So you want an adjustable vacuum advance?

[Ivan]

Well, here is the answer:

I am fighting the ping at 3500 to 4500 that is so prevalent on these. I think I have about the same problem that Craznuk is fighting. In the process I kept thinking about the TSB saying they made a different dash pot for this express purpose. So I did some investigating and noticed there is a glob of epoxy on the top of the dash pot. I used a drill and some heat from a torch, and this is what I found:



So, now with a flat blade screw driver, I can adjust the vacuum advance amount.

It got dark, so I can't say whether or not it cured the ping.

[XJOK2PLAY]

Way to go, Ivan! Cool discovery there.

Makes sense... factory sets it where they want it, then seal it so to prevent smarter guys from 'polluting the enviroment' by doing our own adjustments...

Who cared if it pinged or not once they sold 'em new?
I'm sure in the day it was all about the emissions standards, and trying to meet them.

You da man!

[3Phase]

Octane Adjuster?

Nice digging, Ivan!

My '74 Corolla station wagon had an octane adjuster sticking out of the advance pot right where that screw is. The Toyota only required a couple of clicks in either direction to adjust the timing for the octane of the fuel and a full turn was a lot!


Regards,

Scott

[Ivan]

This pod has a pretty fine thread to it. I imagine that coupled with the distance from the centerline to the pin the pod actuates means that, in terms of degrees, one turn isn't going to be a lot. Would be interesting if I had a timing light to gauge how much each turn actually makes.

[tw1980]

Good job Ivan!If we ever meet up I owe you a cold beer for that one.

Terry

[GARTHXS]

hmmmm

I would love to hear your results

[Crazcnuk]

Sure makes testing simple. I will have to go 'modify' mine.

I took the insurance off mine today, as I can't ride it the way it is.

I still don't think it's a timing issue. No one has been able to explain why it would start all of a sudden after 3 or 4 years of riding.

At this point I am ready to strip it and throw it in the river, again.

[Winterhawk]

Could it be a carbon buildup that is glowing and igniting the mixture prematurely?

[Crazcnuk]

I doubt it. I only have 5-6000 miles on the top end.

[Ivan]

While this definitely helped the situation, it didn't fully cure it. I think there is something else wrong. Its pretty loud on mine, just like Craz indicated on his. I am not sure how much of this is from the windjammer, since it is my first fairing. everything is loud with it on. But mine definitely sounds like its pinging. I have some more investigation to do, since Mine is a mix and match with an old engine and the 4R0 reluctor and pickups. Might switch everything over to the 2H7 setup. I need to figure out wether or not the TCI is a direct swap or if wiring changes are needed.

However, I can't think that the alternate dash pot that Yamaha released would be anything more than one with the stop set deeper. I think on one that has the slight ping, this would be the ticket.

[dpotter58]

While this definitely helped the situation, it didn't fully cure it. I think there is something else wrong. .

better get it right...

[Ivan]

better get it right...

If it doesn't get right, I have a back up plan.

I don't think its engine mechanical, it doesn't sound like it. Might be carboned up. The engine was sitting for who knows how long, and I know nothing about the history. The intake valves were gunked up with carbon, so it could be a carbon issue, like Winterhawk suggested. I will make some smoke signals tonight, probably piss off the neighbors.

If nothing else, the 79 is raring to go. It has a better seat too. Just not as smooth or comfortable as the piecebike.

[crazy steve]

That is a handy thing to know. But you'd have to do some dinking around to figure out if that screw is simply a stop (just to limit total advance) or if it changes the spring rate, and the timing across the rpm range. I've run into these before (on both cars and bikes), and one thing they had in common is they're both very sensitive to small changes.

As to the increase in noise, yeah, a WS of any sort will magnify sound and sometimes scare the h**l out you with all the 'new' noises you hear...

'78E original owner

[Ivan]

I believe this one is just a stop. There is a spring under the setscrew, but that just keeps the screw from rattling around. On the opposite end of the setscrew is a peg. It doesn't appear to alter the spring rate. However, there is a slot on the outside of the screw that also looks as if there is an adjustment for the return spring. If you look in the picture, you can see the slots outside the screw. I didn't look into it that far.

[crazy steve]

If it's just a stop, that rather limits it's usefulness, particularly for what you're trying to do. In all the 'store-bought' ones I've used, the adjustment altered the rate that the advance came in, but usually not the total advance. Reducing the total will not have good effect on fuel economy, and these things do rather badly enough as it is...

'78E original owner