SV 99 looses rear cylinder on higher speeds - SV650.org

19-03-15, 08:11 PM

Hi guys, me again...

So I changed the spark plugs, got my carbs balanced and bike sounds great and idles at 1.200 RPM instead of 3000 like it was before.

I went for a ride with my buddy. We were on a motorway and doing around 120KMh when I felt power loss. After few seconds the engine stalled and I had to stop on a hard shoulder.

Engine started quickly after few attempts and I was going on 1 cylinder for about 1km when the second one fired again and everything was great.

So I continued and tested this issue again - went above 100kmh and same thing - lost one cylinder but it came back immediately and the engine didn't stall.

Went back home below 100Kmh for about 15km. Everything was perfect on low speeds.

Ordered used rear coil and the lead - installed it and tested it again Today - same issue.

Where to look next?
The two wires that go to the rear coil?
New Spark plug is damaged?
ECU ?
Engine problem?

I'm lost. Thanks in advance!

Bibio · 19-03-15, 08:18 PM

could be a chaff in the loom somewhere.

or you have a sticky float needle in the carbs.

19-03-15, 08:31 PM

"chaff in the loom" ???

So you say it's nothing to do with the cables leading to the coil? They don't look well protected at all...

Bibio · 19-03-15, 08:55 PM

get them cleaned up and some ACF-50 would not go amiss. also the main high tension wire looks a bit iffy, take it off and see if its corroded and if it is cut back and make sound or get another coil.

20-03-15, 09:45 AM

Well everything is cleaned now. This photo was taken a month ago so it doesn't look that bad :P

Also as I mentioned above, I have new coil and coil lead as I believed this is my problem - it turnes out it's not

Which one is the high tension wire?

Bibio · 20-03-15, 01:13 PM

the one that goes to the spark plug.

20-03-15, 02:34 PM

I got that one new also, along with the coil and lead so no problem there..

Bibio · 20-03-15, 02:45 PM

only other thing to check would be the float bowl needle valve. if the bike has been sitting for a while they gum up, when you put fresh petrol in they free up but sometimes there is some gum left. you could try a fuel cleaner in the tank.

20-03-15, 03:14 PM

That's taken care of also. Carbs cleaned and balanced 2 weeks ago.
Tank cleaned fully. Fuel Cleaner in the tank month ago. Flushed with fresh petrol.

I called my mechanic earlier as he did my carbs. He's betting on electrical problem and he's talking about the wires going into the rear coil

Bibio · 20-03-15, 04:41 PM

what happens if you give WOT in each gear?

19-03-15, 08:11 PM	#1
JohnyMST Guest Posts: n/a	SV 99 looses rear cylinder on higher speeds Hi guys, me again... So I changed the spark plugs, got my carbs balanced and bike sounds great and idles at 1.200 RPM instead of 3000 like it was before. I went for a ride with my buddy. We were on a motorway and doing around 120KMh when I felt power loss. After few seconds the engine stalled and I had to stop on a hard shoulder. Engine started quickly after few attempts and I was going on 1 cylinder for about 1km when the second one fired again and everything was great. So I continued and tested this issue again - went above 100kmh and same thing - lost one cylinder but it came back immediately and the engine didn't stall. Went back home below 100Kmh for about 15km. Everything was perfect on low speeds. Ordered used rear coil and the lead - installed it and tested it again Today - same issue. Where to look next? The two wires that go to the rear coil? New Spark plug is damaged? ECU ? Engine problem? I'm lost. Thanks in advance!

19-03-15, 08:18 PM	#2
Bibio Member Mega Poster Join Date: Jul 2008 Location: here as devil's advocate Posts: 11,568	Re: SV 99 looses rear cylinder on higher speeds could be a chaff in the loom somewhere. or you have a sticky float needle in the carbs.

19-03-15, 08:31 PM	#3
JohnyMST Guest Posts: n/a	Re: SV 99 looses rear cylinder on higher speeds "chaff in the loom" ??? So you say it's nothing to do with the cables leading to the coil? They don't look well protected at all... Last edited by JohnyMST; 19-03-15 at 08:35 PM.

19-03-15, 08:55 PM	#4
Bibio Member Mega Poster Join Date: Jul 2008 Location: here as devil's advocate Posts: 11,568	Re: SV 99 looses rear cylinder on higher speeds get them cleaned up and some ACF-50 would not go amiss. also the main high tension wire looks a bit iffy, take it off and see if its corroded and if it is cut back and make sound or get another coil.

20-03-15, 09:45 AM	#5
JohnyMST Guest Posts: n/a	Re: SV 99 looses rear cylinder on higher speeds Well everything is cleaned now. This photo was taken a month ago so it doesn't look that bad :P Also as I mentioned above, I have new coil and coil lead as I believed this is my problem - it turnes out it's not Which one is the high tension wire?

20-03-15, 01:13 PM	#6
Bibio Member Mega Poster Join Date: Jul 2008 Location: here as devil's advocate Posts: 11,568	Re: SV 99 looses rear cylinder on higher speeds the one that goes to the spark plug.

20-03-15, 02:34 PM	#7
JohnyMST Guest Posts: n/a	Re: SV 99 looses rear cylinder on higher speeds I got that one new also, along with the coil and lead so no problem there..

20-03-15, 02:45 PM	#8
Bibio Member Mega Poster Join Date: Jul 2008 Location: here as devil's advocate Posts: 11,568	Re: SV 99 looses rear cylinder on higher speeds only other thing to check would be the float bowl needle valve. if the bike has been sitting for a while they gum up, when you put fresh petrol in they free up but sometimes there is some gum left. you could try a fuel cleaner in the tank.

20-03-15, 03:14 PM	#9
JohnyMST Guest Posts: n/a	Re: SV 99 looses rear cylinder on higher speeds That's taken care of also. Carbs cleaned and balanced 2 weeks ago. Tank cleaned fully. Fuel Cleaner in the tank month ago. Flushed with fresh petrol. I called my mechanic earlier as he did my carbs. He's betting on electrical problem and he's talking about the wires going into the rear coil

20-03-15, 04:41 PM	#10
Bibio Member Mega Poster Join Date: Jul 2008 Location: here as devil's advocate Posts: 11,568	Re: SV 99 looses rear cylinder on higher speeds what happens if you give WOT in each gear?

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