installing carb on manifold

Norman

LORD VADER Moderator
Staff member
Jan 16, 2008
2,605
2
38
67
pampa texas
Easy way to make a leak free carb to intake manifold.
Light coat of silicone rtv on intake manifold but do not get the stuff on the very end of the manifold you don't want it in the carb.
Take your carb and push it on the intake manifold and just as you get it almost all the way on twist it a little and try to line up the casting seam on the carb with the casting seam on the manifold. While holding it in place tighten up the carb mounting bolt. You can ride it now or wait a day. To check for a good seal while engine is running spray the seal area with carb cleaner or starting fluid a change in rpm will mean you need to do it again which I have not had to do again as it worked every time so far.
Norman
 

jasonh

New Member
Jun 23, 2008
1,590
0
0
36
Longmont, CO
yep I did this like a month ago and it worked out great.

I found though that the stock bolt was kind of lame to tighten (trying to hold one end with a screwdriver). When I get around to it, I'm going to try to find a better one.
 

vwine

New Member
Jan 27, 2010
93
0
0
33
germany
Easy way to make a leak free carb to intake manifold.
Light coat of silicone rtv on intake manifold but do not get the stuff on the very end of the manifold you don't want it in the carb.
Take your carb and push it on the intake manifold and just as you get it almost all the way on twist it a little and try to line up the casting seam on the carb with the casting seam on the manifold. While holding it in place tighten up the carb mounting bolt. You can ride it now or wait a day. To check for a good seal while engine is running spray the seal area with carb cleaner or starting fluid a change in rpm will mean you need to do it again which I have not had to do again as it worked every time so far.
Norman
I just did this to my bike. My bike laggs alot of speed... my kit use to be really fast... (34 mph)
but I moved it over from my speed bike to a cruiser which is now hitting... I would guess 15 mph And would Idle Rediculously high... so i did the carb cleaner trick to find a leak.. and i spayed it near the manifold and my idle dropped some.. So I did the sealing trick and now my Idle is AWESOME.. I can hear the true sound of my new SBP expansion muffler. it sound great. But the speed problem persist.
it seems like its not getting enough fuel or something.. my sparkplug is burning tan and the clip is on the first notch on the needle. it has a drastic loss of speed and power then gains it back, then drops again.... dunno why. like i said its only toping out at about 15 mph or so...
 

kla63

New Member
Jul 15, 2009
111
0
0
NEW HAMSHIRE
I just did this to my bike. My bike laggs alot of speed... my kit use to be really fast... (34 mph)
but I moved it over from my speed bike to a cruiser which is now hitting... I would guess 15 mph And would Idle Rediculously high... so i did the carb cleaner trick to find a leak.. and i spayed it near the manifold and my idle dropped some.. So I did the sealing trick and now my Idle is AWESOME.. I can hear the true sound of my new SBP expansion muffler. it sound great. But the speed problem persist.
it seems like its not getting enough fuel or something.. my sparkplug is burning tan and the clip is on the first notch on the needle. it has a drastic loss of speed and power then gains it back, then drops again.... dunno why. like i said its only toping out at about 15 mph or so...
its getting too much gas try going alittle less on fuel cock i did that too mine no more bogging or cut outs !!!
 

vwine

New Member
Jan 27, 2010
93
0
0
33
germany
its getting too much gas try going alittle less on fuel cock i did that too mine no more bogging or cut outs !!!

KLA63,

Holy crap... That was all it was this whole time...
I just went out and opened it only a quarter of a turn instead of half and BAM!!
I dont think I have ever gone that fast on one of these things...
SO SO Fun and scary lol, you were exactly right, and it didnt bogg at all.. it felt like unlimited power.. the only thing keeping me from going faster was the vibration lol. Thanks alot man. VWxct2
 

kla63

New Member
Jul 15, 2009
111
0
0
NEW HAMSHIRE
KLA63,

Holy crap... That was all it was this whole time...
I just went out and opened it only a quarter of a turn instead of half and BAM!!
I dont think I have ever gone that fast on one of these things...
SO SO Fun and scary lol, you were exactly right, and it didnt bogg at all.. it felt like unlimited power.. the only thing keeping me from going faster was the vibration lol. Thanks alot man. VWxct2
Your Welcome !!!! like i said find where yours runs good and remember the postion i mark mine with a sharpie i make a black line on pet cock that i can see looking down!!!! and in the earlier post i gave you just cut up anold inner tube !!!rap around where your mounts are that should take care of some off the vibration!!!! you can also fill your handle bars with sand that will take some vib out of your hands as well..... glad i could help enjoy your ride!!!!! if you have any questions drop me a line !!! [email protected] or gas bicycle motors Home dance1
 

