1988 CBR250 (mc19) - scary bang noise

[Newo]

Ok,

So this morning I get up and head down to the garage to start my bike in preperation to leave for work. I turn the key, check the kill switch and hit the start button, rolling on the throttle just a tad (as it normally won't start otherwise) then all of a sudden as the engine turns over it makes a loud bang. Sort of like a fire cracker going off and the engine then stops.

Not sure whats going on, I decide to give it another go to see if I did any serious damage and the damn thing wouldn't stay running. Wouldn't idle, just kept on dying. Would stay running as long as I held the throttle. It sounded very sick as well. I'm no expert at all, however if I had to guess I'd say it almost sounded as if one cylinder wasn't working.

So anyway, I adjust the idle so that it will stay running while I examine it some more, still can't figure it out. Running late for work now so I decide to just ride it as is.

It was totally gutless and had no throttle response at all. Still... had to get to work somehow, and I was running late. After about 3km or so, it started to get some response back and it sounded a little healthier. another 800m or so and I get to work, turn it off and forget about it for now. I was late and the boss wasn't happy.

After work, I start it up and it starts first try. The same as it has any other day. Idles normally (after I undid the adjustment I had made earlier) Sounds healthy, runs well.

What on earth happened this morning? Will it happen again or get worse?

[bogan]

Could be a plug or two, intermittent sparks could cause the big bang, and poor running. Would be the first things I'd have a look at anyway.

[SMOKEU]

Changing the plugs on them is a bit of a cunt of a job, although it's well worth doing if you're unsure of when they were last replaced.

[The Pastor]

Changing the plugs on them is a bit of a cunt of a job, although it's well worth doing if you're unsure of when they were last replaced.

nah its not hard mate, just gotta take the radiator off first

[ducatilover]

Coils, plugs, fuel filter and vacuum leaks. Or possibly the fuel pump was being a prick.

[SMOKEU]

nah its not hard mate, just gotta take the radiator off first

The radiator doesn't have to be removed completely - it's just 3 clamps that have to be released so the radiator can be pushed out of the way slightly.

[ducatilover]

The radiator doesn't have to be removed completely - it's just 3 clamps that have to be released so the radiator can be pushed out of the way slightly.

I'd say old RM would know this, he is the kaumatua of CBRs

Everyone knows you go through the sump to get them anyway.

[The Pastor]

The radiator doesn't have to be removed completely - it's just 3 clamps that have to be released so the radiator can be pushed out of the way slightly.

you got it, EZ as. smaller hands help with the tight spaces tho lol

[SMOKEU]

you got it, EZ as. smaller hands help with the tight spaces tho lol

The dreaded #3 plug nearly had me in tears.

[Newo]

Thanks for the suggestions. I'll keep a close eye on it. It was strange indeed, seems to run alright since though :S

[racefactory]

Na RM is a total n00b when it comes to cbrs, don't let him get near it. I think it's safe to say I'm a fucking pro at cbr plugs now mate, let me know if you get stuck.

Definitely sounds like plugs man, had exactly that before.

[The Pastor]

Na RM is a total n00b when it comes to cbrs, don't let him get near it. I think it's safe to say I'm a fucking pro at cbr plugs now mate, let me know if you get stuck.

Definitely sounds like plugs man, had exactly that before.

now maybe people would stop making me fix there cibbys!