Coil burning out??? Carb problem? *Update*

[rob_scott92]

Hey guys,

Bikes been playing up abit recently (Besides burning oil )

Noticed it a few months ago when i was on the motorway, I'd only been on for about 20 mins probably doing just over 75.
I went to overtake a succesion of cars in the slow lane, got up to around 85-90 (95 used to be pretty much my top speed) When i just lost power! The bike slowed to around 60 and wouldn't really pull onwards at all.

So theres me trying to figure out what had happened for a while, when the bike started to speed back up so i could at least keep up with traffic. There was no change in throttle when it sped up BTW.

So after this event it seems to do it every time i go on the motorway, which gets a tad annoying as used to do the motorways as a quick route to college

Anyway, i bought 2 new plugs for it after this happened, the day before i was going to ride to wales with my uncle and his mate.
Bike was running OK, but on the way back we stopped for one of the guys to catch up, engine off. The guy catches up then we set off again. This time about 5 mins in I lost a cylinder! was running really rough and would hardly touch 40. rode like that for a couple of mins, pulling the clutch in every so often to see if revving it would make any difference to the noise it was making..... it didn't, but then the same as before, it burst back into life and got me home fine.

That was the last time it happened, although since then i havent been to wales, and i havent been on the motorway so i suppose it hasn't been under any great 'stress'. Although it does sometimes seem more gutless than usual

So after all that rambling........ Does this sound like the coil could be burning out? I dont think there's a proper way i can test it is there???
I'm thinking either that or perhaps the carbs may need a clean out and balance.

Thanks in advance guys!
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First bike: 1982 Suzuki Gs 125 'The beast MK1' > 1988 Honda Cb 350's' FOR SPORT! (Good ol' oil burner!) > 2001 Suzuki Sv 650 's' Made it out of the 80's! > 1997 Honda Cbr 600f :p

[pepperami]

You can take the coils to a main dealer and they should be able to test them for you for very little pennies, my local Yamaha dealer did .
You need the manual, as that will have the specs for that particular coil.
I believe that even Haynes manuals have the specs in them?
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I am the sum total of my own existence, what went before makes me who I am now!

[vmax12]

drain carbs or take off n strip would be a good place to start

[rob_scott92]

[Blue_SV650S]

I'd try for loose connectors / wires. I'd also drain the float bowls whilst in situ ... I doubt it is the coils, but would check the caps
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The purpose of life is to fight maturity.

[rob_scott92]

Ok, i havent been out since the original post, but i was just reading my manual maintenence section.
It says about inspecting and cleaning the fuel screen (At the tap) every 4000 miles. Now i've done at least 3500 in the time that i've had it and i doubt very muchly that the guy before me had done it all, soooo.......

IF the fuel strainer/screen/WHATEVER was partially blocked, would that mean that it would sometimes struggle when at high revs for an extended period of time (In this case now about 10 mins )
For example, the more 'demand' for fuel would mean that some bits of crap could get dislodged and cause the problems???

and just to clarify, i'm looking out for bits of crap in the fuel when i drain the carbs, or would i look for not much fuel coming out

Cheers
____________________
First bike: 1982 Suzuki Gs 125 'The beast MK1' > 1988 Honda Cb 350's' FOR SPORT! (Good ol' oil burner!) > 2001 Suzuki Sv 650 's' Made it out of the 80's! > 1997 Honda Cbr 600f :p

[Vincent]

[tahrey]

From my older-car forum days, i'd suggest either carb icing (bit early in the year for it though, but maybe just getting cold and being affected by that), or plugs overheating. Or maybe overheating in general. It kind of fits with the whole "ok when cruising, but loses the plot after going fast for a short while" symptoms.

Try cooler plugs, make sure the engine/radiator's getting enough airflow, your air filter hasn't got a hole in it, carb heater is functioning etc.

[rob_scott92]

Ok just a little update ( I know its late but i forgot the other day )

Since posting i have taken it on the motorway on a total of 4 journeys...... AND ITS BEEN FINE!

Only thing i can notice now is it seems to 'snatch' when at constant criusing throttle, which i beleive is a sign of unbalanced carbs.
Another thing, after a 30 minute stint on the motorway full throttle (80+ ) it pops like mad when i slow down! (Had a few killer backfires at cat&fiddle last week too )
Am i right in thinking this is rich mixture? I remember a while back one of my plugs was a little black when i checked it. The other one was perfect colour at that time.

Cheers

Also, there is a bit of a gap round where the downpipes meet the exhaust. so that could be a contributing factor to the backfiring.
____________________
First bike: 1982 Suzuki Gs 125 'The beast MK1' > 1988 Honda Cb 350's' FOR SPORT! (Good ol' oil burner!) > 2001 Suzuki Sv 650 's' Made it out of the 80's! > 1997 Honda Cbr 600f :p

[Digit]

When you shut down with the engine still revving on the over run the suction on the carb is high, thus fuel is drawn into the engine, but little air. This means that the engine is now running rich, the fuel that enters the exhaust can then detonate, 'back fire', but only if there is sufficient air to produce an explosive mixture, thus if the detonation takes place within the exhaust system there must be an air leak in that system.
Petrol cannot burn without the presence of oxygen.

Roy.
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Happy daze!