Question about sealing carbuetor to the intake

[Nevada]

We've finally got some good weather coming this weekend, so I'm thinking I'll get out of the comfy warm house and into the garage to get my current and 1st build finally running.

The engine is a silver eagle 66 with the standard NT carburetor. Kit doesn't have anything in it that looks like it designed to seal the carburetor and I was wondering what's the preferred method for making sure I've got a good seal between carb and intake manifold.

Thanks in advance for suggestions!

 

[MotorBicycleRacing]

The engine is a silver eagle 66 with the standard NT carburetor. Kit doesn't have anything in it that looks like it designed to seal the carburetor and I was wondering what's the preferred method for making sure I've got a good seal between carb and intake manifold!

O ring.
I used to have to buy O rings to put in the Carb throats to seal them.
Now the carbs I get in the kits come with O rings already installed in them.

Sent from my SCH-R720 using Forum Runner

 

[Nevada]

Gotcha! Thanks! So it just sits in the throat of the carb, all the way in and the intake manifold jams up against it? I don't recall that there's any sort of recessed groove in the manifold that an O ring would sit down into.

 

[MotorBicycleRacing]

Gotcha! Thanks! So it just sits in the throat of the carb, all the way in and the intake manifold jams up against it? I don't recall that there's any sort of recessed groove in the manifold that an O ring would sit down into.

You got it.
The end of the intake seals against the O ring in the Carb throat.
Home Depot sells plastic boxes of 10 O rings.

 

[crassius]

O rings are needed on CNS carbs, but NTs work OK as long as you're sure you get it all the way onto the intake - I usually measure inside the carb, then scratch a line on the intake to be sure it's on all the way

 

[mapbike]

I just smear a thin to medium amount of Permatex Gray or Black silicone around intake tube careful to keep it just to the end of tube with any getting inside the tube, I slide the carb onto the intake tube slowly with fuel bowl pointing straight out toward clutch lever arm and then when carb bottoms out on tube I twist carb into correct position and tighten clamp to secure carb tightly on intake, been doing mine this way from day one and never had a carb to intake air leak on any of my engines, the silicone will fill all gap and slots in carb neck and seal it perfectly without needing any O ring, I tried using the O ring method once and didn't like that it keeps intake tube from securing solidly agai nst carb so I went back to the silicone method, either way is fine of course, but I like the silicone seal much better than the O ring becuase the silicone acts as a seal and also a medium holding adhesive between carb and intake which I think is a good thing considering the vibes these engines produce, and if your careful the carb can be remover and reinstalled multiple times after the silicone cures without needing to add more silicone, just pull carb straight off without twisting and it will slide off and back on and reseal just fine.

Not claiming this way is the gospel here fellas so dont throw any stones, just my way and my opinion on why I like it best.

Peace, map

 

[2door]

I also use a sealer. I swab the throat of the carburetor making sure I fill the gaps where the carb is slotted. A silicone based sealer is okay as long as it is gasoline compatible. Most aren't. Read the label.

'O' rings work but you must press the carb tightly against it to get an air (vacuum) tight seal when you're tightening the clamp. Simply sliding the carb on and not tight against the 'O' ring will not assure you of a good seal.

One thing you need to look for whichever method you choose is that the slots in the neck of the carburetor haven't been cut too deep and expose a small area to the atmosphere. I've found this on two carbs. Sealers will take care of this. 'O' rings won't.

While you're at it pay close attention to the intake manifold gasket and the gasket surfaces. Almost without exception the chromed steel intake flange will have a warp from the welding process. If that surface isn't lapped flat the gasket will leak no matter how tight you make it. The aluminum intakes are usually better but they have been known to crack/break. I never use the cast aluminum intake manifolds.

Tom

 

[MotorBicycleRacing]

O rings are needed on CNS carbs, but NTs work OK as long as you're sure you get it all the way onto the intake - I usually measure inside the carb, then scratch a line on the intake to be sure it's on all the way

The OP has an NT carb and it is highly recommended to seal the intake either with an O ring
or some kind of sealant.

Working "OK" without any sealing means air leaks in a lot of bikes and that ain't OK with me.
I am talking about joint experience with over 1000 carbs sealed with O rings and it just plain works to seal against air leaks.

the Home depot O-ring is the #11 in the Danco 10 pack
3/4" OD x 9/16" ID x 3/32"

The latest Speed carbs I get work great because the Z clip on the nut
which tightens the carb on the intake stops it from turning so you can
push the carb against the 0-ring and tighten the nut without needing
3 hands.

The 0-ring is below the 4 slots in the throat and does not block the intake.

 

[Nevada]

the Home depot O-ring is the #11 in the Danco 10 pack
3/4" OD x 9/16" ID x 3/32"

Perfect! Thanks again! No guessing now, which size to get.

 

[mapbike]

Ill stick with my sealer method much lss chance of an air leak, the O ring method can also work no doubt but using a sealer like I do and other such as 2door mentioned will insure that all the slots in carb neck along with any possible imperfection are well sealed and it also helps the carb to be more secure on the intake tube, I tried the O ring method one time but could easily see how there is much more chance for an air leak if the carb isnt pressed tightly against the O ring when clwmp on carb is snugged down.

Just like many other things I say to each there own on this but the simple fact is that in this application using a sealer instead of an O ring is a superior methos because of how the NT carb neck is made with such a shallow area for the intake tube to seal into it.

Best wished

Map