Topic: needle settings

[petercb750]

Hi all - I've just put carbie rebuild kits through my 72 750, having also done a complete engine swap. They have now been tuned and balanced,  but during the tune-up if a mixture screw was wound right in the bike still ran and didn't stall. Would this indicate that it's running too rich?
They are now only wound out about 1/2 a turn each, but it seems to be running pretty good.
I set the clips on the needles to the 2nd notch from the bottom (which is where the old ones were when they were on the old motor) - is that too rich do you think? What is the standard position (assuming everything else is ok and there are no air leaks or anything)?? I'm running standard exhaust and an oiled foam air cleaner in a standard box, and I'm assuming that the jets were standard issue (I used K&L kits) but didn't think to check - derrr 
I haven't done more than 1 mile on it since the tune, but hope to give it a decent road test in the next couple of days.
Any thoughts from all you experts greatly appreciated.......
Peter.

[Bob Wessner]

You don't mention whether the exhaust and airbox are stock. Assuming they are, here are some carb specs. The second to last column on the right "JN" is the jet needle position, i.e., notch the clip should be in, all things being equal that is. There could be needle taper differences between the kit and what was in there. Good luck, hope this helps.

http://www.hondachopper.com/carb.specs.html

[petercb750]

Thanks for that Bob - another stupid question, is that JN position from the top or the bottom? And that's a good point you make about the possible variance in the taper - probably going to be a case of trial and error!!! Anyway, it's good to be on the road again (with apologies to Willie).
BTW, I did mention stock pipes and airbox.

[Bob Wessner]

BTW, I did mention stock pipes and airbox.

So you did. Only had one swig of coffee by then, eyes not focusing yet.  I believe it's from the top. Can't say I ever gave it much thought though since "3" would be the middle notch of the five and that's stock for mine and runs fine there.

I mention the taper because I started out with kits on my carb clean/rebuild. I was noting some rich conditions after installing the kit. Found two things that differed quite a bit between the kit and what I was replacing.   One was the float valve. The kit valve had a "very" stiff spring under the tip and the other was the jet needle taper. The kit needle was much more slender at the lower end which would correspond to the lower throttle settings. Someone here suggested I get a drill bit gauge and slide the two needles in the appropriate diameter one and see how far down the both go. Sure enough, the kit needles were more slender. I ended up going back to my stock needles and float valve. Having done that, the air screws ended up pretty much where Honda suggested as did the needle, middle notch.

[petercb750]

Cheers! Might run it for while, see how the plugs look, and maybe lift them a notch if needed. Thanks for your input - much appreciated. 

[Bob Wessner]

That's pretty much what I did. First some around town, low speed riding to sort out the air screw settings, and then a plug chop at higher speed to sort out, confirm the needle setting. Good luck. Carbs are fun. 

[Bob Wessner]

One other thing I noted with mine. Once you get to sorting out the high speed needle settings, it's pretty straightforward plug chops and an adjustment of one notch either way usually does it. I had more trouble with the idle/low speed settings with the air screw until I realized just how sensitive they are to adjustments. Usually a 1/8th turn either way has an affect, just ran it around town, pulled the plugs, adjusted, cleaned an reinstalled, repeat as necessary. Just don't over adjust or you find yourself going back and forth too much.

[petercb750]

OK - have been for a decent run, and checked plugs - all 4 very sooty and carboned up (but reasonably dry). Definitely too rich - and despite tune is getting progressively hesitant out of corners or just off idle (which is a bit erratic) as if plugs are fouling, so to me it sounds almost certainly like too much fuel? Exhaust smells rich too. So anyway can address that with needles etc as discussed earlier in this thread.
Bike seems to be going ok, but better at higher revs than low. I didn't do an actual plug chop at speed, but hadn't done much slow riding before I had a look after the run.
BUT, and this is the scary bit, have got some thin black oily discharge coming from around #4 exhaust port/flange area and splashing back onto motor, plus same at the balance tube between the two pipes on that side - not heaps of it, but a couple of thin dribbles. Oil in tank is still clean and looks nothing like what is appearing in those spots - could that indicate that it's swallowing gobfulls of fuel and not burning it all and pushing it back out the pipes (and mixing with old residue etc in there)?? If that's possible, what confuses me is that the plugs didn't seem to be wet, which I would have expected if there was that much fuel going through, AND it only seems to be on #3 and#4 side. There is also a trace of oil smoke from that side (which might have got a bit worse near the end of the ride, but is not that noticable at idle), but am wondering if that can at all be contributed to the symptoms described? Also these pipes were on the old motor which had major oil burning problems on the same side, so the pipes may well have some oil left in them.

If anybody suggests that this sounds like internal issues like rings, I'd better stay away from sharp objects, and lock up the cats because I'll be looking for some to kick
Pete.