Building a Ht Motorized Bicycle or Three.

[Theon]

Give us some pics Sub,
Two stroke exhaust systems have me enthralled,
I have a few ideas for exhausts, but moding a dirt bike exhaust was pretty easy, and I figure they know what there doing, as the dirt bikes are built to compete against each other.
But a nice pipe don't just make your bike go better, you can hear it's going better.

 

[Davezilla]

I agree on the pipe... You can definitely hear the difference between a good pipe and one that just lets the exhaust out...
My opinion is the same about the dirtbike pipes, they're designed for a wide powerband instead of something like a road race pipe that just needs to make max power.

I got another set of plans for my other engine when it comes to gearing it as well. Since we only have one speed and we need to make the best choice for what our road conditions are, we usually end up gearing lower for areas where there are a lot of hills etc, but if we live somewhere nice and flat, we can gear for higher speeds and give up some acceleration.
My solution for this is to use a pocketbike CVT transmission and gear the bike to reach around 40 to 45mph at max power, the CVT will reduce the gearing so small hills won't be a problem and acceleration will be much better. I ordered this one... http://www.partsforscooters.com/CVT-Transmission?sc=33&category=132687&whence= and will need to make an adapter plate as well as use the centrifugal clutch they make for these engines. The rear shaft sits further back than our clutch shaft so it's going to take some minor fab work in this area too as well as beefing up some of the CVT parts so it'll last. The transmission it's self seems to be able to handle the stress our engines put out but the front outer pulley and the rear inner pulley will need some more metal welded in and then the variator weights may need to be modified to be a little heavier or lighter once it's all installed and rideable. I'm in no hurry to get this done and I'll most likely buy another set of empty cases to do my initial mods to but I should have that setup operational by the end of this summer, I just need to take my time and measure twice cut once etc, but it should work. I've seen these same CVT units connected to a 125cc 2 stroke and do just fine so it should hold up to my engine once a few beef up mods in the right places are done.

 

[sub66]

on the pipe it sounds like the sbp. below that it sounds like an airplane. it has the backpressure for top rpm and more low end. thinking that cant work is ridiculous copycatism.

i dont know how to make it simpler. ogh well......

dave the cvt sounds wide. it wont fit my 2000 dollar dirt jumper w a boutique frame.

 

[Theon]

Very curious about the CVT,
Have wanted one for a while for my CAG Tadpole.
But can't find one in OZ and don't like paying extra shipping from the states.
Will you run it at engine RPM?
As the clutch shaft has 4 to 1 reduction.
It could get a little bulky hanging of the side of the motor.
Not doubting you Dave, just can't picture what you have in mind.

 

[Davezilla]

Ok, on the CVT, here's what I'm going to do, I'll need to run it at engine RPM since it's designed to run in that rpm range to begin with, This means I can eliminate the clutch system on the engine all together. the cases will need to be cut and modified with some plates to hold a set of bearings and the sprocket shaft extended, or a separate jack shaft to get teh power from the right side of the engine to the left side etc... I'll have to figure that part out, but I got a real good idea how to do it. I may even take the pulleys etc off the frame and make my own plate to mount everything to make the install easier and more compact, but it looks like I can use a centrifugal clutch that's for the China Girl engine to send the power to the variators, then plate mount the transmission system with bearing supports on each side of the engine for the sprocket shaft, I want to avoid welding onto the sprocket shaft so I may incorporate a jack shaft which would give me a little more gear ratio control. This is still in the infant stages where I'm designing a mounting system to fit this CVT to the China Girl engines so I ordered the centrifugal clutch kit so I can use the clutch and see if those housing bolts will line up with this transmission, and if it'll be a strong enough connection if it does line up. From the looks of both setups, it may bolt right up, but need some reenforcing brackets.

For the 4:1 ratio from the engine's clutch shaft, the CVT has a small gearbox that also turns at 4:1 so this ratio will still be there except that the gearing will start at around 10:1 then spool up to just under 4:1 so the final ratio will be close to what it was before the CVT. The CVT will overdrive just a little so I can keep the same gearing on the final drive as well and have the same effect as a slightly smaller sprocket at higher speeds when the load on the engine is lighter like on a flat straight aaway or going downhill etc. The transmission also reverses the rotation direction just like the clutch gear does so there won't be a problem there either.

 

[Davezilla]

The pocketbike CVT's are hard to find over here too, it seems that they were made for the x-1 (and maybe the X-2 and X-3) pocketbikes, but not all of them have the CVT, most of them came with the chain driven transmission which is pretty much junk. I see them on ebay from time to time, but highly overpriced at like $189 or so, then the same seller has them at his regular online store for $109. I got mine from Amazon.com for $79 and there are a few other scooter sites that carry them for $79 to about $110, not sure if any scooter shops in OZ have them or if they can get them without the super high shipping price.

 

[Theon]

Sounds really cool.
I like CVT.
And still want one for my tadpole.
I've really got to get this Goat finished, then the Tadpole is coming back to the shop.
Shift kit really sounds a lot easier than what you have planed for the China girl, But the CVT should get you some good take off power especially if you have an adjustable clutch.
Get the revs up to 3000+ before the clutch cuts in and she should 'spool up'.

