Oh well hope next time you clean your carbs you will take those out for inspection. Old rubbers are never good lol 
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Breaking up @ 4500rpm
- Thread starter NorazDad
- Start date
Re. the timing unit, another thing to watch is the cogged nut that secures it to the camshaft. If the nut loosens timing will advance drastically and the timing unit body will beat itself to death against the alignment pin in the camshaft. Your best hope in that scenario is that you'll have the presence of mind to shut down quickly. If you try to "ride through" the misbehavior you'll hole a piston.
Sounds like a good point to install the e-advance he has to avoid the possible holed piston. 
No Jet, it's being aware of these problems and as a general maintenance issue ensuring they are regularly checked.......
A holed piston can be caused by getting the timing wrong........this can be caused by setting the valves wrong, getting the timing at the Stator wrong, An air leak in the manifold making it run lean.............An E-Advance won't stop these other issues
A holed piston can be caused by getting the timing wrong........this can be caused by setting the valves wrong, getting the timing at the Stator wrong, An air leak in the manifold making it run lean.............An E-Advance won't stop these other issues
It's a question of degree of risk, Skull. I've done postmortems on around eight XS650 motors with holed pistons. In every motor except one, a defective mechanical timing unit was responsible. In three of them the cogged nut had loosened and destroyed the timing unit body. In the rest the tips of the weights had worn so that the advance curve had stretched, and the owner, "helper," or incompetent paid wrench had set timing at the retard mark without checking timing at full advance. Also, lubrication of the ignition shaft and tension of the bobweight springs impact the advance rate, so in addition to being more reliable, electronic advance operation is more stable. But each to his own.
Hi Skull I understand. I was just suggesting this as he has it on hand. If a simple rubber o ring below the washer on the idle mix screw was not looked at multiple cleaning of the carbs, to me the risk is there. Obviously he can do what he wants. Just observations I guess.
Techman
XS650 Member
This is definitely a hot topic..... But just think for a moment, Yamaha designed this mechanical advance at the origin of the production XS-1 650 four stroke engine in 1970. It is still a functional device in the early model bikes, to present day. At least the units that do not have Yamaha TCI. There are so many XS650's still running strong with the mechanical advance. Yes, with some higher miles wear issues may be evident, but replacement parts are available. I still enjoy the points and condenser, it just does something to me. I continue to have points, condenser and mechanical advance in all of my 650's. MikesXS continues to offer the reproduction mechanical advance. Thank you Mikes! I do hear one concern of MikesXS mechanical advance. Some of the installers are using the weight arms to hold the unit while tightening the 6mm inner rotor nut to secure. The pressure on those small tabs is what weakens the weight arms.That installation video would be nice. Some of the pros can manipulate the install with the entire unit assembled and secure the larger tab nut with ease. I believe the novice should disassemble the unit when received and build out. Thank you 5Twins for the alignment mark note and photo. Not paying attention to this set up throws a few newbies off. Along with progressive technology you now have the opportunity of upgrading to a hall sensor (solid state) ignition with electrical advance. I think it is great that no matter your choice these machines keep going and going and going....(getting close to fifty years)
pamcopete
Ride.Enjoy.Life is Simple
Techman,
Which hall sensor and electrical advance would you recommend?
Which hall sensor and electrical advance would you recommend?
NorazDad
NorazDad
Ok Guys, I think I have finally come to closure on this issue, meaning my original post of breaking up @. It has been quite a journey. In review, I have cleaned and re jetted my carbs...but not totally in that I needed Michael Coffey to vapor clean and find the buggered air mix screw washers that were probably preventing the bike from running at it's optimum. Basically, I have new carbs that I can continue to play with the jets if I am so inclined, but not today. Was that the ultimate problem?, No. I checked and installed a new coil, re soldered all of my ignition oriented connections for the umpteenth time. Someday I will just do a whole new loom, but not today. I replaced my Pamco with a modified Pamco and replaced the E-Adv with a mechanical auto advance. I will probably go back to the E-Adv some day, but not today.
So here it is...It was a vapor lock problem with my gas cap and fuel line. I did do the tests of running gas out of the bowls. It ran, but I did not run it for five minutes. I should have. I tested gas running out of the tank. It ran, but I did not test it for five minutes. When I declared success and relief several posts ago, I was running about a half a tank of gas and the bike did my five mile loop just fine. So the other day, I thought I'd do a hundred mile run just to see if I could. So I went to the gas station, filled it up with premium and went for a ride. The bike bogged down and died three miles in. I was pissed. WTF!!! So I let it die. I stewed for a few minutes, then I opened my gas cap and closed it and the bike started right up. I couldn't believe it. Oh, and I had just installed a new gas cap seal that I had found in my parts drawer.
