Engine won't start - backfires out the exhaust

[S2art]

Another update...if anyone's interested...

Just for the record I chose not to crank it with the plugs out to clear the cylinders. I turned the fuel valve off the other day and cranked it before and after work... hoped it would shift any left over fuel into the exhaust. You'll probably tell me it was all for naught as there's still fuel in the bowl.

Anyway, plugs came out and replaced them all. This way if it still doesn't start I can atleast rule the plugs out and look at the carbs. The plug for cylinder 1 wasn't visibly wet although it had a definite fuel smell. Plugs 2 - 3- 4 all had fuel residue around the edge. The actual condition and colour of the electrodes looked fine I think - no build-up, no signs of wear, however they were more black than brown. Also gave the air filter a clean while it was out, but it wasn't exactly dirty.

Managed to get it all re-assembled with no leftover bits. Went to start it and I swear it caught for a second straight away. After a few more cranks I realised I'd forgotten to turn the fuel and choke on. After a few more cranks the battery was starting to go so I stopped there and it's on the charger overnight. Thinking about it there's only a small mount of fuel left in the tank and it's bound to be in the reserve level, so I'm feeling confident with a freshly charged battery and more fuel she should hopefully start.

Fingers crossed for tomorrow night. Thanks again everyone.

[SS90]

They are vastly different.



Yes. I'd actualy forgotten about this myself. I mean, who fuck uses Keihins!

shouldn't that be who the fuck uses Kymco?

Never seen that on a multi before, or have I missed something?

[meowmix]

Sounds positive!

And yep, the accelerator pumps are actuated with the throttle butterfly and squirt fuel as much as you can twist. Just a note, my carbs are only 5 years old, and I didn't spot any on some mikunis from '81, maybe its a recent thing? [/hijack]

[quickbuck]

Erm, what do you mean quickbuck?

Disconnecting the pickup lead will completley stop any spark happening whatsoever.

Think about it.

If the pickup lead is disconnected, the coil can't fire.

Sorry,
I read PLUG and got confused.
A better word would be connector.

But remember there is electrons coming out of that connector too.... potentially.

But, yes, that would all but disable the ignition.

[S2art]

Thanks everyone, she's up and running again... phew.

[Sam I Am]

fingers crossed for ya tomorrow

[SS90]

Sorry,
I read PLUG and got confused.
A better word would be connector.

But remember there is electrons coming out of that connector too.... potentially.


But, yes, that would all but disable the ignition.

It's ok, I see you are in Bulls.....Don't worry, I spent the first 5 years of my life there.... I get confused easy too!

I wouldn't sweat too much about the voltage coming out of a trigger pulse wire, about 0.5amps......

[imdying]

It would have gone without taking the plugs out etc... they're too often blamed and not nearly as trouble prone as people make out.

Carb'd CBRs, like a lot of bikes of that era, require a specific method for starting them... most un Honda, but that's the way it is. The fresher the bike, the less picky they are, but still somewhat funny.

Once you've owned that bike for a while, you'll know exactly what to do to start it first time every time; more importantly what not to do. Those CBRs seem to be pretty picky about how much gas you give them when cranking, i.e. don't even think about touching the throttle.

Of course, problem is, once you've upset it, that's it, they need to sit a little before they'll go.

The best ways to combat this are:
- Keep it tuned up
- Learn the 'trick'
- Keep the battery fully charged

As they get older, they tend to get sensitive to poor condition batteries. Having said all that, kept well tuned and having spent some months with it, you'll probably only have trouble once in a blue moon.

There is a danger of arcing a plug and setting the bike on fire turning it over with the plugs out. However you should be able to see, given how hard it is to get even your working assembled motor designed to do nothing else to fire, that it's a pretty small possibility.

[quickbuck]

i.e. don't even think about touching the throttle.

I have been told not to bother on any bike... by some wise man who has cleaned many sets of plugs......