CBR400 NC23 Carb gaskets

[Hadies]

on the hylomar blue. I used these to seal my NC30 carbs and they've worked a treat. No problems.....yet

Good luck with the bike!

[Wozza]

To check which cylinders are firing, when you next start the engine from cold, feel the headers to see which ones heat up. If any don't got hot that'll indicate a pilot jet blockage (if it is a blockage). To check the main jets do the same but hold the revs higher, after letting the headers cool down.

[The Novice]

fantastic tip - thanks Wozza, i did notice that it seemed to pull ok at full throttle but anything less seemed to be 3 cylinders. It must be a blockage in one of the carbs somewhere as its the only thing I have touched!

[The Novice]

I did what you said, when ticking over one of the headers stayed cold, the rest were hot - so obviously firing on 3 cylinders.

I let them cool down, then started it up again, kept it at about 6k revs for about 5 seconds then switched off, all headers were hot.

I think.....that means a fueling problem rather than mechanical or electrical - i should, hopefully be able to just strip the one carb down and find the problem (pilot jet?)? Agree?

[Wozza]

One question - do you know if it was firing on all cylinders at tickover before using the sealant?
It could well be a pilot jet blockage, but not firing on all cylinders at tickover can also be a symptom of carbs needing balancing, which could be an easier job than carb removal and stripping plus resealing. Got some vacuum gauges?

[Cammo]

yes - used hylomar blue - sealed it a treat but i expect you are right and some has gone in one of the carbs somewhere - I was careful too ! but i did put a generous bead on ! hopefully i can find the particular carb easily.

Just a thought but I have a feeling that the nc23 carb float bowls could be the same as the nc30 carbs. Rick Oliver does a set of repro float bowl gaskets for nc30 for 6 quid, they work great.

If anyone could stick a pic of nc23 carb float bowls up I can confirm whether they're the same.

I used to use gasket sealant but was afraid of potential issues like maybe above.

[The Novice]

It was running fine beforehand. It ran ok for about 20 miles after i sealed the float bowls too. then next time i went on it, 3 cylinders. I stripped it all down and cleaned it up again last night - , resealed, with a v thin bead and put back together.......fired up this morning with my fingers crossed.....but still 3 cylinders - still the same one not getting hot at the header running at tickover.

I dont have vacuum guages - i suppose i need to check its sparking first but havent a clue how to get to the spark plugs at the moment !

[The Novice]

Got to the HT lead, side panels, tank and airbox off...again!... and knocked together a tester with a couple of nails in a block of wood (like the hint in the haynes manual!) to check if that particular HT for the dodgy cylinder is sparking, yes it is.

I am waiting for a spark plug tool from wemoto to arrive so i can check the actual plug as they are so deep i havent got anything that gets to them....if that sparks too (fingers crossed it doesnt) then i am back to looking at the carb again.

Assuming it is sparking fine, it may well still be a blockage somewhere - as it was running ok beforehand so i will strip the carbs off again at that point before i send it off somewhere for them to be balanced (as that will cost me money!)

[The Novice]

the damn spark plug is good. took carbs off again and went crazy with the carb cleaner . battery went flat on trying to get her going again so i have to let that charge now until i can start her up again. I am not having much luck at the moment.

I really dont understand what the problem can be now - last resort is to get it balanced or just send it in to the garage to sort as i am getting fed up with continually taking the carbs off !!!! although it takes me no time to do at all now.

fingers crossed it starts up fine tomorrow . i have swapped plugs over 2+3, swapped pilot jet and float+needle between no 1 and 2 carb to try and rule things out so if the same cylinder is still lazy a number of things eliminated.

Have i missed anything obvious or anyone have any tips?

[blueflag]

If you are anywhere near me (Warrington) and you'd like to borrow them I have a set of starting rollers. As long as you have access to a car or van they should save your starter motor!