1973 carb 3 overflowing and high idle speeds

[AAchops]

Just got myself a cb chopper and it was obvious the carbs had problems, thing wouldn't even idle. I took apart the carbs and all the floats were off and carb 3 had a stuck float valve. Finally, I got the float valve unstuck and adjusted all the float levels to the level it says that should be in the service manual, cleaned the slow jets and mounted the carbs and the thing ran pretty well. However, now carb three runs gas from the overflow drain if I kick too many times while its cold. I think somehow the bowl is filling up from being flooded but then just staying full, but that is just a guess. I would say about half a cup of gas comes out after shutting off the petcock and if i don't shut it off it will keep dripping.

Also, although I don't have a tachometer on this honda chopper I would say that the engine is idling around 2k most of the time, but if I mess with the idle screw I can get it to idle perfectly at what my ear would say is right around the 800 to 900 range. But...if I lay on the throttle or a strong wind blows it'll pick up and rev pretty hard.

I haven't had them tuned, but I set the air screws to service manual 1 and 1/8 turns out from seated and have been trying +- 1/8 turns on them to see if anything will change and I honestly haven't noticed a difference.

Looking for advice on directions to take. I live in colorado at like 5k feet and had a friend suggest a different jet size and I am thinking about just doing a full rebuild but I am new to hondas. I am just going off other forum posts and the service manual at this point.

Thanks

Thinking I should probably rebuild the carbs and get fresh rebuild kits.

[TOOLS1]

I am assuming that since you say "73" in the topic, you have round top carbs. Your overflowing problem could be that your needle valve is not sealing, or you have a crack in the little brass overflow tube in the float bowel. Your idle problem sounds like a vacuum leak, check the rubber boots between the carbs and head for vacuum leaks. Spray starting fluid around the boots with the engine running, if the engine speeds changes, you have found the leak.
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[Re-run]

Did you replace any of the float needles? How about clean the seats? There are only 3 reasons for leaking bowls.
1: most common is the float needle not seating. Either the needle is bad or the seat is dirty.
2: second most common is the float is still not sitting right. Either still not set right, or the float has a crack in it and so does not float properly.
3: The brass tube is cracked. This is very hard to see so the best way to check is to remove the bowl and fill it with gas and see if it leaks.
4: I guess there could be 4, the drain screw is not sealing.

A shop tach is not expensive, $30 clams or so. Hook it up and see what it reads. You will need this anyways for proper tuning of your idle mix. If you still have points, you can get a dwell meter with tach function. This gives the absolute best points setting and an accurate tach.

You likely have an air leak. Either the boots are dry, cracked or otherwise not sealing, OR the other thing many overlook, the straps have stretched out and are not tightening properly.

Being higher altitude, you may need smaller jets. Before you spend the cash on those, try to get it tuned first. You may just save yourself money and time. Without knowing where it was bought, it may already have the right jets for your altitude.

[AAchops]

No I didn't replace the float needles, but I did clean them out. Specifically on that carb. The float needle was stuck so I soaked it in carb cleaner and then after a little bit of tinkering it got nicely unstuck and moved smoothly when the float did.

Thanks for all the replies. I am wondering, since the boots seam quite old and I can only find a boot set for that model engine/carb for around $100...is there any way to use some sort of standard tubing like radiator hosing and just tighten down on them with some hefty clamps?

Also, where would I go about looking for the right jet length? is anyone in Denver?


EDIT: I wanted to mention that carb 2 had the stuck needle, I cleaned it. Carb three is the one that is overflowing and when I took that one apart it had a significant amount of gas inside it, even after turning the carbs upside down to drain them. All the parts seemed to be in working order, however I did not check the floats to make sure they weren't cracked or malfunctioning. I just set them to the service manual suggested float height.

[Re-run]

Jets don't have a length really. It is an orifice diameter. So you could 5 next to each other and they would be about the same size. The inside hole is what determines the size.

Depending on how bad your boots are, they can be restored somewhat by boiling them in a type of oil and water mix. Wintergreen or something like that. You can't really use radiator hose as the manifolds are angled and that would be hard to do in the short amount of space available.

New boots are the best way to go as even the restoring oil trick will be relatively short lived.

Now, the genuine parts will run about 2 each, david silver spares has aftermarket ones for 45. No idea how they work, but they have em.

[TOOLS1]

Here you go for boots http://www.ebay.com/itm/161540198279?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT For jets, you can still get them from Honda, or go to vintagecb750.com
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[AAchops]

Thanks guys, gonna go for a quick rebuild and new boots on these bad boys and see what happens. How important is tuning the carbs with gauge to sync them? is it mostly performance or what?

[TOOLS1]

Very important!!!!!!! An engine with out of sync carbs will sound like it is tearing itself apart, and have a hard time idling.
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[shinyribs]

True. ^^^^

I recently synched a set of carbs. They were close, but not perfect. Sounded really clunky and had vibration at idle. Synch is paramount.