150cc GY6 2 Seater Topping Out At 24

[AltuveRules]

Hey guys, I've been working on this junky 150cc GY6 mini-buggy for a while. Got it running but my top speed is 24 I took the cvt apart and clutch side was pretty rusty, but I couldn't the darn thing apart no matter what I did. Variator looked fine. The thing sounds good to me; it screams like crazy it just won't GO I'll post a pic of it and a WOT plug shortly. Ideas?

 

[AltuveRules]

Here are some pics

 

[Bwdeaton]

You could take off the chain and the CVT cover and rev it out to see if it engages all the way like it should. If it is revving like crazy and not going anywhere then it is probably the variator not moving all the way like it should. I have a Gy6 kart and it only goes about 29-30mph anyway.

 

[Bbqjoe]

I see your problem right there!

You don't have your spark plug in it!!!

 

[Mr. Spindle]

I see your problem right there!

You don't have your spark plug in it!!!

Don't be silly, it's either his gear ratio or his variator, but it could be rev lever stuck on carb a bit. (Probably stuck his gum on it) take off the carb, clean it well. If it still doesn't work get a new plug and/or check your variator or get a new variator.


Wait, Spindles?

 

[AltuveRules]

I think I'll rev it with the case and chain off and see what happens. Wait, actually joe's got the answer I got a brand new carb on it (had a side cover bust on the original and couldn't find a replacement) and I have the cable tightened to pull it to WOT and still had to add a spring to get it to return . The cable isn't real stiff either . Anyway, that's not the problem. I've heard the gearing for these chinese pieces of junk can come bad stock, so I'll post a tooth count asap.

---------- Post added at 08:26 PM ---------- Previous post was at 08:24 PM ----------

Oh, and I already checked the variator (seemed fine but idk) and the plug in the pic is brand new.

 

[Blmpkn]

Those 150s will only get a moped to 50+/- and that's with half the gross vehicle weight and far less than half the rotational mass (wheels,tires, axle)

That being said, 25-30 sounds about right to me. putting lighter variator weights in it MAY offer an increase in performance. Peak HP is made around 8k in those motors, if you delay the "up shift" of the cvt a bit by installing lighter weights you'll at the very minimum notice a boost in acceleration, and quite possibly see an increase in top speed due to a higher engine speed by the time your cvt has fully engaged.


I suggest getting a tachometer, and playing with your weights&springs. I cut ten minutes off a ten mile commute on a 50cc moped with just cvt tuning.. So believe me when I say there's definitely room for improvement. If your still not happy with the performance.. Try a performance exhaust and ditching the airbox for a cone filter. Cams and big bore kits are cheap and plentiful for those motors as well.

 

[AltuveRules]

Thanks for the reply! I've been meaning to order a tach forever, I finely did it. I have a 5hp kart that is much smaller but it will hit almost 30, but then again the acceleration is terrible lol. I'm thinking it's a better investment to just to get a motorcycle engine than invest in this thing much more the rollers/sliders, but I'll definatly give that a try I also need to get an air filter (stock one was ruined). I'm currently running straight carb Any particular one you recommend? Thanks again!

 

[gman3850]

well for these karts everything pretty much has to be perfect or they dont work good

To start of make sure your valves are adjusted, if they are off these engine suffer poorly.

so a checklist for you

1. valve adjustment
2. make sure rollers/ siders are clean and installed correctly
3. get a gates performance belt (dont slip as easy
4. deglaze (or get a new clutch) complete unit is like 35$ on amazon


now you get into the gearing
5. determine rear tire size (23")
6. determine internal primary gear ratio (most are 13/40)
7. determine internal secondary gear ratio (mine is 23/47)
8. multiply these together to get your internal gear ratio. (so 6.288)
9. determine outer gear ratio (mine 14/33 = 2.357)
10. multiply these together to get your final (14.822)
11. so going back to my tire sire we plug all this into a speed calculator and at max 7k rpm which i hit i top at 32mph



so now if we take all my calculations and put them to yours and it looks like you run a 21/22 stanard tire (which is undersize for its rating) plugging them in (messure my stock ones came in at 20") you get a top speed of 28mph.

so you are leaving 4mph somewhere on the table. it might be theat your gearing is different or your motor is worn out so it wont turn as fast, or a multiple of other things

 

[AltuveRules]

Perfect a list! I'll check the valves tomorrow. I ran it on jackstands with the cvt cover off and the belt went to full reduction so I don't have slider/variator problems. I couldn't get the clutch apart not matter what I did to that rediculous 38mm nut. Tips? idk maybe I'll just get a new one. How do you determine the internal gear ratio (when I get there)? Thanks a ton!

 

[AltuveRules]

Alright, adjusted intake to .005 and exaust to .006. Both gaps were to small. No difference. Now how do I calculate internal ratio?

 

[AltuveRules]

Ok I just did the lame (and easy way of checking ratio by spinning the tires once and counting how many times the clutch spun. It came out to around 17.25: 1. Plugging in my variables with 7.5K rpm is 24 mph exactly. That must be correct, but I don't see how it's factoring in the cvt. Does the cvt reach a ratio higher than 1:1?? Anyway looks like I'll be regearing this thing. What do you guys recommend? Internal gears or sprokets?

 

[AltuveRules]

Just counted the external sprokets. 16:32.

 

[gman3850]

are you sure you did the checking the tirres way right, you need to put a referance point on the tires and cluctch and spin the tire to see how many times tit takles to get the clutch bell to go around once.

my old kart has same internal gearing as mine does now but with 25's and a 16/42 gearing and i still topped around 29-30

 

[AltuveRules]

That's exactly what I did. And it matches my speed exactly. Any idea what gearing set to order? Should I open it up and count up the teeth?

 

[gman3850]

well youll need to open up intranal gear box to see what your gears are and than u can order diffrrent ones to suit your needs. 3/4 ryobi impact takes the clutch bell nut off easy.

 

[AltuveRules]

Ok will do tommorrow. I've had the clutch off before so NP.

 

[armyvet]

Your losing hp running without a filter.definitely lean.once you get filter check your rollers could be worn out.

 

[AltuveRules]

Does the plug look lean? I posted a pic in first post. It looks fine to me.