Bringing back an 80 Special

[crazy steve]

It's not the ignition box that does the curve; it's the mechanical advance behind the pickup coils and the vacuum can that moves the coils. These are calibrated differently between the '78-79 bikes and the 80s. The early units bring in more advance, and do it sooner IIRC.

The difference in the TCI box is the early box uses 1.5 ohm coils (and a ballast resistor), the later box uses 3 ohm coils and no resistor. As long as you match the coils to the box, there's no difference otherwise...

[cywelchjr]

Hey Steve:

Thanks for pointing this out to me.
I checked the XSpart finder and I found the pick up coil assembly is the same on the E's F's and the SG. The Ignighter Unit assembly Black box is :
4RO 8230510-00 for the SG and 2H7 8230510-10-00 for the E's & F.

If I used one of the boxes from the E-F bikes would it give me the more agressive curve?

I think that parts finder is incorrect. The E,F,G and S models of the latter two all use the same basic timing assy although the timing parts for the E IIRC have a more radical timing curve, and the replacement vacuum advance for the G and H series provides a little less vacuum advance than the E and F units.

E, F and G all use the same igniter box (the S models as well) with the H and SH using the 4RO igniter, which includes the RPM related advance in the igniter while still using the vacuum advance. Then the XJ got rid of the of the vacuum advance and went to the (I believe) 10M unit which does both RPM and vacuum advance electronically using a box that hooks to the #2 carb like the vacuum unit on the older models.

So basically 78 - 80 use the same type of timing unit with the only difference being the assembly with the weights on it and the vacuum advance between the 80 and the earlier ones.

[crazy steve]

Yeah, Cy's right about the boxes; couldn't remember all the differences....

[cywelchjr]

It's not the ignition box that does the curve; it's the mechanical advance behind the pickup coils and the vacuum can that moves the coils. These are calibrated differently between the '78-79 bikes and the 80s. The early units bring in more advance, and do it sooner IIRC.

The difference in the TCI box is the early box uses 1.5 ohm coils (and a ballast resistor), the later box uses 3 ohm coils and no resistor. As long as you match the coils to the box, there's no difference otherwise...

Umm, no. Up to 80, it's the same box, in 81 the switch to the 3 ohm coils AND the switch to electronic advance replacing the centripetal portion happened. Up through 80 you still have the 1.5 ohm coils and the 2h7 box.

So, an 80 special would have the same box as a 78 standard, just in a different position. However, the centripetal advance (which is outboard/on top of the coils not under them) has a different curve from I believe both a different cam on the weight levers and different springs. Additionally, later vacuum units had less advance in them, but up till late in the 80 model year at LEAST if not 81, they had the same vacuum advance as the earlier models, the unit with less was a replacement unit to solve a knocking problem (and apparently didn't even always solve it).

That is one thing that has not been mentioned, that the newer heads with their larger valves and lower compression can't use as much advance as the earlier engines anyways, unless your willing to use higher octane fuel than the bike is rated to require, assuming you can get it (which we can't in lovely communist california).

[crazy steve]

...Additionally, later vacuum units had less advance in them, but up till late in the 80 model year at LEAST if not 81, they had the same vacuum advance as the earlier models, the unit with less was a replacement unit to solve a knocking problem (and apparently didn't even always solve it).

That is one thing that has not been mentioned, that the newer heads with their larger valves and lower compression can't use as much advance as the earlier engines anyways, unless your willing to use higher octane fuel than the bike is rated to require, assuming you can get it (which we can't in lovely communist california).

I dunno about the vacuum units being the same; that's what I thought too, but Three-phase posted the '78-79 and '80 vacuum curves from the FSMs and those showed two distinctly different curves. The Clymer manual doesn't have this info, and I think the parts fiche is only showing a 'close enough' generic replacement. If you really wanted to get into it, there's this thread: http://www.xs11.com/forum/showthread...ustable+vacuum ... that leads me to believe you could recalibrate the vacuum advance at least somewhat if you wanted to invest the time. This thread has the '78 curves in it, and IIRC the later vacuum units had slightly more advance but took more vacuum to achieve it so were slower to come in. The other thing that's interesting to note is the Clymer manual timing procedure shows you setting the idle timing to the 'F' mark for both the standard and the special. After disconnecting the vacuum advance and running the motor at 5200 rpm, the standard timing should be 36 degrees, but the special is only 31; 5 degrees less. So in spite of the parts fiche showing the same advance unit for both bikes, the standard unit has more advance. That would be the unit you would want.

This isn't the only possible discrepancy you'll find in the parts fiche. Remember, they don't say these are exact replacement parts, only that they're 'replacements'. Another interesting thing I turned up is the fiche shows only the '78-79 standards as having the 'good' cams, with the '79 special using the later-type cams (which may explain the difference in the advance curves). So all '79 motors are not created equal...

