Motorcycle Forum banner

1 - 3 of 3 Posts

·
ZAMM Fanatic
Joined
·
2,732 Posts
Discussion Starter #1 (Edited)
Seems to be a little confusion here about carburetor cleaning versus rebuilding, etc.

How about we start with a definition. Rebuilding a carburetor means taking it off the bike, complete disassembly, cleaning of all the critical passages (jets, vacuum ports, etc, TESTING those tiny passageways to make sure they're open (with compressed air, carb cleaner fluid, etc), replacement of rubber seals, gaskets, o-rings, needle seats, ADJUSTMENT of float levels, etc, re-assembly, and so on.

No, spraying the outside of a carburetor with carb cleaner to make it shiny won't "fix it."

No, "blowing it out" whatever that means....

YES, Gumout Carb Cleaner is INCREDIBLY toxic AND flammable, puhlEEZE

*keep a fiar stankwasher nearby...
*get as little on your hands as you have to
*use brake cleaner FIRST, and THEN go to carb cleaner
*Berrymans works good
*there are soakers, personally, I'm a non-soaker, I'm a compressed air guy

Yes, soaking those rock-hard carb boots in a mix of wintergreen oil and Xylol? Xylene overnight will soften them right back up, it's like MAGIC!

Yes, you need to TEST your floats in a cup of gasoline to make sure they actually float and aren't pinholed, soggy, whatever. No, DONT use water....I'll tell you why someday... a great story, actually...

No, you don't want to run steel wires through tiny aluminum passages to unclog them (a single strand of copper wire is better) UNLESS compressed air, carb cleaner from the straw, etc FAILS to open them.

And the copper wire breaks off and yo'ure FORCED to use a steel wire off a wire brush to extract it...

Yes, you NEED to understand which is your idle and which is your main or "high speed' jet and ensure both are open and capable of flowing fuel.

Yes if you understand HOW your carburetor works, and how it is misbehaving, you should be able to go immediately to the idle or high speed section and ONLY fix the one having a problem... or at least know where to look...

for instance, a lawnmore that won't idle, but "lopes." Do you know what's wrong? Idle port is clogged up. Throttle butterfly reveals the main jet, engine over-revs, governor shuts the butterfly, starts to die, governor opens it up again...

Yes, you need to understand that "jet" can refer to a tiny passageway OR a brass insert with a tiny hole in it that can be changed, or even a NEEDLE which moves up and down in a calibrated hole...or the hole assembly...

Yes, putting GREASE on a rubber diaphragm will cause it to degrade....but you NEED silicone goop of some sort to SEAL those diaphrams.

NO, you cannot rebuild your first carburetor ALONE, you need someone who's "done it before" to guide you through....

Yes, there are a LOT of parts that can be re-assembled upside down or in the wrong order which will make your "rebuilt carburetor" not carburete properly...

Yes, carburetors mechanically wear out, leak air around the butterfly shafts to where ...you're better off replacing them...

Yes, when the float sticks the bowl will overfill with gas which will either spill onto the ground OR into your intake manifold, flood the engine, wash the cylinders, all sorts of bad things...

Yes, replacing the float needle & seats is an integral part of rebuilding a carburetor...

Yes, there are petcocks AND fuelpumps which LOOK like petcocks aLONG with vacuum-operated petcocks, the goal of ALL is to prevent fuel from gravity feeding from the tank into a sticking carburetor and flooding the engine, etc.

Yes, rebuilding your fuel valve/pump/petcock is as important as rebuilding your carb...kits are available...

Yes, you need to be sure and buy FUEL line and not rubber VACUUM line

Yes, order a carburetor "kit" containing gaskets o-rings, new needles & seats, etc. BEFORE taking a carburetor apart cause you're SURE to damage/tear at least one gasket taking it apart...

