Topic: A 3-Cylinder 400F

[seabird]

Hey!  Thoughts, advice, opinions and wild guesses sought for this problem:

She starts easily - but has never (AFAIK) run on #1 cylinder.  Spark's v.good - just to be sure (grasping at straws here) swapped the plug caps 1 with 4 - result, no change.

Running on 2,3.4 she'll keep going as long as I keep pepping her up, but if I leave the throttle alone, she bogs down and dies  - also she tends to start better with the choke/fast idle lever set at 80% open  (she _is_ a four hundred!)(sounds rough, but that's probably camchain noise - have to wait for all 4 to chime in and get sustained idle before I can attend to that).

Hint here - Having run her up for a few minutes, I whipped tha #1 plug out to check. - No carbon, no trace of unburnt fuel.
Is this going to be what I think (fear) it's going to be?

Thanks guys - the Spring's here - it's sunny outside - I wanna ride!!

Help me out here?

Terry
Seabird

[supersport_CB400F]

I hope I don’t have this problem when my turn comes  ……I also hate getting them bloody carbs off but I rekon it’s your worst nightmare and #1 carb is blocked up 

[Tim2005]

Yep, sounds like #1 carb is gummed up- though with some care you can pull off the floatbowl while the carbs are in position. First I'd open the drain screw on that carb & empty it into something to see what comes out - and to make sure that fuel is getting in there.

[TwoTired]

Well if number one carb isn't getting fuel, it'd pretty hard to get that cylinder to fire.  Could be a stuck float or float valve.  If the carb bowl drain screw won't let any fuel out, then you have a solid lead on the problem.  At any rate, its not that difficult to remove the #1's carb bowl with carbs still on the bike.  You can get to float, float valve, slow jet, and main jet to see if they are clear and working.  Only minor contortions required.   

Cheers,

[seabird]

We progress!

Emptied the #1 float bowl as suggested - lo and behold A couple of nice big rust flakes swam out - checked the insode of my nice new (2nd hand) tank and was appalled at the amount of rust waiting to invade my carbs.

"Rumbled" the tank with a handful of spare bolts and nuts - drained it and checked again - appeared to be nothing loose left - when I removed the internal filter, the "mesh" just fell off - David Silver's had another call from me immediately.

Just for laughs and giggles I kicked the beast over with just the fresh fuel left in the carbs and got that lovely 4 cylinder hum for a couple of seconds.OOooohh yeah!

Even bigger bonus - while waiting for the result of the rumble, finally found out why no Instrument park and tail lights - one wrong connection (PO's favourite trick) and a 7 amp fuse that one of the end caps had come off of - re soldered the cap and corrected the connection - now have all lights at last.

I'll rumble the tank once more before fitting the new filter, then hopefully take my first ride on her on Tuesday or Wednesday.

Thanks to all on the forum who have given of their time and experience for me!

Terry
(Seabird).