building shift gearing

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old motorbike

old motorbike

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Haven't been around for awhile, but keep my motorbikes going.

Have an in frame CAG single drive 26" that I'm building a shift kit for.
I'm looking for an average gear ratio that would be good for a start.

I'll have 3:1 trans, 2:1 to jackshaft, 4:1 to front sprocket.
If I figure right ?, I guess that's 24:1? I'm not good at math!
Then about 1:3 (depending on which gear it's in) to back wheel.
Which would be 8:1?
Don't know how to figure rear wheel rpm, It's an 80" circumference.

That seems like it may not be geared down enough?
would like to keep engine to 3-5k for cruising at about 35mph.

Thanks for any help.
 
old motorbike

old motorbike

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Sep 21, 2008
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Would like to fab this like the SBP shift kit only using a cag engine.
The main reason (other than just fun) is to reduce the rpms for less vibration while cruising and better acceleration. The drivers here will just run you over if you're not fast enough say from a red light. (Then I'll see how long the bicycle chain lasts).

My other bike takes off fast with a cvt, so I can dodge the cars out there.
.duh.
 

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old motorbike

old motorbike

New Member
Sep 21, 2008
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Thanks Dan, For being kind enough to respond. It's always good to see your smiley with the aviators hat and goggles.
I was beginning to doubt of this being of any interest to anyone here.
Parts still coming. New headlight also.
 

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Dan

Dan

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May 25, 2008
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Looks like she is a really comfortable ride. Really like the muffler. DIY? I had just made one out of EMT, electrical conduit. Worked well enough all bolted together. Then got a welder, wohoo, is that thing fun. Just learning do welds are fugly but hold well. Used a plumber's blow bag at the end. Silly dang looking thing. Hope to be able to make one like yours some day. Vid of mine. RiverSide :: whisper drive/HF Engine/clog-Free muffler video by dan3xd - Photobucket

Wanted to ask you about your wheels and fenders. Looks awesome. Whole bike does.
brnot
 
Dan

Dan

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May 25, 2008
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Meant to say OMB, even when no one replies, ya are helping some one. I looked and 75 folks had read your post with out saying any thing. Ya gotta know at least one is some one brandy new to this or wrestling with a problem you found a fix for, and they were shy or worried about asking a "dumb question" So even if ya feel like no one is paying attention, some one is and you helped em. Even if it is just the huge, cool thought of "I could do that"

Yeha! 4 day week end coming! Nutton to do but tinker an' play. We got it good. Happy ThanksGiving!
 
silverbear

silverbear

The Boy Who Never Grew Up
Jul 9, 2009
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I know the feeling about not getting responses. I think part of the problem is that your power unit is different and the set up to transfer power to the wheel sounds complicated. Most here want things super simple and super cheap and super quick using a happy time motor. Also I think sometimes people don't realize that posting a how to thread is time consuming and takes a lot of effort, so it is not appreciated unless they do the same... take the time to take pictures as they go along, explain things, etc. But Dan is right, down the line someone is going to benefit from your sharing and will appreciate what you've done. Both of your builds are interesting and different from what I have know anything about. Your new one sounds like it will have a lot of power. It sure looks good.
SB
 
old motorbike

old motorbike

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Thanks Dan and Silverbear. I really like to play with motorbikes with a passion.
The last one I built (the blue one) must have posted the whole build and no responses. I thought I was too dumb to post on here or everyone was just interested in other certain kinds of bikes. Until I met NEAT TIMES.

After building my first China Girl I wanted something with a little more power.
The cag 2 stroke fit the bill and when available the cvt. Now wanted to do a cvt on the in frame but they've been cancelled. The idea struck me a few weeks ago to make a shift kit.

Either it was gear for acceleration and vibrate at cruise or no accel and cut down on vibs.

Now since I lost my last job, I've had more time to play with this project but no funds. Getting parts a little at a time, with some odd jobs.

THANKS for the encouragement and support.
My prayers are to be useful..shft.
 
old motorbike

old motorbike

New Member
Sep 21, 2008
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Dan said:
Looks like she is a really comfortable ride. Really like the muffler. DIY? I had just made one out of EMT, electrical conduit. Worked well enough all bolted together. Then got a welder, wohoo, is that thing fun. Just learning do welds are fugly but hold well. Used a plumber's blow bag at the end. Silly dang looking thing. Hope to be able to make one like yours some day. Vid of mine. RiverSide :: whisper drive/HF Engine/clog-Free muffler video by dan3xd - Photobucket

Wanted to ask you about your wheels and fenders. Looks awesome. Whole bike does.
brnot
Click to expand...

Thanks Dan, Got the pipe and mufflers from e bay pocket bike parts (cheap)
It also had to be cut and welded to fit. Same, I got a wire welder from Harbor Freight and do "bubble gum" welds.
The bicycle was donated by a local Bicycle shop (an old beach rental bike)
I traded him work on his motorcycles for wheels fenders tires, etc.
The fenders are the cheap plastic universal. Wheels and tires were some he had laying around.
Nice videos
 
BarelyAWake

BarelyAWake

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Jul 21, 2009
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I'll freely admit I've been lurkin' this thread & not commenting - problem is, like silverbear said, it's jus' so decidedly different that while awesome - I haven't the slightest idea how to help ya lol

With the DIY builds in particular you'll get a lotta views and not a lot of comments, on the other hand you are definitely inspiring others with new ideas & I bet there's a buncha folks waitin' ta see how it turns out for ya, I know I am - the gearing for example. While I can't help you with the ratios, I agree that gearing a bike results in a night and day difference! The comfort factor alone is worth it without a doubt, but I don't think you'll hafta sacrifice that to gear for acceleration with six speeds available BTW, you'll prolly be able to have both... but I don't really know 'cause I dunno that engine lol, but I'm pretty close w/just a three speed (HT engine ofc). I can tell ya that the 3/32" 1/2" chain can and will hold up, so long as you have a decent one.

