Electronic ignitions are great once you get them dialed in exactly but you may need to tweak your setting a couple times to find that spot. You may get some minor pinging if set right on the full advance mark. These bikes actually run a little better and stronger with the timing retarded just a hair, plus it cures that minor pinging. By a hair, I mean 2° or 3°, idle timing near the right slash mark of the "range" and full advance just below the full advance slash mark. If you were firing at TDC then your timing was way off, probably by 14° or 15°. That's too much.
 
Indeed.

When I first got the bike, the timing plate was at full stop clockwise, way too advanced. Setting it by the dot was nearly full stop CCW, better, but still firing at TDC at idle. Now, by the light, full advance hits exactly the L mark, loads better. I'll try retarding 2-3* tonight and see how it feels.
 
Indeed.

When I first got the bike, the timing plate was at full stop clockwise, way too advanced. Setting it by the dot was nearly full stop CCW, better, but still firing at TDC at idle. Now, by the light, full advance hits exactly the L mark, loads better. I'll try retarding 2-3* tonight and see how it feels.
Yes 5T. I found out after setting Timing many times in different settings that what u advise above is bang on.My bike will happly idle at 800 RPM at those settings and pull cleanly off that and thru to redline.
 
Ok, my commute this morning was a test of a 2-3* (~3/16") retard. Honestly, I'm not sure if I felt any difference. I did find cold starts took a good 10-12 kicks with the timing mark right on the full advance mark. I look forward to seeing what tonight's cold start will be like with the retard.

I did notice that a regular head shake upon takeoff corresponds with a patch of vibration between 2-2500rpm. I imagine this might get sorted with cleaning, adjusting, and syncing the carbs. Aiming for a smoother, more confident idle too. I had to raise it back to 1500 after a stall headed into a right hand turn while set at 1200.
 
My recent commutes have been a longer route via a highway with light traffic. This afternoon however, I needed to go clear across town and there are no good East/West routes to do so. Twenty or so miles of 35mph surface roads with plenty of congestion.

On the way home I was doing a lot of low RPM cruising, practicing my throttle control for smoother low speeds.

About halfway I started feeling the very slightest miss, like when the bike tells you to flip to reserve. I checked, both petcocks were on and I had filled up with reputable, quick-selling fuel just that morning. Even so, it could've been bad fuel.

I was spending more time in the 3-4000 range, carefully controlling my throttle to keep aligned with traffic. Maybe I had found a spot of break up indicative of carb fouling or a candidate for a new jet size or needle setting. Somewhere about 1/8-1/4 throttle.

But then it started getting worse, and more frequent. Everywhere in the throttle range. Then she stalled but started right up with a touch of the starter while rolling. And she stalled again. This time, no go. The starter would crank, but no fire. A crack of throttle, which she usually likes, didn't help.

The last thing I had done had been to retard the timing 2-3*, so I checked to see if that had come loose. All good.

Tried the starter again and she fired up. But only for a short time. Now I began to suspect whether the Boyer was getting enough juice. Perhaps the stock alternator was able to keep up with the H4 headlight while running at 4-5000rpm, but miles of 3500 wasn't enough.

The last two miles were a push, but I felt pretty good to get home to be confirmed by the voltmeter. 11.98v with the ignition off. 12.3v at idle, 13.04v at 4000rpm. Lights off.

The evening's plans have changed.

The carb and rear end rebuild I planned for the weekend begins tonight with Curly's List.

But first, a frosty one.
 
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Yes, your charging output is low. If the brushes (length) and rotor check out OK, you may need to adjust your regulator to output more volts. But honestly, that old original mechanical regulator is a dinosaur. Even with the output tweaked higher, it's still very inconsistent. One of the best upgrades you can do is to install an automotive regulator. They deliver a nice constant, consistent output so besides better charging, that lessens the wear & tear on your rotor.
 
Hi DB: I'm restoring a '76 C model and have had many of the same experiences with timing and valve adjustments It just keeps getting better and bettter as I ride it.

I am interested in one phrase in your last post: "she saved.300 RPM at any speed". Could you please explain that?

Pete
 
@2M: plugs are ok. They've only got maybe 300 miles on them, maybe a bit too dark, but I had been doing a lot of low RPM cruising and sitting at idle. These are standard copper BP7s.

@MaxPete: Any given speed required ~300 fewer RPM. With proper timing, each combustive event provides more power thus requiring fewer of them. Following the timing adjustment with the light, I observed that it required about 300 fewer rpm to cruise at given speeds.

@5twins: I've been reading up on the reg/rect upgrades you and a few others did. VR-115 and a couple diy bridge rectifiers.

I'm thinking the rotor is ok. 5.5ohms ring to ring, no continuity either ring to ground. Everything in there looks ok. No hint of previous overheating. Stator wire bundle nice and intact as it passes the drive sprocket.