 

[Theon]

I have a worn out chain box for my Tadpole, It looks as though it should fit.
I've been trying to limit my spending, but I think I should go this way, looks as though shipping to OZ through Amazon is reasonable.
Would certainly improve the drivability.
I was going to use a 3 speed nexus, but this would be much better.

 

[Davezilla]

pardon me i lost my cool for 20 minutes.

dave w that work w a 4inch fat tire or remain tucked in?

is all the work normal for cvt or is yours different? whats the story?

thanks what else u got lol?

Don't worry about it, there's a reason I didn't repost a few hours ago...

The deal is that this CVT isn't made for these engines, but they are the smallest CVT transmissions that I know of that can handle the power these engines are capable of, I'll still need to beef up the outer pulley but that's not too hard to do.

Here's the good... they have the same 4:1 ratio at full rpm and light load, fairly inexpensive, small but tough, the final drive transmission reverses the rotation direction just like our clutch shaft does, Gives the ability to gear higher for speed without loss of acceleration, or gear lower for climbing with massive low speed torque. Allows the engine to be tuned for more top end rpm and power and still be able to accelerate from a dead stop. the ratio range of the variators goes from about 2.5:1 up to about .9:1 so that's like running a 90 tooth rear sprocket from takeoff and a 40 tooth at speed using a 44 tooth, I'll be using a 32 tooth once I get this working so it'll be more like going from about a 70 tooth to about a 30 tooth depending on engine rpm and load. Once the variators are tuned to the bike and rider it's easy to keep the engine in it's powerband, adding or subtracting weight at the variator effectly changes how and when it spools up or gears down so if it's too boggy going up the hills, just lighten the weights, or if it can't reach "top gear" soon enough, just add a little more weight etc...

The Bad... It's about 4" wide at the crank pulley side, I may need to shorten the shaft and ditch the case in favor of a 1/2" thick aluminum plate (more fab work) or make up some mounts to offset mount the engine/trans so it don't stick out too far. The sprocket shaft is a different distance compared to our clutch shaft so cutting the engine's cases in the back and adding some plates and carrier bearings will be needed. The sprocket is on the wrong side so either extending the sprocket shaft and adding a support bearing or running a jack shaft is needed. The clutch drum might need to be custom made if it doesn't fit with the China Girl's centrifugal clutch kit.

In other words, there will be a certain amount of fab work that needs to be done before it'll fit and work as well as be dependable
This definitely won't be one of those "bolt on and go" type mods and will probably take me some time and trial & error to make and gather the parts to make it all work. I'll definitely post the whole process once I get started on this project.

 

[Davezilla]

My other idea was to try and use one of those Nuvinci cvt rear ends but I heard they aren't that tough, and still need to be "shifted" manually... but that or a shifter kit would be Much easier than what I'm gonna try to do...

 

[Theon]

You've certainly got yourself a project, but I like it.

 

[Theon]

I've been getting a little done this morning on my case induction motor, photos are better than words.

 

[sub66]

i see it now dave. it would likely look amazing and fast.

i have a variable speed hydro diff on the back of my 15hp lawntractor. im leaning towards that now that we speak of gears. it looks a decent size if u have an imagination. monkeys could do it lol lol. input/ output done.

theon it looks great. use 2-4 times the area that seems logical w loaded jb. cant wait for the next set of pics.

where is ur port heights at bro/ i am doing mine today aswell. i could copy u and we could compare stuff. i was just about to ask u to pick my port heights anyway
im up in arms/ u might as well choose. if that sounds fun to you.... i have a 47 by 38 gt5 cyl.

 

[Theon]

Probably not the cheapest option, but I'm going to use an RSE 4 petal reed bock, modified to suit my brass reed cage,
They are so pretty.
And quite close to what I need.

 

[sub66]

can i cut the skirt off flush w the base? just curious?

 

[Theon]

Shorten piston skirt?
Depends on exhaust side, probably want to keep them similar length.
Port timings?
Can't remember exactly, think I was aiming towards ex opening at 102.
More pics.

 

[Davezilla]

Your reed system is really looking great, now that I see the JB in there it definitely looks like it's going to work as well as last a long time. Are you going to tap the threads into the JB and the aluminum below it or do you plan on running countersunk screws from inside the case?

I'm going to copy the JB Weld part of your idea on mine, now that I see it, I like it.

 

[Theon]

Have taped the threads OS and put two helicoils in each hole.
Worked well, thread was a little tight, but ran a tap through after helicoils and has 'straightened things out'.
My set up will take a DLE 60 reed and block, but I want to try my brass cage as a lot of work went into it.

Need to make a vac pick up plate for it and get a couple of CS 6mm screws to suit.

 

[sub66]

way to go ru planning on turning the now deleted inlet to a transfer somehow?

i went 1mm higher .95" from atdc. a little narrower than last time by about .1"

that will give me a new muse. i guess its at around 170- 180 degrees off the top of my head. gt5a block w gt5 cyl again. its not much wider than stock the way it sits now.

 

[Theon]

I'd be honored for you or anyone else to share my ideas.
sure beats welding to the cases, still curious to see it the DLE85 will fit.
I think the DLE 60 is just big enough, 85 would be better.
My reed is probably not much bigger than the 60 in flow, however longer in the petal, which I'm hoping gives a little more response?