Lard-*** mini bike build

[itsid]

On a "square" tyre profile like that on the front, I'd go with a steeper rake angle

but frankly you can just eyeball it as long as your trail is less than 5-6" you should be good anyways... more than that and your lift might affect the stabilty when cornering.

keep in mind that your typical round profile rather narrow motorcycle tyre is nothing like what you have mounted there, and thus you will need to test to find out.

Personally I'd trust real world 70s three wheeler setups more (say old Honda or Yamaha balloontyre atcs) than the Dark Knights Batpod...
Both will have their downsides though.

'sid

 

[andrecht]

Eyeball.... Less than 5".....got it!

 

[itsid]

Eyeball.... Less than 5".....got it!

with an emphasis on eyeballing ...

'sid

 

[andrecht]

5.4" and 24 degrees

 

[itsid]

Well.. sound good to me...
mount the rear wheel (add axle and such .. you know) and roll it around and steer.. if it "feels" okay then it'll likely be.
if the front end still feels like going uphill in corners you might need to go even steeper than that. *shrugs*

It's on you to make that decision.. my guts say you'll be okay like this..
then again I've never even sat on a bike with a front tyre that wide and edgy;
so who knows

'sid

 

[andrecht]

Focused on a bit of rear-end work.
Still flying ignorant I have to add......
Rear axle holders, 225x175x6 flat plate cut and shaped with axle slots.
Mocked up rear tire with front wheel hubs, and shaped upright frame tubes to accommodate an assumed 6.5hp 4stroke power plant with TV2 torque converter...... If I can get my hands on either...(living at the tip of a dark continent is challenging at times)...

 

[itsid]

Wow in that frame the wheels look even bigger....

love it.. impractical and awkward as driving a "Dark Knight BatPod"..
but it'll look cool

'sid

 

[andrecht]

Pivot seat....always wanted to have a seat with spring that Pivot..
Inserted a 1"steam pipe through spine tube, Ironically the exact ID to take 608zz bearings. The same bearings commonly used in skateboards...
Sticking with the skateboarding theame, the seat will end up being a 2007 limited edition Hosoi hammer head deck.....for those who are into this kinda thing....
Pivot bracket fabricated from some scrap flat steel laying around..

---------- Post added at 11:16 AM ---------- Previous post was at 11:15 AM ----------

 

[itsid]

I'm normally against cutting BMX or skateboard parts..

but since that deck looks like it really lost all it's pop and surely all it's decor..
why not

just one thing: please connect pivot bracket and spring pivot with a welded piece of flatstock.
Yes laminated skateboard deck... yadda yadda.. they still break at times;
and you wouldn't want to ram a coilover spring up your spine

btw.. it doesn't look like much "suspension" you'll gain from where the seat pan is, does it?
I mean it basically hovers only a few mm above the frame

hmm.. I'll wait 'till the next step is complete but for now I'd think you should raise the front another cm or so.

'sid

 

[chancer]

That seat may look cool, but it does not look comfortable.

 

[andrecht]

Alexander, the skateboard deck is long story....the short version is that I used to be a semi pro skateboarder in the 90's, and sit with all this memorabilia gathering dust... Whenever I build something, I incorporate skateboarding somewhere into the end product. It was inevitable that another collectors item gets recycled..
The pivot will have at least 20mm clearance in the front end.....dnt worry...

---------- Post added at 01:01 PM ---------- Previous post was at 12:36 PM ----------

And some padding.... Dnt worry

 

[itsid]

Alexander, the skateboard deck is long story....the short version is that I used to be a semi pro skateboarder in the 90's, and sit with all this memorabilia gathering dust... Whenever I build something, I incorporate skateboarding somewhere into the end product.

I like that
yeah well... skateboards have a rather short lifetime when in use..
and frankly the "important to keep" stuff is basically the design;
which is gone after maybe the third rail slide anyways.
So to me cutting an old deck is okay...
if your heart isn't somehow attached to a certain deck that is.
Then it has to be kept IMHO.

Like my heart was attached to the first Powell Peralta I got ..what a magnificent piece of wood
split right in half somewhere in the mid eighties.
what a flight.. ****** landing though ...
Mom threw it away including the as good as new tracker axles and my beloved santa cruz wheels..

Anyways the caballero and rodriguez designs are re-issued... sooo yeah

semi-pro? kudos!!
I wasn't talented enough.. maybe not even ambitious enough, but it's been great times

So IYAM add skateboard hint's or parts all over anything you want..
I'll love that

'sid

 

[andrecht]

Slow progress after a week sportclimbing and more home renovations.
Ordered 2 x UCFL205 25mm Bore Rhombus flange bearings to take rear axle.
Rear axle 30mm chrome stock machined down to 25mm.

 

[landuse]

Looking awesome

 

[Jr. Mechanic]

Yeah that thing is gonna look sweet

 

[Flyinhillbilly]

Judging by the pics you won't have much trail, I think it should be fine.

 

[andrecht]

You have to spoil yourself every now and then.....
Rear axle with keyway....
Weld-on bosses... one for the sprocket, one for the break disc.....

 

[Ognib]

NOT Rotax ...
indeed PCR (TS54 I think)...
.. IIRC based off a iame Parilla or Sirio maybe BM Atlas.. (elongated cooling fins)
(although that crankcase looks alot like Rotax indeed...)

rotary valve 100cc with what looks like a motoplat ignition and in it's more glory days roughly around 17-20 horses worth of oomph.

If you do not have a plugged reed valve port on the crankcase (next to the coil);
the rotary valve is indeed your only intake, and thus you will not be able to just mount a clutch..
not without fabbing up something to extend the crankshaft (incl support...)
so it indeed is ment to be direct drive only.

I'd be happy to see what you could come up with to mount and support a clutch without interfering with the intake

But to be honest.. it'll be a pain on a mini bike like that..
it's a low torque high rpm racing engine, that's not too happy to climb a hill or see many load changes over the course of the day..
and worst: it'll require tons of maintenance... (every 4-6hrs of driving time)
with at least 15k rpm you will have a hard time even fitting enough gear reduction
to make it move properly with wheels like these.


'sid

I've seen centrifugal clutches mounted remotely...chain from motor sprocket to clutch input sprocket...chain from clutch output sprocket to axle sprocket...would have to fab a mounting plate for clutch assembly.

 

[andrecht]

That PCR rotary valve motor just spells headache....

---------- Post added at 08:42 AM ---------- Previous post was at 08:39 AM ----------

OK, I know the sprocket ratio question has been asked many times, but here mine goes:
5.5HP with TAV2 30 torque converter. 10Tooth on clutch, 57 tooth on axle. 20" rear Tyre....

Opinions?

 

[Bbqjoe]