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Jim's 1980 SG Miss September

Discussion in 'The Garage' started by Jim, Sep 26, 2017.

  1. 5twins

    5twins XS650 Guru Top Contributor

    It's pretty common for the carbs to re-plug up after cleaning a nasty set out. Try as you might, you never seem to get every last little bit of gunk out. Filling the carbs with gas and putting them in service seems to finish the job for you, lol. So far, I've had my '83 carbs partially plug the right pilot jet twice and the left choke jet once. Luckily I was able to "fix" the issues by just dropping the bowls, carbs still installed, and removing the pilot jet. Inspecting it closely, I could see gunk in it partially blocking the orifice.
    Raymond, gggGary, Jim and 2 others like this.
  2. jetmechmarty

    jetmechmarty What should I put here? XS650.com Supporter Top Contributor

    I can't remember the last time I cleaned the carburetors on my '83. I can't remember when I last put ethanol in them either. When I swapped them onto my engine change, I believe it started first kick. I guess I'm buying clean gasoline.
  3. 5twins

    5twins XS650 Guru Top Contributor

    It's not so much fresh gas I'm talking about here, it's when you resurrect one that's been sitting a long time and the carbs were all gummed up from that. You thoroughly clean them, yes, but chances are good you'll experience a few "teething" problems down the line as new gas finishes cleaning them out for you.

    My '78 was pretty rough looking when I got it but luckily the P.O. had done one right thing before parking it, and that was to drain the carbs. While they were pretty dirty on the outside, they were pristine inside. I never had any re-plug issues with them. My '83, on the other hand, was parked with gas in it and sat for 12 years, lol. I was surprised to find the carbs still "wet" inside but what was left wasn't much like gas anymore, more like syrup, lol.
  4. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    So... this'll take a little 'splainin. Back this spring I did the choke conversion to put the choke lever on the handlebars à la the 82-83 bikes. That was when the poppin' and sputterin' on startup... started. Before I could look into that, I had my foot surgery. Fast forward a few months and I clean forgot about that. Anyway... it turns out the carb parts swap was the problem. After I got the carbs off, I noticed the choke (enricher actually) wasn't moving as much as I thought it should. I compared it to the 34's on the run stand and it was only moving about 2/3's as much as they were. The bracket the choke cable attaches to has a tab sticking out that was hitting the carb body well before full choke.


    There's a dimple in the choke shaft where the screw tightens the bracket, so positioning is fixed. I debated drilling another dimple... but finally decided to just cut the tab off....

    tab cut.png

    Didn't find anything else wrong. Blew solvent through all the passageways and jets and all looked good. Put it all back together and I now get full choke...


    The SG has always been a tad cold blooded... it wants full choke to start. It's happy now. Full choke and it lights right off and settles into a nice 16-1800rpm idle. As the revs climb, you can reduce the choke to keep a nice warmup idle. Problem solved.

    As for the hanging idle, it's gone:shrug: Rode around town for about an hour and it never hung. The only thing I have now is a little popping on decel.... and I'm not concerned about that... actually kinda like it.
    I did give notice to the carbs though... showed 'em a picture of a Microsquirt and said "jus' one more time..."
    Last edited: Oct 8, 2020
  5. Mailman

    Mailman Hardly a Guru Top Contributor

    Nicely done Jim! :thumbsup: And clean too! :whistle:
  6. madmax-im

    madmax-im Yamaha...Go your own way... XS650.com Supporter Top Contributor

    Jim....Glad to hear you have the issue sorted and also glad you are back on 2 wheels again....:cheers:
  7. Raymond

    Raymond XS650 rider, fettler, setting out on a journey XS650.com Supporter Top Contributor

    Those carbs could see you meant business . . .
    TwoManyXS1Bs, Jim, Mailman and 3 others like this.
  8. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    No mechanical or electrical issue can resist Jim's methodical attack!

    MaxPete, TwoManyXS1Bs, Jim and 3 others like this.
  9. jetmechmarty

    jetmechmarty What should I put here? XS650.com Supporter Top Contributor

    Yeah! We're lucky to have him on here working for us. It's not to be taken for granted.
  10. 5twins

    5twins XS650 Guru Top Contributor

    Hmmm, interesting issue for sure. I just looked at my '83 and that cable bracket tab hits the mix screw tower same as yours did, but I think the choke works OK. I get no popping or hanging idle, and the choke is definitely doing it's thing because the bike will start running rough 10 to 20 seconds after starting unless I back it off. But, this '83 has never cold started as easily and readily as my '78 does. I'm still working to remedy that and this might be another avenue to explore.

    I wonder if the choke plungers themselves are contributing to this? There were two versions used on the BS34s. The later ones used with the cable operated choke had a plastic fitting on the end of the plunger rod .....


    The early version has just a plain brass rod .....


