What Sprockets Are You Running?

#1
Hi, new guy here, been lurking for a few days.

Bought a barely used (original gas in the tank) Baja Racer 97cc and after doing gas n oil change, it was underwhelming to say the least.

Threw a Predator 212 on it and am very happy with the low end torque. Can ride me and my 4yr old son on the bike out in the woods at low speed and it has no problem climbing hills, going through mud, climbing over logs etc.

I love the low end grunt, but I bought the bike for a pit bike and campground runabout. Currently I'd estimate top speed around 15. That's fine by me, but it's making quite a racket at full throttle. Considering the planned use for the bike, I'd like to gear it down but not so much that it struggles with hills (mostly paved, or hardpack at the track and campgrounds) so I can comfortably part throttle cruise ~10mph or so at lower RPM. It's replacing my old 2 stroke 50cc scooter that served me well for 10 years and was more or less silent, so I'm not sure the noise level on this bike will work but thought I'd give it a try. It's a lot cheaper than a quality scooter.

Currently have an off the shelf centrifugal clutch I believe 12t, and whatever factory Baja rear is on there - 70t I believe.

Was thinking of going down on the rear to a 60 or smaller? And not really sure about the front, if I can just buy a new cup for the clutch or if you have to buy a whole different clutch. (mine's whatever the $30 3/4" keyway clutch on Amazon is)

Basics:
Small hills, 200-250lb load, want quieter 10-15mph cruising without struggling on the hills.
 
#2
i run a 12 on the clutch and a 62 on the rear. weigh about 200lbs,plenty of speed and still enough torque to pull the front wheel up if you want. The predator motors have lots of torque.
 
#3
Thanks for the reply.

Think I'm just going to keep it how it is, doesn't seem like there's all that much cruising speed to pick up from a small change, and the clatter from the clutch would increase with a larger change in gearing.

Just going to see how it is at the track in a couple weeks and decide then.
 
#4
Related question.

Would a Comet clone be another means to keep the revs down while maintaining a decent cruise speed? Or do they mostly keep the engine spinning in the powerband at all times?
 
#5
12-64 I use on a Hemi powered DB and it easily goes well over 30 mph . That is with a 15" rear tire , minimal loss of low end as well !
 
#6
Took an actual measurement, looks like overall tire height about 14.5" I thought they were 10, so I guess that makes my numbers a bit more agreeable.

Not really looking for big speed, single rear brake is a bit sketchy... dunno how some of y'all are seeing 40+mph without head tube bearings and f/r brakes.

Found the comet clones on ebay for $75ish. I'm from the twist n go scooter world (built a few crazy 2t machines, one topped out around 65mph with me at 200lbs).

Still kinda on the fence, but I'm leaning towards just leaving it. Think I'll take it to my next track weekend and see what I think afterwards.
 
#7
Threw a Predator 212 on it... I'd estimate top speed around 15....
Clearly, there is more of an issue than gearing here. 12/70= 5.8:1. 212 turning 3600rpm on a 14.8" diameter is just short of 30mph. I have a neighbor with a Azusa/212 running through 10/70 with less noise than the gardener's Honda mower.

Either the brakes are dragging or the CC is slipping. What's the story on the engine? Used,new??
 
#8
Clearly, there is more of an issue than gearing here. 12/70= 5.8:1. 212 turning 3600rpm on a 14.8" diameter is just short of 30mph. I have a neighbor with a Azusa/212 running through 10/70 with less noise than the gardener's Honda mower.

Either the brakes are dragging or the CC is slipping. What's the story on the engine? Used,new??
No, left that outta the updated posts.

New ish engine, been on the go kart for two years. Exhaust manifold worked its way loose. It's fairly quiet now, and even flat out is fine. Installed the digital tachometer this morning, looks like I need to adjust the governor because it's only hitting 2800 flat out on the street.

Really a non issue at this point. Gonna see how she does at the track in a couple weeks. If then I want more, I'll re gear. But I think if I clock the governor to 3500ish I'll have plenty top end (it's not bad wherever I'm at right now, but noticeably slower than my old scooter) and with the exhaust tight, it's tolerable.
 
#10
Add a TAV-2 clone from Amazon or Ebay for $100 or so.. Gobs more torque, more top end! Smoother & less chatter compared to your clutch setup.

Be prepared, additional torque will throw your son off, & possibly you too!
 
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