Spiderbox -5 minute mod gains 4 mph

[metalstudman1]

My wife's stock GY6 150-Howhit motor just quit after a neighbor was driving it and she wanted it fixed NOW. Didn't know what the problem was so I pulled the 125 GY6 off our trashed BX 125 buggy.I test drive it to see how much slower it's going to be and it's FASTER!---What-the? After checking it out I see the sprocket is a 16 tooth and the stock Howhit was a 13 tooth. Of all the mods to make a GY6 150 faster I haven't ever seen this mentioned as a cheap increase in top speed. How come? I verified the difference with a GPS: 16 tooth = 40.1 mph
13 tooth = 36.2 mph

[ckau]

Originally Posted by metalstudman1

Of all the mods to make a GY6 150 faster I haven't ever seen this mentioned as a cheap increase in top speed. How come? I verified the difference with a GPS: 16 tooth = 40.1 mph
13 tooth = 36.2 mph

it's been mentioned before. the problem is, it is not cheap. every motor manufacturer [gy6] uses a different design, mounting style and sometimes rear trans shaft for their gearing. nothing is universal. the only way to change counter shaft gears is to swap a motor or have a custom gear fabricated for a particular motor.
I agree with you though. I have wished many times I could think of a way to make a splined hub one could bolt different tooth count gears too. The ability to simply swap counter gears for different conditions would be ideal. There are several different ratios for the internal trans gear sets that can be found for the 157QMJ and axle sprockets can be made simple enough. Both would give the same results but neither swap is fast or easy.
The concept of having several different counter gears along with split gears for the axle would open up a whole new world in tuning.

[metalstudman1]

I've not shopped for the sprocket before so I'm not aware of the availability.Did I just get lucky and the only two sprockets I have fit from 2 different manufacturers? Maybe Tom can provide some sources?

[ckau]

If both motore were made by the same manufacturer say lifan for example then it is very possible the gears could interchange. On a motor with reverse it may by even more likely. I know that on my yerfs , with no reverse, I have never found a gear with the same spline count that would work as a direct replacement. If you have found something that works. Thats very welcome news. I have dieing to mess with different gear ratios. There are several ratio charts on line, mostly in MX vender sites that give a prety good idea of what a simple gear change can do.

[metalstudman1]

I've sent a request E-mail to a supplier of the BX 125 for pricing and availabilty of the sprocket drive, and do they carry different tooth counts. My assumption was that the Howhit GY6 motors were made made by Lin Hai, the BX 125 says it's supplied from HSP DKM ? Haven't figured out who makes it yet. But I can definiely verify that you can swap these sprockets and that the increase was just over a mile an hour per tooth and only took 5 mins. to do. Also I can't feel any difference in the torque when climbing the hills on our trails either. The 125 motor is only rated @ 6.5 hp. By the way the sprocket drive is #27511-DP200 from the BX 125 parts breakdown list. I'll post the price and availabilty as soon as I get a response for anyone else that wants this mod.

[BuggyMaster]

So you swapped the whole engine over initially?

[metalstudman1]

yes- the Howhit wouldn't turn over fast enough to start even with a jump so I just pulled the 125 motor and made the swap to get her up and running quickly.Wasn't going to fix the BX 125 anyways. I still haven't tore into the Howhit yet to see why it quit when it was performing perfectly. I suspect he rolled it and had it a full throttle upsidedown for some time as there was oil everywhere it shouldn't be!!!!Of course he didn't have a clue as to why it just quit!!!

[ckau]

This has got me excited! let me get a few questions straight. does your yerf have reverse? Did you actualy take the counter sprocket from the BX and install it on the yerf?
Just guessing here but another difference between the two motors may also be in the internal transmission gear ratios. The howhit's do have a low ratio internal gear set for torque while a lot of the others seem to have taller internal gears for better speed. We had a '05 carter that was a dog at take off and couldn't pull a wet noodles from a horse's a$$ but could get a higher top speed. The external gear ratios were identical. Our only explanation to this mystery was the difference in trans gearing ratios. the buggy was sold before we had the chance to pull the. trans cover to verify.
I am running a 13/31 gear set now that's a ratio of 2.39. A 16 tooth may be a touch too tall, that puts it at 1.94. I wanna stay over 2 but pick up a couple of mph. A 14 would be good, a 15 would be perfect. I kill most anybody off the line but after things get rolling it's sometimes hard to keep up. The only advantage I have at that point is handling. and just for you "VAN", driving skill!

