Mach 1 Stock Carb Tuning

[themoudie]

Thank you Jim and Bob.

At present I have a very nice long hill and a very long straight on which to obtain plug colours, but it's not helping with this flat spot coming off the pilot onto the slide.

I look forwarding to reading your findings Jim.

Good health, Bill

[blaat!]

Full disclosure, my SS1 29D has some minor internal corrosion in the slide area and the needle has a small pit about halfway up. I'm not sure if it is enough to impact settings.

I used this amazingly useful diagram to help sort the tuning:

carb tune.png

The cam is the stock Mach 1 gray type with dimensions confirmed by Eldert back in 2012.

The pilot jet is a 55 instead of the stock 50 (so 0.05mm bigger) which is probably why it idles best with the pilot screw turned all the way in. I meant to confirm with the AFR gauge that turning the pilot screw in is leaning it out but forgot. Will do that next time I have the gauge installed.

The slide is an 80 which I understand is stock on a Mach 1. I don't have others so this is all I have ever used.

The atomizer/needle jet is a 265.

The needle is an M14 and the standard setting should be with the clip in the second (from the top) notch. I needed to lean it out based on the gauge so I dropped the needle by putting the clip in the first notch.

At the same time I leaned out the more open throttle position by moving from a 120 main jet to a 118 main jet I had on hand.

When I made these two changes the bike ran SO much better. Unfortunately some of it comes down to the brass you have available.

On a related note, I purchased a M7 needle from Eurocarb because they show the diameter specs (but no length specs) on their site and this needle is similar in profile but ever so slightly larger in diameter overall. I figured this would allow me to go even leaner and move the needle back up using the clip/notches. Since the M14 was at its limit in the highest notch I wanted to see if I could go even leaner to test the performance. Basically go beyond in both directions and settle in the middle. Unfortunately I think the M7 is shorter (gotta compare it to the M14 next time I have it out) so it starts leaner but quickly goes too rich.

Hope this is helpful!

[Bevel bob]

Modern fuels are often different to what was set up for. I would check your fuel level Bill. Raise till starts to drip then lower a couple of mm. I am using A 110 main and a 260 needle . All are weaker than your set up apart from a 60 slide.

[themoudie]

Aye Bob,

Blat not Bill!

Mach 1 is a bit exotic for me, I've never been in the right place at the right time!

Good health, Bill

[blaat!]

I tend to think it as the wrong place at the wrong time, and poor judgement
Circa 2011:

DSC01852.JPG

No idea what I was thinking.

Good point about the modern fuels Bob. The refining process has evolved in 60 years no doubt and the gas I'm currently using is 10% ethanol.
260 needle jet can't currently be had at any price! Like I said... the brass you have