what did you do to your motorized bicycle today?

[GearNut]

Just a simple test before you go tinkering with the carb and manifold:
Try engaging the enrichner (choke) a little at a time and see if doing so improves the condition. If it does, then yes, you are running too lean. If it gets worse then you are running too rich.

 

[Blakenstein]

ahhhhhh dang it !!!!


all this time i have been running a brigs and straton air filter retro fittted to my cns v3 carb,and it was running like a angry ape with slight four stroking across the board..... i just got my preformance 90 deg filter from SBP and hooked it up and my bike sat for the weekend...... well took it to work today and i cant take her over 20mph ~! if i try and give it more than 1/2 throttle she bogs out as if there is no fuel, if i try and go up a hill it bogs out like she looses power, if i try to ease the throttle up it helps a little but then sputters and bogs out untill i let off the throttleback down to 1/4 or below a half throttle !

its like i lost all my power and the bike is way way to lean ! the tone of the exhaust changed also ! it used to have a deeper more dirtbike-ish sound and now its a sharper pingyer sound ????

there is no waay the new air filter could allow that mutch more air in that i am running this lean could it ? it was slightly ritch before now its way way to lean.

i am thinking i got an air leak on my intake gasket that is presant when i give it the gas and the suction becomes to great it leaks. or mabey when changing the filter i moved the carb and its the infamouse cns clamp on iar leak ?

mabey the main jet got clogged coincidentaly at the same time i swapped the filter ? it feels like a clogged main jet ... like as soon as i pass half throttle someone shuts off the gas !

i checked fuel flow from the tank and it runs through the petcock just fine and runs through the filter just fine and runs out the end of the hose that goes to the carb just fine, actualy it flows realy well ! so i know it getting the fuel, i even hooked it up and undid the float drain screw wile hooked up and watched it drain out the bowl drain hose, it drainned out just as fast as it did from the tank so there is no obstruction at the float valve needle.

what do you think, does the SBP 90 deg filter flow that good that i need to rejet 3 sizes bigger ? or is something else going wrong here like a clogged main jet ?

You said it's runnin way too lean,..is there anyway on that carb to make it not run so lean??? Evrytime winter comes for me, it's blood sweat and tears all over again, my gas /air ratio has to be right on perfect or it does not run. ...it bogs out bad. My carb is the same type that the Echo leaf blowers come with..I dont like them, but i manage to keep them working.

 

[rogergendron1]

Just a simple test before you go tinkering with the carb and manifold:
Try engaging the enrichner (choke) a little at a time and see if doing so improves the condition. If it does, then yes, you are running too lean. If it gets worse then you are running too rich.

hey i wish my choke worked but ...... it came straite from grubee drilled offf center on the choke pilot jet hole ...lol ... they missed the choke circut and drilled srtait into the float bowl ! so my choke is ussless and if i do activate it , it drains my float boal !!!!


thuss i disconected it and capped it off with the plunger and spring inside blocking it off to stop the float bowl from drainning lol

so i can not trouble shoot my cns with its choke

i realy do love this carb, i had it on my previous motor, a grubee gt5 that was ported to the max and set up for WOT running !!! it reved up and ran the sh@t !!!! it was a verry powerfull bike and i got it tuned up real good with this exact carb ! now that it on a dax f80 new motor i got, and just passed break in, i am having trouble here.... this motor is set up for all around power and it was given a port an polish to match,

a moderatly heavy port and port time corections, piston ramping, high comp head, titainium wrist pin, free flowing exhaust, everything port matched, and a 16mm ID bore intake to match the carb bore.

it was running beautifull with some slight 4 stroking across the board when NOT under load, reaching speeds of over 30 with a 44 rear during break in ! (7,000rpms !)but after swapping the filter to a SBP 90 deg angle one and letting it sit, the problem manifested and now i cant go over 20 ! its like once i pass half throttle and the needle leaves the main jet it bogs out like its not getting any fuel, but from idle to 1/2 throttle it runs just as it did before... perfect ???

i am under the impression this carb has 3 circuts and i know its more difficult to tune than the nt carb with only 1 circut, thats why a lot of people give up on it, but having three circuts to me is to its benifit making it more responcive over the range of jets if one can tune it right vs the nt single circut and boring throttle respoce, i can tell a differance between the 2 carbs in throttle responce and the cns when tunned has way beeter and a lot snappyer responce than any NT !!! so i would like to keep using it and the go get a NT for 20$ responce is not warented her LOL

i am going to pull it off the bike in a few ..... after i finnish my coffie and see whats up, IE: pull it appart and give it a compleat over haul and check for leaks on the intake gaskets, i saw last night a wet spot around my cylinder intake manifold gasket that should not be wet, this is an indication that it may be leaking at higher rpms causing the lean condition but who knows untill i get it all apart lol

 

[Greg58]

Roger I don't know if this will help, on my cns2 the short tube that goes to the filter base was allowing fuel to be vacuumed from the bowl. Mine has only one tube, I removed the tube and plugged the hole in the back plate then used a weed Wacker in tank filter as a vent. Anytime air flow has to change direction like the 90° filter it slow down the flow, the same as it does in HVAC. Yours could be creating more vacuum and drawing fuel from the bowl, mine did what you are saying and thats what I found.

