Not reaching top speed

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Davezilla

New Member
Mar 15, 2014
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For cleaning the carbs... I use brake cleaner for Everything at my shop and it works great for carbs too. Just spray a quick shot and let it soak for about 5 seconds then give it a good blast and it should look like new... For carbs that are really gummed up bad or loaded with varnish that's already dried and hardened, Berryman B9 Chem Dip will get those clean as new again after soaking for about an hour or more... Some of the Really bad ones I'll throw in the Chem dip at closing time and let them soak overninght.
Also get a set of welding tip cleaners which is about the size of a key fob and costs about $5 or less, these work great for clearing badly clogged jets and tiny passages, on some of the worst carbs, like one that's sat for years with fuel in them that's long evaporated and clogged up all the jets and passageways, these will work wonders.

Gotta agree on the speed carb swap... still running way too rich for your setup... So now you got another carb? this is good because the jets for both the NT and speed are compatible so you can take the jet out of the NT and solder it shut so you can get the feel for it when your bits come in, this will also allow you to always have a jet in your carb while soldering and drilling so no downtime... or at least a whole lot less downtime.
 

thirdorangutan

New Member
Mar 19, 2015
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Austin, Texas
So I just rode my bike with the new carb again. I parked it in my garage but smelt gas. Gas was pouring out of the plastic air intake. I took off the air intake to see that the small hole under the choke was pouring gas. Why is this??? That hole is the overflow hole right? If it is that means my float bowl is filling up too much, leading me to believe that my float is messed up. What do y'all think
 

Davezilla

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Mar 15, 2014
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Sounds like your needle and seat valve is stuck open... this happens if some debris goes down into the carb from the fuel line and it'll prevent the needle from seating and closing the valve when the float goes to the top.
Shut off the fuel from the tank's petcock valve, remove the carb, and check that there's nothing obstructing the needle and seat valve and it should stop dripping.
 

Davezilla

New Member
Mar 15, 2014
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Also, don't use the petcock valve on the carb it's self, just leave it open all the time and shut off your fuel from the tank valve. The reason is because the petcock valve on the carb has a small rubber disk inside with 4 holes in it and turning the valve open or shut can cause small chunks of rubber to shed off this disk and either clog up or hold open the needle and seat valve, or these small particles can also block your main jet while riding and your engine will sputter and die, then when you go to re start it it'll start just fine but sputter and die a few seconds later.
Remove the carb and the float bowl, then check in the bowl for little tiny pieces of black rubber, if you got this in there, clean it out and don't use that valve to shut off or open up the fuel, just use the one off the tank.
There are a few threads about gutting out the built in petcock valve on speed carbs because they either leak, restrict fuel flow, or like in my experience, shed off rubber particles that were constantly blocking off my main jet or holding my needle and seat valve open.
 

Davezilla

New Member
Mar 15, 2014
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San Antonio Texas
Whats the seat valve? Will I have to take off the float bowl to access it?
Yes, take off the float bowl, then slide the pin that holds the float lever on and the needle valve will drop out, be careful of tiny parts as some of these needles have a tiny spring and piece of metal inside... best to disassemble over a paper plate to catch small parts if they fall out to prevent loss
 

2door

Moderator
Staff member
Sep 15, 2008
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Littleton, Colorado
The needle valve is pushed closed by the float as it rises in the bowl. Any small particle can get lodged in the seat where the needle fits and will hold it open so fuel will continue to flow into the bowl. Then you have fuel leaking out of the carburetor.

A good in-line fuel filter will keep trash from the fuel tank from getting into the carb but as was explained, the 'Speed' carb has an inherent problem shedding rubber pieces down stream of any filter. So much for "Speed" :)

Tom
 

mapbike

Well-Known Member
Mar 14, 2010
5,502
109
63
Central Area of Texas
I use acetone to clean parts before soldering or painting.
That stuff gets all the oil residue off pronto.
It's cheap in the small cans. Brake cleaner works, not sure about carb cleaner, it may have an oily component.
carb cleaner has no oil, I dont recommend things out of my backside, I tell others what I use personally because I know for a fact it works.

