Engine bogging

[Lowandslow]

Another post on bogging issues with the 2010 CNS V2 carb.
Engine starts great-no choke needed. Runs and idles good and revs up fine with no load on it. Motor bogs down under load and 1/2-Full throttle. So far I have tried all the needle clip positions. The problem gets worse as you go up the clip (lean) and better when you go down (rich). I have adjusted the air mix and idle screws every possible combination with the needle clip positions and the bogging remains no matter. Currently I'm set in the 5th notch and the air/mix screw 2 turns out. Runs pretty good but still bogs out under full throttle. Choke helps the WOT somewhat but will kill the motor at idle. Spark plug shows black but not wet/oily. New motor running 25:1 mix. NGK plug gapped .025. plug wire and boot aftermarket copper-core. Carb inlet sealed with sealant and intake gasket cut from gasket material and sprayed with copper gasket sealant. Fuel petcock and filter were replaced and gas flows out in steady stream. Gas cap vents o.k. All seems to point to carb issues, I feel like its starving for fuel in the top end. Suggestions? I was thinking of a larger jet maybe.

 

[Lowandslow]

Nope. Tried it. No noticable difference.

 

[Hammond Egger]

It sounds like you've got all the fuel problem bases covered. Probably a shot in the dark but I would look at weak spark under load. Maybe clean up the area where the mag is grounded and make sure the screw is tight.

 

[that guy on a bike]

I think there's a lot of us out the sruggling with this carb. something is wrong and hopefully someone can figure it out. Same bogging problem with mine. I tryed all needle adjustments, and moved the float tab to ride at every position there is . There is only a one spot it will run and not overflow so I don't think that is the problem. sealed the spacer and gasket that slips on the inkake. Then after port matching the intake and the exhast I put the carb back on and sealed all around the intake clamp. No air getting in there. seems like i have good spark don't know under load. Also drilled my fuel valve out and increased the flow. With the bowl off the carb I have plenty of flow to the carb. I'm thinking maybe larger jet as well. Just seems to be starving to me. I can slowly gain o.k. speed on flat land if i play with the choke a lot. It will start and idle with no choke, and when you rev it , it sounds fine. Just won't go when I'm on it. I'm so frustrated seems like its gotta be simple. and there are so many people with the same carbs acting the same way. Lets put our brains together and figure this out please. Don't care how many times I have to take it apart

 

[Lowandslow]

Man...that is totally like my bike. I also feel like it's fuel starved at the high end under load. I was wondering if the chinese jet these to work with the 48cc engines and they fuel starve the 66's. I'm willing to drill my jet ever so slightly just to see what happens.
I also wonder if the jets in these are all the same or if the just put in what 'kinda' runs.
An assortment of jets could come in handy with these! We'll figure it out.

 

[that guy on a bike]

I'm with you bro. as soon as I find a bit I might have to try it. I also heard that it might be too big already but it doesnt make sense to be able to rev wide open but when its loaded it bogs down. Needs more gas underload right? Wish i did had an assortment pack. I could just try them all. don't give up man. I feel better knowing its not just me. But I feel bad knowing what your going through. Weather is getting better, can't wait to get this worked out.

 

[Lowandslow]

Well I'm no qualified engine tuner but I've heard enough fuel starved engines to know when she ain't gettin' enough gas. Just gotta figure out why. I've read posts both ways
some say too much and others say not enough. I just feel like mine is a case of not enough.

 

[that guy on a bike]

O.k. I found an old 1/16 bit that I ground down to an unknown size ( little larger than the jet i have). Drilled out the jet , put it in, and she fired right up. Took a quick spin and had more throttle right from the start. unfortunatly don't have time to really try it yet . Might have to go a little bigger , I think this might be the root of the problem. keepin my fingers crossed.

 

[Lowandslow]

Cool. I have some # bits and will start there also. I'm glad to know this may be the right course.

 

[that guy on a bike]

Hold up. I think I went too big. Just took a little ride and I have awesome acceleration, and it idles great but have a top speed about 18 or so. It takes off like a bat out of ****, but then just backs off at a steady slow pace. Doesn't sound right ( like maybe too much fuel) and dosent reach the higher rpms it used to. It acually performs better now with a quicker throttle response. It just lacks the speed it used to. quicker than walking i guess. Don't drill too much. take it slow and see if it helps. Think I might be in the market for a new jet ( maybe a variety pack). Or maybe that NT carb. I've been hearing about. Almost ready to give up on this P O S if you know what I mean

 

[jokesonu]

I think there's a lot of us out the sruggling with this carb. something is wrong and hopefully someone can figure it out. Same bogging problem with mine. I tryed all needle adjustments, and moved the float tab to ride at every position there is . There is only a one spot it will run and not overflow so I don't think that is the problem. sealed the spacer and gasket that slips on the inkake. Then after port matching the intake and the exhast I put the carb back on and sealed all around the intake clamp. No air getting in there. seems like i have good spark don't know under load. Also drilled my fuel valve out and increased the flow. With the bowl off the carb I have plenty of flow to the carb. I'm thinking maybe larger jet as well. Just seems to be starving to me. I can slowly gain o.k. speed on flat land if i play with the choke a lot. It will start and idle with no choke, and when you rev it , it sounds fine. Just won't go when I'm on it. I'm so frustrated seems like its gotta be simple. and there are so many people with the same carbs acting the same way. Lets put our brains together and figure this out please. Don't care how many times I have to take it apart

