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More carb questions.

  • Thread starter Thread starter birkeloc
  • Start date Start date
B

birkeloc

Guest
Hey there again everyone, sorry if this has already been answered, but I can't seem to find any info about jetting my carbs for altitude (5400 ft, to be exact). I have a 79 gs550 with all stock parts and I'm currently rebuilding the carburetors. I noticed a couple oddities, though: I'm using Paul Musser's article on VM carb rebuilds, and what he calls the bleeder or pilot jet doesn't seem to exist in my carbs; the manual says not to mess with the pilot fuel screw (I'm guessing because it's so easy to damage?); the pilot air screw in my rebuild kit seems ever so slightly wider at the tip than the screw currently in the carb, is this a problem? And finally, the pilot air screw on carb #3 is jammed and stripped, to the point where I don't think I'll be able to get it out with anything less than a Herculean display of might involving a power drill and a screw extractor. Any ideas as to how it might have gotten so messed up (all the other pilot air screws came out easy as could be), and/or tips on getting it out? And actually I guess this is the final question: one intake boot between the cylinder head and the carb is cracked; where can I get a replacement, along with the o-rings that go between the boot and the cylinder head? I can't seem to find the parts online. Thanks for all the help everyone, you've truly been great!

P.S. There's about 57 questions in this posting, so tens of thousands of respect points to anyone who can answer all of them. Also, as for the high altitude jetting, the current main jets are 50's and the needle jets are 80's. Does that sound right?
 
Thanks for the tips, that article on carb theory was great. I'm assuming that correction factor charts are probably different for different carburetors, and I'm having trouble finding one for mine. Any ideas? Thanks again.
 
Don't confuse parts with incorrect terminology.
A "bleeder" is another word for the needle jet. It has holes in it to help atomize fuel. The jet needle slides up and down through the needle jet.
Yes, you do have a pilot jet. I think you've confused that too with the main jet. Your stock main jets would be 80. Your pilot jet is 15.
If that stuck/stripped side air screw is adjusted wrong, that carb will have some issues, depending on its adjustment. You may be able to get it out by etching in a new slot that fits your screwdriver and then use some heat, such as a blow dryer, to help swell the pot metal carb body more than the brass screw. Turn it inward first, clean threads with a straight pin/spray cleaner, then try to remove.
Do not use rebuild kit air/fuel screws unless you know they're damaged. Same for any main/pilot jets. Under normal conditions, the screws/jets will be fine with a little cleaning. Nothing to gain by replacing "old" screws/jets. ANY difference with new screws/jets can/will adversely effect performance.
Before making any jet size changes, I'd try simple pilot fuel/side air screw adjustments first (if necessary) and test.
To properly clean the screws/passages, you should remove them and replace their o-rings. Just lightly seat them (fuel screws/underneath) and count how far out they are and keep a record. Fine tuning will be fairly easy if the other basics of tuning are done right.
As for the side air screws, don't worry about recording their settings. Upon initial testing, just set them at 1 1/2 turns out and then adjust by the highest rpm method described at this site. This will work for your specific elevation. Between the pilot fuel and side air screws adjustments, you should be good for basic cruising around. If you have other jetting issues at wider throttle positions, let us know and we'll try to help.
 
Thanks again for the info, the terminology can be quite confusing. It seems everything I look up has a different name for the same parts. Now I'm just waiting on some o-rings for the intake boots and I'll be set (hopefully). I'll let everyone know how it turns out!
 
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