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| 150cc GY6 and Under Engine Tech GY6 and Smaller Technical Discussion Forum |
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#1
03-09-2019, 04:08 PM
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Help please.
I have a 150 American sports works 1501 fox.
The man I bought it from said it was a 2010 but the lady at the dealership said 2013 when they worked on it. It only runs 29mph. On a slope I got 33mph but thats it. It needs new bearings in front right wheel but I dont think that will help the top speed much. I have been told it should run about 40mph. The engine compression is 175 I was told. It have 1,500 miles on it. I was also told I needed calipers all around. They was stuck but are free now best I can tell. Im no machine but it seems like the transmission isnt opening up all the way. The reason I say that is because I can hold the gas at 70% throttle and get near full speed and then gas it the last 30% the cart only gets louder but doesnt gain much speed. Any ideals would be helpfull. Sorry for the long post. Lol 
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#8
03-10-2019, 02:43 PM
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Its actually a manco fox but American sports works bought them out. The cart is almost identical to the 150 hammerheads that i saw at the dealership.
Im wondering if the belt isnt being stretched enough for whatever reason.
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#9
03-10-2019, 05:11 PM
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#14
03-13-2019, 04:46 PM
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When you get around to checking the belt and clutch, put the buggy on jack stands and rev it up. See if both pulleys open and close properly, and see if the belt is going all the way up on the front pulley. There should be an obvious wear pattern on the clutch from the belt. Make sure it's the right belt too. Too long or too short can cause issues.
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#15
03-17-2019, 03:12 PM
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I got into the transmission and found a very worn belt. One tooth was gone. Inside everything is cover with small black fuzz. I assume all this is from the worn belt and needs cleaning before installing a new belt. I also noticed the fan side of the belt was much more worn than the other side.
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#16
03-17-2019, 05:20 PM
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Check the variator making sure it has 3 plastic guides and they are not worn or broken, check the rollers by rolling on a flat smooth surface looking and listening for flat spots. Clean with compressed air and reassemble with parts as needed. Remove the clutch by separating from pulley ( remember the clutch is under spring pressure from the torque spring when removing the large thin nut), Inspect the pads and mainly the drum for overheating check 3 springs (should not be able to move shoes at all), Disassemble the clutch pulley halves and clean with degreaser and grease as instructed. All this can be found in video's on You Tube.
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#18
03-20-2019, 02:12 PM
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You have to try hard. It doesn’t separate super easy.
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#19
03-20-2019, 03:30 PM
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#20
03-20-2019, 08:31 PM
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If you put it on jack stands and rev it up make sure it's on solid footing. I almost got taken out by a riderless 4 wheeler shooting out of a guys shop and jumping the road yesterday. Just lucky I was on a 40 mph road and seen it coming. Pretty sure it broke ol boy's hand when it got caught in the frame (revving it up) and it dragged him across half his yard. It didn't look pretty.
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#21
03-20-2019, 08:41 PM
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#26
03-25-2019, 11:05 AM
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Clean the cover and put a bead of RTV on cover set aside and let skim on top then dust with some talk then install cover but lightly press cover to case to even out RTV, remove cover and let sit overnight to dry. The talk will keep sealant from sticking to case so when you remove cover gasket will remain on cover for many removals.
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#45
04-29-2019, 09:20 AM
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A bigger rear sprocket will increase torque more than changing the rollers, but it will also have a bigger effect on top speed. For serious hills though, I think a gear change is the only option.
Contrary to what most people experience, I didn't lose any top speed when I changed to lighter rollers. The only reason I can think of is I took a lot of weight off my buggy? IIRC I used 11 or 12 gram rollers. The light weight of the buggy also helped a lot with acceleration and hills. Keeping the valves adjusted made a pretty decent power difference too. Last edited by liduno; 04-29-2019 at 08:59 PM.
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#46
04-30-2019, 11:26 AM
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The best thing to do is to increase engine power with a port and polished performance head with a performance camshaft, and if you have weak compression you could go with a big bore drop in kit which will enhance the head and cam work. Don't waste your time and money with performance cdi if DC volt or hot coil. After you increase engine power than you can fine tune with appropriate rollers and torque spring. The GY6 150cc engine was designed for a scooter, 100 pounds wet. Now you put this engine in a 3-4 hundred pound buggy which will work fine for small kids. Big kids need more engine power.
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#48
04-30-2019, 10:13 PM
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Have you checked valve lash and timing of cam to crankshaft? You will also have to check jetting. Does it fall flat even when slowly throttled? Hold hand close to carb air intake but don't completely block just enough to restrict air then open throttle to see if any change for the better. Keep in mind the carb will suck your hand if too close. If it improves than jetting is too lean.
