New Grubee Skyhawk can't get high rpms or go uphill. Bogs down.

[Shlink]

I just finished putting my bike together about a week ago. I started breaking it in with 24:1 and the stock spark plug/wire. Its cold here in NJ, but I can get it running pretty quickly.
The problem is with the clutch in, I can barely get it past half throttle without the engine bogging down. With the wheel engaged I'm lucky to get 1/4 throttle going down a slight hill. Going up a very very slight hill the motor bogs down completely and I'm forced to pull the clutch in.
One thing I find very strange is if I go down a big hill with the clutch out, it still only lets me throttle about 1/4-1/2 way. Even with the motor slowing the bike down, I can't give it enough gas to make the wheel spin.
My first thought was I just need to break it in for a while, but after 50+ laps going up and down my street with no change at all, I decided to replace the spark plug, boot, and spark plug wire. Just put those in today and still no change. (plug gapped at about 0.025)
If I'm patient I can kind of lure the bike into high rpms with the clutch in for a second or two with careful feathering of the throttle, but not consistently.
I'm open to all ideas.
Is it possible the bike still just needs to be broken in more? I've used probably 1/4 a gallon of gas so far.
I could also take a video if anyone would like to see whats happening.

 

[Hammond Egger]

A video is worth 1000 words.

 

[kipharley]

Sounds like you either have an air leak or your not getting enough fuel.
Try a search to find your solution if you can't get it straightened out post again! Someone will point you in the right dirrection! Kip.
[email protected]

 

[skiball83]

Check that your magneto is perfectly aligned on both sides of the magnet. If it isnt it can be giving you a weak spark. I also agree with kip. Check your not getting an air leak most likely at the intake or where the carb goes onto the intake. I used black rtv gas resistant sealant from autozone in both areas. Make sure your head bolts are properly torqued. Also and this is where I had my problem. Take off your exhaust and blow through it. It should flow easy. If it feels like blowing through a straw its clogged. I fixed mine by drilling out 5 holes with a 1/4" bit through the cat(new epa muffler and cat combo for skyhawk gt5). Another thing to check is to take off the bottom of the carb and check to make sure that your float isnt cracked or stuck, or there is no gunk in the jet. If your running the stock screen fuel filter get rid of it and put on an inline one from any auto parts store or lawn mower repair shop. Hope this helps. Maybe the gurus/pros here have some better answers for you, but this should get you started. One more thing make sure your choke is off. Down position.

 

[Shlink]

Hey, thank you very much for the responses. I'm still trying to diagnose the problem but have been busy.
I checked the exhaust pipe and it flows freely.
I tried spraying WD-40 where the carb meets the intake while it was idling and it did seem to die, but not after just a sprits, more of a solid spray. And its possible the engine died on its own. I'm going to do the same test later but with starter fluid instead(don't have any right now). It should be easier to tell if the engine is reving than if it dies down.
The way this carb meets the intake I originally thought there was a giant leak because theres a plastic sleeve that doesn't go all the way around the intake pipe. I took it off and messed with it and tried to clamp the carb down tighter, but then realized thats not what makes the seal anyway. I think the intake is supposed to sit all the way against some rubber in the carburetor, which is weird because theres nothing to tighten or anything to improve the seal other than pushing the carb on very hard before securing it in place. I'm not sure if filling it with silicone stuff would do anything.
I'll post more updates as they come.

 

[kipharley]

Don't use starter fluid could damage your inards! take your carb and intake off and with a magic marker paint the mounting surface of your intake.
Then with a sheet if sandpaper on a flat surface,nice flat table top,drill press table,ect,ect.
Hold the sheet of sandpaper with one hand,with the other hand hold the intake flat on the sandpaper and sand the marker off in a x pattern.
Holding it FLAT.when it"s gone you know your mounting surface is flat.
On your second pic,what's that between the slot on the top of your carb?
A screw-driver burr? don't try to "over" tighten if you break off one of those tabs your going to have a big leak that the only fix will be a new carb.
That little supplied screw should do the job.
If you think you need silly-cone.Don't!
Go to the auto parts store and get some gas resistant rtv.Kip.
[email protected]

 

[Venice Motor Bikes]

Try a NT carb... you can buy one for $20. They are very user friendly!

 

[Shlink]

Try a NT carb... you can buy one for $20. They are very user friendly!

Alright.. Where is a good place to order one of those? After I try plugging it up with some sealant I'm ready to give up on this carb.

Either this is a horribly flawed design or I'm doing something wrong.
When I took it off this time there was some exhaust sludge around the white plastic bushing. So I'm positive air can get in here.

