1974 tx650a Hotrods316

[Hotrods316]

Hi everyone!!!!!

Thanks for all the bits and pieces of help so far from me posting in others’ threads. Getting there.

I will make this my official introduction thread and a time piece to the process of bringing this back. Found from here it’s a cinnamon brown 74 tx650a.

Got this bike from spongebobs pineapple and been fighting all the old corrosion and PO cobbling. I’m brought things back from the before-this one is the next.

I cleaned the carbs, acid cleaned the tank, rebuilt petcocks.

Douched the engine and got it spinning free on the kicker by hand, drained and cleaned the sump (strainer/filter mod to come).

Need to pull clutch and get the tighter starter spring. It pulls on a feather and someone whacked the heads of the clutch screws
That’s another project for another day.

Toleranced the cam chain tensioner.

Valves look good clearance wise.

Got antsy and tried kicking, wore myself out and said okay time to do points, lol.

I’m setting points, I have static timing going well on the F mark with my points 12v light.

I have a question the points remain open for a whole 360, then 180, close and the open on the fire? This seems correct as far as a 720 degree firing cycle for standard 4 stroke, but is this correct for the xs650? I’m new to this model bike, played before on a xs400 so used to Yamaha and peculiar traits but wanted to ask the brain trust.

Also can’t find the official “spring wake up drill thread “ so don’t be afraid to say hey check this with your replies, if you’re nice you won’t hurt my feelings

Thanks pics and much much more to follow

Matt

 

[Wagner73]

Found from here it’s a cinnamon brown 74 tx650a.

Also can’t find the official “spring wake up drill thread “ so don’t be afraid to say hey check this with your replies, if you’re nice you won’t hurt my feelings

I can't either, but I believe there is one (or more) here. Hopefully someone smarter than me will chime in?!

 

[Jim]

I have a question the points remain open for a whole 360, then 180, close and the open on the fire? This seems correct as far as a 720 degree firing cycle for standard 4 stroke, but is this correct for the xs650? I’m new to this model bike, played before on a xs400 so used to Yamaha and peculiar traits but wanted to ask the brain trust.

Correct dwell is about 90 deg of crank rotation. So the points close about 100-110 deg BTDC and open about 15 deg BTDC.

 

[Wagner73]

I can't either, but I believe there is one (or more) here. Hopefully someone smarter than me will chime in?!

Here is a short thread that might help...

https://www.xs650.com/threads/starting-after-long-term-storage.66394/#post-839836

 

[Hotrods316]

Okay I did the static timing. Read the kickstart threads and she gave a good cough on first kick after priming. I felt good knowing things were working. Two or three attempts later it fired right off!

Now to buy an “antique dwelling meter” felt like snatching the parts counter kid when he said to look in antique shops.

Need to final set the timing because hard time idling without choke on… feel good having heard it run

Found the tach is frozen, whittled up a plug until I can rebuild the gauge.

Found the air idle screws may have been too tight from a tech bulletin and opened them up to the 1-3/4 called for in the bulletins and went to kick , nothing! Then realized I pulled the battery

So I’ll grab a new digital timing light with dwell I guess and try to set everything then.

Feel like clutch may not fully disengage, but maybe there’s enough friction with the rear up on center stand. When it was running I would pull clutch lever, click into gear and the real wheel would start driving before I let out the lever. Mind you I have not adjusted anything in the clutch yet, just me rambling about all I remember

Now I’m really squirreling because I have the rear wheel apart and doing the service and checks I been reading on.

 

[Wagner73]

Okay I did the static timing.

Now to buy an “antique dwelling meter” felt like snatching the parts counter kid when he said to look in antique shops.

Need to final set the timing because hard time idling without choke on… feel good having heard it run

Feel like clutch may not fully disengage, but maybe there’s enough friction with the rear up on center stand. When it was running I would pull clutch lever, click into gear and the real wheel would start driving before I let out the lever. Mind you I have not adjusted anything in the clutch yet, just me rambling about all I remember

Static then dynamic timing is the most important. Be sure to carefully adjust the points gaps with a feeler gauge before setting the timing.

Forget dwell. As I've stated before, my dwell tach went by the wayside about the time points did the same on most engines i.e. late '70's / 1980. That said, even at the time, I only found it useful on distributors that had externally-adjustable points e.g. Accel, etc. so you could dial-in while running. Otherwise, just a keen feeler gauge adjustment on a set of conventional points worked fine. The dwell could be used as a secondary check but IMHO, not needed nor much value there i.e. start-check-stop-tweak-start-check ad infinitum.

As for the clutch, of course be sure it's adjusted correctly (maybe even service the release mechanism if you're so inclined), but on the center stand it takes very little incidental friction to let the rear wheel turn. In fact, with oil in between the plates, that may be enough if your rear brake is quite free.

 

[Hotrods316]

Ok hope I can catch more eyes… 2m 5t… the rear brake drum needs the divot towards the axle because the flats are slightly different correct?

 

[Wagner73]

Ok hope I can catch more eyes… 2m 5t… the rear brake drum needs the divot towards the axle because the flats are slightly different correct?

