Thundercat Idling/Sparking Issue

[MAR5H7]

Hello there
Iv recently replaced my plugs as due on milage and at first they were a quick and responsive
I have now done about 700 miles on them, and now the bike refuses to idle for more than 10 seconds, sometimes it will just die

I am well aware the carbs are desperate need of balancing but thats not the main issue with it

The problem is during warm up stage (choke) and low running speeds, you can hear the bike not sparking, sometimes until 30 mph!!!
my mate heard it when I pulled away and you can also see QUITE A BIT of petrol coming out of the exhaust pipe D: which leads me to believe its only running on 3 cylinders??

NGK spark plugs in, now I will add a note, when I took the 3rd spark out (one of the middle bitches to get) It was EXTREMELY difficult, and when I finally got it out after hours of labouring, I found out why, the spark plug thread had a lovely little like a few notches down making it a sod to get out
Not sure if that helps??

Cheers guys!!
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Ex: CBR 125 R 06', ZXR 400 96' (RIP), Bandit 650 06'
Owned: SRAD 600 97'
Current: YZF Thundercat 600 96'

[weasley]

I doubt you have liquid fuel running out of your exhaust; condensed water perhaps?

Mine started running on 3 a while ago and whilst I was convinced it was a carb issue, as the problem seemed to be throttle position dependent; it turned out to be a failed spark plug cap. These simply unscrew from the end of the HT lead and you can measure the resistance across them (should be 10k ohms IIRC). Failing that it could be a duff lead or a coil (these are a bit of a PITA to get out).

However, the fact it won't idle suggests you might at least need the carbs balancing and the mixture and idle speed setting up.
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Yamaha XJ600 | Yamaha YZF600R Thundercat | KTM 990 SMT | BMW F900XR TE

[MAR5H7]

[steady eddie]

Has the bike been laid up for a while? If so, could be blocked pilot jets. Or throttle position sensor... Or even a problem with no 3 pot

Google "Bikers oracle", there's a good Thundercat forum on there
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Fz50>Ts185>Rd125Lc>Cb250n Superdream "Deluxe" (!)>Kmx200>Tdr250>Yzf600 Thundercat>
Current bikes: 1997 Fireblade RRV & 1989 KMX200

[weasley]

And a better (more active) one at www.yamaha-thundercats.org

Declaration of interest: I am an administrator of this one.
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Yamaha XJ600 | Yamaha YZF600R Thundercat | KTM 990 SMT | BMW F900XR TE

[Walloper]

The thing you were phannie-ing about with is the most prbably cause of your symptoms.

Ensure you have the caps on properly.
Also may be worth fitting a set of HT leads.
They are only made with a carbon filament so any rough handling can damage the lead. If they are still soft/felxible then that may not be an issue.

If you can run it with the tank off you can disconnect each plug one by one to find if there is a 'dead one' (bad connection).
Also let it idle and rock the bike that may show a broken connection. (but I doubt it).

You could also have a dodgy plug . Pulling the caps off with show this though and if it shows a dead plug at No. 3 as you say then swap the plug at No. 3 with the plug at No. 2, 4 or 1. If the fault stays with the plug then the plug is bad.

I never balanced the carbs on my T'cat and ran it for three years form new.
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W-ireless A-rtificial L-ifeform L-imited to O-bservation P-eacekeeping and E-fficient R-epair

[weasley]

I have balanced my carbs once in the bike's 15 year life and the ONLY thing that has ever stopped it running anything less than 100% was the plug cap.

If one cylinder is not firing you can usually tell because the downpipe is much cooler than the others; that at least narrows down your hunt.
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Yamaha XJ600 | Yamaha YZF600R Thundercat | KTM 990 SMT | BMW F900XR TE