 

[Greg58]

Roger I now see the picture of the hoses, they were not there when I did the post above, it still sounds like a lack of air flow to me.

 

[mapbike]

rogergendron1, My suggestion is to check the spark color/plug chop and see if it shows a lean run condition and if you really want the CNS I guess you'll have to work the bugs out of that through the process of elimination, personally I'd be running either the little NT carb or a RT carb/Dellorto clone, with just simple jetting either of these works fine on a 40+MPH china girl build with correct gearing and are almost 100% maintenance free, simple to tune and as long as the fuel is filtered so no junk gets in they just work all the time every time.

Hope you get the issue worked out asap, but if that CNS keeps giving you grief the NT or the RT carb from Dax is an excellent way to go, NT is very easy to tune and only comes up short to the RT in one thing, throttle response, the RT does have great throttle response and better low end power, but I have seen no advantage on the top end with the RT, I like the RT carbs, but the NT is hard to beat for all around simplicity and reliability in my experience and I have been clocked at 45+MPH running the NT carb on my first dax GenIV build.

Best wishes rogergendron1 hope you get it worked out soon.

Peace, Map

 

[rogergendron1]

Roger I now see the picture of the hoses, they were not there when I did the post above, it still sounds like a lack of air flow to me.

lack of air flow into the carb from the filter ? when i blow through the filter via the 90 deg rubber part it offers less resistance than the cheaper paper ones i had in before, i could feel a resistace to those other 2, the SBP one offers none i can feel. i just tore down the carb and well the main jet is clean and the idle jet was clean ???? mabey one of the 3 channels are clogged and preventing fuel flow ? i sprayed them out, then i noticed the float bowl pin was off center and mabey causing the float to stick but that will be fixed when it goes back together and i may adjust the float lvl but dont think i need to since it has been just fine for the last 2 builds .


plug chop would show slighty lean, but it bogs suddenly lol so it runs perfect right up to the bog spot .... so i assume the plug would show a well running motor as it does, since it cant run at the bog....

 

[rogergendron1]

stock main jet was real tiny.....say .69 or .70mm

i squeezed a .74mm saftey pin i found through it, and it was real tight so i slowly worked it in twisting it around untill it slid in easy and snug.

main jet is now .74mm or .0285

edit.... it squeezes in snugly so i know its actually a size smaller... .73mm or .028 in

i guess you dont need micro drils to enlarge a jet lol just a bunch of differant small saftey pins and a vernier caliper !!! i found one that was .74 2 sizes biggger than stock main so i used it and fed it through carefully

 

[mapbike]

stock main jet was real tiny.....say .69 or .70mm

i squeezed a .74mm saftey pin through it and it was real tight so i slowly worked it in twisting it around untill it slid in easy and snug.

main jet is now .74mm or .0285

edit.... it squeezes in snugly so i know its actually a size smaller... .73mm or .028 in

Order you these two items and you can drill the jet to exactly where you need it, and if it ends up being to big just put a small piece of solid wire solder in the jet heat it with propane torch and re-drill it, this is the best way I have found to jet the carbs correctly, cheap easy and it works perfectly, been doing it to mine since I started playing with these engine in 2009, Tom/2door and other taught me that little trick early on and it is best way to go in my opinion.

Links:

http://www.widgetsupply.com/product/WB05.html ($3.97 wire gauge bit set)

http://www.widgetsupply.com/product/SHG3-840.html ($2.97 Pin Vise for bit)


Map

 

[Greg58]

I have a drill set with a pen type drill handle, the solder and drill method is what I do also. The one thing I have learned is everyone of these engines are different, what works on one may not on the next. On my 48cc with the cns2 I'm at a 66 drill size, that's where the plug color got right. On other bikes I've tuned the stock jet (71 I believe) was OK. These things are very simple, that's why they drive us crazy!

 

[mapbike]

I have a drill set with a pen type drill handle, the solder and drill method is what I do also. The one thing I have learned is everyone of these engines are different, what works on one may not on the next. On my 48cc with the cns2 I'm at a 66 drill size, that's where the plug color got right. On other bikes I've tuned the stock jet (71 I believe) was OK. These things are very simple, that's why they drive us crazy!

DITTO..!

