Update: Carb cleaning and drivability

[nwrider]

Thanks for the info.

Ben

[fiat-doctor]

Add me to this as well...  you inspired me to yank the carbs off my '83 and clean them.  Mine ran well, but had an inconsisitant idle when warm...  sometimes wanted to die, and othertimes idled too fast...  found both carbs had stuff in the float bowls and also the mixture screw area was infested with tiny bits of "something"...   did not even have to replace the gaskets... just lots of spray carb cleaner and lots of compressed air.   Idle is excellent now and it seems to run better at part throttle as well...  should have done this last year!!
Steve

[QBS]

Ya'll are welcome.  Took the bike out for its' first road since putting it all back together.  Starter system is operating perfectly.  Charging system at idle is steady 13.2 VDC.  Don't know about Volts at speed because I was too busy hangin on because the bike is screaming like I can't ever remember.  When you pull the trigger on it, you better have it pointed in the right direction because you're fixin to be there.

It is much more cold blooded than before.  But starts within two crankshaft rotations from stone cold with full enrichner and within two crankshaft rotations when full hot, and no enrichner and no throttle.   However, after sitting for an hour or so, it requires  approx. 20% enricher to start.  Hot idle is perfect, steady, not ragged, and wonderful.

There is disapointment.  The off idle flat spot that I've been trying to completely eliminate is still with me to a small degree.  It is much much better than when I first started down this road.  And, it is slight enough that it can be easily compensated for when riding.  I'm going to eventualy replace all my vacume lines in the hope that that will help the flat spot and cold naturedness.  But even if that doesn't help, I'm still very happy because it is running so much better overal.

Question for Carb Gurus:  Can the cold naturedness be dramaticaly improved by idle mixture riching or not?

[Night Vision]

as far as your flat spot goes... besides ancient vacuum line leaks... you can try adjusting the flapper door opening timing by sliding the vacc pot back and forth. Jason swears by having his open a wee bit more than just resting on the rubber bumper at idle.

it's a little tricky to adjust because you turn it over to unscrew and adjust it, and when you turn it right side up, it closes more than you'd think.....

as far as cold starts goes.... I can adjust the pilots so she starts good when cold... or runs great when warm... I choose the latter

[Lucky]

certainly worth a try!

[JDArgonaut]

QBS, you have motivated me to take care of my carbs! Luckily for me, I have Lucky's DVD so that should help out quite a bit. The only question I have is where did you get your rebuild kit from? I really don't want to start it until I get that in hand. I did a search on ebay again this morning, but was unsuccessful. Any suggestions?

All In,
JDA

[QBS]

No rebuild kit used here.  Carb top gasket is normally very reusable unless someone has mistakenly glued it down.  Jets don't wear out.  So, unless someone has mistakenly reamed them out, they should just need to be cleaned.  There is a rubber "O" ring associated with the pilot needle jet assembly.  Both of mine were in good shape so they were reused.  About the only componets that might need to be replaced are the needle valves and their seats. I am super paranoid about breaking an '83 carb top float mounting pedestal (btdt), so I just left the float needle valves alone.  They weren't leaking too bad before, and I've got in-line fuel cut off valves installed, so I figured that if there was a leakage problem the cut off valves would handle it.  As it turned out, after being ultrasonically cleaned, they now hold pressure.  But I still don't trust them and continue to use the cut off valves for overnight or longer storage.  There are "O" rings associated with the float bowl drain screws.  In spite of much use over the last 26 years, mine are still in very serviceable condition and didn't need replacement.

As best as I can tell, a rebuild kit for one carb could only include the carb top gasket, the float needle valve and its' seat, and the two "O" rings.  Aside from the butter fly shaft, nothing else wears, moves, or is effected by exposure to fuel over time.  There are tiny gaskets associated with the venturi, but that part rarely requires removal and the gaskets (if not lost) are reusable.

In my case, necessary disassemby (and nothing more), and cleaning were all that was needed.

[Lucky]

There are 2 seals on each trottle shaft, not generally a seperatly available part.  i don't have specs, but Rick G. says they match a Polaris part. 

Jason Morris says 2 number 6 (i think, i forget) orings can be substituted.  i tried this but have two problems with this:
1) the orings are a bit wide & if you tigten the shaft nut all the way they bind.
2) orings are not designed for the torsional stress this puts on them & i don't think they'll last.  I had to put a small helper spring on the throttle linkage to be sure they close fully :(