Electrical and rear end question, possible engine question

[smiles79]

Ok. 1975 XS650, pods, free-er exhaust, pamco, clubmans, brat seat, shock extensions, blah blah blah.

First, the electrical issue. It is intermittent, but sometimes I have no turn signals (front led, rear incandescent, aftermarket flasher), horn, or brake light. Not sure about the tail light, I think that filament is just blown. Sometimes they all work. Never have a problem with the headlight, starter, or ignition. Ideas?

Rear end issue: There is an intermittent scraping noise (kinda sounds like the sound your breaks make when they need to be replaced), but it will happen when I'm not braking, and stops when I swerve to the right (continues when I swerve to the left). I'm not overly familiar with drum brakes, do they make a noise like this when they need to be replaced? Ideas?

Lastly, my engine is making a noise. Sounds like it could possibly be a pre-detonation nosie? Kind of a pingy noise (man this is hard to explain). I'm probably not running very good gas, and I think the compression is higher than stock. This one I'm kinda just wondering if there are any common issues that should be checked.

Thank you for taking the time to look at my plethora of issues,

Smiles

 

[Downeaster]

Ok. 1975 XS650, pods, free-er exhaust, pamco, clubmans, brat seat, shock extensions, blah blah blah.

First, the electrical issue. It is intermittent, but sometimes I have no turn signals (front led, rear incandescent, aftermarket flasher), horn, or brake light. Not sure about the tail light, I think that filament is just blown. Sometimes they all work. Never have a problem with the headlight, starter, or ignition. Ideas?

Almost certainly a wiring issue. Loose/dirty connector, grounds likewise. There's a thread on here about cleaning the connectors, find it and use it.

Rear end issue: There is an intermittent scraping noise (kinda sounds like the sound your breaks make when they need to be replaced), but it will happen when I'm not braking, and stops when I swerve to the right (continues when I swerve to the left). I'm not overly familiar with drum brakes, do they make a noise like this when they need to be replaced? Ideas?

A little harder to diagnose. Check for loose rear axle nut and adjusters allowing wheel to shift slightly, loose brace arm on brake caliper, loose chain guard. Put the bike up on the center stand or otherwise elevate rear wheel and see if you can move it around.

Lastly, my engine is making a noise. Sounds like it could possibly be a pre-detonation nosie? Kind of a pingy noise (man this is hard to explain). I'm probably not running very good gas, and I think the compression is higher than stock. This one I'm kinda just wondering if there are any common issues that should be checked.

Crappy gas is highly likely, especially if the compression has been bumped up. Also, check the timing, might be a tad advanced. I'd also adjust the cam chain tension and the valve gap just because.

Thank you for taking the time to look at my plethora of issues,

Smiles

Added this as my reply embedded in your message didn't count as a message...

 

[smiles79]

Thanks! I haven't gotten into the engine at all other then replacing the ignition and timing it. I assume there are threads here for setting valves and cam chain tension?

 

[5twins]

On the rear end, I'm thinking maybe your wheel bearings are bad. The drum brake backing plate forms part of the axle spacer stack on that side. When the axle is tight, that backing plate (and the brake shoes mounted on it) can't move. However, if your wheel bearings are worn out and loose, the wheel could wobble around on the axle, and the brake drum could scrape on the shoes at times. To really check the bearings, remove the wheel, stick your finger in the bearing hole and rotate it. The inner race should turn smoothly and there should be no play or slop between the inner and outer race.

Even though the drum brake itself probably isn't the cause, that doesn't mean it shouldn't be serviced and renovated. Chances are, it's never been serviced since it left the factory. The procedure is pretty straight forward and simple. Basically, it's just a dis-assembly, thorough cleaning, and (minimal) greasing of all the moving parts. The procedure is outlined here .....

http://www.xs650.com/forum/showthread.php?t=25632

 

[smiles79]

So with increased compression, how should the timing me adjusted?

 

[5twins]

When setting the timing on these, you have to check it twice (in two spots). You need to check it at idle (retarded) and most importantly, at around 3K RPM where it will be fully advanced. This second check is more important that the first because this is where you will spend most of your time running.

If you still have the stock mechanical advance, some wear may have occurred on the unit. These are designed to advance the timing a certain exact amount, something like 25°. When they get old, worn, and loose, the amount they advance grows. That means even though you have the timing set correctly at idle, it may be too far advanced at full advance.

The idle timing spec is given as a 4° "range" (13° to 17° BTDC). This allows you to compensate for some advance unit wear. You may need to set your idle timing more retarded, over near the right slash mark of the F "range", to insure you're not over-advanced at full advance.

Shoot for a full advance that doesn't go past the full advance slash mark. Even better is slightly before it like so .....

What you ask? Run the full advance timing slightly retarded? Well, actually, you're not. Your model's full advance spec is 40° BTDC but the very early models only fully advanced to 38° BTDC. The change was made early in '71 to, in Yamaha's words, "... permit smoother, and more synchronized, idling." The bike will actually perform a little better at high RPMs and high speeds this way, at the expense of a slightly lumpier idle. Oh, and it helps cure the ping too.

 

[XSLeo]

Stock timing is good for most any compression. Set it as a stock engine. Pay particular attention to full advance. On your 75 it has marks for TDC, idle timing and full advance. With the idle at 1200 rpms idle timing should be between the marks. when slowly reved up the rotor mark should move over toward the left. At about 3000 to 3200 it should reach to but never past the full advance mark.
To advanced timing can cause pinging. Low octane fuel can cause pinging. The two together can burn holes in pistons.
I never run regular fuel, at least 91 octane and then only if I can't get 93.
On your electrical I would do as Downeaster mentioned, clean all your connections. On the grounds clean bare metal to clean bare metal. On any connections a dab of dielectric grease helps prevent corrosion.
Leo

 

[smiles79]

Thanks for the great info! Does the timing not need to change being as the compression is upped (I'm not sure by now much and I don't have a tester)?

 

[smiles79]

Thanks everyone! Sory Leo, I posted my previous response at the same time you did.