Schwinn High Timber hi speed build

[graydog8josh]

I have a schwinn High timber 26" bike with:
26 x 1.95 semi slicks
415 chain with 41t sprocket and rag joint
thatsdax premium f80 engine 66cc(60 something cc)
upgraded chain tensioner with a 10t sprocket off ebay
nt carb, stock jet size #70, clip is in center position
low profile SBP air filter
the intake i modified with a 90 deg copper pipe jb welded to make the motor fit in the frame
ngk iridium bpr7hix plug SBP
BGF expansion chamber
I have the tank double bungeed to a rear rack due to issues with cable routing.

Ive seen reports of speeds ~ 35-40 mph but i can only squeeze on 28 on the flats and the engine will get me to 33mph top downhill screaming bloody murder.

1: What can I do to hit my targeted high 30 speed goal?

2:will a #41 chain increase my top speed?
3: will a 24 x 1.75 tire and 24" rim increase my top speed?
4: will changing the carb jetting increase my top speed?
5: how about taking the dremel to the intake pipe?


As is, it runs rather smoothly, it just lacks that top end I feel would make me comfortable in town. Not trying to break any land speed records, just want 35 mph WOT on flats.

oh yeah, and im running 91 octane pump gas 20:1 mix.
I weigh 190lbs.

 

[graydog8josh]

http://motorbicycling.com/archive/index.php/t-12717.html

 

[graydog8josh]

I'll just chuckle if you tell me to lose weight. Im built like a footballer, unless i lay in bed for a year im not going lower than 180lbs.

 

[Ilikeabikea]

Just burn regular gas and go to 32:1 mix. You are running to much oil..

 

[biknut]

These are my recommendations

Get a 36T rear sprocket. I can run 35 mph with mine. 30-33 is easy cruise.

You're running too much oil. 28:1 is good enough for break in. After that follow the oil manufacturers recommendation, or at least 32:1. Most synthetics run about 40:1 or higher.

Rejet you carb. Assuming you have an NT, try a 68, or 66, with the needle clip in the second from top position.

Try a NGK BP6HS spark plug. In winter you can run BP5HS.

That should get you to 35 mph.

My Flying Horse 80 motor is basically stock, but it has a Speed carb, with shorty intake manifold. A modified exhaust, but still as quiet as a stock muffler. Nothing done inside the motor. For the record I weigh 230, and my bike weighs 57 lb

 

[2door]

How many miles/gallons of fuel does the engine have on it? You will not get top performance on a new engine or one with less than a couple of hundred miles. Give it some time. They aren't easily broken in.

As for the rear sprocket, yes the smaller, 36T will increase your top end but if you have hills to climb you might have to pedal assist if they're steep.
All of the other suggestions given above will help but run that little guy some before worrying too much about performance.

Keep an eye on your intake manifold. It's going to fail eventually.

Tom

 

[graydog8josh]

here are pictures of my jb weld job on the carb.

Does anyone have any hard data on how much opening up the intake tube from stock improves top speed or torque or hp or anything?

I think i might take the dremel to it.

 

[graydog8josh]

How many miles/gallons of fuel does the engine have on it? You will not get top performance on a new engine or one with less than a couple of hundred miles. Give it some time. They aren't easily broken in.

As for the rear sprocket, yes the smaller, 36T will increase your top end but if you have hills to climb you might have to pedal assist if they're steep.
All of the other suggestions given above will help but run that little guy some before worrying too much about performance.

Keep an eye on your intake manifold. It's going to fail eventually.

Tom

I have ~ 200 miles on this engine.

I would prefer not to have to pedal uphill.

what horsepower do these motors make? I saw a post where someone was making 8, doing the hybrid thing, is that reliable?

 

[graydog8josh]

"Get a 36T rear sprocket. I can run 35 mph with mine. 30-33 is easy cruise."

who makes the best 36t? is kings the best. Are the aluminum sprockets pretty high quality? I just bought the 41t from dax because i thought that would be the most the motor could handle.

"You're running too much oil. 28:1 is good enough for break in. After that follow the oil manufacturers recommendation, or at least 32:1. Most synthetics run about 40:1 or higher."

My new tank of gas is 32:1, so maybe ill see something change


"Rejet you carb. Assuming you have an NT, try a 68, or 66, with the needle clip in the second from top position."

