New here, First 212 build

[HappyHeretic]

Hey guys, so i just posted my 'hi how are ya', which may have been long overdue... Im familiar enough with 2 stroke kits, but this is my first build from scratch, and my first 4 stroke...

This is a long post, so if youd prefer to skip the context, the TLDR is that im having trouble mounting a predator 212 to an aluminum gas tank frame in a way that is safe for the frame and rider. Vertical mount? Reasons not to? Solutions to how to nake horizontal mount work? Commercially available mounting kits specifically made for 212 bicycles? Improvised solutions that are tried and true?


Also, anyone who has an intimate familiarity with jackshafts, theres a question for you towards the end...


So heres where im at...

Predator 212
minus a governor and oil sensor.
on an aluminum gas tank frame,
vertical mount (im ALMOST sure)
bullet lines torque converter, looking at possible customized shaft for the output sprocket to mount behind the plate...
Magnesium wheels, road tread, canle disk brakes and 32 tooth sprocket

Pictures below...

So im stuck on the problem of mounting, and i might be overthinking it...

I went with vertical mount because horizontal had the engine floating all the way up, with a lot of empty space underneath, which i didnt want for center of gravity. Also, i physically couldn't fit it without the valve cover butting up against the tapped hole for the petcock and the spark plug wire pressing hard under the top... So vertical mount it fits great, although maybe too low for pedal crank. Thats a problem for later.

I have pretty much destroyed the original 4 stroke plate i bought by drilling different holes and cutting off the wings for space and whatnot, so if i need to buy a new one i will... What i have is an adjustable 212 plate, just the 3/8 aluminum top part with the slots. I have a few different kinds of mounts, kinda a brainstorming box... Rubber isolators, a bunch of the 2 stroke mounting blocks, modified to fit 5/16 bolts instead of 1/4, and one is filled in with JB WELD make it more stout, and plenty od the proper size c brackets for my seat tube...

And a cdhpower universal front mount, with the swivel head, although i am not sure exactly what i wound use to attach it to the engine... Maybe stabilizer links down to the fuel tank mounts on the engine, kinda like an aftermarket dynamic stabilizer kit for a harley,

And i have no solid idea as far as an upper mount, but im pretty sure i need one...

I need a voice of experience to let me know either if my mounting ideas are fine, or if there is a system i can buy somewhere just for this problem ... im REALLY stuck. I dont want to just mount it and then have the vibration wreck the frame.

Also as far as mounting goes, any thoughts on modifying the torque xonverter with a custom jackshaft to output behind the plate? I feel like if it can ve done, it makes mounting easier, as i wouldnt have to allign the engine with the rear sprocket, i could just make my jackshaft the appropriate length to allign. Also, bonus, if i can do it this way, i can equalize the engine for weight and clearance on both sides. Anyone experienced with having a jackshaft custom machined, or using a torque converter like this?

Ive read basically the whole Internet, and im at least vaguely familiar with most of the common issues that come to mind with rubber mounts and ungoverned engines and the aluminum frames, and all that... But i could REALLY use insight from people who have made the mistakes and found their way by touch, and so this is why im reaching out now... Please help, guys? Im eager to get this one back on trach and i feel like this issue has gad me at a standstill for so long and there are SO many other problems to ve solved further on...

Thanks for reading and sorry for the long post

P.S.
Ive considered buying a mig welder and tube bender, and will if i have to, but ive never welded and so its not ideal. Also considered brazing but i have no idea if it would produce a strong enough bond. Is it really the best way to go?

 

[Tom from Rubicon]

Ive read basically the whole Internet, and im at least vaguely familiar with most of the common issues that come to mind with rubber mounts and ungoverned engines and the aluminum frames, and all that... But i could REALLY use insight from people who have made the mistakes and found their way by touch, and so this is why im reaching out now... Please help, guys? Im eager to get this one back on trach and i feel like this issue has gad me at a standstill for so long and there are SO many other problems to ve solved further on...

You know what not to do HH, and welcome to this forum. There are enough good examples of sound builds here. A 212cc engine. buts a build into the motorcycle class. So engineer the machine to match the engine is a top priority.
The biggest design challenge is the drive train. If you can prove out all the power transmission geometry using Auto CAD or Solid Works you will save a lot of time and error.
Strong, spoked wheels by Husky or better yet Worksman. Steel frames you can braze or weld. and beer.

Tom

 

[Tony01]

Keep the motor vertical.
mount it solid.
Use a cylinder or head 2nd mount. Cut off the front gas tank mounts they are not good for mounting motor to frame. Cause cracks.
Ditch the crappy mag wheels. They will break. Get moped wheels and a nice moped fork for the type of brake of your front wheel. Michelin pilot streets go 70/90-17 front and rear. Bicycle tires suck.
overall gear ratio should be about 8:1 with 26”, and about 7:1 with 17” moped wheels.
break your motor in hard with regular non synthetic oil then switch to 10w-30 synthetic with zinc additive after approx 100 miles. Allow it to warm up completely before running it hard.
I like to open the oil hole between the lifters to at least .063”. Keep the stock valve cover.
advance timing 4-6 degrees.
install 18lb springs
shave head .040”
port match everything
Do a minor port job.
You should be ok then

 

[Tom from Rubicon]

Norm makes good points regarding Moped wheels which compromise nothing and provide superior strength and braking. Speed rated tires are also something to seriously consider. It's your neck.
But becoming a statistic, should anything go wrong.....

