Just made a dwell reading

[spikeygg]

I finally got it tuned properly tonight!

I'm guessing the last guy who messed with the fuel mixture didn't realize that the WOT switch was busted (stuck always on). So he/she turned the K-jet fuel mixture WAY lean (counter-clockwise). It was so far down that it took basically one whole clockwise turn to get the duty cycle to show something besides 95%!

Anyway, yesterday I realized that I have an o-scope that I could use on this to REALLY see what's going on (DUH!). So I busted it out and made the measurements, it's cakewalk with this setup. Then I hooked both the cheapo dwell meter up and my o-scope and shot the video so you could see what I was seeing once I had it dialed in.

These are o-scope shots of the experiments from the manual:

Unplugged O2 lead (40-50% steady), my reading ~50%
Idle Unplugged DC.jpg

Grounded O2 lead (87% minimum), my reading ~95%:
Idle Grounded DC.jpg

1.5V O2 lead (20% maximum), my reading ~11%:
Revved 1.475V DC.jpg

Enjoy!

[David T]

So what WAS the problem getting the allen wrench into the mixture screw?

[spikeygg]

So what WAS the problem getting the allen wrench into the mixture screw?

The problem was that I had a cheap set of allen wrenches. I was using a large set that I bought at harbor freight long ago, they are made of the black material. Trying to use the wrench in that screw top ended up rounding out the allen wrench. I went to a friend's house who had another 3mm allen, but it was black and had a ball end. I told him I was looking for a flat-ended one and he took it to his grinder and removed the ball. He let me borrow that one and it got rounded out too but I was able to enrich the mixture a little before it became unusable. I have a set of silver metal allen wrenches but they are on a ring and the long end is attached to the ring so I am unable to use those for this application but they seemed much higher quality and less likely to become rounded.

I was toying with the idea of using JB weld to shore up the insides of the screw top so that I could use the allen wrenches that I had, when I decided to purchase some good silver allen wrenches as a last-ditch effort. I looked around in town but nearly everything I found locally is made of the black material. Last week I ordered this set of silver metal Bondhus allen wrenches from amazon. They are MONEY and work very well for this application. No slipping, no rounding, no issues. Last night I tried it out and was able to turn the screw and dial in the mixture.

-Greg

[David T]

When you grind an allen wrench you destroy the hardening making the wrench much softer and easier to round off. Instead of a "set" all you needed was 1 tee handle 3 mm allen wrench. Glad to hear you got it sorted out. Make sure you use a good plug that won't come loose in the hole over the mixture screw.