I am finding a .6v drop from battery voltage at what I take is supposed to be the brown wire. The one on the brush with only one screw? It's green on my bike, but it's the only one getting voltage between it and ground. The other, 3 screw, brush is attached to the longer black wire and sees no voltage between it and ground.

I had thoughts of doing a complete electrical rebuild from scratch someday hence. As my daily ride, through sometimes heavy traffic, I'm leaning toward the reliable, low rpm full voltage charging of a PMA. How much does it make sense to dig deep into upgrading the stock system if a PMA was already on the sort of distant horizon?

Update on the rest: New rear tire and brake shoes installed. Whoa, that's a big nut on the drive sprocket!
 
Things have reached a good stopping point.

Rear end: New tire and brake shoes installed. Old chain and sprockets (17/33) removed. New lock tabs, front and rear, on order. New chain and sprockets (18/34) ready to go. Swingarm nice and solid, freshly greased. MMM mentioned using silicone sealant on the front sprocket. Which surface gets it? The splines or the face of the countershaft seal?

Carbs: Dismantled quite a bit. In pretty good shape. Slides fell slowly during the diaphragm test, no light leaks either. 1/2 tsp of greyish grit in each float bowl. Floats are empty and seem to be intact. I now can see what size drivers I need for the jets. I'll pull those and start cleaning tomorrow after the hardware store. I have to pull and replace the little brass screws on the throttle shaft due to a Previous Owner's mangling of the threads. Both throttle plates need centering. If I'm pulling those screws, should I go ahead and replace the throttle shaft seals? If so, I think that's the last of the rubber bits to be removed. May I then put the whole body in a can of Chem-Dip? The Mike's carb boots show their usual wear. A new set from 650central are standing by.

First thing tomorrow is a hardware store run for a bunch of stainless hex head hardware and drivers for the jets. Then a continuation of carb cleaning.

Reassembly will hopefully happen on Wednesday when I arrive back from the outdoors to meet a package of supplies on my step.

Oh, yes, the throttle and clutch cables have been given the old drip by drip oiling. Thanks 5Twins.

With the tank, seat, air filters, carbs, and rear wheel off, the electrics took on prominence and stared at me all day. And I stared back. I'm not sure how long I can let that rat's nest go.
 
If I'm pulling those screws, should I go ahead and replace the throttle shaft seals?
I would. I'd replace those phillips heads with allen/hex head screws also.
You may have to drill the old out if they have been mangled too much. It can be done, slow and steady.
IMG_20160815_211358_245.jpg
 
Besides the butterfly shaft seals, the only other rubber parts in your '76-'77 carb set are o-rings on the needle jets and the tips of the choke plungers. But full dipping the bodies is usually not required. You only need to insure the various passageways through them are clear by blowing cleaner through them. Even if you dipped the bodies, you would still need to blow the passageways through afterwards. Your bike seems to be running OK so I doubt you have any blocked passageways.

3M was probably talking about sealing the sprocket to the steel sleeve it mounts against. If you don't get a good seal there, oil can leak out. This is why the sprocket nut is so tight. It has to make a metal to metal seal both there and on the sleeve's inner end inside the motor. Many leaks from this area aren't the oil seal in the case but rather this sprocket to sleeve connection. I used some regular gasket sealer on mine but I can see silicone sealer working as well. You can also put a little under the lock washer and nut on the front of the sprocket. The big key to sealing this area is having the nut tight, really tight, 72-94 ft/lbs.

A PMA is not an improvement in my opinion. It won't work any better or more reliably than a stock system in good shape. It will substantially lighten your wallet though. Don't fall prey to the PMA sellers claims that you need one and the stock system is crap. It's total bullshit and just a sales pitch. With a few low cost upgrades, your stock system will perform just fine. Start watching eBay for a VR115 or it's equivalent. They can usually be had for $10 to $15 if you're patient. In the meantime, you could adjust your old stock unit to increase it's output. Here's how .....



Your original rectifier should be fine for the time being as long as it's functioning OK. You can upgrade it down the road sometime. The biggest benefit comes from the regulator upgrade. When you do get around to it, you might consider the unit from a later model XS500. This is a more modern version of the unit used on the 650 and totally enclosed in a heat sink. I know you have motorcycle bone yards in Phoenix, maybe one could be had cheap from there. The plug will need to be changed (female to male spades) then it will plug right in .....

XS500Rec2.jpg
 
Hi All:

Sorry to be pain, but I have to comment and correct the ~300 RPM drop at any speed. This statement simply cannot be correct.

Regardless of the efficiency of the combustion processes, the relationship between engine crankshaft RPM (as shown on the tachometer) and road speed in a manual transmission vehicle (car/truck/motorcycle/tank ....whatever) is totally fixed by the combination of the primary drive ratio, the gearbox reduction ratio (i.e. which gear the vehicle has engaged at a given moment in time), the final drive ratio and the outer diameter of the tire. This assumes of course that neither the clutch nor the tires (or treads in the case of a tracked vehicle) are slipping. Thus, to generate a given road speed in a given gear, the crankshaft must be turning at a fixed speed - no matter how well or badly it is running at the time. Some of the those late night oil additive adverts often claim to reduce engine RPM at a given road speed - but tests by knowledgeable people have confirmed that this is bunk.

