Predyno 99cc......the ultimate daily cruiser!
- Thread starter scotto-
- Start date
scotto-
Custom 4-Stroke Bike Builder
Motojoe2492
Member
I really like the brake rotor on the jackshaft... Have a write up on how to go about the rotor mounting? It would be greatly appreciated! I plan on doing the same to my Genesis Astra when I install my 70cc Loncin 
Not that I'm doing that well with my project it has been a slow assembly reassembly process that has yet to be completed but by the end of the week I'll likely have it capable of the task of rolling along on oil and gas. They last few items are ready to attach. I like your idea but the 4 stroke engine your installing with the GIGANTIC aluminum mount weights at least 1/2 of the estimated 80 lbs of the project I'm working on. I don't see it possible to run a large engine on a bicycle frame and wheels and not have big problems with one or the other. I'm employing out of the box 66 cc a simple jack shaft shift and a thee speed Nexus which I will mount a roller brake to eventually. I don't want to tell you your idea is misleading but I've doubt the project will work on a bicycle wheel set and worse not keep up with one that will. No less good luck I've yet to post a timed 0 mph to estimated mph video I've seen near none of those but I'll get around to it sooner or later..Anyway good luck on your build.
runnermike
Member
Scotto
I'm currently, or going to start, a Dyno build. What did you use for a rear hub? I measured the rear dropouts and its 110mm. Did you spread your dropouts to 135mm to get a disc break hub in there?
I'm only asking because I'm unable to find a 110mm disc hub besides the Dam good engineering one.
Thanks
I'm currently, or going to start, a Dyno build. What did you use for a rear hub? I measured the rear dropouts and its 110mm. Did you spread your dropouts to 135mm to get a disc break hub in there?
I'm only asking because I'm unable to find a 110mm disc hub besides the Dam good engineering one.
Thanks
scotto-
Custom 4-Stroke Bike Builder
Hey Mike,
I used the Grubee HD axle kit hub and it is 135mm spacing at least. I did spread the rear stays a bit using both feet pushing the inside of the left stay while pulling with both hands on the right stay in a seated position.
Just do a little at a time and measure as you go. It's kinda tough but don't get to carried away as you don't want to fatigue or kink the metal by going Superman on it
. A true precision way of bending the frame how you want it 
It's better to leave it a little bit snug, than having to pull it together with the axle nuts.
The reason I use the Grubee hubs is they have four sealed bearings, they are made of steel and already drilled for 36 12G. spokes and the flange or freewheel threads onto the hub keeping a fairly true running rear sprocket.
Sure they are kinda cheap and heavy, but they are also inexpensive and rather strong as well.
Motojoe2492
Member
What size is that rotor you ended up with on the jack shaft?
I can only seem to for 160mm and if I do the same as you did, I like the cleaner look of the small one.
I can only seem to for 160mm and if I do the same as you did, I like the cleaner look of the small one.
scotto-
Custom 4-Stroke Bike Builder
If I remember correctly, I cut down a 185mm rotor to about 90mm. I don't like the look of anything much larger in that area of the bike.
Motojoe2492
Member
Yeah, I like the subtle touch it adds. Does it give you any issues stopping with it that small?
scotto-
Custom 4-Stroke Bike Builder
Not at all, I leave it detuned just for a touch of braking power and let the engines compression do a lot of the braking. I dial it so you can't lock up the rear wheel.
Motojoe2492
Member
Niiice. It works that way even with the centrifugal clutch? Been a while since I've ridden anything with one...
scotto-
Custom 4-Stroke Bike Builder
Yeah the clutch doesn't disengage till around 2,000rpm when decelerating.
On my 212cc the engine braking is three to four times more powerful using the same clutch set-up. Just like a real 4-Stroke
Motojoe2492
Member
Awesome! I love it haha. I can't wait to put your ideas into action
scotto-
Custom 4-Stroke Bike Builder
Did a little work on the 99cc yesterday as I snapped a bolt on the rear hub drive. I also drilled out the main jet on the 19mm carb as it was needing more fuel with the engine modifications.
I rode to work this morning and coming home was hitting 7,990rpm! With the gearing I'm running this equates to 53.8mph.
Might just bring this bike back to the races to see what it can do....it goes really well for 99cc 4-stroke.
I rode to work this morning and coming home was hitting 7,990rpm! With the gearing I'm running this equates to 53.8mph.
Might just bring this bike back to the races to see what it can do....it goes really well for 99cc 4-stroke.
scotto-
Custom 4-Stroke Bike Builder
Yes indeed, this thing is running like no ones business.....I think it might see some track time at the end of this month, no matter who's riding it
See you there, regardless...
Well the bike made it to the track but the only person that was there to race it was me. I'm certainly not complaining because the bike was running good and it placed very well in the mid-range class overall.
Took a first place finish in the lower horsepower mid-range class and a second place overall in mid-range.....not too bad for the daily cruiser (commuter bike)!
I did change the exhaust (from long, to short) for the last 2 mid-class races and I do think it benefited a bit from that.....gave it a bit better lower-end which is good for that short track.
This bike is always fun to ride as it handles very well and cruises at a decent speed for keeping up with traffic as well as good hill climbing ability. Hopefully one of my boys can make it to the next race at Grange in October and get a taste of the fun racing of motorized bicycles.
Tony01
Well-Known Member
Is that an RLV muffler on the end of it? Does it rob much power? I been riding with an open header for a little while and its getting old. I rode to the gas station today with no helmet and the noise was appalling.
Also what size carburetor is that?
AND.!! how you like that drum brake in the front. How's it compare to a 200mm disc?
Also what size carburetor is that?
AND.!! how you like that drum brake in the front. How's it compare to a 200mm disc?
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scotto-
Custom 4-Stroke Bike Builder
Yes, that's the RLV mini and I don't feel it robs any power at all. It makes a lower, throatier tone and is much easier on the ears.
19mm carb.
That drum brake works fine and I like it a lot. It doesn't have the braking power of a 200mm disc brake.....more comparable to a 160mm disc.
Tony01
Well-Known Member
Thanks man that is great info. 19mm for a 79cc!! Wow must be a very fast bike. I been wanting to put a bigger carb on the flatty as the intake port is about 21.. I think I will go and get the 20 since the displacement is about double, but it doesn't flow like an ohv. And the disc vs drum seems there is no definite answer on the web, until now. Thanks!!