Potential timing issue

[BobH]

I have a 79 XS650 which I cannot get to run properly. It has straight pipes(1.5") and stock jetting which should indicate lean issues, but bike runs rich. It has a Pamco and after searching through threads I noticed a short video checking the mech advance. My advance does not snap back like the video, but it does go back. Will this affect timing. Bike will idle but upon throttle it will shoot a flame out the exhaust which I assume is a timing issue? I also guessed on the valve settings, the bike started life as a 650 special and I adjusted the valves to 006 intake and 012 exhaust. I am no mechanic and would appreciate any help before I totally screw this bike up. There are only 4900 miles on motor. Thanks for any response.

 

[hardrock785]

sounds like the bushings that the advance is on needs to be cleaned n regreased, if i remember right that rod comes out from the left side. clean er up stab it back in there. springs might be a little weak to. curl the ends a little tighter with a needle nose.

 

[BobH]

Thank you, also where can I find info on where my valves should be set? 79 650 special, should I be using 004 intake and 006 exhaust, or 006/012?

 

[5twins]

Actually, you will probably like .006" exhaust and .003" intake best. The intake spec for your '79 may be .004" but they will probably tick like crazy using that. They did on my '78. The .006" and .012" spec was only for the very early model years, like the 1st and 2nd, but I'm pretty sure Yamaha issued tech bulletins and reduced that shortly after the bikes were released. There is a factory shop manual on-line for free here. It will give you all the info you need .....

http://www.biker.net/

 

[BobH]

Thanks 5twins, just came up from my garage where I re-set valve clearances to .004/.006. Bike started and seemed to idle better also less breakup with throttle. Still coughed a flame from right side exhaust... But it's getting close. I'll take a look at that manual, fix a flat front tire and take it for a little ride. At least a little more encouraged today. Thanks again

 

[5twins]

Lubing the advance rod is a maintenance item on these bikes, even though it was never mentioned as such in any of the Yamaha manuals. It doesn't need to be done very often, like maybe every 5 years or so, but it does need to be done. Yours along with most others has probably not seen an advance rod service (lube) since it left the factory.

Will this lack of lube effect your upper and lower timing settings (advance and retard)? Probably not but it will effect how smoothly and consistently your timing moves between the two settings. It should advance in a smooth curve gradually as the RPMs increase. Yours may be hanging and sticking, then jumping to full advance quickly when the revs get high enough to over-power that sticking. Sure, this could be the cause of your flame throwing. See post 12 here for advance rod servicing info .....

http://xs650temp.proboards.com/thread/1372