Sputter

Grizzly · Full Member Joined: Sep 15, 2006 Posts: 17 Location: VT

Bought a '79 XS650 w/ 15k miles stock. Ran good for a couple of hundred miles....

Began stalling and misfiring. Especially after warming up. Mostly at low RPM's. Laying on the throtlle brings it back to life, but makes for a fast ride!

Emptied gas tank, rebuilt petcocks, stopped gas leak.
Replaced coils, wires, plugs.
Lubed ATU (still sticks sometimes a little).
Checked point gap.
Checked gas tank vent.
Replaced battery.

Just now sprayed throttle valve spring area on left carb and cleaner went into combustion chamber and out exhaust as white smoke, but didn't run any better. Thinking carb rebuild.

Any ideas??????

Grizzly

Jack · Full Member Joined: Mar 15, 2005 Posts: 411

Rebuild the carburetors,that should solve the low RPM stumble,most likely the pilot and needle jet circuits have slight trash blocking fuel transfer..........Jack

Grizzly · Full Member Joined: Sep 15, 2006 Posts: 17 Location: VT

Forgot to mention that I took off the float bowls and cleaned the needle valves and pilot jets. I can try it again. Also replaced the ratty old air filters.

Grizzly

ajohnson · Full Member Joined: Jul 13, 2006 Posts: 17

you checked the timing? thought i'd mention it just in case.

Grizzly · Full Member Joined: Sep 15, 2006 Posts: 17 Location: VT

Nope, didn't check the timing yet. I haven't got a light: or can I set the static timing first?

Grizzly

Grizzly · Full Member Joined: Sep 15, 2006 Posts: 17 Location: VT

Just found the timing instructions in the manual. Will do it tomorrow.
Thanks, Grizzly

ajohnson · Full Member Joined: Jul 13, 2006 Posts: 17

you can guess at the timing by eyeballing, but this is obviously not that accurate. If you go to any auto store you should be able to get a test light (looks kinda like a screwdriver with a wire out one end and a lightbulb in the handle) . Have you got points or electronic ignition? Point's timing is real easy with a test light. Just clip the wire on to the arm of the point and stick the point of the "screwdriver" into the fins of the motor to ground. As you turn the motor over (with ignition on) the light should come on just when the wheel is at the "f" mark. If it doesn't come on, or comes on too early, your timing is off. It doesn't take much to make the bike run poorly so you should try to get it as exact as possible.
Come to think of it, I haven't gotten this far on my XS, but have adjusted timing on other bikes and the technique should be mostly the same. Good Luck.

Grizzly · Full Member Joined: Sep 15, 2006 Posts: 17 Location: VT

Thanks

I'll try the static timing first and then maybe buy a light.

When I spray the carbs it goes through the throttle rod opening and burns up. How about if I try to plug the leak with greese to see if it makes the bike run better?

Grizzly

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

deleted

Grizzly · Full Member Joined: Sep 15, 2006 Posts: 17 Location: VT

I didn't see these seals included in any carb kits. Are they available anywhere? or do I go the hardware store route?

Grizzly

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

Grizzly · Full Member Joined: Sep 15, 2006 Posts: 17 Location: VT

OK frustration setting in.... I'll be alright by tomorrw.

Butterfly seal as you described, soft and pliable. Didn't understand why it was grooved so I packed it with grease. Stil ran like crap. (groove go in or out?)

Went to the timing. Moved both sets of point so they opened with mark over the F. Couldn't move the plate quite far enough for the right points however. Made sure ATU closed. Points open when lead wire to ground goes from zero to infinity ohms?Opened ATU, too far advanced by about 5-10 degrees.

Crossed fingers....

Bike didn't even start, poped once. Must have messed up the timing bad.

Now what? thanks for bailing me out.

Grizzly

jazzyrigged · Posted: September 18, 2006, 9:34 am Post subject: Re: Sputter

Sounds really familiar. I just got done rebuilding my carbs and replaced the points wires cap plugs and condensor. Initially when I was working on them I messed around with the points and must have messed the gapping up. Did the same exact thing. There is a light at the end of the tunnel. Once I reset the gap and had everything in place to specs, fired up and took the wife and I on a great ride. Runs better than it ever has.

I would suggest clean the carbs REALLY well. Pull every part out and clean it thoroughly, and make sure the air passages are clear. You can't be too anal retentive in this process. Try compressed air after using carb cleaner.

Trust me, I've slammed many a door and even put a small hole in the wall due to frustration. You will be able to fix your bike, so don't let frustration get the best of you.

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

A trick I used with my 68 supersport with points was to remove the points - use a fine ladies fingernail file (double sided) let the points close on the file surface - and gently file off the peaks and uneven spots - (letting the points close on the file gave me matching surfaces when they closed)
this would give me a better gap reading and give me another couple of months on the points - I was poor -

jim

Grizzly · Full Member Joined: Sep 15, 2006 Posts: 17 Location: VT

Wow, I love that thing... even though I only got it 5 miles around the block before it crapped out again.

It's been a while since I had done the points thing. I had a moved the point gap screw by error and crossed the left and right
wires.

Set gaps,timed. Started right up ran pretty good, cleared up and ran great, both exhausts hot. By the time I got back home It was only firing on the left side and leaking unburned gas out the right carb.

I wondering about the condensors....
Probably will buy a new set of points (can I get the mounting screws?)
Tomorrow a may take the bottoms off the carbs and reclean the needle and seats and pilot jets. I'm hesitating pulling off the carbs totally because of the syncro thing.

Anyway the one short ride made my day. Keep the advise coming, I can use all I can get.

Thanks, Grizzly

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

If your leaking gas out the right carb - I would look at float level - and the conditon of your float needle and seat valve as well as the O ring holding it in.

If you have a timing light - just hook it up to each plub and observe the firing. .
Since these things fire exactly opposite - they still should sync up with the timing marks - If it's flashing - you know you have spark - or at least juice going to the plug - the plug may be so saturated with gas it will never fire again.

Jim

Grizzly · Full Member Joined: Sep 15, 2006 Posts: 17 Location: VT

Just an update.

I found two large chunks of gasoline rust on top of the needle valve seats.

Runs great, enjoying the ride.

Thanks for all the advice.

Grizzley

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