GT5 Super Rat bogging issues

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Toastman

New Member
Feb 28, 2011
11
0
0
Macomb, IL
I have recently joined the club with a GT5 Super Rat on a cruiser frame. Myself and another forum member are having the same problem, or so it seems. Both our motors bog out at higher rpm's. Mine also seems to "load up" on fuel and you have to baby it up to speed a bit. I already put the spare head gasket on due to blow by gas, tried the spare spark plug, and brought my octane to at least 93 without ethanol, 25:1 mix. The only thing that seemed to help was the octane boost (NOS brand, full 6pt boost), it helped a bit with performance and reduced pinging a bit. The other member I mentioned said he tried another carb with the same results, I will soon try this to when I meet a buddy this weekend. I do wonder though if the main jet is just too big. I lowered the clip one notch to the middle, and it seemed a little worse. This leads me to think it might be the new built in CDI. Hopefully i can soon rule out the spark plug with a NGK this thursday, via autozone. Although I am still keeping the carb as the possible problem, I'm leaning towards poor ignition at high rpm's. Here's a great link to an ignition upgrade I want, not sure it will work with my ignition setup though. But I am awaiting a reply from the guy.

link:
CDI Ignition for the Chinese 48cc HT engine
 
Last edited:
bare bones

bare bones

New Member
Jul 12, 2009
123
0
0
Austin
Toastman said:
I have recently joined the club with a GT5 Super Rat on a cruiser frame. Myself and another forum member are having the same problem, or so it seems. Both our motors bog out at higher rpm's. Mine also seems to "load up" on fuel and you have to baby it up to speed a bit. I already put the spare head gasket on due to blow by gas, tried the spare spark plug, and brought my octane to at least 93 without ethanol, 25:1 mix. The only thing that seemed to help was the octane boost (NOS brand, full 6pt boost), it helped a bit with performance and reduced pinging a bit. The other member I mentioned said he tried another carb with the same results, I will soon try this to when I meet a buddy this weekend. I do wonder though if the main jet is just too big. I lowered the clip one notch to the middle, and it seemed a little worse. This leads me to think it might be the new built in CDI. Hopefully i can soon rule out the spark plug with a NGK this thursday, via autozone. Although I am still keeping the carb as the possible problem, I'm leaning towards poor ignition at high rpm's. Here's a great link to an ignition upgrade I want, not sure it will work with my ignition setup though. But I am awaiting a reply from the guy.

link:
CDI Ignition for the Chinese 48cc HT engine
Click to expand...
I have tried changing the plug out with the NGK and I didn't see much improvement. I hope you have better success than me. I may try and double up the head gaskets to relieve some of the compression while the engine breaks in. Who knows may be worth a shot---a shot in the dark that is :):-||
 
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Toastman

New Member
Feb 28, 2011
11
0
0
Macomb, IL
I thought of trying that too. Another member said that the new super rat CNS carb has a 68.5 main jet. He suggested starting at 66 and going down. I feel pretty confident the carb's main jet is just too big.
 
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Alson

New Member
May 16, 2010
71
0
0
Kankakee Illinois
My buddy got a super rat, and it ran fine right out of the box, we looked at some of these forms and found out to set set the air fuel screw at 3 1/2 turns out but didnt get the idea right yet and got to go 33 so far. The only thing he was upset about was the frount mount, he has a cruser and the motor mount was to small tryed a u-boult deal and the studs are to wide for the plate and the holes needed to be reamed out. Anyway he went for the hole in the frame mount new alen head boults and got it done. No carb issuess
 
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CaliRebel

New Member
Apr 4, 2011
74
2
0
Santa Barbara, CA
I could have sworn I heard someone say to tune the carb at between 1 & 1 1/2 turn out from all the way in. The epoxied preset is at 3/4 out from recollection.

Unless you mean 3 half turns out in which case that would fit with what I've read on the forums....
 
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driftology

New Member
Jun 22, 2010
125
2
0
campbell, ca
if it helps on my idle air screw is out just enough to see one thread on it and my needle is set at the 3rd clip from the top. it was originally set at the 2nd but it was running lean. i might still be a little lean but the motor pulls and pulls. i feel like it will rev forever. i wish i new how high these engines can rev safely. wonderful motor so far. just wish i wouldnt get any blow by at the head gasket.
 
