Fun with Carbs!

Well, I thought I'd put up another update of my bike's status. Currently we are sitting with a pile of parts, and I am in need of more parts from Chacal.

Like many others that I have read about here, I was rather intimidated about taking the carbs apart, but I knew it had to come eventually. I decided to start with one carb, and after getting it apart, it wasn't so scary! It turned out that each carb has a flaw, and none of them are alike, hopefully none of them will be too expensive or hard to fix. Below are a few pics of the problems I am having so maybe I can get a few opinions on what to do!


I started out with cylinder #1 and I just worked my way down the rack. Number 1 seemed pretty clean when I pulled the float bowl. The PO told me they were cleaned about a year ago, but it can't hurt to see if they were really cleaned.

I got everything out and apart, and the only thing wrong with #1 is a float needle with a loose tip. I doubt this can be glued back, so on the "to order" list it goes! After looking at the different parts Chacal offers, can any one recommend getting a whole set of needles, or just buying the one I need? The mesh filters all seem ok, but have definitely seen better days. I know it means more money, but I would also like to do things right instead of cutting corners.




Number 2 was also pretty clean, so perhaps they did clean them out! However upon further examination, I found that my secondary jet is badly stripped. It looks clean enough, so I might hold off on replacing this one.




Also found on #2 was a slight problem with the diaphragm. The plastic ring on the top is split. Does anyone know if this requires immediate replacement?




On to #3, the first thing I encountered was a stripped bowl drain screw, guess I need to add an easy out kit to my list! Number 3 seemed to have a bit more buildup than the rest, so I don't know if this is just because they were unable to drain it, or if it was not cleaned.

I don't have a pic of the stripped drain screw, should have snapped one!


And finally, carb 4. The bottom end was as clean as 1 and 2, but I encountered a problem under the hat. As can be seen in the following photo, the diaphragm did not seat completely in the ring before it was fully assembled. If you look closely in the photo, you can see where it left a slight ring inside the top of the hat. The diaphragm seems like it is fine and should be reusable. I wonder if this, combined with the bad ignition coil could have caused the running problems I had with the #4 cylinder.




So now I have a nice row of carb parts awaiting further cleaning, some more parts, and reassembly.



At least they will have a nice home on the new carb manifolds the GF got me for Christmas! I just hope all this work pays off in a few months, having to rebuild your first bike before you can ride is hard on these warm days, especially when your brother has a new bike and can ride anytime it warms up!

 

I'm not sure,but I think that the diaphragm retainier ring is suppossed to have that split in it. I would recommend replacing ALL of the float needles,as they are likely the originals that are now over a quarter century old. And it makes sense to replace them as long you have the carbs apart.

 

That is a nice organized pile of dissected carbs you've got there! I bet you did well in biology class when you were younger.........


a) Remember, "externally" clean has almost nothing to do with "internally" (inside the tiny fuel passageways) clean.......

b) I would buy all four needles. Actually, the needles and seats, but it depends on your budget.

c) that stripped pilot fuel jet can probably live to fight another day, but they're so cheap, I'd replace it. And besides, if you don't remove it, you really can't access the tiny passage behind it and make sure that it is zestfully clean and flowing freely.

d) split diaphram ring.......common problem, and yours has not only a "split" but a complete fracture and has really, REALLY expanded, reducing the pressure on the diaphram (see "e" below for further insights). Not a great thing, but as long as the rubber diaphram is not split or puckered in that area, then it should be okay. If not, replace the entire piston/diaphram unit.

e) a vacuum diaphram that does not seat completely (or that has tiny pin-holes in it) will not hold the vacuum signal as strongly as the others will, and thus that vacuum piston and the main fuel needle that it controls will REACT DIFFERENTLY (more slowly) to the vacuum signal in that carb as compared to the others. This can be a big problem! Make sure that the vacuum diaphram is not truly damaged, and make sure that it can re-seat itself into that little channel properly. Using some silicone grease to "glue" the lip into that channel while re-assembling the sping and the hat is a good way to make sure it stays in place during re-assembly.

 

I have a question about this: I've been using this method, it works fine. But then I got to thinking (dangerous, I know) about the fact that gasoline and silicone are not the best of buddies. Would it be better to use a petroleum based grease (ie; vasoline) in this (and possibly other carburetor) applications?

 

Thanks for the advice guys, I guess I will start replacing the older parts, there is a growing list of parts I will eventually need!

