What systematic checks for cause of single cylinder running?

[Edcase]

Going to take the monster to bits tomorrow to try and find the cause of what I think is running on one cylinder.

What are the obvious causes and in the order of easiest to check?

thanks
Ed

[svstreetfighter]

Not really systematic but when I suspected mine was running on one cylinder (a while back now) I spat (yummy) on the front exhaust header pipe and it didn't evaporate....ergo the front cylinder was not firing. I checked fuel flow through the carbs, all good, and traced it down to a dodgy spark plug (which in my case was sparking, but replacing it cured the problem straight away).

The other approach you could use (as many have suggested already) is take it down to Rosso Corse in Bethnal Green and they'll probably find the problem in minutes :thumbsup:

HTH

[Edcase]

Will I cause damage riding it from Dulwich to bethnal green with 1 cylinder?

[Edcase]

I think maybe I will just try changing the plugs and see if that cures it, anyone know what plugs I need for a 92 M900? The website I looked at listed the m900 as 97>?! Are they the same as the 91> 900SS?

[svstreetfighter]

I use NGK Iridium DPR8EA-9 in my M900 '94

Give Ray or Marcus a bell at Rosso Corse (020 7780 9764) about riding it on one cylinder. I think it may put undue strain on the remaining cylinder which could lead to costly damage.

HTH

[benson]

Try to avoid one cylinder if you can if only for the noise! I had to ride mine on one for about 8 miles - just try not to strain it too hard and if you can avoid stopping then great!

The plugs are DPR8EA - widely available at most bike shops and Hein Gerick always have a good supply.

If it runs on two when you change the plugs i'd still recommend getting to the Rosso Corse but it's Marcus' stag weekend so best to leave it until next week now - and they're closed on Mondays ( I do so hope they don't do themselves permanent damage!!) but give them a ring - they've got my monster as I type and I'd trust them totally to do a good job with yours...

All thes best!

[Edcase]

Lovely, very helpful thanks guys. The vespa is back on the road and I have a HG just up the road in stockwell. The more I think about it the more I am convinced its plugs, it started a couple of weeks back on that very hot sunday we had, I had the missus on the back and in stop/start traffic in central London and it got very hot. it started getting jerky on part throttle, then it was the next day I had the single cylinder issue.

I am also going to drop to a 14T on the front as she can be a bit clunky in traffic!

[benson]

Best of luck and hope it gets sorted for you soon!

[jerry]

1st plugs, 2nd check plug cables by swopping , 3rd change coils by swopping ,

jerry

[Edcase]

turns out it was just plugs after all!

They were very very black, assume that is from overheating? Or overfueling?

Gonna book it in this week for a general service too.

[benson]

More than likely over fuelling - the service should sort it out for you.