Yes, once you've rebuilt a half dozen carbs it becomes simple, like child's play, cause they're all basically the same from a Holley 750 double-pumper on a 426 Hemi to a Carter AFB on a 389 GTO to a Brigss & Stratton carb to a BING to ...blah, blah, blah

Yes, if you have adjustment screws, NEVER turn them more than one turn in any direction attempting to adjust ANYTHING... unless you're a pro... and NEVER remove them from the carb ....unless you're a pro, AND have a kit to replace the little rubber o-ring that removing it just damaged/dropped on the floor...

YES do all your disassembly over a big ole white towell so you don't loose the tiny parts...

YES, the biggest problem you're gonna have is bowl screws refusing to come loose (steel screws in an aluminum body = white rust = frozen in) and a small air IMPACT wrench (butterfly or 3/8 gun style) with a hardened #2 phillips bit is the ANSWER, not stripping it out with a bigger screwdriver and more force...

Yes, letting old fuel congeal sitting in a carb bowl over the winter (or for year) is indeed how to gum up a carburetor...

Yes. stale fuel has a bad, stinky smell to it.

Non-alcohol fuel plus a little STABIL, runt he engine 5 minutes, and then DRAIN it in the spring and refill with FRESH fuel is the BEST way to avoid having to rebuild carbs...

And yes, if you don't know an idle jet from an accelerator pump, by all means ORDER the carb kit(s) you need and PAY an experienced motorcycle mechanic $100 per carb to rebuild them FOR YOU unless you WANT to spend 12-15 hours mastering carburetor repair...

YES, after investing several hours in a carb rebuild put a BRAND NEW FRESH fuel filter inline so all the rust/crap in your tank doesn't contaminate your brand new carb rebuild job....one fleck in your float needle & seat and yer done...

And above all..

START by reading (or re-reading) "Zen and the Art of Motorcycle Repair" because achieving the proper state of mind BEFORE beginning carburetor repairs is of utmost importance...

And that's all I have to say about that...
 

·
Premium Member
Joined
·
5,271 Posts
Good post.

Note that he didn't say anything about replacing the jets - most jets don't wear, and only need replacing if damaged, or clogged so solidly that they would be damaged just clearing the blockage. The exception is the needle jet/jet needle in a piston-operated carb, which bangs around with vibration, making the intermediate range mixture too rich.

Also, don't forget that, in most vehicle carbs, there are at least two jets per circuit - one to regulate the fuel, and one to regulate the air used to bubble the fuel in a mixing chamber above the fuel jet. If the air jets are blocked with, say, bits of an air filter that failed, the engine just won't run right. Small engine carbs often don't have this feature, but it's something to look for.
 

·
Registered
Joined
·
3,162 Posts
A few more

In a multi-carb bank.do not mix the parts from one carb to another. I watched a pro use a sonic cleaner on the small bits while he went at the passages one at a time. He did not even crack another carb open until the previous one was done. Doing it this way did not slow down the process in the least

And just to disagree with Mr Wade a bit. Learn to grind a proper JIS or Japanese Industrial Standard point on a hardened Phillips bit or just buy a JIS in the first place. Japanese motorcycles do NOT use Phillips bits,but by experimenting by grinding a spherical point on a Phillips, a perfectly acceptable substitute can be produced that will not cam out.

Sometimes it is easier to remove the rear fender and then the airbox before removing the carb bank. It beats the hell out of breaking something due to the fact that petrified carb boots can effectively reduce the clearance it takes for removal. It is also perfectly OK to spray WD-40 or penetrating oil at the joining point to get the carb out of the boots.

If the bike is a V-4 Honda Magna buy the very best rebuild kit. It comes with a videotape for good reason because they really are that difficult to remove from the bike. That is one carb I took to a shop and I am glad I did.

Why not test your completed carb for leaks on the bench? Place a test fuel tank 3 feet above the carb and test it that way before mounting it on the bike.

Just to clarify a previous point of Wade's-- if you squirt it in one hole ,it better come out another hole. Of course I am referring to carb cleaner using a straw to blow it through the carb passages.

Now I need to order the Zen book...
 
1 - 3 of 3 Posts
Top