XS750 Starting Woes

[manas]

I replaced the oil, oil filter and battery on my XS750 today and was hoping that she might start. However, although the starter motor worked I could not get the engine to catch. I could also hear the starter motor wind down as I let go of the starter button.

Could someone please take a look/listen and give me some advice on what to look at next? The previous owner replaced the spark plugs but I'll take a look at them tomorrow. What else?


http://www.youtube.com/watch?v=wgCdnE1Ol60

 

[TheCoffeeGuy]

No a critical thing you can hear the starter wind down, it usually does but is drowned out by the motor running. After you crank it like that in the video, pull a plug and see if its wet. if its wet then you are getting gas as a rule, then you either don't have enough spark or none at all.

if its dry then you probably are not getting gas into the cylinders..

it always gets down to gas or spark.

Fuel or Fire.

Suck, Squash, Bang, Push

 

[manas]

Thanks CoffeeGuy. Couldn't check the spark plugs at the time because I didn't have the right tool available to pull them out at the time.

 

[manas]

Replaced the spark plugs. Unfortunately the local Canadian Tire did not have the Yamaha specified plugs but they gave me another set of Champion plugs that they said are compatible with the motorcycle.

This is what the old plugs looked like :

I'm guessing the carbon deposit is due to excessive rich mixture. In any case, they were replaced.

Also checked the voltage across the battery terminals. Sat at around 12.6 Volts:

However, when I start the motorcycle with the switch the voltage across the terminals drops to below 12 volts. This is a problem, right? I can't imagine why however, since the battery is brand new and has been charged.

Any suggestions?

Oh, and I also tried to see if the motorcycle would start if I connected the battery to my charger and set it yo jump start mode, in order to see if it was actually a battery issue. No success there either.

 

[TheCoffeeGuy]

with the plug out are they sparking?

the first plug looks really dry. Crank the bike over a few times with full choke. Pull a plug immediately, is it wet?

the voltage probably drops because of the draw from the starter.

 

[manas]

Re: Re: XS750 Starting Woes

with the plug out are they sparking?

the first plug looks really dry. Crank the bike over a few times with full choke. Pull a plug immediately, is it wet?

the voltage probably drops because of the draw from the starter.

I checked the new plug and they were sparking fine. The plug that I photographed was the old plug and I hadn't really cranked with that today at all so it would have had to have been dry. I'll check again for wetness and report back.

With the voltage drop..are you sure about that? I thought I had read that the voltage should stay above 12 even while engaging the starter? Perhaps I'm wrong.

 

[manas]

Re: Re: XS750 Starting Woes

with the plug out are they sparking?

the first plug looks really dry. Crank the bike over a few times with full choke. Pull a plug immediately, is it wet?

the voltage probably drops because of the draw from the starter.

I pulled the plug soon after cranking for a few seconds and it was dry. When I place my hand next to the slides of the carburetor I can feel air getting sucked in, but obviously without a compression tester I don't know if its creating any useful compression/suction.

I might open the carburetor up again and see if I missed anything, although its unlikely.

 

[TheCoffeeGuy]

If you are checking the carbs, go to basics.

Is there enough gas to be above the reserve spout?

Does gas flow through the petcock?

When you open the drain screw, does gas come out?

What are the high speed and idle screw set at?

Do the floats operate easily?