Poor starting when engine is cold

Wady93 · Post by **Wady93** » Wed Jul 20, 2016 5:00 pm

Hi all I'm having some problems with my gk76a . It is a pig to start when cold of the button will start of a bump straight away . When I bought the bike it had a few problems e.g wiring was a mess I've sorted all that I've checked all the starting circuit for the correct resistance and voltage all working as it should I have also replaced the carb seals which I have seen so much about still no look . Running out of ideas now

SevenThreeSeven · Post by **SevenThreeSeven** » Wed Jul 20, 2016 7:45 pm

I'll take a shot:

When you start a modern (ECU controlled) motorcycle or car the ECU will increase the coil dwell-time to compensate for the resulting lower battery voltage during the period of time that the vehicle's starter motor is drawing big amperage. Obviously, an older motorcycle or car doesn't have this ability to compensate so it's very important to make sure the coil-to-spark plug electrical pathway is absolutely up to spec.

The old-school Ignition Control Box on your GSX-R doesn't compensate the coil dwell time during cranking. As far as I know (from my GSF-400 Bandit) the Ignition Control Box uses the same dwell-time throughout the engine's entire RPM range, from cranking speed all the way up to red line.

When you "bump start" your GSX-R it starts right up because the coils are getting full (normal) battery voltage during their dwell-time. When you try to use the bike's starter motor to turn over the cold engine the coils are not getting full (normal) voltage during their dwell-time so the spark plugs end up producing a weaker spark (possibly even a very week spark if your HT leads are not in tip-top shape).

I think you can test the HT leads for their Ohm resistance (I think there's an Ohm specification given in the service manual).

Post by **dobbslc** » Thu Jul 21, 2016 11:20 am

I've had similar on a few GK76A's.....
You need a new good quality battery to start with. Check all the earth points and other connections. Try jumping it from a good car battery, make sure the crocodile clips are on good. If that helps from cold then it's probably and electrical fault, if it makes no difference is the poxy carbs!
I've also found that turning the mixture screws up to 2.5 / 3 turns out helps a bit.

Wady93 · Post by **Wady93** » Thu Jul 21, 2016 4:47 pm

I first replaced the coils when I ghave t the bike as I wasn't getting a spark checked them with a multi meter they were dead so replaced them . I'm gonna have a tinker with the carbs and balance them see if that helps I've just went to the bike and it started of the button took a while tho

SevenThreeSeven · Post by **SevenThreeSeven** » Fri Jul 22, 2016 5:52 am

So... when you say that you replaced the coils are you saying that you also replaced the HT leads at the same time? Or are you running the bike's original HT leads with the new coils?

If you are using the bike's original HT leads have you tested them to determine if their Ohm reading is up to specification (per the service manual)?

Wady93 · Post by **Wady93** » Fri Jul 22, 2016 7:49 pm

Yh replaced the leads aswell tho these were not brand new I got them of eBay how do I check them ? Cheers

SevenThreeSeven · Post by **SevenThreeSeven** » Fri Jul 22, 2016 10:15 pm

This video, starting at 4:20 in, the guy shows/describes the inner parts of the HT leads.

https://www.youtube.com/watch?v=mMK8XNuJ7lg

Wady93 · Post by **Wady93** » Sat Jul 23, 2016 8:59 pm

Cheers I'll give that a go tomorrow . If they are knackered were can I get some new ones

Poor starting when engine is cold

Poor starting when engine is cold

Re: Poor starting when engine is cold

Re: Poor starting when engine is cold

Re: Poor starting when engine is cold

Re: Poor starting when engine is cold

Re: Poor starting when engine is cold

Re: Poor starting when engine is cold

Re: Poor starting when engine is cold