CYLINDER NOT FIRING HONDA 550F2 1979

yamaha888 · L Plate Warrior Joined: 17 Mar 2006 Karma :

Trying to help out friend who owns 4 cylinder Honda 550F2 1979 from new . Only done about 2K!!. mostly laid up. Tried to start number 4 (RH) not firing,it sparks ok, carbs were drained and mechanically cleaned incl jets.. Compression good. He thinks it is carb related ? Not sure. Also to Mot needs headlamp parking bulb as exist but can't trace a supplier for parts generally. bulb is 12v 4w small .Anyone any ideas? Sad

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Yamaha 888

tonyyzf · Brolly Dolly Joined: 13 May 2005 Karma :

First off, check its not the plug by swapping it with the plug from number one cylinder, they sometimes show a spark but wont fire.

Next he'll have to check he rebuilt the carb correctly.

To help you narrow it down, it can't be the coils or points cos they are in pairs, 1 & 4 and 2 & 3, the fuel supply should be paired too, carbs 1 & 2 and 3 & 4 should be supplied in pairs. so if one cylinder is off its usually related to the plug, plug lead or individual carb, unless of course there's something more serious wrong with that cylinder but doubt it cos you say the compression is ok.

One thing he could check in the carb, where the main jet screws into a brass fitting in the bottom of the carb, unscrew this fitting and remove the air corrector tube, it might have furred up seeing as how its been laid up.

The bulb is easy to get, its just a standard 12v/4w small bayonet bulb that most cars and bikes used to use for side laights and dash lights etc, should get it at Halfords or any good garage workshop.

Rit · Trackday Trickster Joined: 24 Jan 2006 Karma :

Post or PM me with a pic of the bulb with someone holding it for size. I may be able to help.
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bish777 · World Chat Champion Joined: 11 Nov 2004 Karma :

buy a new float valve for carb 4, as its most likely allowing cylinder 4 to be flooded.
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Nath · World Chat Champion Joined: 28 Jul 2004 Karma :

I didn't think you needed a side lamp for an MOT?

Tried checking for an air leak between the carb and head? I would suspect the pilot jet, because my own 550F1 was only running on 3 cylinders due to a blocked pilot jet (you'd think it would pickup when the throttle was fully opened, but it wouldn't). If you can't blow through it, then it is blocked - Sometimes you can push a thin piece of wire all the way through but the jet will remain blocked, so don't rely on pushing stuff through it and assuming it to then be clear.

Both the K model and F model 550 carbs have overflows, so you'd know if the float valves were sticking open.

You're lucky that it's no 4 that is playing up, since it is easy to take the float bowls off the end carbs with them still attached to the engine.
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