I had the same problem as you guys here's what I did. I took that carb off and threw it in the garbage and bought a cheap nt carb off ebay. I think I read on here somewhere the guys ebay store is boygofast. Anyway this carb was 12.50 + shipping. It just has a lever butterfly choke and the top of the slide screws down. Put that one on last friday and it runs better now than it ever did. It four stroked a little at full throttle so I dropped the needle one notch and its pulling hills like nobody's business now. I just kept looking at that cns carb and I was like what were they thinking having to have a hose gasket in there so I gooped that all up but still wouldn't pull a load.

bicycle Motorized BIKE GAS ENGINE parts - Carburetor | eBay

Best 20 bucks I ever spent that thing had me pulling my hair out.

 

[karryhunt]

OK guys try this......

http://motorbicycling.com/f34/engine-sputtering-higher-speeds-18229-3.html#linkbacks

 

[Lowandslow]

In response to Nougat's question: throttle response is good,comes down after high rpm just fine. I still feel it's in the jet so......I got some #drills 67-71. Stock was a #70 so I tried a #69 and put it all back together. I will test tomorrow after work, don't think my neighbors would appreciate WOT runs down the street and around the block tonight!

 

[Lowandslow]

Had a chance to test the bike tonight, and she ran much better with the jet drilled out. Night and day difference! So here is where I am currently: The jet was drilled out with a #69 bit. The needle is in the 4th notch down and the air mix screw is 2.5 turns out. I'm still on break in mix @24:1. Hope this helps all who are struggling with this carb. Don't give up on it. Not a bad carb if you can get it tuned. I still feel like it starves very slightly @ WOT, may go to #68 bit but will wait and finish break-in first before doing that. My observations on this carb are: the carb seal at the intake must be done using sealant or an air leak is likely. The float may not be set correctly at the factory and lastly the carb may be under-jetted as mine was. I'll continue to mess with it and tune it until I break it and am forced to buy another one!LOL.

 

[that guy on a bike]

Thanks Lowandslow for not giving up on it. Keep us posted on how it continues to run. Think I'll try to fill my jet and drill it again. My homemade bit went a little big on me. Bike still runs better I'd say. It definitly doesn't bog down the way it did. I think we might have this almost figured out. More gas is what I was thinking all along. These carbs definitly need to be sealed, very poor design. Also when my float was not adjusted right the pin would get stuck open and gas would run out the overflow. I think this was happening after hitting bumps and potholes, believe me or not i'm telling you. My tab was bent too far down and the angle it hit the pin it would wedge. Let you know if I find out anything else. still not convinced this thing could ever run the way i want it.

 

[guy3gy]

hay this mite help my motor boggs to under the magneto cover see if you are leaking oil my seal is bad. if it is leaking fuel out not going to have enuff to burn which will make it bogg sorry about the spelling guy3gy

 

[rohmell]

I had the same problem as you guys here's what I did. I took that carb off and threw it in the garbage and bought a cheap nt carb off ebay. I think I read on here somewhere the guys ebay store is boygofast. Anyway this carb was 12.50 + shipping. It just has a lever butterfly choke and the top of the slide screws down. Put that one on last friday and it runs better now than it ever did. It four stroked a little at full throttle so I dropped the needle one notch and its pulling hills like nobody's business now. I just kept looking at that cns carb and I was like what were they thinking having to have a hose gasket in there so I gooped that all up but still wouldn't pull a load.

bicycle Motorized BIKE GAS ENGINE parts - Carburetor | eBay

Best 20 bucks I ever spent that thing had me pulling my hair out.

I think that is the solution to the problem; just get rid of that expensive and complicated CNS POS and go with the simplicity and easy-to-tune/adjust characteristics of the NT.

 

[richard1994]

ive got the same sort of problem with my bike no but my bike wont start with out having the throttle open and just takes its time getting up the revs and it sprays fuel out of the air filter side i dont know how to fix it changing the idel screw doesnt change anything hope one of you guys have an idea on how to fix it

 

[that guy on a bike]

Sorry Richard (my name is Richard too) I don't know an easy fix. My carb. went through a stage like that too. I did get it to start better and now if gas comes out , its out the overflow line and not through the filter. You might try adjusting the float tab. I had a little sucess with messing with mine. There is a fine line between running, not running, and constant gas overflow. I think I found the spot but now I have other issues. Just ordered a NT carb. If yours is a cns carb. I don't know what to tell you but what ive already tryed in this post. Sorry, and good luck.

 

[that guy on a bike]

Just got my new NT carb. Problem fixed. Thats all I got to say. Better, simple design. Clamps on better and tighter than the CNS. Looks cleaner, works better, and now I can enjoy. Might have lost 2 or 3 mph top speed. Almost seems faster because it works. no bogging at all. My advice to everyone who has problems with the "Speed Carb.". Just buy a NT and spend some time riding for a change. I found one for $14.99 + shipping. Thatsdax.com. Well worth the money. ordered on sunday and was here today. Can't beat that. I did also find jets for the CNS at Piston bikes but now I don't think i'll have to work on that POS ever again. Will sell my slighly used CNS to anyone who wants to mess with it . As for me I am sold on NT, and its only been an hour since i put it on . Good luck anyone who has the determination to keep on trying with theres.