My guess is that your tach is reading a bit lower - perhaps due to reduced vibration. Even though they are driven by a rotary cable (look on the RH side case of the engine right near the front of the case), tachometers are actually electromagnetic devices and they are sensitive to vibration and variations in the rotating speed of the cable itself. They really only give an approximate engine speed reading and shouldn't be taken as total gospel. My tach was swinging from one value to another until I lubed the cable and then it settled down and read quite steadily - at the lower value.
 
5Twins, I'll sit tight on the PMA and follow your suggestions there. And thanks for clarifying the sprocket sealing.

MaxPete, your logic rings true. I was amazed by that magnetic connection when I opened my tach to put the shaken bits back together, and am not surprised to hear that it is less than gospel.
 
More digging.

A Previous Owner had used a rebuild kit including the incorrect jets. 27.5/135 is not for a 77D. The pilots had some of that grey grit on them, too. The air jets are pretty mangled and the o-rings look a bit crispy.

Jets, fuel and air, to be ordered.
 
Not a problem DB. As it happens, a few years ago one of my graduate students made a similar statement in a class about some ignition system enhancements that he had made to his manual tranny '71 Mustang (I am an automotive engineer and a prof) and he and I had a spirited debate that took about 20 minutes of lecture time to sort out (during which half the class was cheering for him and the other half for me). Anyhow - I convinced him and so its all good.

I would add that our bikes do have really decent instruments - but the electromagnetic aspect of how they operate can be a puzzle sometimes. The reason why the EM aspect is GOOD thing is that if something gets hung up in the instrument, the EM components can simply "slip" and not destroy the whole unit the way that a little gear train would in the old days. That is also why my tach was oscillating from a low to a high value - the cable must have been binding a little and not rotating steadily and that "wobble" was confusing the EM system in the instrument. When I lubed the cable, the rotation rate settled down and so did the instrument. BTW, the same thing would apply to a speedometer. If your speedo oscillates - try lubing the cable and making sure that it is routed as straight as possible.

On the PMA issue - I agree with 5Twins that the stock system can work just fine - but I did replace my crusty old voltage regulator with an automotive unit (combo rectifier/regulator) and it works great. I did it mainly because the rectifier unit was badly corroded and I didn't want to chance it and the stock regulator can be...a problem. I got the combo unit that MikesXS sells, but I found that it would not fit underneath the battery box as suggested, so I made a very simple and cheap little mount out of an 8 inch hose clamp painted black and a zip-tie (see photo). That arrangement gives it just enough flexibility that the thing doesn't shake itself to pieces, but it is secure and won't get tangled up with the chain or swing arm. It is also nearly invisible - and removing the voltage regulator left a little bit of room inside the LH sidecover for some storage space. To make the mount, I just drilled a hole in the clamp and screwed the V-R-Rectifier unit to it and anchored the other end of the unit to the bike's frame with a black zip-tie. A cheap, simple, robust and effective mount - the ideal engineering solution (just add beer and its perfecto).

I also bought a PMA rotor and stator which I will install this winter - mainly to save the grief of dealing with the alternator brushes. Replacing them isn't a big task but on my previous XS650 (a '75 B model which I owned 40 years ago - back in the 1970's) - the darned things wore out every 6-9000 miles or so. Once I was stranded on a lonely highway with a very annoyed girlfriend. Amazingly, about 10 minutes after we coasted off the road, a guy on another XS650 came along and he had a spare set of brushes with him - which he gave to me on the promise that I would always carry a spare set and that I would give them to another XS650 rider who was stuck. I kept both bargains because luck like that just doesn't happen very often.

Anyhow, I'm hoping the PMA unit will prevent future occurences of stranding (the girlfriend is long-gone - but oh well).

Cheers,

Pete

Regulator-Rectifier_El-Cheapo-Mount.JPG
Regulator-Rectifier_Unit.JPG
 
Another stopping point.

Both carbs have been completely disassembled and cleaned with Chem-Dip, carb cleaner, and compressed air. I've taken them as far as I can go until new jets and throttle seals arrive. I know a dip wasn't required, but they sure do look nice.

I've inhaled enough petrol and laboratory products, it is now time to breathe some fresh air out-of-doors. I'm not sure if we're doing a simple car camp or a quick backpack, but we're sleeping in the trees.
 
Check the slide needle too. Sometimes those aftermarket rebuild kits contain a generic replacement, a Y-22, and it's totally wrong for your carb set, way too short.
 
Its always good to take a break from a challenging project to regain perspective and calm frayed patience. You're doing a great job on a really nice bike - riding will come soon!

Pete
 
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