Cold Cylinders x 2

[Hound_Dog]

G'Day guys, the 82 is back in my shop. Carbs synced, timing checked, leads, coils, plugs all good. Starts easily, idles ok runs ok to 5k but pops on decel. Problem; cylinders 3 and 4 not firing. Measured pipes at head with laser temp gauge with constant temps on 1,2.5 and 6. 3 & 4 much colder. I definitely have strong spark at both these cylinders so assume it can only be fuel. I am guess carbs need to come off. Pilots blocked? Any advice appreciated. Cheers.

[daves79x]

Maybe, but 3&4 are paired throughout the ignition system. You might have spark at idle, but something is breaking down. Swapping coils is easy to try. But more likely it's a spark unit going bad and on the '82 you can swap them too. Unlikely, but possible is the pulsar unit. Those are the things I'd look at.

Dave

[Hound_Dog]

Thanks Dave, will check it out. Cheers mate.

[cbxchris]

G'Day guys, the 82 is back in my shop. Carbs synced, timing checked, leads, coils, plugs all good. Starts easily, idles ok runs ok to 5k but pops on decel. Problem; cylinders 3 and 4 not firing. Measured pipes at head with laser temp gauge with constant temps on 1,2.5 and 6. 3 & 4 much colder. I definitely have strong spark at both these cylinders so assume it can only be fuel. I am guess carbs need to come off. Pilots blocked? Any advice appreciated. Cheers.

Before you take the carbs off , check the float heights,use the clear pipe , connect to overflow pipe on bottom of float bowl, undo drain screw, and fuel should be level with one of screws at front of carb ! There is thread about it on here with pics, which is very good . ps fuel levels could be too low !

[cbxchris]

viewtopic.php?f=20&t=10466&p=83717&hili ... eck#p83717 Hound Dog , in this link there is a picture of what i mean , hope you can open it !

[Hound_Dog]

viewtopic.php?f=20&t=10466&p=83717&hili ... eck#p83717 Hound Dog , in this link there is a picture of what i mean , hope you can open it !

Cheers mate, got it.

[FalldownPhil]

I am with Dave on this one being 3 & 4
Phil

[Hound_Dog]

Update. I have tested the electricals. Shorting pulse generator as described in the manual shows good spark on all plugs. Swapping spark units made no difference, ditto coils. I have changed all leads just to be sure and still have 3&4 cold. At start up, 1,2,5,6 are all untouchable within seconds, 3&4 can be grasped for minutes and dont come up to anyweher near the temp of the other pipes.

Again I lean towards fuel but would appreciate any commenst from the Gurus.

[Hound_Dog]

G'Day guys, the 82 is back in my shop. Carbs synced, timing checked, leads, coils, plugs all good. Starts easily, idles ok runs ok to 5k but pops on decel. Problem; cylinders 3 and 4 not firing. Measured pipes at head with laser temp gauge with constant temps on 1,2.5 and 6. 3 & 4 much colder. I definitely have strong spark at both these cylinders so assume it can only be fuel. I am guess carbs need to come off. Pilots blocked? Any advice appreciated. Cheers.

Before you take the carbs off , check the float heights,use the clear pipe , connect to overflow pipe on bottom of float bowl, undo drain screw, and fuel should be level with one of screws at front of carb ! There is thread about it on here with pics, which is very good . ps fuel levels could be too low !

Chris, I will check this next. The bike ran very well last time it was in my shop. The clueless owner took it to a dodgy local mechanic who did something he called a "service", paid a stack of money not even knowing what had been done.

[letxbruce]

I'll be interested to hear the resolution on this problem. The odds of two carbs being almost totally out of service as opposed to an electrical gremlin seem very remote. I hope more will be revealed later and you will be soon experiencing the rush from 7000 rpm to redline.

[Hound_Dog]

I'll be interested to hear the resolution on this problem. The odds of two carbs being almost totally out of service as opposed to an electrical gremlin seem very remote. I hope more will be revealed later and you will be soon experiencing the rush from 7000 rpm to redline.

Agreed. I'm going thru everything again tomorrow. Will update and hopefully the old girl will scream again soon!

[daves79x]

That's interesting. The carbs will certainly have to be looked at to eliminate that possibility now, but it's still odd for an electrically paired set of cylinders to be dead because of plugged idle circuitry. But it is certainly possible.

Dave

[Hound_Dog]

Eureka! Fart arsed around with it today. Pulled leads on 3&4 and fitted other plugs. Spark at idle but as revs increased spark became almost non-existant. Given that I have swapped spark units around with the same result, would this then mean the pulse generator for 3&4 is rooted?

[tevan]

How about coil.. you can change leads around on them for a test.

[Hound_Dog]

How about coil.. you can change leads around on them for a test.

Already done.