• Calling BS: The GY6 engine can't reach 12,000rpm, can it?

  • Have a controversial viewpoint related to the sport? Turn up your BS meter, raise your red flag, and hash out your buggy gripes and pet peeves here! Keep it reasonably civil, and present your case!
November 2019 Forum Retirement
Due to lack of extra personal time (and too much spam), I'm retiring the forum and setting it to a read-only state. No new registrations or posts will be accepted as of 11/09/19. However, all information will stay up and searchable. If you spend a few minutes searching, you'll find the answers you're looking for. We may re-open the forum next spring.
Have a controversial viewpoint related to the sport? Turn up your BS meter, raise your red flag, and hash out your buggy gripes and pet peeves here! Keep it reasonably civil, and present your case!
 #11928  by CheethaSpeed
 Sat Apr 07, 2018 8:43 pm
I’m not an expert like you but I’m not sure I’d be telling people they should expect 12,000 rpm from any stock gy6. It would be a fluke and not typical. I’d believe your custom build, but stock :roll: I guess if you could find a long enough down hill run then maybe you could get a stock gy close or in neutral

I’ve been around a few and none got much more than half that rpm in my limited experience. But that’s just a dozen or so. I’m sure you see thousands. Maybe the 12 or so I rode were all duds

All that efi stuff is confusing me. I would need something pretty plug and play. I’m sure you’ll have the home town gy6 guys covered. I’m not experienced to mod ardruno, but I would come see you for a week end of hands on watching you mod it for me. I’m sure the R&D would benifit you for those vtwin predators that are used in everything. But it looks like you modeled the growth on other people people expanding the platform much past gy6 in the near future past release. I wish I had some skill here but it’s a foreign language to me. I do have a motor to play with tho...let me know when cash and limited skill is all I’m lacking for efi and I’m in. Sounds like my universal front hubs idea are not as exciting, but I bet you could be selling them a lot quicker. -I had to try....I still got no front brakes.
Last edited by CheethaSpeed on Sat Apr 07, 2018 9:12 pm, edited 1 time in total.
 #11929  by Travis @ Buggy Depot
 Sat Apr 07, 2018 9:12 pm
Stock Howhit engines on Yerf Dogs definitely do see up to 12,000rpm safely and under normal riding conditions, I've seen it consistently over the last 15 years. Keep in mind that there are several "stock" configurations of the GY6. The Howhit variant is capable of revving to 12k due to its 27/24 valves. And Yerf Dog riders are routinely able hit that 12k due to lower overall gearing compared to other models.

At 6000rpm, you won't go over 15mph on a GY6. Clutch engages at 3k, then the CVT works to maintain 6500rpm during acceleration until max ratio, then the GY6 winds out to what the head and cam can support. In the case of the stock Howhit, it's 12k.

Also, you might find it interesting that my best and most powerful GY6 engine builds have a maximum safe speed of 9,000rpm, but produce substantially greater power and will smoke a stock 150. They can and will run up to 12k as well if you hold your foot down, but not safely.
 #11930  by CheethaSpeed
 Sat Apr 07, 2018 9:26 pm
You are the expert. All the Howits I’ve seen don’t run. I’m sure at the fault of neglect and misuse and no maintenance and not their own. I’ve not been around them much either. I just got the yerf for the BDX hd parts but it was a bare frame. All the gy I have rode all are cheap Chinese throw aways on various atv and buggy’s and a few Hondas. Most wouldn’t hit a true 30 mph unless the grade was favorable. The on board speedos are liars. The faster you go the more they lie. If they were great stock you wouldn’t have to build them. 5,000 rpm would blow mine up in short order in stock trim so it still sounds high to me, but it’s not my area of expertise.

12k is the highest rpm claim for a gy6 with a quick google search here. Next is 10,250 next fall 8 and under. I just never knew. Seeing your clutch engagement at 3k makes more sense. But must mean the gy is not making much of anything until then in the rpm range. I’m making 32 ftlbs before your clutch engaged.

Your own video shows how much stock gy 150 suck
I believe they have potential and your builds are great. If stock was great you’d be Building something else.

I may end up with one of yours on my next one, so Im Not hating. I’m driving to Atlanta not because myvt365 has a stock 150. I’m looking forward to the comparison but I would expect to accelerate quicker but his top speed is greater. Partly due to his larger rear tires.
Last edited by CheethaSpeed on Sat Apr 07, 2018 9:45 pm, edited 7 times in total.
 #11932  by CheethaSpeed
 Sat Apr 07, 2018 9:50 pm
Alright the 12k is impressive and I’m just jealous sorry guys.

Now you get efi for low dough before me. I’m already planning build #2 tho -looking like a big boy efi gy

I’m excited to see what all you come up with beside hubs. Let me know what you need from me. I’m full of opinions, but I also have a few bucks that may be more of more assistance.
 #11954  by CheethaSpeed
 Sun Apr 08, 2018 2:02 am
Hmm, if My vtwin beat can Shawn in a head to head in Atlanta I’m on my way to Virginia next haha. My money is on the torque vs rpm. But I haven’t seen any hp or torque figures. And I already underestimated the rpm greatly. I’m guess around 15 to 18 hp with about the same or less torque. Idk. But I do have the added ability to quickly change my gearing to suit riding conditions for different challenges.