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#51
05-13-2019, 07:32 PM
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I got my 12 gram rollers today. My old rollers were 12.8 geams. The new ones are 12.4 grams. My questions is, could my old rollers been 14.5 grams new? Seems like they lost alot of weights. They did have a big flat spot.
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#52
05-13-2019, 07:40 PM
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The BuggyDepot site has my cart under Manco 7150 and American Sports works 7150. Bot say stock rollers was 14.5 but they only have 12, 10, and 9gram rollers. Seems like they would offer the stock rollers for my cart. Do get me wrong I think the 12s will be much better for my terrain.
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#54
05-15-2019, 11:02 AM
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I found a big problem on my kart. The series of bars/frame that run above the motor has broke loose. I think it was like that when I bought it 6 months ago. I dont know if it can be wielded back or not. If not I will have to by the whole thing which id a couple feet wide. It bolts on just above the axle and again above the motor near the gas tank. Looks like a expensive fix to me.
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#58
05-21-2019, 07:52 PM
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I still got a broke frame and my verified fit gaskets didnt fit.
One the other hand the new 12g rollers really helped. Seems like alot more torque and seems faster on top or atleast as fast. Really happy with that upgrade. I'm kinda confused about the top end but not complaining.
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#59
05-21-2019, 08:59 PM
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I know that goes against most reports, but if it's just a matter of gear ratio then it kind of makes sense. Unless of course I am totally missing something..lol
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#60
05-22-2019, 09:38 AM
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The lighter the roller the higher the rpm needed to move that roller up the ramp. The motor will only make power up until 7500 rpm even if a no rev limit cdi is used. With lighter rollers the top rpm limit will be reached before the top power curve. Lets make it simple , you have a 3 speed manual trans. Now you replace 1st gear with granny low ( lighter rollers) and third gear becomes second gear. Top end speed will be reduced.
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#61
05-22-2019, 11:07 AM
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I'm not being argumentative, I just don't see the correlation to a 3 speed manual transmission?
The gear ratio on a cvt is directly effected by where the belt rides on each pulley, as long as the rollers allow the pulley to travel it's full range of motion how can it effect top end? I get that the lighter rollers will effect when the pulley starts to move, so that will effect when the belt is engaged, much like a high stall torque converter in an automotive transmission. I understand the higher the RPM is when the belt is engaged, the better low end power you'll have. But as long as the RPM is high enough to allow the rollers to allow full range of motion, won't the final gear ratio be the same no matter the weight of the roller? Kind of like your 3 speed analogy, this would be like changing first gear to a granny gear but leaving the 3rd gear ratio at 1 to 1 Lets go with 7500 RPM, both pulleys at full range of motion, one open, one closed. Shouldn't the top speed at 7500 RPM be the same regardless of roller weight? I mean 7500 RPM is 7500 RPM, and the belt is riding at the top of one pulley and at the bottom of the other. Doesn't this mean the final ratio is the same as it was with the 14g rollers? And again, I'm not trying to be argumentative, I'm just trying to understand whats happening. I agree that most report a loss of top end when changing rollers, but this was not my experience, nor was it the OP's experience. Are you saying the lighter rollers don't allow full range of motion from the primary? If that's the case, then yes the final gear ratio would be different if the belt never reaches the top of one pulley and the bottom of the other. But again, this has not been my experience.
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#62
05-22-2019, 01:25 PM
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Just cause the belt climbs the pulley fully does not mean you are going the same speed. The engine is not built around the gearing the gearing is built around the engines power curve. The lower the rpm when belt reached top of pulley the longer you will make power to speed the vehicle. If rpm's are max when belt reaches top of pulley you will not pickup any more speed
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#63
05-22-2019, 03:17 PM
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With all that being said I'm sure there's a curve. Meaning, if the engine can't reach top RPM because of a lack of power it wont reach top speed, I also suspect the belt wouldn't go through it's full range of motion, in this particular under powered scenario.. I would think this would more likely happen with heavier rollers not lighter though. If the rollers were too heavy it would essentially try to shift to the higher ratio too fast for an under powered engine Last edited by liduno; 05-22-2019 at 03:29 PM.
