Coils or carbs?

[c_dug]

Hi all,

I picked up a really tidy low mileage Fazer 600 from a fellow BCFer on Monday for a good price. It was bought in the knowledge that it was running on three cylinders for a while when first started, something I witnessed on the test ride. This is a recent development, it has been kept unused for around a month or so prior to me buying the bike, but when it was last used regularly it was fine.

My assumption at the time was that some of the jets were a bit clogged up, and that a good ride would sort it out. However having now done something in the region of 200 mile or so on it, I'm beginning to suspect it might be the coils or HT leads, the symptoms have me a bit stumped though.

It occasionally seems to bog down at around 3-6krmp, but ticks over dead smoothly and runs perfectly at anything above 7krpm. If you thrash it for a few minutes then it runs nicely for the next 5-10 minutes, but then begins to bog down again at the same sort of revs.

If you ignore the bogging down (for instance last night it was chucking it down so I didn't want to thrash a new bike in the wet) it gets worse and worse until it's on the verge of unridable, but again if you force it through the bogged down spot and thrash it (when I made it to the dual carriageway) it soon clears up. The rain could potentially be a factor in this, but I've only ridden it in the rain once.

It seems to be dropping one cylinder, and then two, which is what has made me suspect it's the coils. But to my knowledge coils would get worse at high revs instead of better - or am I mistaken?

I figured that if it was the carbs at play, it wouldn't keep getting better and then worse again?

So, what do you think?
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I am a bellend, I am a man of constant sorrow, I am a gummy bear, I am a rock.

[MarJay]

Have you checked the spark plugs...?
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F; Cheap project: CBR900RR FireBlade
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[temeluchus]

Drain the float bowl on the offending cylinder.
____________________
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[jaffa90]

As suggested by temeluchus,
Pilot jets work mostly up to 2/3,000 rpm then the main jets take over providing you have a vacuum and carb slide diaphragms in good order.

[Hahadumball]

does sound like the carbs.

pre-warning the carb and airbox are an utter pig to get back in.
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[MarJay]

You have read the bodyguard Fazer thread right?
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F; Cheap project: CBR900RR FireBlade
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[stinkwheel]

9 out of 10 fuelling problems are electrical. But it's easier to strip carbs so that's what everyone does.

Find which pot or pots it's dropping out then start swapping ignition componants over and see if the problem moves.
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I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Hahadumball]

[sickpup]

[ADSrox0r]

[c_dug]

[stinkwheel]

[c_dug]

Also, relevant information for what difference it makes.

1999, 16000 miles, k&n air filter, sports "not for road use" exhaust, dyno-jet kit fitted around 2,000 miles back (and has run fine since then - until now).
____________________
I am a bellend, I am a man of constant sorrow, I am a gummy bear, I am a rock.

[chris-red]

I'd change the plugs, it's a simple relatively cheap and probably worth doing anyway.
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Well, you know what they say. If you want to save the world, you have to push a few old ladies down the stairs.
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[c_dug]

To my knowledge they were done quite recently, but I guess it wouldn't do any harm!
____________________
I am a bellend, I am a man of constant sorrow, I am a gummy bear, I am a rock.

[Hong Kong Phooey]

[temeluchus]

Usual suspects for a single uncooperative cylinder

Rotten ht lead, usually at the join between the cap and the lead but occasionally at the coil

Duff plug cap

Float bowl full of water

Duff spark plug

Spark plug tunnel drain blocked and the tunnel has filled with water

Seeing as it idles ok i would suggest draining the float bowls- water effectively reduces the amount of fuel in the carb giving odd results. This can be done without removing anything.

Then inspect the ht leads and caps for rot

Then look at the coils themselves and the plugs.
____________________
Some shite cruiser. Now with guns and FREEDOM!

[M.C]

[haroman666]

Just to throw another option out there.

I had a similar problem on the CBR where it bogged between 7K and 10K rpm but only when the throttle was wide open.

I chased it for fucking ages carbs, coils etc etc. I check everything to do with fuel and electricity.

And then one day, when I was changing the cam-cover gasket, I thought I'd check the timing so I knew how to do it when the time may come.

Well blow me... Timing was out. Inlet was retarded one tooth and the exhaust advance one tooth.

I rectified it and it transformed the bike. Blew me away it did.

So... Whilst I doubt you have a timing problem, it's just an option to look at with a badly running new bike.
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The mistresses: 2000 Honda CBR600f, 2000 Honda VTR1000