With the ratio questions, have ya asked Jim at SBP about it? I'm building a DIY jackshaft using some of their components and TBH I just cheated and asked him & he was happy to help.
 
5

5-7HEAVEN

Well-Known Member
Aug 2, 2008
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old motorbike said:
Thanks Dan, For being kind enough to respond. It's always good to see your smiley with the aviators hat and goggles.
I was beginning to doubt of this being of any interest to anyone here.
Parts still coming. New headlight also.
Click to expand...
Interesting build for sure! I love your frame-mounting plate for the CAG engine.

I know EXACTLY what you mean about doubting interests in your project. In another forum, I have a thread with over 5,500 views and 150 threads. LOL, most of the threads are my own. Like yours, my project is not your normal engine/bike/transmission, but a frame-mounted GP460 5hp+ with shift kit. Problems that arose were project-and-engine-specific. I was lucky that Detonator Tuning had pioneered a similar project.
 
5

5-7HEAVEN

Well-Known Member
Aug 2, 2008
2,661
240
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old motorbike said:
Haven't been around for awhile, but keep my motorbikes going.

Have an in frame CAG single drive 26" that I'm building a shift kit for.
I'm looking for an average gear ratio that would be good for a start.

I'll have 3:1 trans, 2:1 to jackshaft, 4:1 to front sprocket.
If I figure right ?, I guess that's 24:1? I'm not good at math!
Then about 1:3 (depending on which gear it's in) to back wheel.
Which would be 8:1?
Don't know how to figure rear wheel rpm, It's an 80" circumference.

That seems like it may not be geared down enough?
would like to keep engine to 3-5k for cruising at about 35mph.

Thanks for any help.
Click to expand...
Yes, that is 24:1, which is a good start. My ratio at that point for my GP460 engine is 28.64:1...

You also need a good pedalling ratio, so an SBP 30-tooth inside chainring connects to an 11t-34t rear cassette. Your pedalling ratio is inversely proportional to your engine gear ratio. With this 30t chainring, it will be very easy to pedal, and your engine will especially love the 34t sprocket from a standing start.

Here are your ratios, comparing my 28.64:1 gear ratio to your 24:1 starting point:

First gear-34t.....32.46:1.....yours is 27.2:1.....
Second gear-26t.....24.92:1.....yours is 20.8.....
Third gear-23t.....21.95:1.....yours is 18.4:1.....
Fourth gear-20t.....19.09:1.....yours is 16:1.....
Fifth gear-17t.....16.23:1.....yours is 13.6:1.....
Sixth gear-15t.....14.32:1.....yours is 12:1.....
Seventh gear-13t.....12.41:1.....yours is 10.4:1.....
Eighth gear-11t.....10.5:1.....yours is 8.8:1.....

Your engine needs more rpm at 35mph, maybe 6200rpm, using 5th gear.
 
Last edited:
Russell

Russell

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Apr 19, 2009
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Yes I am another watching your post but posting. Mostly because I am not ready to attack my next project.(have a cag 2cyc with a cvt sitting for a year now ). I will be looking even closer at your thread once I start.
Keep up the good work.
 
M

meerkatt

New Member
Nov 4, 2010
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oxford
Just a little concerned that you wanna run a cag at those revs. I have not seen a cag make enuf power to pull a petal off a flower under 5000rpm and torque is pretty much pathetic down low too. I know your reduction box & jackshaft will help with torque but they do eat horses. I wonder if you cant go bigger on yor crank sprocket?
My 2cents, if ya reckon you got the ponies to get away with it I would love to see it. Oh ,and that u join before your mufflers looks cool but any pb/minimoto/cag freak will tell you youre throwin away horses there too, very restrictive.
 
5

5-7HEAVEN

Well-Known Member
Aug 2, 2008
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meerkatt said:
Just a little concerned that you wanna run a cag at those revs. I have not seen a cag make enuf power to pull a petal off a flower under 5000rpm and torque is pretty much pathetic down low too. I know your reduction box & jackshaft will help with torque but they do eat horses. I wonder if you cant go bigger on yor crank sprocket?
My 2cents, if ya reckon you got the ponies to get away with it I would love to see it. Oh ,and that u join before your mufflers looks cool but any pb/minimoto/cag freak will tell you youre throwin away horses there too, very restrictive.
Click to expand...
Can you explain why you would want a bigger crank sprocket?
 
M

meerkatt

New Member
Nov 4, 2010
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oxford
just to get the revs up. most cag clutches dont kick in till 6k, racing clutches are often set to 8000rpm , thats where the ponies live. unlesss you run really light springs youll get nowhere and burn clutches at 3-5k
 
old motorbike

old motorbike

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Don't know about how high the stall rpms are on the clutch. Guess about 4-5k to lock it.
The stock motor really has a lot of torque and could use weaker springs in the clutch. right now I have 1 spring stretched out so it can stall at lower rpms.

I'm going to try to take a video today with a gps and see what it's doing.

Did get the shaft, bearings, key way and have some of the sprockets and chain.
 
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