Daniel Black, Mailman and I have been discussing our carb conundrums.
As I reported a few days ago after syncing with an ATF manometer my carb mix screws were quite a bit off. Should be 2 ¼ turns out.
Right was 1 ½, and left was 3 ¼. It was running great but I know they should be a lot closer than a 1 ¾ turn difference. 5twins recently discussed this in Mailman's thread.
This was bugging me.
Daniel-san gave a gentle nudge that maybe a pilot circuit was still blocked in spite of how many times I had been in there, or maybe the right float was off spec.
Rain day the other day so I was ‘forced’ to spend the afternoon in the shop.
I was going to finally rebuild the 78/79 carbs from Black Betty, my 78E next project and see what might happen if I installed them, but then thought I might just as well tear into these again if they’re off. When they were previously rebuilt, installed new Mikuni stock sized Jets, new needle valves, new o-rings, new OEM throttle shaft seals, new choke housing gaskets and new XSDirect floats. (Didn’t know better at the time, should have, but OK so far)
Come to think of it, there WAS a glaring omission in this thread:
"Chronic complaints about carb pulls and installs".
Came real close to griping about it this time 2M.
Everything was clear in all circuits, but that's not to say I didn't dislodge something without seeing it.
Also had noticed when coming to a stop my idle will drop 200 - 300 RPM's or so and then climb back up after about 5 secs. or so.
DB suggested raising floats to 23mm might help with the fuel sloshing/starvation issue on rapid decel.
After 170 km / 105 mile test ride mostly highway miles, she ran great, pulled hard through all the gears, but still had the idle drop coming to a stop in neutral.
DB again suggested it might be clutch related as he had experienced a similar problem when clutch drag was a contributing factor on his Stella. Spent some time messing with clutch adjustment. Seems to be a recurring theme around here lately. Shifting when running/warm was no problem but I could not get it to shift into first when bike was off/cold. Pulled the left case to make sure all was good, ball bearing was there. I had previously lubed worm gear but took it apart again, greased everything up, cleaned up some chain lube spatter.
Took quite a bit of fiddling but finally got it. Turns out I was too tight. Using that tighten until you feel the point of resistance while lightly fanning the clutch lever to stack everything I was over tightening. Additionally I may have also done too much adjusting at the lever end thus reducing the available range of motion for the worm gear arm.
Kept backing it off and finally found the spot.
After 100 km/60 mile mostly highway test ride today, she's still running great, pulling hard, but idle drop of 200-300 rpm when I come to a stop is still there. Doesn't stall but idle drops and then climbs back up to setting.
Other than that, all’s still good, or at least as good as can be for an engine that needs a top end job and is burning a lot of oil. Gonna enjoy riding out the last couple of chilly months of our season here and then let the games begin.
Oil consumption is staying pretty steady at a rate of a litre in 600 miles so my valve seals and rings haven’t magically fixed themselves.
Mileage is averaging 52.1 mpg.
I had also noticed a lot of tach needle bounce of 200-300 rpm's at 3500 and up. Mailman suggested lubing tach cable. This had been done last summer before any miles but did again now and bounce is down to almost nothing, about 0.5 rpms. Thanks Bob!
So carbs now: Factory spec 2 1/4. New settings Left 2 3/8, Right 3. Tuned by ear and dead cylinder method. For now gonna call this close enough and done.
I am curious though and do have a couple of questions:
- Could it be that the needle tips on the mix screws are worn differently thus causing the settings to be different or are there other internal carb differences that cause this?
- Carb and clutch adjustments have done nothing to eliminate the dropping idle when stopping situation. Could this be related to a weak, tired motor that needs a rebuild, or is there something else going on?
Thanks again guys for all your input and direction here and elsewhere on the forum that has answered tons of other questions.