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How do I know if my old Honda's carbs need cleaning?

This is a discussion on How do I know if my old Honda's carbs need cleaning? within the Honda forums, part of the Manufacturers category; I just recently bought a 72 Honda CB350F and have gotten it to run. I don't have much motorcycle experience, ...


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Old 09-20-2007   #1
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Default How do I know if my old Honda's carbs need cleaning?

I just recently bought a 72 Honda CB350F and have gotten it to run. I don't have much motorcycle experience, and I'm not sure whether I need to clean the carbs on it. How can I tell if I need to? I have some spray carb cleaner, and I'm thinking I'll just spray it in there, but would like to know if I need to take it in.
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Old 09-23-2007   #2
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Default How do I know if my old Honda's carbs need cleaning?

If it's runnin' rough or sat for a long time, like a year or longer, then the carbs need cleaned. The only way to do it right is pull them off and remove the float bowls, float needle and seat, main and pilot jets and air screw passage. All that needs cleaned. For around $80 you can buy carb kits that come with a new slide needle, float needle and seat, main and pilot jets, air screw, and gaskets. You'll need as many sets as carbs your bike has. To me that's the easiest way, just replace the jets. You'll still need to clean the main jet extension and all passages with good carb cleaner. Then you'll need to adjust the carbs and possibly have them syncronized. Just spraying carb cleaner over the outside and down the throats won't cure clogged jets and passages. I never had luck with pour in the tank carb cleaner. If it runs good and smooth now it probably doesn't need a carb cleanin'. if you don't want to do it any competant bike shop can do it for you and adjust and synconize them for about $150, maybe more depending on how gummed up they are.
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Old 09-26-2007   #3
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Default How do I know if my old Honda's carbs need cleaning?

Thanks for your response. Is that $150 per carb, or for the whole assembly? I kind of want to do it myself but wonder if it's worth the trouble.
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Old 10-02-2007   #4
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Default How do I know if my old Honda's carbs need cleaning?

It's just a guess but I would think $150 for 4 carbs plus parts. You can do it yourself but I would just pop the float bowls off and not mess with the slides or take the carbs off the part that holds them all together. Pull them off and flip them upside down. Take the bowls off. Remove the floats by taking the little hinge pin out, the needle should come up with it. Remove the main jet with a wrench. Remove the pilot jet with a good screwdriver that fits it good. DO NOT FORCE THEM! They are only brass. Remove the air screws that are on the sides of the carb, there should be little springs behind them. Now you can hose carb cleaner through the carb and passages.

While the jets are out try to see through them. Hold them up to the light and see if ya can see through the holes. The pilot has a little wee hole in the middle. If its plugged up you can either run a small wire through it or replace it if ya buy the carb kits. The main has a larger hole but on the upper part of it there are a couple little holes, these have to be clean. You can run a wire through them too. I don't like to use drill bits in jets because runnin' a bit through them can enlarge them. Inspect the float needle by seeing if there is a ring around the tip, replace the needle and seat if there is. Once ya got them all clean put them all back together, set the float level and such.

To set the float level you can get into the ballpark by putting the floats back on with the needle in the seat and flip the carb upsidedown. The float arm should be parallel with the gasket surface on the float bowl. That will get ya close.

Replace the air screws then turn them the whole way in until they lightly bottom out. Turn them back out about a turn and a half to 2 turns. That will get ya close. Put the carbs back on and see how it runs. Do yourself a favor before you take them off and pick up a shop manual for your bike.

The cool thing with buyin' carb kits is you get all new jets, float needle and seat, air screws and gaskets. That way there you won't have to screw with tryin' to clean the old stuff up plus you get new float bowl gaskets. You can find carb kits on Ebay or by doing an internet search for CB400 carb kits. Theya re around $20 per carb.

It's up to you whether you think it's worth the trouble tackling it yourself. Pick up a manual anyways and read up on it before you decide to do it. If you think it's over your head and you don't have a friend who works on bikes around then it wouldn't be a good idea to do it. What do you think it's doing that makes you feel it needs done? It may be something else wrong.
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Old 10-07-2007   #5
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Default How do I know if my old Honda's carbs need cleaning?

There is a good video showing how to do this on YouTube. I can't post the link cuz i'm a newbie but you can just search "carburator rebuild" or "Carburator cleaning"
hope this helps.
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Old 10-08-2007   #6
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Default How do I know if my old Honda's carbs need cleaning?

There is a good video showing how to do this on YouTube. I can't post the link cuz i'm a newbie but you can just search "carburator rebuild" or "Carburator cleaning"
hope this helps.

I found the link:

http://www.youtube.com/watch?v=USqw8tYDUbw



1976 Honda CB550 (http://www.somemonkey.com)
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Old 10-12-2007   #7
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Default How do I know if my old Honda's carbs need cleaning?

Yeah, that video is pretty useful. I ended up doing it myself but with a little help from someone who knew what they were doing. Bike is running great now. Thanks.
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Old 10-19-2007   #8
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Default How do I know if my old Honda's carbs need cleaning?

Sweet. Have fun with it. Kinda cool to get somethin' going that's sat for awhile huh?
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Old 10-24-2007   #9
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Default How do I know if my old Honda's carbs need cleaning?

Yeah, definitely. It amazes me that with a little work this ancient hunk of metal becomes a working bike again. It was definitely worth it to buy a fixer-upper; the restoration experience has been very rewarding.
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Old 10-29-2007   #10
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Default How do I know if my old Honda's carbs need cleaning?

I've got quite a few bikes running after sitting for a long time, including one that sat outside for 6 or 7 years in the weather. Each time I got one running it was a rewarding thing. Even gettin' old snowblowers and chainsaws going after years of sittin' is pretty cool. I've got an old Homelite saw from the early 60's (sat in Dad's barn for 8 years or so and covered in about an inch of dust) and an old Toro Sno-pup (sat for close to 13 years) from the early 70's in running condition because of that same enjoyment. They both get used. Even old trimmers and mowers are kinda fun to get runnin' again.

You got a good bike in that CB350. It's somethin' you don't see everyday.
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