Heres are pics of what the inside looks like. The intake pipe sits in here with that plastic bushing (that blatantly is not to keep gas in/air out, its just there to hold the carb to the pipe) and presses up against the back piece of rubber. Its hard to tell in the pictures but when the pipe is up against the back rubber, the outer rubber piece sits around the outside of the pipe. but just barely.

and this next pic is shining a flashlight into the carb, so you can see that theres only roughly one centimeter of rubber between the end of the pipe and the outside world, with nothing actually clamping it down.
This design is blowing my mind...

Sorry for all the super close up blurry pics but i'm really trying to get the message across.
Does anyone agree with me that this is a really BAD design?
Or is it possible that I don't actually understand how it works?


If I try to seal this up with gas resistant RTV should I spread it everywhere inside and out with the pieces off, then put them together? Or should I put everything on tight and then try to seal it from the outside. I'm really worried about getting the stuff inside the carb if I were to put it where it really needs to be (all in/around the rubber part)

EDIT: Heres a video too, lol.
http://www.youtube.com/watch?v=JcgOl3-gius

 

[cory151]

I had this same issue that you referenced in the thread that I posted in with videos for examples. All I can say is ditch that thing, the fuel isnt being metered properly regardless of the adjustments made.
Lastly after switching to the NT speed Carb I have yet to have anymore issue and the NT has poorer (in my opinion) sealing setup to keep from sucking air.

I set to all available jet levels as well as every conceivable float level to no avail.
I even gave it to another guy around here with a bike that wanted to try a CNS and he had no luck with it either. The one that is sold with the kit is garbage.

 

[skiball83]

When I ran that carb I used sealant on the intake and made sure it was in all the nooks and crannys. It ran a lot better, but since then I now run an NT carb. It is just so much easier to deal with. No more guessing just riding.

 

[cory151]

Let us know when your NT is installed, are you running a 66cc or a 49cc? If it is a 66cc you likely want to bumb the jet one groove richer after reading the plugs. I know I did and it runs perfect now. Good luck.

 

[KCvale]

It's the 2010 CNS carb.
http://motorbicycling.com/f34/inside-2010-grubee-skyhawk-cns-carb-25062.html

I haven't found a way to make my 1st one work yet, bought an NT, but I have 3 more to play with now.

 

[Shlink]

Let us know when your NT is installed, are you running a 66cc or a 49cc? If it is a 66cc you likely want to bumb the jet one groove richer after reading the plugs. I know I did and it runs perfect now. Good luck.

Cool thanks. I've got a 66cc. I ordered an NT from spooky on Friday so it should be here soon.

 

[KCvale]

I just hope CNS carbs can actually be made to run right. I have 1 48cc and 2 66's new ones here with them and I only ordered 1 NT at the time.

And whats with gasbike making you pay for something that won't work?
I know that is the only way they can be imported to meet 2010 EPA, but forcing us to eat something like that opposed to just offering to let you swap for something that actually works at no charge is a rip I think.

Or maybe that's how it meets new EPA rules, it won't run! hehehe.

 

[Shlink]

Woo hoo!
My NT came today. I slapped it on and it ran like a charm!
I did have a little trouble up a steep hill but compared to the CNS its spectacular.
I'm going to play with it more tomorrow and check the plug color. I bet I can make some adjustments and get more power out of it. But as of right now I've got zero complaints.

 

[cory151]

Once the motor is broken in youll have more power too.

 

[breno]

Keep ur eye on the crank seals with these too sometimes u can get duds if u do run into trouble grab urself the double ribbed type seals and yeah like everyone else said keep ur motor clean and look for any signs of leaks around the whole motor thats usually a give away of where ur loss of performance is.
Personally I run the speed carb on the 3rd clip from the bottom and regularly clean the air filter for max air flow. ur plug should also tell you alot to I generally notice mine with the 3 prongs has 1 prong a light coffee colour and the other 2 are a coffee colour with a little bit of black carbon on it. running 20-1 on the conservative side.
Seems to beat everyone else I see around and I way 98kgs but usually thats because there a Z box pos.

 

[mr.charlie]

after lookin at the pics of the obvious air leakage issue...what i'd like to know is this a common problem to this style carb?.....and if so might this correct the problem?

1) get a small automotive brake cylider hone

2) hone out the throat of the carb

3) get some sheet shim stock and make a sleeve

4) slide carb on and check with light..then seal exterior

just a thought.....if it worked then maybe people wouldn't have to purchase another carb?