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#64
05-23-2019, 10:10 AM
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Look comparing a gear driven trans to a cvt is like comparing apples to oranges however they are both fruit just like the traditional vs the CVT. If you take your car or truck on the highway with say a 3 spd auto or manual trans and drive all is good but if you put the trans in 2nd and drive on the highway will you need to shift into 3rd for it to drive normally? The same is true with a cvt trans. By replacing with lighter rollers you are in effect changing the transmission gearing. With the stock setup from idle 1000 rpm to hit the throttle and at 1100rpm the buggy starts to move, the belt will reach the top of pulley at 5000 rpm high gear. Since the engine is 2500 rpm lower than the max power the buggy will continue to accelerate until peak rpm of 7500. After 7500 rpm the engine will make no more power so in the case of a no rev limit cdi the rpm's may rise the engine cannot produce any more power. Now lets put lighter rollers in say 14 to 12 gram rollers. Starting from idle 1000rpm now you accelerate and the buggy starts to move at 2000 rpm 900 rpm higher than stock. When the belt reaches top of pulley the engine is at 6000 rpm. Now the engine will only increase power for 1500 rpm which will give you a lower top speed. Now there are only 2 ways to compensate the loss. One is to replace the variator with a performance variator which is if I remember correctly 2mm larger diameter or by building engine in such way as to increase the power curve so the engine will continue to make power above 7500 rpm.
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#65
05-23-2019, 11:40 AM
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I agree a cvt isn't like a manual transmission, I was just using your analogy as you compared the two. My thinking is more like a pinion gear and a spur gear.
If the primary is the pinion and the secondary is the spur the final drive is the same once the they have both gone through their full range of motion. If the final top rpm is reached[7500] and both the primary and the secondary are at full range, how can the mph be any different? Again, I'm assuming top rpm is reached and both pulleys are at their full range. Mathematically I can't see how it would lower the top speed. If the rollers were so light that the pulleys didn't reach full range, or if the diameter of the rollers were different so the pulleys never reach full range, then yes I can see that lowering the top speed. Within the proper weight range, and roller diameter, the only thing I see lighter rollers doing, is putting the engine at a higher rpm for acceleration. It will use up a little more gas too, but well worth it if you ask me..lol Last edited by liduno; 05-23-2019 at 11:54 AM.
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#66
05-23-2019, 01:40 PM
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Again it has to do with shifting the engines power curve, where is the power being used. As I said earlier. In the stock setup when belt reaches top of pulley engine speed will still increase depending on how much power the engine can still produce. By lightening the rollers the max rpm range for power is reached sooner before top speed. Drive your car/truck and pay attention for when the trans hits high gear, does the vehicle still pick up speed in high gear? Now try the same thing except to not allow the vehicle to go into high gear, do you still go as fast? Although it's apples and oranges the theory is still the same for they are both transmissions but one shifts with gears or plates where the other shifts using rollers. My experience with droping 14-12 you loose about 2-3 mph the lower the weight of rollers the more top speed lost
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#67
05-23-2019, 03:43 PM
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Let me start this reply by commenting on how on any other forum this would have already broken out into name calling and keyboard gansterness..lol I like that we can discuss this without getting into an argument
 Now back to your reply. Your analogy is based on going to a higher gear or staying in a lower gear. The cvt at full range is essentially in ''high gear'' The lighter rollers do allow the engine to rev up higher before engaging the belt, and they do keep the RPM higher while the belt is going through it's range of motion. But once the belt is at the top of one pulley and at the bottom of the other pulley, it is no different then if the rollers were heavy. The rollers don't change the top RPM of the engine and they don't change the final position of the belt and pulleys. Think of it this way. If you started rolling down a hill with the pulleys maxed out, the buggy would take off slow as hell, but would eventually reach top speed at 7500 rpm. It would be able to maintain this speed even if the hill gradually leveled out to a flat rd. It wouldn't matter what weights were in there, because you started with the pulleys maxed out. So as long as the pulleys are maxed out the top speed will be the same.
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#69
04-17-2020, 04:55 AM
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I finally got some extra cash so im looking for suggestions on tire brand and size. Im looking to upgrade a few things. Maybe different sprocket size, cdi, kandN air filter. Any suggestions?
In the winter i plan on putting more money into it but for now I need tires and a few cheap upgrades.
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#70
04-20-2020, 11:18 AM
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Your kart comes with a 32 tooth sprocket- if you want more torque (hill climbing) get a bigger/more tooth count-of course more top end speed go smaller. Getting taller tires will help in better ride as long as the tires don't rub anywhere, wider tires add more traction in most cases-picking a tread design is based off what the surface you're on most of the time.
I like the ITP holeshot tread for the rear -20x12x10 or 20x11x10 should fit no problem, the hole shot fronts or mudlites work well- Maxxis Razr are excellent tires too!
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