And with lower compression, you can run more advance, not less. Rick, one thing to remember here is you'll only see maybe 2-3 hp more at best with the early advance units under ideal conditions, and only at certain points in the power curve. I think you could get nearly the same results by running a bit more initial timing and maybe using one grade better gas. If you can get the early standard mechanical advance, I'd use that but the vacuum unit is much less important as it only comes into play under part-throttle, 'cruising' operation. If you have all the bits by all means use them but don't stress about it

[cywelchjr]

And with lower compression, you can run more advance, not less. Rick, one thing to remember here is you'll only see maybe 2-3 hp more at best with the early advance units under ideal conditions, and only at certain points in the power curve. I think you could get nearly the same results by running a bit more initial timing and maybe using one grade better gas. If you can get the early standard mechanical advance, I'd use that but the vacuum unit is much less important as it only comes into play under part-throttle, 'cruising' operation. If you have all the bits by all means use them but don't stress about it

Your right, I was somehow thinking backwards. But, there has to be a different issue, because they had to come out with a replacement advance unit with less advance because of a knock at part throttle on the 80 and 81 models.

[crazy steve]

Your right, I was somehow thinking backwards. But, there has to be a different issue, because they had to come out with a replacement advance unit with less advance because of a knock at part throttle on the 80 and 81 models.

I suspect that had more to do with the lean factory jetting rather than the timing. Remember, the dealer was prevented by law from tampering with the carbs, so timing changes were their only fix...

[Rickrod3]

What about big bore kits?

When I get back to it I'll examine both vacuum set ups.
Maybe since I'm not in a rush I'll see if I can find the stock parts.(potential tuning nightmare)
The early spare engine I have looks be be in better shape it might be worth keeping it whole and saving it if I need it for my F.

I would imagine a big bore kit affects the tuning in the same way.

Thanks guys learning alot here.

Rick

[cywelchjr]

I suspect that had more to do with the lean factory jetting rather than the timing. Remember, the dealer was prevented by law from tampering with the carbs, so timing changes were their only fix...

Actually it had been decided that the method used on the older bikes with the plastic cap still allowed owners to tweak it, so they put it under that little cap, and there was a hidden item the dealer could order so they could adjust mixtures when setting up the bike, then put new caps in to plug them off.

[crazy steve]

Actually it had been decided that the method used on the older bikes with the plastic cap still allowed owners to tweak it, so they put it under that little cap, and there was a hidden item the dealer could order so they could adjust mixtures when setting up the bike, then put new caps in to plug them off.

Maybe, but I remember having some early-eighties cars that didn't even have idle-mixture adjustments, sealed or otherwise; the mixture was determined by the carb machining and there wasn't any way to change it. My '85 motor home is like that, as was the '81 Cougar I had; just a blank spot were the screws had been on prior carb models.

The EPA had gotten pretty hard-nosed by that time...

[Rickrod3]

Frame welding & painting ????

What kind of metal is the frame made of?

Is it chrome moly?

What is the best paint I could use?
I'm limited to rattle can.

Is enamel better than lacquer?

[cywelchjr]

What kind of metal is the frame made of?

Is it chrome moly?

What is the best paint I could use?
I'm limited to rattle can.

Is enamel better than lacquer?

I think enamel is a little tougher than lacquer, and I believe it will handle spilled gas and oil a little better, but if you have a way to get the frame good and hot, 500 deg ceramic high temp stuff may be toughest of the rattle can stuff. The problem is you have to get it up to a couple hundred degrees to cure it, which wouldn't be a problem he is Ca in the summer (just sit it in the sun for a few hours, you could fry eggs on it), but might be a problem otherwise. I do know though that the high temp ceramic worked well on the control pods on my XS400, so it might work well, but then it did sit in the sun, so maybe it got a cure from that?

PS, I don't know if you can cure the stuff with a propane torch or not, I would think you could but that might be a lot more work than you want to do.

[natemoen]

PS, I don't know if you can cure the stuff with a propane torch or not, I would think you could but that might be a lot more work than you want to do.

Not unless you have the hog burner style torch that you hook up to a 20 pound or larger tank.

Where do you get ceramic spray paint. I have not ever been able to find it anywhere other than ordering online?

[crazy steve]

What kind of metal is the frame made of? Is it chrome moly? What is the best paint I could use? I'm limited to rattle can. Is enamel better than lacquer?

The frame is mild steel, so no 'special' welding methods are needed.

As far as rattlecan paint, I'd use enamel over lacquer as it doesn't chip nearly as easily. There's some single-stage epoxies out there that are a bit better, but more expensive; not enough better to make them worth it IMO.

If you have an air compressor, give some thought to picking up a cheap HVLP spray gun and using a catalyzed paint. Nothing in a rattlecan will give the same durabilty, and a quart of paint (plus catalyst/reducer) will be enough to paint the whole bike.

[natemoen]

quart of paint (plus catalyst/reducer) will be enough to paint the whole bike.

Well that's if you want the whole bike one color, otherwise you would need two.