no spark...

PenniesEarned · Full Member Joined: May 23, 2008 Posts: 23

I'm very new to motorcycles and how to work on them. I recently aqquired a 75 xs650. The left exhaust backfires like a mother especially when I rev her. When I'm driving its just as bad. There seems to be a hesitation when driving it and definetely isnt getting near enough power. A friend suggested that I pull the spark plug wires while running. I pulled the right and she died instantly. I pulled the left and not only did it keep running but it got rid of the backfire. I tried to arc the plug with a screwdriver and didn't get any type of spark. Whats next from this point. Thanks again, I am definetely a newb when it comes to this stuff.

Shannon60 · Posted: June 3, 2008, 6:58 pm Post subject: Re: no spark...

the best thing that i could tell you is to seek a qualified technition as your trouble could be many things starting with carbs being out of sync or dirty or a improperly adjusted set of points these are very common problems for what you are describing

jimmythetrucker · Full Member Joined: Mar 12, 2008 Posts: 1283

We here say "Left" and "Right" when looking at the machine from the rider's perspective.

Pull both spark plugs and look at them. What do you see? Is one black, burned and oily wet? Is one of them a nice, tan color? Describe them both as best you can. Let us know what they look like.

PenniesEarned · Full Member Joined: May 23, 2008 Posts: 23

Well the plugs are fairly new but the plugs are as follows. The right plug is tan with slight black on tip and a little of the bottom and very dry. The left plug is all black and oily and smells a little gasoline. Which also brings me to my next newb question. Should both my petcocks be turned on? I have a friend with an old triumph that only has one turned on. Are these the same way? I've had both turned on the whole time. Thanks

-Ryan

weekendrider · Posted: June 3, 2008, 10:46 pm Post subject: Re: no spark...

You want the left to look like the right. It could be fuel mixture, intermittent spark, or timing? Have you gotten a manual yet? The best $100( or less) you'll spend, a Clymers and Yamaha model specific manuals. Even if you don't wrench on it you'll understand what's being done.

jimmythetrucker · Full Member Joined: Mar 12, 2008 Posts: 1283

PenniesEarned wrote:

Well the plugs are fairly new but the plugs are as follows. The right plug is tan with slight black on tip and a little of the bottom and very dry. The left plug is all black and oily and smells a little gasoline. Which also brings me to my next newb question. Should both my petcocks be turned on? I have a friend with an old triumph that only has one turned on. Are these the same way? I've had both turned on the whole time. Thanks

Don't worry about the petcocks just yet. Now you've got the plugs out it's time to run a compression test on both cylinders. Hold the throttle wide open and crank the engine while you hold a compression gage in the left spark plug hole. When the gage is pumped up as high as it will go, note that reading. Then test the right cylinder the same way and note that reading, too. When you get that done, get back to us and tell us what the compression readings are.

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