Chacal, the diaphragm seems ok, but I think I will replace it eventually, unless you have some good used ones :wink:

I guess I need to get a few more cans of carb cleaner, I used one can doing one and a half carbs, and I know that #2 still has a clogged enrichment port in the fuel bowl.

On another note, am I correct in understanding that the pilot screws need to be around 3 turns out to start with? I screwed the old ones in before removing, and #1 was 1 turn out, but there was some white buildup/corrosion in the hole, so it could be wrong. I didn't want to screw it in any further and risk damaging anything. The other 3 carbs were all pretty close to 3 turns out, probably 2 3/4 to 3 1/4.

Thanks for the help guys!

 

pederacer I'm in the process to rebuild the carbs too. I took everything apart and put the carbs bodies in a pot with a Simple Green solution, I will said that was 10:1 ratio (water-SG) and kept the the water hot (not boiling). After 20 minutes I was impressed how well they look.
Rinsed with hot water, blowed all passages with compressed air and finally sprayed carb cleaner over and into it. Blowed again and done., pretty carbs ready for assembly. Just an idea to save a few bucs.

 

Yes, 2-/12 to 3 turns out on the fine-threaded mixture screws is a good startingpoint.....but those settings will eventually have to be adjusted as you do a real engine synch and carb adjustments.

Also, please be aware that quite a few----perhaps 60-70%----of "first time" carb cleaning/rebuilding efforts end in frustration and failure, and it's mainly due to NOT doing a thorough enough job of internally cleaning the tiny, miniscule fuel passages within the carb body (and the fuel bowl starter circuit, which you are aware of and thus will remedy). The air passages within the carb body are (relatively) huge, and do not normally accumulate fuel sludge and varnish, and don't need too much attention; the fuel passages, particularly the pilot passages, are tiny beyond belief and even a "speck" of old varnish, grit, crud, etc. will cause problems.......in essence, that restriction becomes an "unintended" fuel metering jet, with very real consequences. This is why you want to get really, really anal in cleaning them. Many times, simply "dipping" or "boiling" the carbs out is NOT sufficient; you have to do all that AND mechanically probe (scour) these passages with tiny, fine wires to loosen such material, and THEN blast it away under pressure with carb cleaner, compressed air, etc.

And you might have to repeat that process a few times to truly get them clean.

And the fuel supply passages....which are rather large......also get filled up with accumulated junk and debris, and also tend to require mechanical intervention to loosen and remove such build-up.

The absolutely worst outcome that can occur is that your "cleaning" efforts results in loosening, but not fully removing, such stuff within the internal passages; and once you get fuel and vacuum pressures working through the carbs again, all that gunk THEN starts moving again, and re-clogging things up (fuel circuits, float needle valves, etc.).

Don't be fooled by having the VISIBLE areas of the carbs clean; although that's important, too, it's the invisible areas that matter most, and they had better be spotless, too.......or you'll probably soon be undertaking Carb Rodeo #2, after many frustrating hours spent trying to "tune" a set of carbs that no amount of tuning will ever set right!


P.S.: if it helps, image that type of "white corrosion" not just in that huge idle mixture screw port, but everywhere within the carb's internal passages, and think about what effect such particles will have within fuel passages that can almost be measured on a micron scale!!!

 

You are right Chacal. This is the third time that I pulled the carbs apart and I still find wrong things because I didn't pay attention in previous attempts.
Clunk test, enrichment circuit, throttle gaskets, etc. everything need to be perfect. Taking shortcuts has been my worse mistake.
Finally I learn my lesson and I will not put these babies together until I'm 100% sure that everything is right.
Patience and attention to details are the keywords for a successful carb rebuild.

 

OK, So I guess what you guys are getting at is, clean everything as good as I can, and then clean some more :wink:

Luckily all the big stuff seems clean enough, the carbs pass the clunk test, and all but 1 enrichment circuits spray the recommended 5+ feet. So I guess I need to pull all those jets out, and get to cleaning those as best as I can.

Also I guess i will also pull the butterfly valves and replace those gaskets. I was hoping to cut a few corners, but if I am going through all this effort, I guess I should do things right.

Also, does anyone have any suggestions on the silicone grease? I want to make sure I do things right and not cause further problems. I also wonder about the simple green suggestion as well, I have access to some aircraft grade simple green through work. I read the bottle and saw that it is safe on aluminum, but I didn't check the price. I'm sure it probably won't be cheap.

Thanks for the advice and suggestions guys!