[metalstudman1]

My Yerfdog is identical to yours-05 model ,no reverse (bought mine as a basket case and rebuilt it) The BX125 is an 05 as well. Once again the sprockets are "identical" other than the tooth count. It would make no difference with the motors anyway as this was a direct gain on the same engine and machine so we know you can get a 16 tooth sprocket for your Yerfdog. I don't know how fast the spiderbox was with the Howhit -I didn't run the GPS on it till the motor change just to prove to my wife that it was faster with the 16 tooth than the 13 tooth. And I think I've already found a supplier with the 15 tooth for $20. I can't really tell much of a difference on the bottom end as it still climbs the same, It does feel like it has a better mid-range now as that's the rpm's most used when running our trails.
Ckau do you know how fast yours is with the stock 13 tooth sprocket in mph's?

[SYCARMS]

This is an easy swap but as CKAU has said there are different spline counts,and as it will make top end faster it will suffer on the bottom end and most buggy owners don't want to sacrifice bottom end. This would best work with modded engines. The main problem is that you have to find a sprocket off a buggy that had 14 tooth and no reverse since the buggies with reverse do not use splines for they bolt to the rev box. Every GY6 I have ever worked on be it with or with out reverse uses a 14-16 tooth small sprocket' would immagine a scooter to use the smaller sprocket. You are the first one I heard of with a 13 tooth on a buggy. Monday I will make a few calls to see if I can locate one for you. TOM

[ckau]

Originally Posted by metalstudman1

Ckau do you know how fast yours is with the stock 13 tooth sprocket in mph's?

mine will top out at an average of 35mph according to a vapor trail tec. Ironically, my biggest gains in mph alone came from the front heim fix and 22" tires on the rear. At top speed the buggy feels like it simply runs out of gearing.
Many thanks for the ordering link MSM, at that price, it's worth the gamble

Tom: the gear is a 13. All my early model howhits use that same gear. I can't remember what the spline count and dia. are right now but will you need that info if you can do a search?

just out of curiosity, anyone know what the procedure is for producing internal splines? Are they cast , punched or machined.

[metalstudman1]

For the forum members that need a visual! There was a difference in the two sprockets as you can see- 1/8" in shaft length. I looked at the alignment on the kart and it wasn't noticable. The internal spline count is 19 and the shaft is 3/4" for those that need that info. Hopefully the pics speak for themselves.

Tom: here's a pic of a BX 125 supposedly made by DKM/DK motors or Jehm.

[ckau]

if the spline count and shaft diameters match, thats all I need. The shaft on the BX unit can be cut down to get proper alignment. Thanks for finding this discovery.

[metalstudman1]

Originally Posted by ckau

if the spline count and shaft diameters match, thats all I need. The shaft on the BX unit can be cut down to get proper alignment. Thanks for finding this discovery.

Are you going to buy the sprocket from the supplier I sent to you? if not I will- just for a spare for when I get the Howhit 150 running again. Also I have 22" rear tires with 18" on the front -So your gains in top speed should be 39 mph. We were out karting this afternoon and I paid close attention to my wife climbing the hills and listened to the rpm's- it doesn't bog down any- so your fear that it might be too high a ratio may not be as bad as you think. I'd think on your big flat track that extra top end would help you walk away from your buddies in the straight away!!!

[rich1]

Originally Posted by ckau

This has got me excited! let me get a few questions straight. does your yerf have reverse? Did you actualy take the counter sprocket from the BX and install it on the yerf?
Just guessing here but another difference between the two motors may also be in the internal transmission gear ratios. The howhit's do have a low ratio internal gear set for torque while a lot of the others seem to have taller internal gears for better speed. We had a '05 carter that was a dog at take off and couldn't pull a wet noodles from a horse's a$$ but could get a higher top speed. The external gear ratios were identical. Our only explanation to this mystery was the difference in trans gearing ratios. the buggy was sold before we had the chance to pull the. trans cover to verify.
I am running a 13/31 gear set now that's a ratio of 2.39. A 16 tooth may be a touch too tall, that puts it at 1.94. I wanna stay over 2 but pick up a couple of mph. A 14 would be good, a 15 would be perfect. I kill most anybody off the line but after things get rolling it's sometimes hard to keep up. The only advantage I have at that point is handling. and just for you "VAN", driving skill!

Hey..Ive got some driving skills..Ill give you a run on the track with Vans old buggy. next weekend !

[ckau]

Originally Posted by rich1

Hey..Ive got some driving skills..Ill give you a run !

Bring your "A game!

[rich1]

Originally Posted by ckau

Bring your "A game!

Hummmmm... I dont have a A,B or C rating for my performance cuz i dont play games !

[metalstudman1]

I didn't need this and just curious if it would work.Just put it on and it does except it needs to be cut down. I'm returning this one as I ordered a 15 tooth and got a 14 tooth instead- If they send me the one I ordered then we now know you can fine tune your Howhit GY6 from 13 tooth thru 16 tooth with very little expense and effort.I'll post if they come up with the 15 tooth and provide pics.

[metalstudman1]

The supplier just called and let me know that the 15 tooth sprocket is currently out of stock and they do carry it- this resolves the idea that this sprocket was mis-advertised.