Yes acetone will work also, Brake cleaner works good as well, using straight gasoline works fine as well.

Personally I like cleaning with carb cleaner above all others since I can get a can for about $2 and with only two short sprays on the jet its ready to solder.
 
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Davezilla

New Member
Mar 15, 2014
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San Antonio Texas
Yup... the Speed carbs have that inherent problem and it shut me down a few times right after my first build until I saw what was causing it... and there's no way to put a filter between that valve and the fuel inlet so I took mine apart and gutted it, basically, I took the valve off the carb and drilled right thru it so there's no on/off function there anymore, then I cut the small switch lever down flush with the body and covered the whole part with JB weld... One could just as easily buy an 8mm banjo bolt and fitting to run the line directly into the carb and be done with it but my redneck engineering kicked in and it held just fine until I could install a new NT carb.

There are a few threads in here somewhere showing how others have gutted their fuel valves on the speed carbs too, but I think the best solution really is to just swap out the fuel valve for an 8mm banjo fitting... no more rubber particals to clog up your main jet or leave your needle and seat valve stuck open and you'll be able to connect your fuel line just as easy without the "redneck engineered" look.
 

mapbike

Well-Known Member
Mar 14, 2010
5,502
109
63
Central Area of Texas
Yup... the Speed carbs have that inherent problem and it shut me down a few times right after my first build until I saw what was causing it... and there's no way to put a filter between that valve and the fuel inlet so I took mine apart and gutted it, basically, I took the valve off the carb and drilled right thru it so there's no on/off function there anymore, then I cut the small switch lever down flush with the body and covered the whole part with JB weld... One could just as easily buy an 8mm banjo bolt and fitting to run the line directly into the carb and be done with it but my redneck engineering kicked in and it held just fine until I could install a new NT carb.

There are a few threads in here somewhere showing how others have gutted their fuel valves on the speed carbs too, but I think the best solution really is to just swap out the fuel valve for an 8mm banjo fitting... no more rubber particals to clog up your main jet or leave your needle and seat valve stuck open and you'll be able to connect your fuel line just as easy without the "redneck engineered" look.

Im scared to even get involved in the speed carb discussion since I've run several of them and never had an issue with rubber peeling off and getting into bowl from the shut-off on the carb.......!!!

Well, that probably just did it and I just released the Speed Carb gremlins and now I'll start having heck with mine...LOL


Id rather have one of these instead though....
 
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Davezilla

New Member
Mar 15, 2014
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San Antonio Texas
I'd definitely like to have that red gremlin... There's just something about them that makes them look really cool... My oldest sister had one back in the 70's and I always wanted that car... lol
 

mapbike

Well-Known Member
Mar 14, 2010
5,502
109
63
Central Area of Texas
I'd definitely like to have that red gremlin... There's just something about them that makes them look really cool... My oldest sister had one back in the 70's and I always wanted that car... lol
several years ago I built a 406 cid smblk chevy it ran high 11sec-low 12sec quarter mile in a 71 chevy C10 long bed, I can just imagine an engine like that in a Gremlin set up right.... what a ride that would be....lol

Sorry for the hi jacking with this post, I just got to day dream8ng and had to say something about it....!
 

thirdorangutan

New Member
Mar 19, 2015
74
0
0
Austin, Texas
Ok, so I just rode it with the non jetted speed carb. I got it up to 28!!!! as I was riding it ran out of gas!!! I went back and put some gas in it and am now only getting 20!!! I have no idea what happened. Same gas, nothing got changed.
 

Mike B

New Member
Mar 23, 2011
2,256
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Central CA
When you were low on gas the carb bowl was not full and so you had a "leaner" mix.

That's all the verification you need.