reasons a carb may be leaking gas?

[Iahawk]

thought I'd 'float' this one out to the board...my 96 Helix with Keihin CV carb (same type as on our Kymcos) leaks some gas during use. I've smelled gas for a while and only recently felt my hands all around it to feel it wet on the bottom.

I have new jets and am waiting on a gasket kit before i pull it to clean, etc.

Just thinking out loud...and in general...there are only a few reasons a carb would leak gas..right?

1. bad float needle/seat seal letting too much gas in
2. bad float..has a hole in it and is filled with gas, not 'floating' properly
3. leak at gas line inlet
4. leak at gas drain valve on bottom of bowl
5 ummm...any other 'usual suspects'?

I did lift up the slide inside the carb to check its function (make sure it slid smoothly) and I noticed it had some fuel on the main black, plastic body of the slide after I lifted it up and let it drop a few times..thought that was odd..

I'll know a whole lot more in another week or 2 when my parts arrive and I pull it apart..but just checking with the carb experts to see if I'm missing anything obvious. Have a great Friday night!

[CROSSBOLT]

I vote for sinking float or funky float valve. Inspect for cracks in carb body but that is a huge long shot. Fuel level too high if slide wet.

[Stig / Major Tom]

Think I'd be disconnecting the battery in that 25yr old wiring harness...until gas leak is sorted😊
Stig

[john grinsel]

As Helix veteran---four new ones, 175,000 miles, probably needle valve, age!---I would also buy spare intake manifold, they crack on regular basis.   I think latest Helix had carb brace to keep it from shaking around so much.

[Iahawk]

Stig - but I could just outrun any fire, right? just ride a little faster? 

John - you and Karl are both leaning toward a bad needle, I'm leaning that way, too. Yes, I do have a new rubber intake coming along with my other parts as mine appears to be original. Mine is also from before they started adding that brace.

I need to order a needle...I can get cheap chinese rebuild kits for the Helix, which i'd prefer to avoid...but the OEM needle is showing $23 on Revzilla...wow! While many parts are dirt cheap for the Helix some are getting pricey.

A new plastic float is $44! Honda discontinued this carb last year so buying the individual parts is the only way to get OEM..but it's pricey.

[Iahawk]

so i just called my local motorcycle store and ordered a new needle and float..$80.. I should have ordered this along with my other parts last week...if I'm cleaning and rebuilding a 26 yr old carb it only makes sense to replace the needle and float.

I found a good source for Keihin jets...called jetsrus.com.

I went ahead and ordered a backup pilot jet for my S200 and the slightly larger factory spec main jet (#118 vs the 116 that's in my scoot). I also ordered 2 pilots for my Helix (1 to put in, 1 for backup) as well as 2 recommended larger main jet sizes to try (#112 and 115 to go with my OEM #110)

So I'll have new jets,  gasket and o rings, carb bowl screws, needle and float. Combined with a good cleaning the carb should be running like new.

I'll let you know what I find when I pull the carb apart.

[Stig / Major Tom]

Stig - but I could just outrun any fire, right? just ride a little faster? 

Was thinking of it parked in your sparkling garage....2:00AM....dripping....looking for a 12V spark....

Stig

[Rusty Teeth]

Was watching my old school small engine repair guy with a small flexible tube in his mouth. Asked what are you doing, he has a test hose connected to the gas inlet and holding the carb up to eye level. Stated he was setting float height. He said he was putting a small amount of air to see when his new needle and seat was installed to test float height. His original problem was a leaking carb. Better way than I had been doing it! 

[Iahawk]

I should learn my lesson...ordered OEM needle and float from local Honda store on Saturday...got a call today that the parts were in ($80...gulp...)..but here in 4 days! (and probably more like 2 if order was placed on Monday morning).

Placed other, larger, OEM Honda parts order with Revzilla on Tuesday the 10th...checked status...still pending... nothing has shipped, etc...

my local shop is more expensive but they always seem to get parts in very quickly...and I get the added benefit of having an excuse to visit them in person to pick up my parts..and look at the new bikes!

[Stig / Major Tom]

My problem with our local multi-brand dealer is how long they delay placing an order for Honda parts.
Started driving half hour further to a Honda Power Seller dealer.(only sell Honda products ) They got parts for our motorcycle and scooter pronto! snd, yes, loved spending time browsing there😊
Stig

[randyo]

I also vote for sinking float, I can't count how many times I have been baffled by one, now I'm older and wiser

[Iahawk]

wanted to give an update on the carb. My parts all arrived by Monday but I was in Chicago Tues through Thursday this week.
Got back home and wanted to dive in. Removed the carb - not difficult, just a lot of hoses to remove (coolant, fuel, vacuum, etc.). Also removed the rubber intake manifold (to be replaced with new).

Pulled it all apart and cleaned it all up in preparation of installing new parts and gasket/ o rings.

There were no obvious reasons for the leaking gas but it appears the float was too high, allowing too much gas in. It's a plastic, non adjustable float. The new float seems to be in a slightly lower position when it's fully raised.

New float, float needle, bowl screws, pilot jet, main jet, bowl gasket, auto bystarter o ring, air/fuel needle o ring, a couple other o rings...and she's all put back together. the carb has been apart as one of the bowl screws was all buggered up.

i got the carb back on the scoot and all the little hoses reconnected. i still HATE the little clamps the manufacturers use to clamp the various hoses. i usually destroy them while removing. I'm glad i bought a huge set of replacement clamps.

The only thing left is to hook up the 2 throttle cables and get them adjusted correctly. My first try was not working..the throttle was difficult to open and it had little return force...will have to mess around with that today. My garage was 90 degrees last night (32.2 C) so it was not a pleasant work environment.

Hoping to get it back and running today so i can ride tomorrow. I upjetted my main from the factory 110 to the highly recommended 115. I'm curious to see if the mid to upper range changes.

some pics included for your viewing pleasure.

[Iahawk]

all right..got everything hooked back up..idled for a while to make sure nothing was leaking...and went for a 13 mile ride.

The gas leaking problem is solved. I don't smell any gas at all and the underside of the carb is dry..not wet with gas like it has been.

All signs point to the float being too high (and the needle tip looked a bit worn, too)

With the new, bigger main jet it does feel like the mid range is improved. From about 20-40, when I give it the beans it really seems to pull strong.  i do only have about 500 miles riding experience with the old jet..but the new one seems to be a keeper.

Here's hoping for a cool down (100+ degree heat index today..tomorrow more of the same).

[Stig / Major Tom]

I bet it's in the low 70's, or below......at sunrise😊
Stig

[Iahawk]

I bet it's in the low 70's, or below......at sunrise😊
Stig

yes....yes, it probably is...too bad i never see the sunrise!