[BMXpert]

Noob here guys...

Cag 47cc. I installed the Boost Bottle last night, plastic spacer on the bike, and I DID install the hose barb on the bottom.

So I start it, and it revs at full throttle like mad. I shut it down, figure it's the throttle cable/carb interface, nope appears ok. I go through the cable run and it appears eveything is seated ok.

So I start again, and it revs at full throttle. This time I have it choked and have not a lot of throttle control in the choke position, but when I just start to take it off of choke, it revs at full RPM again like mad, quickly, I give it gas to see if I have throttle response, and I do have some, but I shut it down. I figure it's an adjustment in the throttle pin.

I started it with the throttle pin c-clip in both top and bottom positions with the same exact result. Still trying to chase down what in the ****** is going on. I read that the Boost Bottle port on the bottom end has problems, so I attemp to pinch off the tube out of the port with an adjustable (it's maybe not 100% shutoff, but darn close).

I start again...still rev at full rpm, this time it comes off the stand and almost blasts across the garage. Ok, so it's got to be something in the adapter/reed/carb assembly. I pull the whole thing. No splits in the plastic, reeds are straight, gaskets are intact. I bolt it all back together in a painstaking criss cross pattern turn by turn to make sure that I don't flex the plastic adapter out to cause a leak...everything looks good.

I start again...and AGAIN the SOB revs at top RPM nearly uncontrolably !

It's got to be something with the Boost Bottle I installed last night. The thing of it is, I hit about 34.4 mph with a 100cm circumference setting (the actual circumference of these tires is 86.5 cm), so a 15% decrease in circumference is ~30 MPH, which is not too bad since I'm ~175lbs...

Guys....I swear...I'm ready to run this thing over in my Jeep for an hour and then set it on fire, and dance a freakin' jig around it! This has GOT to be something simple that you guys have run into before. I'm all for getting an entire new carb set up if that will alleviate these issues with a adapter port to accept a top mounted barb fitting...

Guys...I am begging...any ideas ?????

 

[patthehat033]

LOL one word: Backwards.

Go to the top of your carburetor and take out the little black cylinder and the long groove should be on the opposite side of the idle screw. If the long groove is on the side with the idle screw it'll act as if it's in full throttle.

Or if you did not put the black cylinder in all the way it will act as if it is in mid to full throttle as well. Check both of those things!

 

[BMXpert]

LOL one word: Backwards.

Go to the top of your carburetor and take out the little black cylinder and the long groove should be on the opposite side of the idle screw. If the long groove is on the side with the idle screw it'll act as if it's in full throttle.

Or if you did not put the black cylinder in all the way it will act as if it is in mid to full throttle as well. Check both of those things!

10-4, I am "pretty sure" that this is not the case, but I'll check it again and let you know.

Thanks

 

[ASTALKER123]

Man I had the same exact proublem. Went through the carb reeds gaskets so many times I coould do it with my eyes closed. In the end my intake is cracked. It didnt look like it was nothing could be seen tell I put some pressure on the carb then it showed its self.

Mine was real had to start. Then when it did it went to full throt nothing I did maid a diff. Take a good look at your intake.

 

[BMXpert]

Just tried it...no dice...I am very careful about making sure the notch is engaging with the idle screw as I can feel it "make" and slide down.

I understand totally what your saying...but man..this thing is ready to blast off to outter space...Is there anything else I should be checking ?

 

[BMXpert]

Man I had the same exact proublem. Went through the carb reeds gaskets so many times I coould do it with my eyes closed. In the end my intake is cracked. It didnt look like it was nothing could be seen tell I put some pressure on the carb then it showed its self.

Mine was real had to start. Then when it did it went to full throt nothing I did maid a diff. Take a good look at your intake.

Did you have a plastic intake ?

 

[ASTALKER123]

Yep its plastic. Mine went so hard it spun the chain .

 

[BMXpert]

Ya, I have burnout marks in the **** garage now....I'm just wondering if there is anything else I'm not seeing....

 

[ASTALKER123]

start the bike and spray wd around the intake and see if your ideal changes. Also take your chain off tell you get it fixed.

 

[patthehat033]

If you have not tried the advice I gave you go ahead and try that and get back to me.

Also take off your air filter and look inside the carburetor, is the throttle needle visible or can you see through the carburetor to the intake. The most common reason for this is just that you have throttle needle and black cylinder incorrectly put in or it is not in at all.

