New 650 lover...need diagnostics from some old pros!

[belville1780]

So I am long time yamaha enthusiast...and I was actually given a 75 650 as a gift! I am a horrible mechanic and only know enough to confuse myself. The bike has been running great for the past week. Clutch started acting funny a couple days ago....nothing there until the very end of the handle. Didnt think anything of it, I just figured it was going to need some adjustment/TLC. Then today I went out and kicked it over and it fired right up like it always does and was good for about 2 miles. Then it started to hesitate from a dead stop, once I was in the power it was strong and sounded good. I went back home and shut her down. Came back out after 15 minutes or so and it fires right up but just doesnt sound quite right. Its idling really high (i didnt touch a thing) So I took off for another lap around the block and same thing...a little hesitation at low rpm but pretty good if I am on it. No smoke of any kind, no fluids leaking...but the clutch feels even worse now than it did before. When rolling to a stop and the clutch pulled in its idling really high. Then as I take off its kind of bogging/hesitating/missing a little until I get into it, then the power is all there.

I cleaned the carbs REALLY good about a week ago, plugs probably need replaced. Has brand new gas. Fires up first kick everytime. actually seems like it wants to idle a little better with just a bit of choke?

Any ideas, based on my jumbled up rambling list of symptoms?

This site is an unbeleivable wealth of information, really excited to be a part of it.

Any pointers or ideas would really be appreciated.

 

[retiredgentleman]

So I am long time yamaha enthusiast...and I was actually given a 75 650 as a gift! I am a horrible mechanic and only know enough to confuse myself. The bike has been running great for the past week. Clutch started acting funny a couple days ago....nothing there until the very end of the handle. Didnt think anything of it, I just figured it was going to need some adjustment/TLC. Then today I went out and kicked it over and it fired right up like it always does and was good for about 2 miles. Then it started to hesitate from a dead stop, once I was in the power it was strong and sounded good. I went back home and shut her down. Came back out after 15 minutes or so and it fires right up but just doesnt sound quite right. Its idling really high (i didnt touch a thing) So I took off for another lap around the block and same thing...a little hesitation at low rpm but pretty good if I am on it. No smoke of any kind, no fluids leaking...but the clutch feels even worse now than it did before. When rolling to a stop and the clutch pulled in its idling really high. Then as I take off its kind of bogging/hesitating/missing a little until I get into it, then the power is all there.

I cleaned the carbs REALLY good about a week ago, plugs probably need replaced. Has brand new gas. Fires up first kick everytime. actually seems like it wants to idle a little better with just a bit of choke?

Any ideas, based on my jumbled up rambling list of symptoms?

This site is an unbeleivable wealth of information, really excited to be a part of it.

Any pointers or ideas would really be appreciated.

Clutch................have you adjusted it correctly down at the left side cover, followed by setting free play at the lever?

Hesitation, does not want to rev..................could be pilot circuit partially blocked i.e. is pilot jet clear/mixture screw set correctly?

Plugs may be fouled?

Even if you have several other problems, the voltage at the battery must be in the correct range for the engine to run well. Before you turn on the engine should have about 12.4 volts. Run the engine and should see 14.1 volts at 3000 rpm.

 

[angus67]

agreed on pilot jets.
An easier way to see if the charging circuit is responding, is rev the bike, and if the headlite gets briter, its making energy, but that dosnt mean its making its way to the battery though.

 

[belville1780]

Thanks for the advice...going to do plugs tomorrow. Will check battery too...that makes good sense...havent checked that at all. Going to have to do some reading on pilot jet/mixture screw...that might be above my pay grade.

Thanks again for the help.

 

[Fleksta]

When mine started bogging/hesitating like that it actually turned out to be a stuck gas cap vent. It would build up a vacuum, choking off fuel flow. A new rubber seal was all it needed.

 

[5twins]

I suppose we should throw timing into the mix here, or more specifically, the advance unit. Yours might be sticking in the advanced position.

 

[weekendrider]

Or the beginning of the end for a throttle shaft seal.
You did say, XS650 love her right.
Welcome to the site.

 

[Travis]

I'm thinking it might be an air leak as well.

 

[hotdog]

I suppose we should throw timing into the mix here, or more specifically, the advance unit. Yours might be sticking in the advanced position.

dont confuse the poor guy.....lol

 

[Tomterrific]

I see two special things that happen to new owners of old XS650's. One, the pilot jet gets a bit of dirt blocking it. Two, the advance sticks because the rod that runs through teh cam isn't lubed and sticks.

Start your bike from cold and take off teh choke. Does the bike idle on one cylinder? If one pipe isn't getting as hot as the other then that cylinder may not be metering fuel through the pilot jet. You can pull out teh mixture screw and spray carb cleaner inside to blast teh dirt back into teh float bowl. It's spray and pray but sooo much easier than pulling the carbs each time.

Pull off teh cover over teh end of the cam on the right side. you can fiddle with the advance mechanism to see if it is moving smoothly and freely or binding a little. The rod needs to come out, be cleaned (rubbed with light oil) and greased. Lube the flyweights where they move also.

Tom

 

[Take Warning15]

I looked a bit on the forum about the advance unit sticking but have a quick question about it. How does the rod come out? Do the points' assemblies need to come off or can I just slide the rod out of the advance side?

 

[retiredgentleman]

I looked a bit on the forum about the advance unit sticking but have a quick question about it. How does the rod come out? Do the points' assemblies need to come off or can I just slide the rod out of the advance side?

The rod can be removed from either side. Pay attention as there is a small pin on both ends, you don't want to lose. The points don't need to be removed.