I appreciated your breakdown of the clutch engagement. The hold at mid 6 reminds me of my wife’s car pedal down. Prob also why I never heard close to 12k. My comet 44d has three setting to adjust the spring for some adjusting the rate the over drive scales in speed. Low spring tension faster acceleration more tension and it hold lower gearing on the driven pulley longer before starting to overdrive. Or rather less underdrive. I don’t think I ever been over low 30s to get past max engagement. Is the gy have adjustments as you increase power or change terrain? Mine does. I’m sure gearing and tire size effect it also. Most I have riden Have 22” or larger tires vs the yerfs 20” which hurts acceleration and could delay that hold longer or just not have the power to get there.
 #11956  by CheethaSpeed
 Sun Apr 08, 2018 3:25 am
Really if you think about it, a gy is very similar to a gx just with the cvt built in. I’m sure that is over simplistic. I understand they are not mechanically identical. One doesn’t start until the other quits in the rpm. I know at 175cc that is still some 40cc short of the most popular gx size and and full 464 cc less than my small vtwin gx. Big vtwin would net another 54cc. One needs the rpm to make power, one will blow up At 1/3 rpm of the others max. I’m roughly at 5:1 range final ratio range. I would imagine it would be a higher number for the gy with that high an rpm. Which results in the best real world performance? More rpm and higher ratio or more power with a lower ratio-I don’t know. But that is the big diff to me as I see it. But I’ll add a rear view mirror so I can keep an eye on you :P
 #11989  by Travis @ Buggy Depot
 Mon Apr 09, 2018 10:41 am
CheethaSpeed wrote:
Sun Apr 08, 2018 3:25 am

Which results in the best real world performance? More rpm and higher ratio or more power with a lower ratio-I don’t know. But that is the big diff to me as I see it. But I’ll add a rear view mirror so I can keep an eye on you :P
Horsepower is the best indicator (against weight) for how the machine will accelerate. Torque is accounted for in HP, as horsepower is a measure of how fast that amount of torque can get work done (accelerating you).

Both have their merits. Which is better for each person depends on what kind of build they're going after. In general, I would go with a high RPM, high HP engine in powersports, for ripping around. For utility and doing work (or very tough terrain and technical riding/climbing), I'd go with a high torque engine. CVT's do a very good job of making either work for either application though. I'm confident my GY6 184 is able to go anywhere and climb anything a torque converted GX (of any size) can.

With a GX versus modified GY6, I believe we'll be pretty evenly matched from 0 to 30. Acceleration would likely be a bit better in the GY6 depending on the final weight of both machines. Your higher torque is an advantage at speed, as resistance begins to increase from aero drag. I'm sure you'll have a higher top speed.

A little 150 - 185cc engine holding its own against much larger engines is a great testament. It's all about that thermal efficiency :D

I need to carve off enough time to finish the dyno this year. I'm looking forward to getting HP/TQ numbers for our engines.
 #11996  by myvt365
 Mon Apr 09, 2018 11:46 am
Travis @ Buggy Depot wrote:
Mon Apr 09, 2018 10:41 am
CheethaSpeed wrote:
Sun Apr 08, 2018 3:25 am

Which results in the best real world performance? More rpm and higher ratio or more power with a lower ratio-I don’t know. But that is the big diff to me as I see it. But I’ll add a rear view mirror so I can keep an eye on you :P
Horsepower is the best indicator (against weight) for how the machine will accelerate. Torque is accounted for in HP, as horsepower is a measure of how fast that amount of torque can get work done (accelerating you).

Both have their merits. Which is better for each person depends on what kind of build they're going after. In general, I would go with a high RPM, high HP engine in powersports, for ripping around. For utility and doing work (or very tough terrain and technical riding/climbing), I'd go with a high torque engine. CVT's do a very good job of making either work for either application though. I'm confident my GY6 184 is able to go anywhere and climb anything a torque converted GX (of any size) can.

With a GX versus modified GY6, I believe we'll be pretty evenly matched from 0 to 30. Acceleration would likely be a bit better in the GY6 depending on the final weight of both machines. Your higher torque is an advantage at speed, as resistance begins to increase from aero drag. I'm sure you'll have a higher top speed.

A little 150 - 185cc engine holding its own against much larger engines is a great testament. It's all about that thermal efficiency :D

I need to carve off enough time to finish the dyno this year. I'm looking forward to getting HP/TQ numbers for our engines.
Cheetah Real world you don't say I have a mile long drag on street legal roads we can pull flat on lets see what my 175cc will do hahaha like I said have seen what mine will do and watch when I fuel inject it hehehheheeh and to top this off lets do it at night where my 11 pole is at full use :shock: :shock: :shock: maybe we can get some hot woman to launch the flag hahahahahah and to top it off to make it back to my house its all hills we can really test them up hill and compare numbers and times sounds like a fun day! might I add the 150cc couldn't make it up my driveway hahahah we can get a cute trophy as well . Ill even add a winch to pull your mirror equipped yerf back as im smiling in mine hahahahahah. Top it off with a few brooskies steak on the grill and a bon fire I like this plan.