79cc Predator Build
- Thread starter Kletus
- Start date
TheNecromancer13
Active Member
How's the acceleration? Judging by your gearing you might have some trouble. Also you might want to secure that exhaust pipe a bit better or it will eventually break from metal fatigue caused by the vibrations.
Acceleration is poor up to 25 MPH then it starts to turn on. It hits the governor somewhere between 43-45 MPH. The engine is box stock. Might need to go to a 46-48 tooth rear sprocket. Speaking of that exhaust, Its a header I ordered from EBAY. It burnt my leg when I pointed it towards the rear so I turned it around. The extension is a weed eater wand with a 3/4 inch elbow and a muffler I ordered from EBAY. This bike started out as a Gasbike GT80. I wish I had known about "That's DAX" before I bought that crappy thing. The bike is a Micargi Huntington Beach Cruiser and the mirrors are stock Harley Davidson take offs my next door neighbor gave me. The vintage speedometer I bought from this guy on Ebay. http://www.ebay.com/itm/stewart-war...931131?hash=item3ae38f6e7b:g:xm8AAOxyHE5RquUL It is very close to my digital speedometer. Not bad for 50 bucks and free shipping. This bike is a work in progress. Thanks for the tips.
TheNecromancer13
Active Member
I find that about a 13:1 gear ratio works well for me. I'm 155 lbs. Also you might consider switching out the #35 chain sprocket instead, as it will be much cheaper to replace. Also why not remove the governor?
TheNecromancer13, All the engine drive chains are #415. I have a 46 tooth sprocket that I want to try before I buy anything else. I may remove the governor at some point if the top end speed is to low. I am waiting on a Max Torque six shoe clutch to arrive. Then I will install it along with the 46 tooth rear sprocket and see what happens. All critiques and advise are welcome.
Best Regards
Best Regards
Tony01
Well-Known Member
Put a green spring, or black spring with 6 heavy shoes in your max torque clutch, will help your takeoff.
TheNecromancer13
Active Member
If you need info on governor removal or gear ratios, or pretty much any other aspect of 79cc motorized bicycles, here's pretty much everything I know: http://www.instructables.com/id/79cc-Motorized-Bicycle-From-Scratch/
Potato_In_Exhaust
Member
That little 49cc 4 STROKE ain't gonna hit the 45 mph mark!
culvercityclassic
Well-Known Member
Says 79cc Predator Build PIE, that will do 45 with the right setup...
Tony01
Well-Known Member
Nobody wants to turn it 6k tho, its only a predator
Potato_In_Exhaust
Member
The Original Thread Starter has a stock motor and he claims to do 45 mph. I mean, come on! On a little 79cc 4 stroke motor no less. Even with a 212cc Predator motor hitting 45 mph stock is hard to believe!
TheNecromancer13
Active Member
If you're hitting 45 you're going to burn up your clutch on takeoff really fast.
culvercityclassic
Well-Known Member
Pie when you going to step up and meet some of us? I am a newbie so I am still learning a bit form the post, Tony has helped me too.
Yeah, I really have to baby it till it reaches 25 MPH. If I don't the whole bike shakes and vibrates. Feels like the clutch is locked because the engine really labors. The magic number is 25 mph then I can give it throttle. When it hit 43-45 mph I was on a long level stretch with a light wind to my back. I like the low RPM's at 30 MPH but I'll probably increase the number of teeth to 36 on the rear sprocket to improve the low speed performance. My Max Torque six shoe clutch came Saturday and then I found the 415 chain was to narrow to fit on the #41 clutch sprocket so now I am awaiting the #41 chain to arrive.
TheNecromancer13
Active Member
What tooth counts are you running on your sprockets right now? I run 11-36 on the first stage, and 9-36 on the second stage, and I top out at 38 mph with the governor removed and some other performance mods. However I can take off from a standstill if I need to (although it shakes a lot until about 8-10 mph, so I usually pedal up to 8 before giving it gas), and can climb almost any hill without pedal assist. I weigh 155 lbs. I have found that for my weight, the sweet spot for speed and acceleration is between 13:1 and 14:1, right now I'm at 13.1:1. My friend who I built a bike for weighs 180, and on her's we did 14.7:1 which seems to work well, although she tops out at about 34.
I'd suggest instead of switching out the rear sprocket, you switch the first stage driven sprocket for a 36 or 40t, the current one looks like about a 22t, which means you'd have to run something like a 50t or 60t rear sprocket to get decent acceleration. Also remove the governor, it does wonders and isn't that hard.
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TheNecromancer13
Active Member
Is the first stage #35 or #41 chain?