Ive got a 66 from SBP in the mail. when i rejet it will change my needle position? I definitely cant get it to run smoothly on any position but the center right now.

 

[2door]

8 horsepower is more a myth and wishful thinking on someone's part. The Chinese 2 stroke is designed to produce somewhere between 2.5 and 3 horsepower in the stock configuration. 8 horsepower? I doubt it. Consider that you're dealing with 66cc of displacement and a vehicle/rider weight of about 300lbs. Properly tuned and geared you will probably be in the 25 to 35 mph range. That's normal for these bikes and the engine you have.

One thing you MUST keep in mind. It's a motorized bicycle, not a motorcycle. That's a distinction that is hard for some to understand. Your bike is 'motor assisted' and that means in some cases the pedals will be needed. Up hills is possibly one of them unless you gear for them. But if you gear for hills, your top end speed will suffer.

Tom

 

[graydog8josh]

http://motorbicycling.com/showthread.php?t=14204&page=6

this is the thread i was refering to.

 

[biknut]

here are pictures of my jb weld job on the carb.

Does anyone have any hard data on how much opening up the intake tube from stock improves top speed or torque or hp or anything?

I think i might take the dremel to it.

"Get a 36T rear sprocket. I can run 35 mph with mine. 30-33 is easy cruise."

who makes the best 36t? is kings the best. Are the aluminum sprockets pretty high quality? I just bought the 41t from dax because i thought that would be the most the motor could handle.

"You're running too much oil. 28:1 is good enough for break in. After that follow the oil manufacturers recommendation, or at least 32:1. Most synthetics run about 40:1 or higher."

My new tank of gas is 32:1, so maybe ill see something change


"Rejet you carb. Assuming you have an NT, try a 68, or 66, with the needle clip in the second from top position."

Ive got a 66 from SBP in the mail. when i rejet it will change my needle position? I definitely cant get it to run smoothly on any position but the center right now.

First off, you need to junk that manifold. That's costing you half your power. Measure and see if a shorty will fit. All you need is 4 1/2" from your cylinder flange to the seat post tube. If that won't work you'll need to buy an offset manifold.

I assume you're using a rag joint for your rear sprocket. Check with kings and ask it they have sprockets that are compatible with a stock rag joint. Be sure and let them know how many bolt holes you have. Their sprockets are very high quality, and will last a long time.

It's ok to make your own intake gaskets. You can buy gasket material at a auto supply. I would try changing the needle right away since it doesn't cost anything, and you don't need any parts to do it, but I wouldn't expect much with your crappy intake. I'm running a 66 jet in my bike, and it will probably work for you, but keep an eye on your spark plug at first to make sure it's not too lean.

With a 36T you will be able to pull up a moderate hill, but steep long hills may need pedal assist.

This is what a 40T sprocket would do for you. I have this gearing at one time and I could cruise easily at 26-30, and top out about 33-34. More than that was screaming the motor.

RPM MPH

1000 4.7
1200 5.7
1400 6.6
1600 7.6
1800 8.5
2000 9.4
2200 10.4
2400 11.3
2600 12.3
2800 13.2
3000 14.2
3200 15.1
3400 16.1
3600 17.0
3800 17.9
4000 18.9
4200 19.8
4400 20.8
4600 21.7
4800 22.7
5000 23.6
5200 24.6
5400 25.5
5600 26.5
5800 27.4
6000 28.3
6200 29.3
6400 30.2
6600 31.2
6800 32.1
7000 33.1

This is what a 36T will do. This is what I have now. I can cruise 33-35, and top out about 38.


RPM MPH
1000 5.2
1200 6.2
1400 7.2
1600 8.3
1800 9.3
2000 10.3
2200 11.4
2400 12.4
2600 13.4
2800 14.5
3000 15.5
3200 16.5
3400 17.6
3600 18.6
3800 19.6
4000 20.7
4200 21.7
4400 22.7
4600 23.8
4800 24.8
5000 25.8
5200 26.9
5400 27.9
5600 28.9
5800 30.0
6000 31.0
6200 32.0
6400 33.1
6600 34.1
6800 35.1
7000 36.2

 

[graydog8josh]

I ordered the offset intake. I didnt think that the bottleneck in my system was the intake since i used a larger diameter pipe, but that will be fixed by monday.
also, when my 66 jet comes in I'll have that on as well.

the 36t sprocket too.