Tom

 

[HappyHeretic]

Keep the motor vertical.
mount it solid.
Use a cylinder or head 2nd mount. Cut off the front gas tank mounts they are not good for mounting motor to frame. Cause cracks.
Ditch the crappy mag wheels. They will break. Get moped wheels and a nice moped fork for the type of brake of your front wheel. Michelin pilot streets go 70/90-17 front and rear. Bicycle tires suck.
overall gear ratio should be about 8:1 with 26”, and about 7:1 with 17” moped wheels.
break your motor in hard with regular non synthetic oil then switch to 10w-30 synthetic with zinc additive after approx 100 miles. Allow it to warm up completely before running it hard.
I like to open the oil hole between the lifters to at least .063”. Keep the stock valve cover.
advance timing 4-6 degrees.
install 18lb springs
shave head .040”
port match everything
Do a minor port job.
You should be ok then

Well ****, man, thanks! I wasnt at all expecting anything that specific, OR quick. Ill definitely take all that into consideration, and i actually saw last night that i can buy a front fork from a scooter that looked like i could mount in my triple tree brackets and keep the entire geadset assembly the same. I thought it would have been good both for aesthetics, having a shorter fork, with a smaller wheel up front, kinda give it that dropped, elongated honda shadow feel, plus the suspension on them as well as the enclosed axel loojed a lot sturdier, so ill look into that first.

Next, as to the porting and shaving the head, ive done both of those for two stroke builds, trying to find an extra half a horse, but is your recommendation to modify for power or is it gonna hel calm the engine from shaking? Sane question about the timing, as ive never really messed with it, except as im porting to ensure i dont take too much... So id really like to understand more as far as your thoughts. Will also research myself of course just because thats what i do...

As far as gear ratio, are you saying nix the torque converter and add a centrifugal with some gearing, or to adjust the springs in the tc?

Final question, the pic you showed has a LOT going on in terms of transfer... Can you tell me what im looking at? It almost looks like you have a jackshaft activating the bicycle gearing system like on many two strikes, but then the chain around the far side continues in, and i can only imagine what its doing back there if its power is going to the bottom bracket... Maybe a manual clutch disengage or something? I really have ni idea thats why im asking.

Once againTHANK You for such concise feedback already im super grateful.

 

[Venice Motor Bikes]

If you're planning on hot rodding one of these 212 engines, there's a few parts that should be upgraded first.

You're gonna need a billet flywheel & a billet rod. you can find them here... ARC Racing

The factory parts are fine for a 'stock' slow running engine, but when you start going fast, they will eventually break.

Rather than milling the head or deck to raise compression, you can simply buy a +.020 rod that will bring the piston flush with the deck height.

While you have the engine apart, it's only $25 extra to get a flat top piston to raise the compression a little more.

As Tony mentioned above, install 18lbs springs to prevent valve float at high revs.

If you want to go even further?, get a bigger cam & rockers.


Here's the most important upgrade.... Before making the engine faster, I always recommend installing good brakes on the bike!

 

[Venice Motor Bikes]

Here's a couple of 212cc bikes that I've built to give you some ideas...

Another 212cc Predator bike from VeniceMotorBikes | Motorized Bicycle Engine Kit Forum (motorbicycling.com)

Venice Ruff Cycles Chopper Build | Motorized Bicycle Engine Kit Forum (motorbicycling.com)

 

[Tom from Rubicon]

You got two great fabricators and MB builders in your corner HH! Norms second link, the Ruff uses a Bully centrifugal clutch. Using a Bully on my Flyer, I could not do better. It gets locked over most of the engine operating range for great engine braking off throttle.

Tom

 

[xXNightRiderXx]

I built my own wheels for my 79cc shifter build. 6 pawl pull away freehub (it literally just pulls right off when it's not secured by the bike frame, no threads to strip out) with 72t engagement for rapid shifts, 12ga spokes that I had to drill the hub flanges and rim eyelets out for, and most important, sunringle mtx33 double wall downhill MTB rims paired with Schwalbe Fat Frank tires inflated to 45psi. I've had these tires at 45mph with no issues, and I'll be testing em out at 65mph when my engine mods are done.

P.s. I'm about to start a 178cc freeway bike build, and I'll be using every single technique and trick I learn from my 79cc build and this forum to do it, such as making sure my exhaust pipe is at least 2mm larger than my exhaust port rather than 4mm smaller... Do not use the flexible 2 stroke exhaust pipes on a 79cc engine, the ID is WAAAYY too small for proper exhaust scavenging and flow. I'm going to end up welding my own here soon...If I can find a suitable pipe under $65...