Attachments

Last edited by a moderator:

2door

Moderator
Staff member
Sep 15, 2008
16,326
123
63
Littleton, Colorado
Guys,
The fuel petcock is NOT a fuel metering device. If restricting the flow helps your performance then you have other problems. Start with the float/needle & seat inside the carburetor. Typically a float that is set too high will allow a flooding, or rich fuel mix (too much fuel to air). Check for trash in the orifice of the needle valve and make sure the needle seats fully and shuts off the fuel as it is designed to do. Raise the clip on the main jet needle. This controls how far the needle is pulled from the jet. The more it is raised, the richer the mixture. The petcock should be full open and the carburetor controls how much fuel is delivered to the engine.
Tom
 

kla63

New Member
Jul 15, 2009
111
0
0
NEW HAMSHIRE
Guys,
The fuel petcock is NOT a fuel metering device. If restricting the flow helps your performance then you have other problems. Start with the float/needle & seat inside the carburetor. Typically a float that is set too high will allow a flooding, or rich fuel mix (too much fuel to air). Check for trash in the orifice of the needle valve and make sure the needle seats fully and shuts off the fuel as it is designed to do. Raise the clip on the main jet needle. This controls how far the needle is pulled from the jet. The more it is raised, the richer the mixture. The petcock should be full open and the carburetor controls how much fuel is delivered to the engine.
Tom
been there done that it never worked !!!!!! this works and there is no problems!!!!! plug exellant awsome power !!!! that what works for me on some bikes so thats what do !!!!! none of these motors are the same !!!!! these are cheap carbs not much too them four notch needle !!!! i've been working on these alot so that s what i do !!!!!! it work for him too !!!! you don't need that much gas too run these little motors !!!!!!!!!.wee. i have one bike with over 15,000 on it still running like a rocket with pet cock at a certin postion!!!!!
 

AussieSteve

New Member
Nov 26, 2009
77
0
0
Nowra, NSW, Australia
its getting too much gas try going alittle less on fuel cock i did that too mine no more bogging or cut outs !!!
I've never heard anything like this before. 2door is right.
By using the fuel petcock as a metering device, you are risking serious engine damage.
If you turn it off a little too far, your engine will run extra-lean, causing overheating and potential seizure of the top end.

If the air/fuel mix is too rich, lower the slide needle a notch for low to 3/4 throttle, or, for WOT, try a smaller main jet.
Also check your float level - should be about 21mm for an NT carb and make sure the float needle valve is clear.

... Steve
 

AussieSteve

New Member
Nov 26, 2009
77
0
0
Nowra, NSW, Australia
Back on topic.
For those who don't mind a little extra work and will accept nothing less than perfect, this is the best way to seal the carb to the inlet, if you have an after-market alloy inlet.
I used a thin 'warding' file, on it's edge.
The groove should be as close as possible to the end of the tube. After cutting the groove in mine, I shaved the end of the tube slightly until the 'O' ring was about 1mm from the end.
It's a good idea to smooth the inside of the slots in the carb, too, so they don't damage the 'O' ring.

... Steve

 

Attachments

Nougat

Active Member
Nov 4, 2009
1,332
2
38
Montgomery, IL
Back off topic -

I also agree that the petcock shouldn't be used as a metering device long term. But I think it's a great way to help diagnose a float height problem without pulling the carb apart and guessing.
 
Sep 20, 2008
1,668
2
0
Clearwater, FL
web.tampabay.rr.com
Back on topic.
For those who don't mind a little extra work and will accept nothing less than perfect, this is the best way to seal the carb to the inlet, if you have an after-market alloy inlet.
I used a thin 'warding' file, on it's edge.
The groove should be as close as possible to the end of the tube. After cutting the groove in mine, I shaved the end of the tube slightly until the 'O' ring was about 1mm from the end.
It's a good idea to smooth the inside of the slots in the carb, too, so they don't damage the 'O' ring.

... Steve

A Very nice bit of hand forming work Steve! I can appreciate what it took to do that.

Jim