So far all of my 66cc engines with NT carbs have liked a jet drilled with either a #72 or #73 wire bit, my RT carbs have both run perfectly with the #70 jet that came with them, only slight low rpm 4 stroking and zero under throttle or at cruise speeds and a nice medium brown spark plug electrode, climate and altitude play a part in all this jetting stuff also, so yes it is not universal when tuning the carbs, it's a matter of running the engine and figuring out what it needs and like the best based on how it is set up and with what exhaust it has which has a lot to do with the amount of air that can flow through the engine.

Map

 

[rogergendron1]

i have pleanty of micro drills .......................... they are in new hampshire 75 miles away at my fathers machine shop though ! i took my vernier caliper and went around the house measuring a bunch of paper clips and saftey pins til i found a pin that was exactly .74mm just about 2 jet sizes larger, right where i wanted it to be, so i reamed it out with that and its around a .72 or .73mm jet now as the pin still fits a little snug so its a lil smaller. if i need more i will go back and ream it out some more with the same pin till it slides through easyer

something to think of if your in a pinch and are running lean and you dont have any micro bits around, just use a small saftey pin ! be shure to measure it with a micrometer or vernier first !

here are the other 2 filters i used,
the large white brigs and straton one ran the best it flowed quite well and there was only minor 4 stroking when not under any load top end was good but plug showed a little lean at high rpms
the orange brigs and straton one caused a lot of 4 stroking, especialy at the midrange and off idle but was useable in a pinch and the top end was perfect
the new SBP 90 deg filter flows with no restriction i can feel by blowing through it in and out unlike the other 2 where i can feel the restriction with my breath.

i didnt think changing to a high flow filter could warrent sutch a major change in jetting like this but but hey when i cleanned out the carb i found nothing blocking anything and the whole inside was spotless that i could tell. also removed the gasket and though it is over compressed and sort of flat from use, it does not seem to be leaking and i forgot that i used gell lock tight type super glue to seal all around the carb flange and plastic spacer ring so there was no leak there. if there are no leaks and there was nothing in the carb than the main jet must be too small right ?

just incase it was leaking, i am making a new intake gasket anyway out of thick 1.6mm gasket paper, this one will be a lot better port matched to the jug and manifold

 

[mapbike]

"i have pleanty of micro drills .......................... they are in new hampshire 75 miles away at my fathers machine shop though!"

And for $10 you can have the right tools for the job where your at now so that you can fix the problem you're having since you are 75 miles from Dads shop .........

If the safety pin does the trick for ya thats great and it served the purpose you needed it for, just trying to help out with the links.

Map

 

[xseler]

Just finished my remade 'Frankenstein II' exhaust. Haven't run it yet, but should sound the same as 'Frankenstein I'............it should......

 

[rogergendron1]

now i am realy confused.....

so the carb is perfectly clean and the main jet is 2 sizes bigger 70 to a 74mm and there are no air leaks what so ever !

yet i am still having the problem ! only now its at around 3/4 to WOT i bog right out and sputter as if there is no enough fuel or i am loosing spark or something.

i forgot to mention that i am running nearly 13:1 comp and i fuelled up my bike before i set it for the weekend ..... soo i suspect i got ripped off and given 87 oct instead of 93 ! that would explain the tottal change of tone in the motor to the sharper tone like its being forced harder and also detonation gets worse the higher up the rpm range you go soo..... i am going to drain my gas and put new gas in that i know is 93 oct and see whats up. i suspect 87 oct run at 13:1 comp can not be good at all !!! lol

another thing it could be is my plug.... i am running a brand new plug but its a (R) resistor type nkg br6hs i am not shure if that could be the problem but i am going to swap back to a non resistor instead to see if it helps.

before i set it for the weekend it ran perfect ! i am stumped but since the last thing i did before leaving it was fuel it up, i am leanning heavivly torwds the fuel ! i think i got ripped off at the pump ....AGAIN ! this has happend before !

 

[Greg58]

I hope that will cure your problem, wow 13/1 is getting up there on these engines. Mine is so low I think it would run just fine on kerosene!,

P.s. I went out to ride the cranbrook that I seldom ride only to find a flat front tire, at least it wasn't the back again. Patched the tube till I can replace it with a good one and off I went, met the new neighbors walking their dogs and found out they ride bikes as well. He told me he picked up two worksmans at a deal , I espressed intrest so he may sell me one for my next project.

 

[xseler]

Guess I just wimped out on soldering and drilling the jets.....just ordered an assortment from Pablo. It's time to start getting every bit of performance that my bike has to offer.

 

[placidscene]

Today I rode my motorbike to the Autoparts store to buy parts to fix my car!

 

[crassius]

done that a lot

 

[placidscene]

It was the best reaction to my bike that I had seen yet.
When I was leaving the parking lot with a 5 quart jug of motor oil in my ammo can rack, this lady watched me pedal and drop the clutch to start the engine.
Her eyes got real big and her jaw dropped! lol She looked completely amazed and in disbelief