    I wonder if one version needs to be pulled out more (or less) than the other to operate correctly? I have examples of both but never compared them side by side out of the carbs. I'll have to do that.

    The only difference I see between yours and my (stock) set-up is where you're clamping your choke cable at. Not sure this would make any difference but anyhow, mine is clamped right at the end of the cable, on the metal ferrule. This is how it came to me and how I've always kept it. Yours is clamped farther back, on the black plastic sheath .....

  11. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    I was gonna ask how your 83 compares...
    I think it would. The nice part is it's easily accessed.... you won't have to pull the carbs to mod the bracket.
    Yeah, I compared them side by side (guess I shoulda took some pics). Internally they're identical. Only difference is the plastic bit and the snap ring.
    In my case, that wouldn't have made any difference. The cable is set for full close and full open. The limiting factor was the tab hitting the mix screw tower before the plunger reached full choke. My setup is a mix and match of bits from various members (thanks guys). Maybe that explains the difference. That or yours has a bit more cable stretch? Dunno... bottom line is if you can get stop to stop, the cable's correctly adjusted.
    If you try it, let us know?
    MaxPete and gggGary like this.
  12. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    ... now that I think of it, I wonder if the tab was intentionally meant to limit the choke to keep the EPA happy. I know that back in that era they were all about trying to lean things as much as possible to meet pollution requirements. Perhaps just another way of preventing overly rich mixtures?
    MaxPete, gggGary, GLJ and 1 other person like this.
  13. 5twins

    5twins XS650 Guru Top Contributor

    You don't get much more travel by cutting that tab off though, do you? Looks like the bracket's set screw will hit the mix screw tower next once the tab is removed, and after not too much more movement.
    gggGary likes this.
  14. Rasputin

    Rasputin XS650 Addict XS650.com Supporter Top Contributor

    I would just like to know are the starter/choke plungers a progressive device or an on/off.
    gggGary likes this.
  15. 5twins

    5twins XS650 Guru Top Contributor

    The plunger uncovers round passageways for air and fuel as it's pulled out, so it's not exactly on-off, but it's not too progressive either. The air passageways get uncovered first, then the fuel feed one. So, I guess if the plunger isn't getting pulled out enough, you might not get the full richness it could provide. You'd get all the air, just not all the fuel. Maybe that's why my '83 isn't cold starting as readily, it may not be getting full choke.
    gggGary and jetmechmarty like this.
  16. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    I just measured the travel on the old style (knob actuated) and new style (cable) chokes. They're both (now) identical at 9/16". Subtract the 1/8 to 3/16" for the tab I cut off and yeah... about 20-33% more travel.


    With full choke now, the plungers reach their travel limit before the bracket or set screw touches the tower

  17. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    Time Warp.
    Been thinkin' about the poppin' on decel. When I originally did the resto, I went back together with #45 pilots because of the pod air filters and aftermarket exhaust. A low speed plug chop showed the plugs as black as a coalman. So I went back to the stock #42.5's. She seemed happy then. This year I haven't been able to tune the poppin' out. That got me thinkin'... Seems the poppin' started around the time I swapped over to the Suzuki iggy box... so I'm running about 5-6° retarded. One of the advantages of being advanced is you can run a leaner mixture because there's more time for the flame front to propagate.... a leaner mixtures burns slower. So based on that, I popped the 45's back in. Figured I'd take 'er out for a 10-15 min run to warm the oil up for an oil change and see if that helped on decel. It did. It was like night and day. I'd reset the mix screws to 3 turns and that sounds about perfect. She now has a rock solid idle at 1200 rpm... throttle response is instant (well, we're talkin' CV carbs here, so that's relative... :rolleyes:) and no poppin' on decel. The time warp finally dissipated... and I pulled back into the driveway about 2 hours later. :er:
    Drained the oil and pulled the filters. This is the second oil change since the resto. First was at about 700-800 miles and everything was clean. This oil has about 1200 mi. on it. Again, everything looked good. No metal to speak of... normal fuzzies on the magnets and one small piece of plastic that I'm guessin' came off the starter gear. Cleaned everything up, reinstalled the filters and topped 'er up with Castrol 20-50. Gonna try and get another ride tomorrow.... only for 10-15 min of course. Unless I can find that time warp again. :smoke:


    plastic bit.jpg

    side filter.jpg
    Last edited: Nov 5, 2020
  18. Mailman

    Mailman Hardly a Guru Top Contributor

    How are you liking your heel toe shifter, is it more comfortable for your foot now?
    Paul Sutton, MaxPete, Raymond and 3 others like this.
  19. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    Yeah, I'm still likin' it. Tenderness in the scar is finally just about gone, so I can do it either way now. I kinda go back and forth.
  20. GLJ

    GLJ Never go faster than your guardian angle can fly. Top Contributor

    Not the kinda thing you want to post on this forum.:eek::redface:

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