Carb Sanity Check - Page 2 - Honda Rebel Forum
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post #11 of 16 Old 04-21-2019, 12:00 PM Thread Starter
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Originally Posted by flitecontrol View Post
You should be able to find a shop that will clean the carb ultrasonically for a lot less if you remove and install the carb. I think Jacks Rebel Warehouse cleans carbs for around $45
WOW, $45? I will take that option over the local shop easily.
I've had this carb off & apart so many times now, sometimes I wonder if I have mucked something.

Yes, I have what some would say is a problem...
2007 Honda Rebel 250 (almost running)
1993 Suzuki VX800 (runs well, restoration nearly done)
2004 Harley XL1200C (needs some serious help)
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post #12 of 16 Old 04-21-2019, 12:43 PM
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Not sure if that's what he still charges, but it shouldn't be much more. Remember, you have to add in the cost of shipping both ways too.

Keepin' all the left over parts. Gonna use 'em to build another bike!

'01 & '09 Rebel 250, '06 Ninja 250, '89 VN 750
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post #13 of 16 Old 04-21-2019, 03:10 PM
 
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Harbor Freight has an ultrasonic cleaner big enough for a motorcycle carb. I saw it used on a youtube video, and it worked. But I have cleaned hundreds of carbs by hand, and only had problems with a couple of them, and that was because I reassembled them wrong. A carb is a very simple device, but it is also a very precise thing. It has to be completely clean and everything has to fit together properly. The rubber and plastic parts do wear out, especially the float needle jet and seat. The float bowl O ring can also go bad. By far the most expensive rubber/plastic part in a carb is the vacuum diaphragm, hopefully that is still good, but I have seen them rotted and torn. To complicate things, the Rebel carb has an enrichener circuit instead of a choke. It's not really complicated, but many people don't understand them. The most common failure on those is the flimsy plastic fitting where the enrichener cable attaches to the carb body. It is easy to see how someone who is not extremely familiar with carbs could make a mistake. For example, did you remove the air/fuel pilot screw, washer, O ring, and spring and clean the passage? Just above that screw is a tiny pinhole in the carb throat which must be clean. If it is blocked, the engine will not idle. It is such a tiny thing it would be easy to overlook if you didn't know it is there. For decades I have been using a small E string for a guitar for cleaning out carb passages without any problems. It is smaller than any carb passage, and stiff, so it will go through the passage without bending. Even an ultrasonic cleaner can fail to completely clean out some of these tiny passages, especially if they have corrosion in them from ethanol gas. A wire will actually physically remove any blockage.

Ethanol gas is another issue. When we had real gas, it would gum up carburetors when they sat with gas in them for too long, but carb cleaner would dissolve that. Ethanol, and the water it attracts, is very corrosive, and carb cleaner will not remove corrosion. You have to do that physically. I have seen carbs so badly corroded they had to be scrapped. The main thing about working on carbs is to not let yourself get frustrated. Use the experience to learn how they work. If carbs never got dirty, they would never fail. Most people who don't like carbs have experienced dirty ones, and think that expensive electronic fuel injection is the answer. But not only do those expensive electronic parts fail, but the injectors get plugged up, just like a carb. Here is a link to the Harbor Freight ultrasonic cleaner video:

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post #14 of 16 Old 04-21-2019, 04:55 PM
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Originally Posted by JerryH View Post
For decades I have been using a small E string for a guitar for cleaning out carb passages without any problems. It is smaller than any carb passage, and stiff, so it will go through the passage without bending. Even an ultrasonic cleaner can fail to completely clean out some of these tiny passages, especially if they have corrosion in them from ethanol gas. A wire will actually physically remove any blockage.
What about scratching the soft carb metal where the passages bend and you can't see what the guitar string is doing? How does the wire get the entire blockage out if it's smaller in diameter than the passage?

In cleaning Rebel carbs, of which I've done many, the only one that didn't get completely clean was one that I polished the brass parts after it came out of the cleaner. Thought some water and compressed air had removed all the polish residue, but it hadn't. More than likely, it was clean before I gunked it up with polish.

Keepin' all the left over parts. Gonna use 'em to build another bike!

'01 & '09 Rebel 250, '06 Ninja 250, '89 VN 750
Putting your bike year and model in your signature helps others help you!
Here's how: https://www.hondarebelforum.com/f19/...re-121087.html
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post #15 of 16 Old 04-22-2019, 03:37 AM
 
Join Date: Dec 2018
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Quote:
Originally Posted by RuralRider View Post
I've had this carb off & apart so many times now, sometimes I wonder if I have mucked something.
This reminds me of another carb cleaning thread where the needle jet seat was installed upside down or was missing entirely. Double check this.

There aren't a ton of important details with the single carb but there are about 5 super important details. The jet seat being #1 since it can easily be left off once it falls out or installed upside down. The curved side of the seat faces the needle, I believe.

Seating the slide diaphragm pretty much perfectly in the carb top groove is #2. If it's not perfectly pliable then Flite had a good suggestion about getting it flexible again with alcohol. " soaking it for a few hours in a solution of alcohol and oil of wintergreen will soften and expand it." Good tip Flite, the carb ninja! Inspect that diaphragm closely and use care when seating it, but don't use red gasket sealant that dissolves in gasoline!

#3 The tiny accelerator pump passages in the cap of the accl. pump. There are 4 quarter moon orifices and if they aren't clean already it's easy to think they are fine because they can be completely plugged so they almost look normal. #3.5 is the accelerator pump jet that is easy to overlook because it is in the throat of the carb and the jet actually faces the venturi so you can't even see it unless you open the valve and look through the carb from the other side with the slide out. To clean that opening takes some finesse with cleaning solvent and compressed air or even finishing sand paper. If anything is wrong with the accelerator pump the bike usually dies immediately upon throttle. Maybe it idles, but it dies with any throttle.

#4 the o-ring and washer around the mixture screw could throw off the performance if left off.

#5 The idle circuit orifices....which are impossible to see so one can only prove them with compressed air or a squirt of carb cleaner that visibly comes out the other end of the circuit.


But the CDI ignition system can easily cause weak spark or intermittent spark that produces problems that initially look exactly like a fuel delivery problem and lead you down a rabbit hole trying to fix a perfectly fine carb. Unless you have spare ignition parts to experiment with all you can do is check the connections at the CDI and spark plugs and battery which only takes a few seconds.

1985 CMX 250

You look much less stupid locking your handlebar lock every night no matter where you park it than looking at the empty space where your bike was last parked.
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post #16 of 16 Old 04-22-2019, 07:27 AM
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Oggy makes a good point. If you haven't already done it, before removing the carb, check the plugs and make sure there is a nice, blue spark when grounding them to the frame.

A little Vaseline helps hold the diaphragm lip in the groove when assembling. If the lip has to be stretched to fit, it has shrunk and probably won't seal.

As one who has put the needle seat in backwards, I can say the engine will still run with it that way, but it will bog down with the slightest throttle. The concave end faces the needle and goes into the jet holder first.

Keepin' all the left over parts. Gonna use 'em to build another bike!

'01 & '09 Rebel 250, '06 Ninja 250, '89 VN 750
Putting your bike year and model in your signature helps others help you!
Here's how: https://www.hondarebelforum.com/f19/...re-121087.html
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