The reason you would have throttle control with the choke on is because less air is able to go through the carburetor to pick up fuel.

Good luck!

 

[BMXpert]

If you have not tried the advice I gave you go ahead and try that and get back to me.

Also take off your air filter and look inside the carburetor, is the throttle needle visible or can you see through the carburetor to the intake. The most common reason for this is just that you have throttle needle and black cylinder incorrectly put in or it is not in at all.

The reason you would have throttle control with the choke on is because less air is able to go through the carburetor to pick up fuel.

Good luck!

Alright...I just checked this further with my m/c mirror.

I can see the black cylinder in the carb. There is a tiny gap at the bottom where it appears to bottom out that can't be any more than a couple mm's. I cycled the throttle, and sure as s**t the cylinder cycled up and down nicely through what appears to be full open and then back to the bottom position. I'm thinking this HAS to be right...I thinking that like ASTALKER123 said, there must be a crack I can't see in the intake.

Does this all sound feasible ? I can't phanthom that one small crack in the intake adapter will cause this thing to run hog wild.

 

[ASTALKER123]

Man mine did. I could not even see the crack tell I put some serious pressure on the intake with a flash light shineing but it will run at full tilt tell I shut it down.

 

[BMXpert]

Man mine did. I could not even see the crack tell I put some serious pressure on the intake with a flash light shineing but it will run at full tilt tell I shut it down.

From your experience, I just put a new intake with the port already installed on order...Thanks for the input.

Dude, I'm amazed that a crack that small could pull that much air, I mean there is a little negative pressure there in the stroke, but c'mon !

 

[ASTALKER123]

From your experience, I just put a new intake with the port already installed on order...Thanks for the input.

Dude, I'm amazed that a crack that small could pull that much air, I mean there is a little negative pressure there in the stroke, but c'mon !

I know what your saying. I actually asked on here cause I was dummfounded as to what was going on. When I finialy slowed down and looked I found the very very small crack.

 

[BMXpert]

I know what your saying. I actually asked on here cause I was dummfounded as to what was going on. When I finialy slowed down and looked I found the very very small crack.

Yeah it's a shame. The bike looks all bad azz wih the boost bottle, nitrous, new velocity stack, etc. and now the MF has to sit until parts come...

 

[CAM2]

If the plastic intakes cracked go to the hardware store and get a tube of Permatex 5 minute plastic welder and fix it til the new one comes.........

When you remove the stock intake from the carb and lose the washers it becomes a problem with the screws bottoming out on the reedplate and cracking the intake.....3 out of 7 cags I bought had cracked intakes from the previous owners not paying attention to detail.......

 

[patthehat033]

If you have not tried the advice I gave you go ahead and try that and get back to me.

Also take off your air filter and look inside the carburetor, is the throttle needle visible or can you see through the carburetor to the intake. The most common reason for this is just that you have throttle needle and black cylinder incorrectly put in or it is not in at all.

The reason you would have throttle control with the choke on is because less air is able to go through the carburetor to pick up fuel.

Good luck!

ASTALKER, might be right. But just check on last thing. When you are looking into the carburetor. Is the long groove of the black cylinder facing you. If so you need to flip the cylinder around, because otherwise it will run at much higher than idle.

But that's just a quick fix, he might be right about the intake as well, but if it was a big enough crack it would just run it really lean/rich and it would rev up and down.

 

[CAM2]

Yeah it's a shame. The bike looks all bad azz wih the boost bottle, nitrous, new velocity stack, etc. and now the MF has to sit until parts come...

We need to see this bike....Can you post up pics?

 

[ASTALKER123]

ASTALKER, might be right. But just check on last thing. When you are looking into the carburetor. Is the long groove of the black cylinder facing you. If so you need to flip the cylinder around, because otherwise it will run at much higher than idle.

But that's just a quick fix, he might be right about the intake as well, but if it was a big enough crack it would just run it really lean/rich and it would rev up and down.[/Q

Mine had a very very small crack and it ran full tilt tell i hit the kill switch.

 

[StrayDawg63]

its totally a airleak some where. as stated before take the chain off and start it and spray some wd-40 or carb cleaner around your intake area, and all boost bottle hose connections. if the revs change when spraying you found your leak. But do not allow any get to the airfilter when spraying.