You don’t NEED an Ultrasonic cleaning machine, though it helps. NEVER rely on an tool or process – you must inspect the results. Remember and prepare now to keep parts for each carb separate from the others. A few zip-lock bags, masking tape and a felt pen can save you a lot of grief later.
Usually, you can reuse everything in carbs except O rings. Most motorcycle carbs have no gaskets but they certainly will have O rings. There are numerous online suppliers of O rings. Note that they have specific sizing for inner and outer diameter and cross section thickness. You can buy complete kits for many carbs but they are often overkill. It is also a good idea to compare original parts to new ones. Sometimes you’ll get new float needles or other parts that are not the same dimensions as the originals.
INITIAL CLEANING – If you don’t have an ultrasonic cleaner, don’t panic. Put the slides, jets & brass parts aside for now. Just soak the carb bodies overnight (12 hours or so) in a 50/50 mix of water and PineSol or similar cleaner at room temperature. Solvent’s don’t do a good job if the solution is near freezing in a cold workshop. Do not soak more than 24 hours or the carb bodies may darken. This will loosen up a lot of the congealed stuff that accumulates in carbs. Clean and inspect using a soft bristle brush like a toothbrush and clean cloth. Then clean the other parts that you set aside before, manually with the same solution and a soft bristle brush. For now, all you want to do is get them clean.
If you have an ultrasonic, give each carb body about 20 minutes, with the same solution at room temperature or a bit higher. Most ultrasonic cleaners a temperature control. On small units, it’s not powerful so I used to preheat the solution on a hotplate first.
With smaller ultrasonic units, you can only do one or two carbs at a time – remember to keep the parts of each carb separated. Once the bodies are done, give the small parts five or ten minutes.
ENSURE PASSAGES ARE CLEAR – you can use is a parts washer, or wash wand – this step is the best way to clear passages and actually check to ensure they are clear.
RINSE – no matter whether you used the soak method or an ultrasonic, when all parts have been washed, rinse them well with clean tap water and blow them dry with compressed air. HINT – turn the line pressure down to about 20 PSI. You do NOT need high pressure to dry parts but most important, low pressure will avoid blasting a loose part into oblivion.
CHECK AGAIN – This step offers you another opportunity to check all passages to ensure they are clear. Once you’ve blown the carb bodies dry and blow air through the passages, here’s how – just squirt a small amount of WD40 or similar very thin lubricant into a passage, then blow out that passage, looking very carefully for the places where the stuff comes out. Now do the same with the other carb bodies for just that one passage. If you find this test shows one carb not acting as the rest, check it, and get it cleared. Do likewise for all passages.
Don’t forget, for carbs with accelerator pumps, check those passages too, especially the nozzles in the carb throat. Sometimes I’ve had to bend a high E guitar string so it’s got a 180 degree bend at one end, feed the wire into the carb throat from the choke end, then position the end of the 180 onto the choke nozzle and clear the nozzle. With fat mechanics fingers, this can be a dexterity test, but when you can reliably shoot fluid out through that nozzle, you’ll be rewarded.
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