combat carb

[ridetheride]

Hodaka gurus-

i need your advice.
My combat wombat has had a strange issue since i did the top end last year.
It starts and runs like a champ out of the gate and stays running great until i let it idle down or cut the engine.
then it boggs down to the point i have to hold the throttle wide open just to keep it sputtering.
if i let it sit for an hour or so it starts up and runs great again.
ive become 99% sure that my carburetor is flooding, causing gas to flow back to my air box and choking the whole system.
for the longest time i believed that letting it sit cooled the engine down- and that that had something to do with the problem; but the other day i noticed gas dripping from the air box and when i pulled the cover everything was saturated with fuel.
ive cleaned this carburetor more times than i can count. its sat for weeks in a soak bucket before. my father and i have always had issues with it so im to the point where i feel like a new carburetor is in order. all of the internals have been replaced and the float is set correctly. i think theres just something completely lodged in the internals that wont come out.
So my questions are-
1. am i even on base with this conclusion?
2. if so, are there any recommendations as to what i should buy?

thanks in advance for any and all advice
-ridetheride

[socalhodaka]

I had one that did something like that after a new top was put on. They put a reed piston on the piston port top end. It would start and ride alitlee but was puking out the back of carb.

[matt glascock]

If it takes holding the throttle open with the petcocks off and running the engine to get it to clear, that sounds like it is loading up. I assume "all new internals" includes replacement of needle and seat. Just for grins, have you unequivocally confirmed that the float bowl overflow pipe is correct and not obstructed and that your petcocks are not faulty in that they allow flow through when in the off position? I would assume that carb overflow would drain through the overflow pipe rather than back into the airbox if the pipe was operating properly.

[ridetheride]

matt- all replaceable parts have been changed out in the last five years- including all jets, needle, seat, float valve. jetting has been done per the hodaka manual. fuel is not coming from the overflow so that probably is obstructed. petcocks are also new and i have a new inline filer as well.
maybe i just need to do another thorough cleaning before i write it off as a total loss?

[dirty_rat]

If you are getting that much gas into the airbox, I would suspect that something is wrong with the float valve and seat. It might be brand new, but if it is scratched it will leak. It could also have some debris holding it open, causing it too leak. Or, it could be the floats are adjusted wrong, allowing the valve to stay open too much. The bottom line is, if fuel is leaking out of the carb then the float valve is not stopping the flow for one reason or another.

[matt glascock]

Ride, before you write it off completely, I agree with your approach to give it one last going over. I have fought this battle myself and what ended up turning the trick was using fine copper wire through all ports including the sneaky little passages cast into the carb body and the overflow vent pipe followed by the better part of a large can of Gumout carb cleaner and a lot of compressed air and (another) new float needle valve and seat to finally resolve the problem. I wonder if the problem is related to some type of warping, defect, or distortion of the carburetor or float that is disallowing proper actuation of the float valve? You might try removing the air boot and performing a careful inspection to see where the fuel is leaking from. There might be a VERY fine crack or defect that would take a strong magnifying lens to reveal. I feel your pain, brother. Good luck!

[Hydraulic Jack]

Verifying that the overflow vents are open should be a simple thing to do. If the fuel bowl is overfilling, the vent tubes are there to carry away the overflow. Verifying float and float needle function is also easy. The float needle must fully stop flow of fuel when the float rises. New floats may be defective but this is usually associated with brass floats. If you have a hollow body brass float, verify that it doesn't have fuel in it. Shake it. It should be completely empty. If it has fuel in it, it is leaking and has to be repaired. It isn't hard to fix, but can be frustrating if you haven't done one before.

Excessive fuel blowing back into the air filter is something else entirely. Frankly that doesn't sound like fuel overflow. There is always a bit of reversion, so it isn't possible to have a carb that doesn't blow a small amount of fuel back out the inlet, but excessive to the point of dripping isn't normal.

I would do some baseline data collection here. Verify compression with a screw in gauge, not one of the rubber tip ones you have to hold down on the spark plug hole. Low compression usually results in excess blowback, and excessive fuel accumulation in the crankcase.

Do a leak test to see if you have a pressure or vacuum leak anywhere, like around the head gasket. While you are at it check your timing. I don't think that is your problem, but check anyway. Check your exhaust pipe to be sure it isn't coked up and clogging the engine.

Make sure your starter circuit in the carb isn't leaking fuel, which can cause rapid build up of raw gas in the crank when idling down a hill. Old starter plungers sometimes have hardened rubber inserts which leaks fuel into the system causing a very rich idle. Such a leak would not be noticed much until the engine is hot, and can play heck with your jetting.

[Bullfrog]

Don't give up on that carb quite yet. If you are a member of the Hodaka Club, log in on the Hodaka Club website take a peek at the club newsletter, "The Resonator Revisited" Vol.1 No. 3. The Captain's Mast article describes all the nooks and crannies of the Mikuni carb . . . and how to clean it.

The description of symptoms certainly suggests two problems 1) float valve is not shutting off the fuel and 2) the overflow vent system is not working. See the article for some hints on how to address cleaning ALL the passages in the carb.
Ed

[ridetheride]

thank you all for the replies! i have plenty of homework to do now. i will report back as i go. next week ill verify compression and do a smoke test while the carb spends the time soaking in a fresh can of cleaner. i should probably add that when my father and i initialy got the bike running some ten years ago we made the upgrade to the electronic ignition from the strictly hodaka store.
just for fun im throwing in a picture from the day i brought it home; and another from after my partial restoration last year

[matt glascock]

Nice scoot, Ride! I love my CW! Its a riot in the woods and not a bad MXer to boot. Mine is ported for reed induction, but I'm getting a piston port CW together for classic class action.

[Bullfrog]

Um, what is a "smoke test"? For those of us with a long enough history to have brushed up against vintage Lucas electrical systems, the mention of the word "smoke" not in direct connection with the word "exhaust" causes nervousness. If you let the smoke out of the wires, woe is upon you.

Ed

[Hydraulic Jack]

Probably will use smoke to verify open carb passages.

[dcooke007]

You tube video on automotive smoke testing.

Danny Cooke

https://www.youtube.com/watch?v=07AzZeaIdfA

[matt glascock]

I've had a few friends who would like to get a hold of one of those doodads.

[Bullfrog]

Thanks for that link Danny. Pretty nifty item . . . at $1,200 it'll be a while before I get one.

Ed

[Bill2001]

Of course, we typically use the spray wand of carb or brake cleaner and see where and how strongly it sprays out. Wear safety glasses, it'll surprise you.

Of course, with carb troubleshooting, note the throttle opening that the problem happens at. This will narrow down which circuit is involved.