put the bolts around the headers back in, i was expecting that to happen sooner or later anyways).

Spark plugs on the weekend i think, assuming it don't happen again in the meantime

[Stu]

so was it wet or raining when it happened? like i say above could have just been damp

[Ingah]

so was it wet or raining when it happened? like i say above could have just been damp

Yeah it was pouring on the way into work when it went - that fact didn't escape my notice. Today it's been fine, but then that's not surprising as it hasn't been raining!

[Stu]

check the seal on the plug cap sounds as if it just got wet and started earthing to the engine

[Tango]

And spray around the plug caps and connections with ACF50 or WD40....or another electrically safe water repellant....

[Colin the Bear]

Some bikes just don't like the wet. My XJ900 will misfire and act up if it rains. Tried alsorts. The old XV1100 doesn't mind the weather.

[Ingah]

And spray around the plug caps and connections with ACF50 or WD40....or another electrically safe water repellant....

 

Done this last weekend, along with changing the plugs. Made sure to put the caps back on very firmly.

Can't say i'm a fan of this deeply-recessed spark plug business, it makes it impossible to use a torque wrench or fingers so over/under tightening becomes a risk.

Slightly worried because there was a little oil on the ends of the old plugs and this engine is far too young to be on its way out already - worst case scenario i have a nicely broken in (55K miles) spare engine fitted to the donor CB i can borrow

Ah wells, no knowing how long those plugs were in there so the shiny new iridium plugs should do me good for a while now

[Tango]

Can't say i'm a fan of this deeply-recessed spark plug business, it makes it impossible to use a torque wrench or fingers so over/under tightening becomes a risk.

 

My Speed 4 had a sort of Box spanner for the plugs as they are deeply recessed...but the top end of the spanner has a hex shape that a socket can fit.....so the torque wrench can still be used.....

[Ingah]

Can't say i'm a fan of this deeply-recessed spark plug business, it makes it impossible to use a torque wrench or fingers so over/under tightening becomes a risk.

 

My Speed 4 had a sort of Box spanner for the plugs as they are deeply recessed...but the top end of the spanner has a hex shape that a socket can fit.....so the torque wrench can still be used.....

 

I think such a tool is available for Honda but it costs not much under 20 quid!

I got me one of these spark-plugs.co.uk/index.php/products/details/Laser...0059/6505 - but the problem is its not long enough to clear the cradle frame so i have to use it with a short ratchet spanner - a big torque wrench just won't fit.

Suppose with that tool, a deep socket, with a torque wrench on the end, would work, i just refuse to pay so much for the Honda tool.

[Tango]

Yeah...I know what you are saying Ingah.....£20 is a bit steep for a plug spanner. The one I used on the Speed 4 was from the tool kit supplied with the bike. I had problems with my Trophy 900 as the centre plug was directly under the central frame spine.....a right pain to get at.... Plugs only need to be tightened to 12-15Nm....which isn't a lot.... finger tight then approx half a turn from memory.

This is a bit cheaper

[Ingah]

Yeah...I know what you are saying Ingah.....£20 is a bit steep for a plug spanner. The one I used on the Speed 4 was from the tool kit supplied with the bike. I had problems with my Trophy 900 as the centre plug was directly under the central frame spine.....a right pain to get at.... Plugs only need to be tightened to 12-15Nm....which isn't a lot.... finger tight then approx half a turn from memory.

This is a bit cheaper

That finger+half turn tightness sounds about right, used to use something like it for the CG and i'm missing the simplicity. Lord knows how irritated a modern sports machine is likely to make me

And i didn't think of checking eBay

[Tango]

TBH Ingah most bikes are the same......steel plug into an Alloy head really don't need to be too tight.....

[Ingah]

Hence why i should be using a torque wrench, i'm heavy handed enough to cause myself a problem

[Tango]

Hence why i should be using a torque wrench, i'm heavy handed enough to cause myself a problem

Yep....been there mate..... Finger tight and half a turn is probably good enough it you can't get a torque wrench in there....

[klingelton]

torque wrench is over rated! i have a friend who follows the haynes manual to the letter. I'm a little more slap-dash, being too yorkshire to "splash out" on a torque wrench!