Help, I've made a hash out of adjusting mixture...

74B, stock, HIF4 carbs, new points, plugs, condenser, wires, timing set per fac. spec. carbs ballanced. Cleaned carbs and had to replace the jet tubes in both (plastic tabs were broken, tubes stuck). Float levels set, double checked, and needle/seats good. Choke gaskets/seals replaced. Valves adjusted, Should be good to go....

But...

I'm having a heck of a time getting the mixture right. Saw the Twist video and numerous posts, but I'm making a self inflected hash of things. Here's where I'm stuck. I don't have any info on where to set the needle jets to get it "in the ball park" and end up chasing adjustments all over the place. It's amazing how tolerent these little engines are of a wide mixture spread! After messing about and fouling the plugs last night I thought I'd take a break and try again this evening with new plugs. :X

Where is a good initial setting for the jets? Should I aim for flush with the carb base or "bridge"? Slightly above, slightly below? I know that won't be the final setting, but I'm just looking to get close, maybe within a few turns, so I'm not chasing the adjustment so much. In the past, I could usualy use the setting when the carbs came off to get close, but these were a real mess with one jet stuck all the way up and the PO "compensated" by raising the float level really high (flooding) so I can't really go back to what I started with. 8-)

Right now both jets are maybe around .025 below the bridge, and it seems to be pretty close, but then the plugs loaded up from my earlier ham fisted adjusting and I think it would be good to put a fresh set in before another attempt. Any advice? :S

Michael,
There are a couple of good articles in the library section on this website. Scroll down to the section labeled "Carburetors & Fuel" and look for them there. If that doesn't help, check back in with the board and I'm sure you'll find the help you need.

Cheers - Dennis

Needle biased to the rear of carb?
Needle shoulder flush to hole?
Start at .06 down from bridge. Use the butt end of calipers. There is a certain # of turns w/enrichment screw but I dont know it.
RS

initial setting of jets--about 60 thou below the bridge. NEVER flush.

http://www.sucarb.co.uk/TechnicalDetail.aspx?id=73

HIFs as i remember its two turns in with adj screw,,make sure both carb jets are down same amount..
Over rich condition will cause cyl wall wash,,(oil from cyl walls..
If its going to take awhile you might add to youy tank a can of two stroke oil ,,100 to one mix
to lube walls ..

Actually in HIF4 carbs, the jet bearing sit slightly below the bridge, and the stock setting for the jet ends up being flush with the jet bearing, not the bridge. The tech books teach to flush the jet with the bridge and then turn the screw X number of times to lower the jet (sorry can't remember X number of times, because what I retained from the info was it was flush with the jet bearing). Hope that helps.

Hey guys!
Thanks for all the advice. Went home last night and changed plugs. Set the jets to .060 below the bridge using my calipers. Started it up and it was running the best yet! Final tweeks were probably +- 1/2 turn on each carb (max). Haven't had a chance to drive it yet, but just based on how happy it was ideling and not filling my garage up with fumes I think I'm really in the ballpark now! FWIW, the SU manuals do indeed state flush with the bridge, though I don't recall seeing a spec on X turns lower. Thats where I originally started and really made a mess of things. Flush with the jet bearing is probably a better "rule of thumb" starting point and probably works out to almost .060 below the bridge should a caliper not be handy. One full turn actually works out to quite a bit of vertical travel, BTW, and (as the manual states) move in 2 "flat" increments (or around a 1/4 turn max). The sweet spot seems to be +- 1/2 turn, so it could easily (as I have proved to myself over the last few days) be over or under shot!