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broken pilot fuel screw tips...

  • Thread starter Thread starter quiktrp
  • Start date Start date
Q

quiktrp

Guest
Hi all-

I have a 79 GS750E, and recently rebuilt the carbs. All four of them have the tips of the pilot fuel screws broken off in the carb bodies. After rebuilding them and getting air to blow through all the passages, I thought I had all the tips out. Not so. After reassembling them with the new screws and installing the carbs on the bike, I have absolutely no tunability with the pilot circuit. Runs ok at idle, but is lean up to 1/8 throttle. I finally had a chance to tear back into them today, and when shining a light down the pilot fuel holes, I can see the tips broken off in each bore.

I did a search to find any tips on removing these, and only came up with a dead link to an old thread by hoomgar.

Attempting to remove the tips, I plugged the venturi in the throttle bore, and plugged the pilot jet. Then I fed 90 psi of compressed air into the pilot air screw hole while poking at the tips with a pick. This wouldn't free the tips, so I'm thinking I'll have to replace the carb bodies. Is there any other tricks I can try? I already had the bodies soaking in barry's carb cleaner for a few days before I rebuilt them, so any varnish should be long gone. I think that I just really wedged them in there when I installed the new pilot screws over the broken tips...
 
Also, other than popping at idle occasionally and some popping while riding at light throttle, it runs great. With an air cooled engine, how can I tell if I'm lean enough to start melting parts?
 
quiktrp said:
Also, other than popping at idle occasionally and some popping while riding at light throttle, it runs great. With an air cooled engine, how can I tell if I'm lean enough to start melting parts?
Click to expand...
Plug chop.
 
mixongw said:
Plug chop.
Click to expand...
How light can the porcelin be before I should worry? No glitter on them though, I guess that's a good sign :)

Do you recommend just doing an 1/8 throttle run and killing it?
 
A light tan color is best. White is way too lean. I look at the electrodes, not the insulator.
 
quiktrp said:
Hi all-

I have a 79 GS750E, and recently rebuilt the carbs. All four of them have the tips of the pilot fuel screws broken off in the carb bodies. After rebuilding them and getting air to blow through all the passages, I thought I had all the tips out. Not so. After reassembling them with the new screws and installing the carbs on the bike, I have absolutely no tunability with the pilot circuit. Runs ok at idle, but is lean up to 1/8 throttle. I finally had a chance to tear back into them today, and when shining a light down the pilot fuel holes, I can see the tips broken off in each bore.

I did a search to find any tips on removing these, and only came up with a dead link to an old thread by hoomgar.

Attempting to remove the tips, I plugged the venturi in the throttle bore, and plugged the pilot jet. Then I fed 90 psi of compressed air into the pilot air screw hole while poking at the tips with a pick. This wouldn't free the tips, so I'm thinking I'll have to replace the carb bodies. Is there any other tricks I can try? I already had the bodies soaking in barry's carb cleaner for a few days before I rebuilt them, so any varnish should be long gone. I think that I just really wedged them in there when I installed the new pilot screws over the broken tips...
Click to expand...

To get them out try a couple of things (guys, correct me if I'm wrong)
A...heat the carb body up and use a screw extractor
B... drill it and try a torx bit
I would recommend A.... I paid someone 20 bucks to do it for me...was well worth the $$ considering they knew what they were doing and I didnt want to chance it...
 
speedzter2000 said:
To get them out try a couple of things (guys, correct me if I'm wrong)
A...heat the carb body up and use a screw extractor
B... drill it and try a torx bit
I would recommend A.... I paid someone 20 bucks to do it for me...was well worth the $$ considering they knew what they were doing and I didnt want to chance it...
Click to expand...
Aren't the tips of these needles a little small to try to drill, or am I missing something?
 
A mechanic that I use did this ... I BELIEVE (could be wrong) it was a 5/64 bit....had the same problem :( He also used a torch to get it out...all I know, he got it out, and I was happy.... (I only had to do it to one carb body, though...)
 
How narrow does the passage close up to? Anyone happen to have a pic of how the passage looks? It would definately help to know what I'm drilling into :)

And when you say heat up, are you talking about a real even heat (like baking in the oven) or using a torch?
 
I had some broken tips in a set of spare carbs I bought. I took a very small drill bit (much smaller than a 1/16 - like a #70 or #75) and clamped it sideways in a pair of needle-nosed vice-grips. Then I reached in the carb throat and pushed the broken tip out with the bit. It worked great for the two tips that were broken and didn't seem to enlarge or damage the hole. Go slowly and be sure to keep it square and push straight down and only on the tip.

Good luck.
 
I've had them break off and drilled them out. Don't remember the bit size, but it was very small.
 
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