Correct

 

[Hotrods316]

Thanks wagner73. My brain gets confused on binary choices lol, I’m like the curved edge ramps look right orientation to lever pull directions and got cornfused!!! lol

About the points, you think the gap is most important, set it to max opening of .014” ? Do this by loosening the actual point mount and adjusting there correct? After I do my static timing of point opening? Is too much gap as bad as too little? Thanks again

 

[Wagner73]

The point gap adjustment affects the timing, so must be done first. 0.14"-0.16" feels right, but check your manual.

Then check/adjust your static timing, and finally your dynamic timing at idle and full advance (3000-3500 rpm) to ensure the advancer is working correctly.

 

[Jim]

Now to buy an “antique dwelling meter” felt like snatching the parts counter kid when he said to look in antique shops.

You can check your dwell without the "antique" meter.

Dwell is nothing more than the time the coil is energized, expressed in degrees of crankshaft rotation. For our bikes dwell should be about 90°.
So, hook your timing light (a 12v troubleshooting light, not the strobe) up to the points you want to check. At about 100° - 105° before TDC the points should close and the light goes out. Take your ratchet you're turning the crank with and place it straight up. Now rotate the crank until the light comes back on. That is the end of the dwell cycle for that set of points. The ratchet should be pointing straight forward (horizontal), showing about 90° of rotation.

Adjust the points (gap) until you hit those marks and congratulations.... you've just set your dwell!

EDITED!! I screwed up on the first go around.

 

[AUTOMAN]

Gap means nothing. Use dynamic timing.
Point cam and/or point rubbing block geometry will vary alot.

 

[Hotrods316]

You can check your dwell without the "antique" meter.

Dwell is nothing more than the time the coil is energized, expressed in degrees of crankshaft rotation. For our bikes dwell should be about 90°.
So, hook your timing light (a 12v troubleshooting light, not the strobe) up to the points you want to check. At just before TDC the points should close and the light goes out. Take your ratchet you're turning the crank with and place it straight up. Now rotate the crank until the light comes back on. That is the end of the dwell cycle for that set of points. The ratchet should be pointing straight forward, showing about 90° of rotation.

Adjust the points until you hit those marks and congratulations.... you've just set your dwell!

Thanks, I had one (dwell meter/tach) some years ago may have lent it out, not in my toolbox .

I had roughly 180* of dwell before the points opened when I was checking things before the fire. I got it to fire after setting the static timing but I didn’t mess with gap/dwell. I will tinker on it after I rebuild this rear brake drum.

Bike is currently destined to be a flat track bike, but I haven’t set my heart to cut anything up yet. It’s a neat looking bike but will need a full rebuild as a nice street bike. So I’m pretty picky on the only stopping power lol

But I don’t want to have timing/carb/engine trouble out on track either that’s just as dangerous in many situations.

I really appreciate the input and help from everyone.

 

[Jim]

Gap means nothing. Use dynamic timing.
Point cam and/or point rubbing block geometry will vary alot.

True dat. But dwell needs setting first. Not enough dwell (points gap too big) and the coils will starve for electrons at high revs.
Too much dwell (too small a gap) and the coils stay energized too much... risk of overheating and burning out the coil.

I edited my post above 'cause I screwed up the first try. Please reread.

 

[Wagner73]

So, I was going to take this offline for schooling just for me, but it may be beneficial to others as well.

So @Jim , please school me. I have used a dwell tach years ago for externally adjustable points i.e. you could run the engine and use an allen key to precisely adjust dwell angle.

However, in the case with these bikes you can't do that, so you are statically adjusting dwell in the traditional way by essentially adjusting the point gap. Crudely, I don't think it's any better than a careful feeler gauge adjustment; more precisely, I suppose if you attached a degree wheel and a static test light, you could get it slightly better.

But is it in the noise, or a real benefit? I'll be honest and admit I have never used dwell on a motorcycle, only careful point gap and timing adjustment(s) , but I'd like to completely understand. TIA!

 

[Jim]

But is it in the noise, or a real benefit?

Mostly just in the noise.
Me personally, I find it easier to adjust the points until I get the 90° I'm looking for rather than using a feeler. But that say more about my hands shaking than anything else.

 

[Wagner73]

Mostly just in the noise.
Me personally, I find it easier to adjust the points until I get the 90° I'm looking for rather than using a feeler. But that say more about my hands shaking than anything else.

Many thanks!

 

[Hotrods316]

*edit l figured out the read drum

 

[Hotrods316]

Can anyone ID this tach? I have searched the literature tech thread but haven’t seen a tach with all 3 lights in it for the 1974 tx650a…???

The central part of the dash has all 4 holes, 2 for turn signals, and 2 round red at bottom, but the labels are gone… redundant lights on the central dash part? Just curious because I can’t id this tach… thanks

 

[Wagner73]

View attachment 372554

Can anyone ID this tach? I have searched the literature tech thread but haven’t seen a tach with all 3 lights in it for the 1974 tx650a…???

The central part of the dash has all 4 holes, 2 for turn signals, and 2 round red at bottom, but the labels are gone… redundant lights on the central dash part? Just curious because I can’t id this tach… thanks

Redline way too high for XS650 (7500 RPM typically). Likely later 3-4 cylinder bike.

Edit: Redline fits XS750 triple but - I think - too many lights.