Good/bad suprise

[rossness]

Hey guys

So I bought a '76 650C last July and have been riding it 4-5 times a week since (Texas winters!). I've done routine maintenance on it (oil, filters, side cover gaskets), some light mod work and cleaned the carbs a couple times. I've been having this weird issue lately where my left cylinder sounds like it's missing, but only when I'm idling and its hot. It pulls through all the gears fine and no sputters all the way through the throttle, never has, only when idling.
I did a compression test, 105 on each side (low but I'm waiting til summer for a complete rebuild). Checked plugs, looked good and changed them anyway, gapped them properly as well. I cleaned and greased my advance, then opened up my points to find this......

Is that a pamco? PO definitely didn't tell me that was installed. I've never taken the time to check the points as it's always run fine until now. If so, that sputter wouldn't be timing, would it?

Any advice appreciated.

 

[peterg]

Yep. That's a Pamco. Look's like an earlier version.

 

[5twins]

Yes, that looks like a Pamco. It's electronic and once set, the timing isn't supposed to change. But, sometimes it does a little shortly after install. I don't know why, maybe new parts "settling in". So yes, you could check the timing, maybe it is off slightly. I would also check the spark plug wire connections both at the coil and at the plug caps. With a Pamco, you should have a single coil with dual outputs (plug wires) now.

I also noticed your plugs are resistor type (BPR). I'm not sure about your plug caps, I don't recognize them. Normally, you want some resistance in the ignition circuit, but only one instance of it. So that means resistor plugs, or resistor caps, or resistor wires - but not a combination of more than one of those items. Resistor wires are usually not used on bikes but check yours anyway. People do strange (and wrong) things to bikes. The normal set-up is resistor spark plug caps and plain plugs. Too much resistance in the circuit can reduce the strength of the spark, "choke" it off so to speak. It may push on through at higher RPMs but maybe not reliably at idle.

 

[rossness]

Is there a way I can test to see if my plug caps are resistor caps? Also, is there a link to how to change timing with the pamco somewhere?

 

[peterg]

www.yamahaxs650.com has all the info you will need to set up your timing.

 

[650Skull]

In post #1 the bike has been running wll for 8 months and all along you didn't know there was a pamco ignition. If your problem has recently materialized that should eliminate the problem of the pamco timing changing due to setting in after installation.

I see oil sitting in the bottom of the cam covers. looks like the cam seals need to be redone, wouldn't think oil would do the circuit bord much good. The Cam seal needs to be replaced.................. this is one thing and this may solve the issue.................also check the leads and such for the correct componants as per 5T's sugestion.

The whole of the Advance rod should have been removed and greased as well as the advance unit. a dry shaft may add to the issues you are having

Go to ........"Tech Menu"............"Electrical".............Look for, ....."Pamco Ignition-wiring diagrams, FAQ, Tips, troubleshooting"...................Comprehensive Pamco thread.

 

[650Skull]

Yamahaxs650.com has all the info you will need to set up your timing.

Good info...................i'm guessing this is how people answered your questions and helped you

 

[peterg]

The gentleman asked for a link to instructions on how to adjust the timing. I provided the link to him. There is a lot of valuable info on the link directly from Pamco Pete. Sorry if you are upset about my reply to the OP.

 

[650Skull]

Yamahaxs650.com has all the info you will need to set up your timing.

Maybe you wanted to include a link but there is nun posted. Not offended, making a point and observation based on evidence posted that does not show any links to Pamco's or any information..........

 

[650Skull]

Ah i see the attempt at a link....................i had to highlight XS650.com, right click and , then open in a new tab/window................Here is a link http://yamahaxs650.com/ ..................just need to click on the link..................all i do is copy and past the link from the search bar into a post

 

[xjwmx]

Is there a way I can test to see if my plug caps are resistor caps?

Better than that. Measure the resistance from the cap through the wire. If you have a dual coil measure cap to cap and divide by 2. For single coil measure from cap to one of the terminals. Find out here on old posts what resistance the cap and the coil secondary should have combined. I'd tell you but I always have to look those things up myself. Bad running that's ok at higher rpm can be a partially clogged pilot (idle) circuit in the carb. Can be lots of things really; you just have to go though all the systems and make sure everything is okay and it will work -- surprise! 'Nother surprise

P.S. Do you have a gas filter in the line, like from the lawnmower section of the auto parts store? If not, might have taken these months for crud from the tank to fubar the pilot circuit.

 

[peterg]

fixed the link above

 

[timbeck]

I'm not sure but in the first picture the left head bolt appears to have a steel or copper washer . However the right head bolt seams to have the original rubber covered washer. Not sure if this part of the problem but the original washers are notorious for loosening.
tim