• I cannot for the life of me figure out this low throttle stutter valves are...

    I cannot for the life of me figure out this low throttle stutter, valves are good, coils fine, what am I missing?

    41 comments
    • Pilot jet, a/f mixture. Is it a new problem or something that's been happening

    • It's been happening for a bit now, but more so now that I've changed the head, I can't cruise at like 10-20mph because the bike just sputters like crazy, but once the throttles up and I'm in the 30-50+ range it's fine

    • clean the carb, sounds like the slow jet has some blockage

    • I'll check that out, carb was basically new when I installed it but won't hurt to look again

    • doesn't take much to block those tiny holes

    • Running a filter or velocity stack

    • Uni filter

    • Joshua Allen kinda harder to tell on video then in person but you can basically get the idea.

    • What size motor / carburetor jetting size so on

    • Stock 150 still for now, 108 main jet on 24mm stock style cvk carburetor

    • I have the 30mm oko coming with the 180 I'm hoping to get that bad boy strapped in soon, but I'd like to get this running as good as possible in the interim.

    • Almost sounds like a misfire hard to tell from his but doesn't seem like bog but more of a skip

    • Yes, a skip or a stutter would definitely describe it, also say I'm off the throttle coasting at about 30-40. When I hit the throttle again it will sorta skip and then start goin

    • Try changing your plug

    • Run a 115 or 118 on your main jet.

    • I'll give that a shot as well

    • Curious why a 108 main

    • 118 on a stock 150 sounds way to high

    • Most of the stock carburetors I have seen come on a 150 they roughly have about a 112 Main

    • Joshua Odom I had the 110 in there before I changed the head a while back and it ran funny, I wasn't aware it was a valve issue at the time so I'll probably go back to 110 now that I know my valves are set proper

    • Any stock style cvk carb I've owned is a 105 main. I've never seen higher out of the box

    • I think China just throws a jet in there what you need to do is when it's spitting and popping like that witch usually means it's running lean. You need to go ride it for like maybe a mile like that in turn the key off and Coast to the side and pull your plug and see what it looks like

    • You have to understand when you're in a steady Cruz your needle and your main jet are both working together so if your main jet is too lean your needle won't be able to flow enough fuel to make the motor run correctly

    • Well it was leaned out before the head change so that makes a bit of sense, I'll try upping the jet and see what happens

    • That's what's strange to me. As soon as I get on the throttle it's golden, it's only from 1/4 to about 1/2 throttle and once I'm above like 30 mph it's totally fine in that higher end range

    • If you take your cvk carburetor apart and you pull the needle out see if there's lots on the needle for adjustment if there is try moving your washer down one step that will raise the needle to allow more fuel to come into the motor during a cruise

    • That will also allow more fuel to go into the motor to at wide open throttle because your needle will be raised higher

    • Just switched to a 114 main and she started up quicker then she has previously gunna take a quick spin around the block and see how it runs

    • Don't seem quite as bad, but still hesitant at that low range, I'll see if I have anything bigger

    • CheckI out scooterfocus.com

    • The way I've always set for low-end which is your idle air mixture screw. Once the bike is fully warmed up screw it out till you reach the highest Idol point on the carburetor once it starts to go back down screw it back into its highest idle point and leave it be.

    • Idle jet is to small lol its lean as soon as it comes onto main and needle it clears up

    • Now there's a solid answer, thanks brotha, I'll look into finding a bigger idle jet

    • Check what size yours is first and clean it really really well if its not atleast a 35 idle id suspect that is cause of sputter alot of 150s come with a 32 which is way to lean once u open up exhaust and intake

    • It's most definitely 35

    • Clean it really well all the holes including the hole in the center id try a 38 if u have always had this stumble

    • Not since day one, but its been a bit now, maybe 6 months or so, I just dealt with it because everything else seems to run solid and as soon as I'm up and going it's not giving me any issues really, now I just work around a more residential area rather then main roads so it's tough to keep the bike under like 25 and still be able to cruise without that crazy sputter

    • For you f*** with the idle Jet you need to adjust the idle screw first. With the bike nice and hot screw the idle screw out or in depending on where it's at till the bike reaches its highest idle RPM. Soon as the rpm tone starts to idle down turn it back to its highest idle point and leave it.

    • Its highest idle point on the screw is also the leanest idle

    • I base my info off personal expericnce tuning 20 or so gy6 engines using wideband setup

    • Soon enough I won't have to worry about it, David Bullock will be saving me from this misery soon hahahaha