I got home with the strongest belief that the full tank did not leave enough air for fuel to flow. I then did the tank drain test again with a clear gas line and I noticed something I never noticed before. I watched a progressive bubble start at the pet cock and work it's way to the end of the gas line, catch it's breath and then start all over again. I opened the gas cap and did it again and saw a similar thing happen. Then, I drained the tank. Took it off. Flipped it over and unscrewed the petcock and heard a whoosh of air when is separated from the tank.
Two things came to mind. One is that the tank was in vacuum and two it was time to examine and clean the petcock.
Well, I dismantled the petcock, cleaned the filters and reassembled and reattached it. Then I did the tank drain test again and noticed that the air bubble was still present, but not so much.
I decided to dismantle the tank cap. I noticed the fiber cap liner was soaked and swelled. I tried to blow through the small hole in the cap and air was not flowing very freely. So I drilled the hole a little bigger in the outside and inside diaphragm. I removed the fiber membrane and I took the little washer out of the inside of the diaphragm. Then I blew through the hole and there was plenty of air. I put the cap back together and closed it and did the drain test again and low and behold, fuel ran clear and without restriction. So, I filled the gas tank and took it for a series of loops in my area. Thirty miles later it was still going strong.
So, was it one thing? Probably not, but I really think that all along, the bike would not run on a full tank because it couldn't breathe. Good thing it only took me two months to figure it out. In the meantime, thanks for chiming in. I learned a lot through this process. Some one was right from the beginning, ns you have the right to brag if you know it was you, but I never completed the tests correctly. However, I now know how to trouble shoot just about everything there is about ignition and carbs and fuel flow.
Thanks for your patience. This XS is ready to run.
Grace and Peace, All. This thread is done...except for those who still want to tell me I told you so. Go ahead, I deserve it.
So here it is...It was a vapor lock problem with my gas cap and fuel line. I did do the tests of running gas out of the bowls. It ran, but I did not run it for five minutes. I should have. I tested gas running out of the tank. It ran, but I did not test it for five minutes. When I declared success and relief several posts ago, I was running about a half a tank of gas and the bike did my five mile loop just fine. So the other day, I thought I'd do a hundred mile run just to see if I could. So I went to the gas station, filled it up with premium and went for a ride. The bike bogged down and died three miles in. I was pissed. WTF!!! So I let it die. I stewed for a few minutes, then I opened my gas cap and closed it and the bike started right up. I couldn't believe it. Oh, and I had just installed a new gas cap seal that I had found in my parts drawer.
I got home with the strongest belief that the full tank did not leave enough air for fuel to flow. I then did the tank drain test again with a clear gas line and I noticed something I never noticed before. I watched a progressive bubble start at the pet cock and work it's way to the end of the gas line, catch it's breath and then start all over again. I opened the gas cap and did it again and saw a similar thing happen. Then, I drained the tank. Took it off. Flipped it over and unscrewed the petcock and heard a whoosh of air when is separated from the tank.
Two things came to mind. One is that the tank was in vacuum and two it was time to examine and clean the petcock.
Well, I dismantled the petcock, cleaned the filters and reassembled and reattached it. Then I did the tank drain test again and noticed that the air bubble was still present, but not so much.
I decided to dismantle the tank cap. I noticed the fiber cap liner was soaked and swelled. I tried to blow through the small hole in the cap and air was not flowing very freely. So I drilled the hole a little bigger in the outside and inside diaphragm. I removed the fiber membrane and I took the little washer out of the inside of the diaphragm. Then I blew through the hole and there was plenty of air. I put the cap back together and closed it and did the drain test again and low and behold, fuel ran clear and without restriction. So, I filled the gas tank and took it for a series of loops in my area. Thirty miles later it was still going strong.
So, was it one thing? Probably not, but I really think that all along, the bike would not run on a full tank because it couldn't breathe. Good thing it only took me two months to figure it out. In the meantime, thanks for chiming in. I learned a lot through this process. Some one was right from the beginning, ns you have the right to brag if you know it was you, but I never completed the tests correctly. However, I now know how to trouble shoot just about everything there is about ignition and carbs and fuel flow.
Thanks for your patience. This XS is ready to run.
Grace and Peace, All. This thread is done...except for those who still want to tell me I told you so. Go ahead, I deserve it.
Congrats NorazDad!! 
Gas caps...…..I turn them upside down and flood them with Walmart's imitation WD40, leave them soaking overnight, blow them out with high pressure air, gobs of flakey yellow stuff comes out, repeat. My GoldWing always had a "Whooosh" when the cap was removed, some say that is normal, with a clean cap it only goes "fizz" now. Some vacuum in the GoldWing tank, but that's a fuel pump system.
Scott
Scott
