Author Topic: Ooo I really f#&%ed up this time! 500/550 carb model differences?  (Read 672 times)

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Offline geoluv

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Ooo I really f#&%ed up this time! 500/550 carb model differences?
« on: September 01, 2018, 05:23:13 AM »
Different model years have different jetting but all supposedly have the same bodies.  Supposedly the bodies are interchangeable between the non-PD carbs so long as you jet them correctly for your year/model.

I wonder how true that is.  I noticed that the hole opposite the secondary jet is threaded on the 069A but not the previous models.  I also wonder about internal air and fuel routing and hole diameters and tunnel diameters etc.

Anyway I was screwing in a cheap replacement #38 slow jet in my number 4 carburetor body and the end below the threading snapped off inside the body.  The part that has the emulsion holes. I can't get it out, it is very small, I don't have an easy out that small and I'm not sure they make them that small.  It would have to be a 2mm diameter easy out.  I tried to grind down a small screw so that just the tip had threads and was small enough to screw into the hole, I got it to grip pretty good, but when I tried to rip it out the snapped off end wouldn't budge.

My options are:
1. Carefully use a drill press and small drill bit the same diameter as the snapped off end to grind it out.  Luckily the opposite end of the carb is flat so it will be easy to drill straight down and not mess up the threads.  Then blow out with compressed air and try my best to determine if the pathway is clear.  If it is clear enough put in old jet.  I think it would be hard to determine if the pathway is truly clear. :(
2. If drilling it out doesn't work I can buy a new carb body.  They seem to be about $50-$60 so I am not pleased. 

Two possible reasons my jet snapped:
1. The carb I was rebuilding was VERY sludgy.  Worst one I have come across yet.  Took me a solid 6 hours to yank the whole rack out, disassemble, throw them in some purple power degreaser, scrape and scrub the hell out of them, then polish the bowls and covers and screws and part of the rack and put it all back together.  I replaced the slow jets because it was proving difficult to get the insides perfectly clean and free of debris that could block the very tiny hole.  I usualy keep all the old jets as long as they don't look messed up.  I might not have gotten the hole perfectly cleaned out and there could have been debris in there that caused my jet tip to snap when I was screwing it in.                                                           

2.  The hole in the carb body could have been drilled not perfectly straight.  Im thinking this could be an option because when I went to look at the old jets I pulled out for indications of what might have cause the new one to snap I noticed one jet tip was a little crooked.  I bent it straight with my fingers.  The replacement jets are lower quality, more brittle, more prone to snapping.   The stock jet might have been strong/pliable enough to bend and not break when threaded into the body, but the brittle new jet might have snapped because of it.   I cleaned out an old jet pretty good to put in as soon as i get the broken tip out.
1975 CB550K1 Candy Jade Green
1977 CB550F2 Candy Presto Red
Countless vintage bicycles

Offline geoluv

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Re: Ooo I really f#&%ed up this time! 500/550 carb model differences?
« Reply #1 on: September 03, 2018, 09:47:57 AM »
Well I was able to drill put the snapped end.  Luckily there is a steel insert, it's not just threaded aluminum, that made it easy to not drill too far or drill out the sides into the threads too much.  I blasted it out with air and shined a light down in it, no brass colored debris at all.  It seems like I dodged a bullet there. 

Still interested in the exact differences in the carb internals.  Maybe one day I'll pay to x-ray one of each model  ;D
1975 CB550K1 Candy Jade Green
1977 CB550F2 Candy Presto Red
Countless vintage bicycles