Dodgy Spark

[kenco]

Hi, Well after a year and a half of having the bike i finally got round to giving it a spin. It the first time having ridden a 650. The bike didn't seem to pull right. When i got back i had a tinker and a few things concern me, Can anyone tell if its normal

With the bike running and sitting on it, i removed the RH HT lead and the engine kept running, it didn't falter. As i put the plug back on ,the engine notes picked up, but when it clicked back into place the engine was running rubbish again. So with the plug removed and hovering above the spark plug (you can hear the cracking of spark) the engine is running smoother. When you take the LH HT lead off the engine dies.

Thanks, Ken

 

[pa23driver]

are the plug caps newer?

how old are the spark plugs?

 

[kenco]

The park plugs and caps are all new

 

[Gordon]

Year and model, and ignition type, please.

 

[kenco]

Hi,

The bike is a 1977 XS650D with standard ignition, coils

Thanks

 

[jayel]

needs a new plug(s) pulling the cap part way off is a old trick to get a fouled plug to fire

 

[Gordon]

Jayel is right. Plug is fouled. Like he said, that is an old trick to try to clean the plug off so you would clear up a misfire. Putting the cap back onto the plug, your not asking for more voltage from the coil to 'jump' the gap, so the spark is just following the easyist path to ground, the fouling on the plug. A plug can and will foul from a sudden burst of excess fuel, maybe a float stuck, coil lost energy, ect. Speaking of coil's, did you measure the resistance of the coil's? There are spec's in the manual and a routine to follow to check them. Remember, they are 33+ years old, so even if they measure good, that doesn't mean they are not weak. They were weak when new, so a new set would be a good investment. Even if just for peace of mind. Forgot, you got a 77.The plug wires do come out for replacement.

 

[pa23driver]

my coils checked good on the resistance values, still couldn't get the bike to fire for more than a few rpms, i was having plug fouling problems too. bought a new dual output coil and switched to a dual lobe cam for single points and she fired right up. not bad for 50 bux

 

[pa23driver]

another perk to the dual output coil is you're only one step away from a Pamco iggy if you decide later to go that route

 

[kenco]

Hi, Thanks for the tips, I have tried another plug and they seem to work. The plug was really blacked up. I'm going to make a manometer and sync the carbs then have a play. The exhaust is basically a straight through with like an offset baffle. I have packed it out a bit with wadding. The air filters are pod type from Ram Air. There so much written about modifying carbs, its hard to decide what to do. You cant get the parts that easily over here so you need to be sure when making a purchase.

 

[XSLeo]

Have you read this www.amckayltd.com/carbguide.pdf