Cbr600f missfire -newbie question

[Alan461]

Hi folks, 1st post on here

Never owned a bike before or tried to fix one but worked on cars a lot (efi and old school carb)

Passed mod 2 yesterday so when it stopped raining this lunch time went for a blat around the local roads on my newly purchased cbr.

After a while it started to run a bit lumpy so brought it back home to see what was wrong.

Turns out it’s not firing on the n/s cylinder, guess it would be number 4 if you looked at it from the front.

Spark plug is clean and makes a spark when in the coil plug thing, (don’t know what it’s called)

From nearly cold it will run lumpy and the other three exhaust pipes get too hot to touch in a few seconds but no.4 stays cold.

If I gently bring in the choke it starts to run evenly and the no.4 pipe gets hot.

Carb fault is my guess but it all looks a bit complicated and scary to take to bits

Any suggestions to sort this out? Many thanksin advance

[megawatt]

It's No. 1 cylinder if it's the one nearest the kerb. Sounds like a carb or vacuum fault. Check the vacuum line between carb outlet and fuel tap. If all OK, clean the carbs, fuel tap and tank thoroughly.

[megawatt]

Where are you?

[Alan461]

Thanks for the reply, I’m in Leicester.

Going to clean the carbs, looks like a blocked jet etc.

[fastbob]

Assume nothing, start with the simplest and cheapest things first and make notes . In this case check the ht lead and plug cap before you go pulling the carbs off . Ht leads can break down especially in wet weather.

[Tango]

Assume nothing, start with the simplest and cheapest things first and make notes . In this case check the ht lead and plug cap before you go pulling the carbs off . Ht leads can break down especially in wet weather.

 

It's got coil packs on it by the sounds.....so I'd swap number 1 with number 4 and see if the problem swaps over. .......However, it does sound like a blocked jet (assuming it's carb and not injected)......

[fastbob]

Assume nothing, start with the simplest and cheapest things first and make notes . In this case check the ht lead and plug cap before you go pulling the carbs off . Ht leads can break down especially in wet weather.

 

It's got coil packs on it by the sounds.....so I'd swap number 1 with number 4 and see if the problem swaps over. .......However, it does sound like a blocked jet (assuming it's carb and not injected)......

 

I guess I'm a little behind the times , a coil pack is all the coils and plug caps in one clip on unit I presume, like on a modern car .

[megawatt]

Nope. One stick per plug. Just looks like the top seal above the plug, with two thin wires to it instead of an HT lead.

[Alan461]

Thanks for your support fellas

Getting the carbs off took me three hours this morning, idle jet was blocked, cleaned it out with a tiny bit of wire.

Everything went back together without anything broken, started ok with a bit of choke, let the headers cool then did the heat comparison and all four were equal along with resumed smooth running. Youtube was useful although it seems working barefoot is the norm of which I didn’t partake.

[fastbob]

Nope. One stick per plug. Just looks like the top seal above the plug, with two thin wires to it instead of an HT lead.

 

What a jolly good idea.

[fastbob]

Brilliant! Glad you got it sorted . Also brilliant is the fact that you took the trouble to let everyone know what you did and what the result was . Sadly this is not always the case. Well done.