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matthurd

New Member
Dec 13, 2010
817
2
0
manchester NH
my advice for anyone with cns carb issues is get the motor running smooth, break it in, and adjust from there. my carb couldn't idle at all if i set it up for best performance, 30 miles later with the same settings the motor kinda idles, and i still got my top speed setting.

i expect it to keep getting better, and after another 50 or so miles i'll make my final adjustments.

@alson, by loosen up do you mean the carb itself is actually able to spin around on the intake? like tunable by hand?

if so i combated that issue by getting a new screw+bolt, the one that comes with the kit is pretty soft metal, go to the home depot, get an m5 screw (i believe it was m5, possibly m6 though) and matching nut ( they come in sets of 2 and are like 40 cents a set at my HD) and swap it out, from there you can really tighten it up and it wont be slipping all over the place anymore.

worked for me.
 
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Alson

New Member
May 16, 2010
71
0
0
Kankakee Illinois
Thanks for the info on the new boult and nut on the CNS-V2 carb. My buddy went to the speed carb now, hes going to change his mix to 25:1 and got a shorter plug NGK BPM6A and he put a extra head gasket in, cause he has a cruser with only one gear and it hard to turn over with one gasket. Let ya know what happenes when he trys to start it
 
Masterm222

Masterm222

New Member
Feb 14, 2009
132
0
0
Billings, Montana
I have been fighting with these CNS carbs coming loose for a while. My solution is to mount the carb on the intake exactly where i want it and tighten it down. Then I remove the carb and intake from the motor and drill a small hole through the carb, plastic spacer and intake. Install a self-tapping screw in the hole with some sealer and wa-la. Carb stays put.

I just finished a build for a customer yesterday and this thing was a P.O.S. For three days I fought with it. Idle fine and rev fine on the stand but on the road It would just bog when I opened the throttle. I had two CNS carbs and an old speed carb to play with. Four different CNS jet sizes, two smaller than stock and two bigger than stock. Every needle setting possible with each jet size and the bike left with the old speed carb. I live to battle the CNS another day.
 
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Alson

New Member
May 16, 2010
71
0
0
Kankakee Illinois
Piston bike is selling the Super Rat. My buddy put a extra head gasket in the super rat, now it starts right up easer and he went to the NT speed carb. He said it bogged after going 27mph, he thinks he knows what it is a air leak hes going to tighten the head boults again and seal the carb better, but it starts right up
 
PatTheThird

PatTheThird

New Member
Apr 24, 2011
49
0
0
51
Southern Maryland
I have the standard gt5 with the v2 CNS carb. My bike runs best with the mix screw run all the way in. I have the carb ring from SBP installed, an automotive plug wire and an autolite plug. My motor starts and runs perfectly. My bicycle chain broke a few weeks ago and i am waiting for parts from my LBS. In the mean time i just give the bike a push and jump on. Bike revs through the range like a top....until it hits top rev, then it backs off 7 or 8 hundred rpm. Like its starving for gas. I'm confident my head and carb are air tight.
 
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kyl 46&2

New Member
Apr 12, 2010
77
0
0
MN
anybody ever a problem with it reving WAY to high? i had mine(super rat) out tonight and after i run wot, pull in the clutch, prepare to stop it revs incredibly high. my ports are air tight. my head is down nice and tight, plug is good. it seems like its running super lean. i keep the choke closed at all times. when ever i open it it bogs out then dies. the cns carb is a pain in the butt. i get it to idle fine but after 20 min or so it does this reving thing. i can't seem to get to the source on this one.
 
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driftology

New Member
Jun 22, 2010
125
2
0
campbell, ca
Dude I was just getting ready to post the same issue. as long as I keep my rides short I'm fine but like you said after a 20 min ride I get the high reving too. everything looks nice and tight. I pulled the plug and it looks good too. it rev so bad that the kill switch won't shut it down.
 
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kyl 46&2

New Member
Apr 12, 2010
77
0
0
MN
starting to wonder if the rubber seals on the cns are junk. i stopped and actually saw my carb start to move. the clamping screw has been swapped out for grade 8 hex head. looks like its time for some lock tight.
 
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