I'm pointing towards the china/puch hybrid thread because i was hoping i could mod my top end when i have some shop time to get the motor to rev higher safely and push my 33-35 speed off of the rev limit.

I also noticed when reading that the originator foureasy doesnt post on here much anymore... so i thought maybe someone would have comparable knowledge about his findings with the two stroke rebuilds.

one more thing. I stumbled upon this while researching the jaguar cdi. My instruction manual with the first motor says to hook the kill switch up to the white wire and to ground, while everything else in the world says that is an auxillary low voltage for lighting. What is that doing? It kills the motor so it works, but i dont think its doing it the way its supposed to. Can someone explain this phenomenon to me in detail?

 

[biknut]

one more thing. I stumbled upon this while researching the jaguar cdi. My instruction manual with the first motor says to hook the kill switch up to the white wire and to ground, while everything else in the world says that is an auxillary low voltage for lighting. What is that doing? It kills the motor so it works, but i dont think its doing it the way its supposed to. Can someone explain this phenomenon to me in detail?

Hooking the kill to the white, or blue wire has about the same result. It shorts the magneto windings together. We're talking dead short. This isn't a very good way to kill the motor, but it's a pretty good way to kill the magneto coil lol. I assume the reason for recommending the white wire over the blue one is because it may subject the coil windings to less current when you hit the kill button.

When the motor is running, the magneto coil makes heat. Hot weather will make it even warmer. When you hit the kill button, it shorts the magneto winding, which takes power away from the CDI killing the motor. The problem is that as long as the motor is turning, the coil makes some power. Before the motor stops completely it momentarily subjects the magneto coil windings to high current. There's danger the coil windings burn up. It's probably not as much a concern in cooler climes.

SBP sells a kill switch which is a rocker switch. It allows you to wire the kill differently, where you can open the circuit to the CDI instead of shorting the windings together. It's a good option to consider if you live in a hot clime.

 

[graydog8josh]

SBP 66 AND 72 Jets just came in the mail. Found a hardware store with metric stuff too. Its a good day for me.

 

[graydog8josh]

Does anyone else have problems with the clutch being loud. I thought i would try using this rustoleum i had laying around on the clutch plate. I can be riding around and if i put a finger on the plate it instantly quiets down.

Took my carb off about to change the jet.

Also trying to press in the new clutch pucks i bought a while back when my bike got moist.
hmm, will i get a performance boost today before dark?

 

[graydog8josh]

oh and i also greased various points on teh bike. I couldnt remember where in teh clutch you're supposed to have grease, mine is always real loud. I got the 3 pins oily but didnt coat them in heavy grease. I cleaned up and regreased in heavy grease the 10 t sprocket and the little and big wheels. Also used this chain lube on my cables and tried to get up in the cable housings.

Does anyone have a good way to grease the bearings on the "flywheel" i guess?
Im afraid of spraying lest i get grease on teh clutch pucks, so i just get a tiny drop on a tooth brush and try to force it in while wiping it off quickly.
Also, what is the correct lube for the flywheel bearing.
Not that i can get to them anyway, i dont want them to all spill out, and i dont have an impact driver to take the whole thing apart.

 

[biknut]

The clutch gear has a big bearing that has something like 40 to 50 balls in it. You can squeeze grease into the crack on the gear with your finger.

A better way to grease that bearing is to remove the clutch gear off the transmission shaft. On the back side are 3 holes. You can use a grease gun to inject grease into the 3 holes.

That will go a long way making the clutch quieter. Some of them are just noisy though.

 

[graydog8josh]

Just got home from a day riding. bike is more comfortable at speeds of 30-31 now on the flats with the 66 jet and moved the needle up to 2nd slot.

However, had not gotten to putting on the 36T yet. eagerly awaiting the speed boost from the 41T to the 36T.


Also, per strong suggestion, put on the BGF z intake, and after some caressing with the dremel was able to get it on. It does sit better in the frame, i no longer have an air filter in my knee while peddling, but i had to remove the SBP low profile air filter and put back on the NT snorkel looking filter.
I included a picture of the 10T idler sprocket i bought , it seems to be much smoother than the roller.

So... put on the 36T tommorrow
figure out if the air filter matters
Head questions... is the straight up 8mm head better than the 8mm slant head?
Also, can i achieve similar tuning to the SBP expansion chamber by chopping and lengthening my BGF banana?

 

[biknut]

Looks like you're getting there now. Good job.