First Build, 4-stroke 3.5 hp on a Schwinn Bike

Glad you got it goin! Throttle reminds me of my Cyclops mini bike when I was a kid. Had a string tied to a frame member under the seat and to the throttle on the carb, used a rubber band off the paper for a return. Had to put your left hand under the seat and work the string while you steered one handed. Glad the rubber band never broke! Kids!! Unless I am seeing wrong it looks like you have non sealed low speed bearings on the jackshaft. I would trade em out for sealed bearings, keep well oiled at the very least!
 
Looks good! I'm noticing with your pictures your engine is a bit different than mine, but maybe some of my pictures and advice will help. The one thing I suggest doing to that engine is getting a good oil based solvent like goof off and peeling of the 100cc sticker, everyone knows it's bigger but there's no sense in rubbing the cops' noses in it :D
 
cannonball2 said:
I would trade em out for sealed bearings, keep well oiled at the very least!
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The whole jack shaft came as a kit. I think it was made for go carts and stuff like this. Yeah, i can see the bearings inside, not really a tight seal.

The collar has a groove in it now, from the bearing. The collar is supposed to keep it from moving side to side, but I noticed that the bearing has a cut a groove in it. I would think that is normal for what it does...

LS614 - "Looks good! I'm noticing with your pictures your engine is a bit different than mine, but maybe some of my pictures and advice will help. The one thing I suggest doing to that engine is getting a good oil based solvent like goof off and peeling of the 100cc sticker, everyone knows it's bigger but there's no sense in rubbing the cops' noses in it"

I found a go cart brake with a handle, but the cable's too short. It has a nice return force, so I will try to get around 70 inches of cable from a bicycle shop and bolt it on and see what happens. =)
 
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Update 2.1

I custom built an exhaust.

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Cool looking pipe...The first time I used one of these engines I was surprised at how quiet the exhaust was without any muffler at all. I'll bet the larger diameter pipe deepened the exhaust note quite a bit....boom, boom, boom!
 
Goldy said:
Cool looking pipe...The first time I used one of these engines I was surprised at how quiet the exhaust was without any muffler at all. I'll bet the larger diameter pipe deepened the exhaust note quite a bit....boom, boom, boom!
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Yeah, it has a really nice sound. A nice deep sound at idle. I will upload video when I get a chance.
 
Update 2.2

I have added a throttle!!! Finally....

I found a go-cart brake caliper and used it for the return spring.
I went to Rock & Road Cyclery and bought a long steel cable and about 70 inches of cable housing.

I then bolted the caliper to the flywheel cover, hooked up the cable (sort of), and then I rode it home. =)

Home Depot didnt have the air filter I was looking for, so I will try Lowe's sometime.

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I really like that setup Kristof! Looks good! Very clever of you, I can tell that you will be a useful addition to this forum :) your chunky exhaust is also REALLY cool :D
 
I have really bad balance, I would need a fork lift to get on the bike but it sure does look cool.
 
Hey Deacon if balance is a problem, maybe a 24incher would be best for ya. Friction drives dont care about wheel size.
 
I know I have a 26 gas a24 e bike and Im going to do a 20inch for a 3.5 hp i just got. The 25 is the only one that wants to throw me on the ground. I come across a good 24" wheel Im going to replace the rear of the 26" with it.
 
Kristof,
I did a rollout test to see what my exact ratio is & its a little different than by just doing the math.
For each 1 full revolution of my driven wheel, my clutch pulley drum turns just a hair over 9 X's.
Meaning I got a 9:1 ratio.
This ratio has my engine (Lifan 98cc 2.5 HP) running in its sweet spot. At max rpm's of ~4500, I get 50mph. It has great acceleration anywhere in the rpm range & right off the line (plenty of torque).
I just recently sent my clutch back to Max-Torque for an upgrade worth mentioning.
Jim@Max-Torque installed stronger shoes, stronger springs, a billet pulley & best of all he replaced the dinosaur oil-lite bushing with a precision cartridge bearing. Best $40 I ever spent (+$12 shipping both ways).
Do the rollout test to confirm your gearing math. I was surprised I had 9:1 & not 8.4:1
-Lowracer-
 
What ive noticed so far is that I have to be going around 18mph for the clutch to fully engage (just like the math says). It has so much torque from 19-25mph that my chain wips back and forth at least a total distance of 2-3 inches and it actually rubs against the frame and fender. At WOT I only cruise around 32mph, I dont know what to do to make it go faster.
 
Kristof,
Forget all the gearing math you did to get the jackshaft geared & all.
Just go out to your bike, get a piece of masking tape or something to mark your clutch drum. Set your valve stem of the rear wheel on the ground facing straight up & count the clutch turns as you walk your bike until the valve stem goes around once & is pointing straight up again.
How many clutch drum turns?
This is your ratio.
I'm guessing that your ratio is way off.
-lowracer-
 
Kristof,
How does that older engine of yours run?
Does it idle well & get up to max rpm smoothly?
Something is definitely outta whack.
I'm at 9:1 & 2.5hp & she takes off from a dead stop real well, then pulls hard all the way up to 50 (4500 rpm). I weigh about 168 and my bike without the engine/rack weighs 42.
Gotta be the engine if you are at 8.4:1
-Lowracer-
 
lowracer said:
Kristof,
How does that older engine of yours run?
Does it idle well & get up to max rpm smoothly?
Something is definitely outta whack.
I'm at 9:1 & 2.5hp & she takes off from a dead stop real well, then pulls hard all the way up to 50 (4500 rpm). I weigh about 168 and my bike without the engine/rack weighs 42.
Gotta be the engine if you are at 8.4:1
-Lowracer-
Click to expand...

Holy crap! 50mph, dang.

It idles really nice, I can make it idle so low that I can hear the valves opening and closing.

It goes up smoothly, except for chain whipping like crazy and grinding metal in the low 20mph. I think engine revs up to 3500rpm, It should be able to go higher.

I weigh around 185. So, 185, plus 20 lb bike, plus 35 lb equipment...
240lbs total and most of it is on the back tire...
220lbs, not including the bike
 
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I bypassed my governor but that really didnt do that much.
My engine was new when I bought it off eBay for just under $100.
New engines definitely have more power.
Pehaps your clutch is shot? Just trying to cover all the bases.
I just got to weighing both my MB's
'The Beast' weighs in at 75.6 lbs curb weight
The wimpy one weighs 48.4 lbs curb weight
-Lowracer-
 
My clutch is brand new, well its broken in now, but practically new.
If you do the math, @ 3500 rpm with my 26 inch tires and 8.4 ratio... I should be going at 32mph and thats what Im cruising at...
So, I need to raise engine rpm somehow, but I dont know how?
Adjust the main mixture screw maybe?
 
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