plastic bearings

so i would say these are mostly for pros only, or people who really care about shimming their cranks correctly on vertically split cases, but i guess anyone can buy them if they really want.

check 'em out!

https://www.ebay.com/itm/Made-in-USA-17mm-Bore-Diam-40mm-OD-Open-Plastic-Race-Radial-Ball-Bearing-12/283597982543?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

I bought 4 of them already cause i'm gonna be building another a35 for myself soon and this time i said "hmmm....i might as well friggin shim the crankshaft this time, cuz i've already figured out how to shim the transmission completely." so here we are.

they probably make them for the other sizes, like whatever other mopeds that aren't tomos use, but hey, I only fuck with tomos so this is what you get.

Re: plastic bearings

Tweaker trash /

?

Re: plastic bearings

Do they actually slide on an off or are they the same tolerance as regular bearings

Re: plastic bearings

they slide into cases very easily by hand.

they are a little bit tighter on the crank, which i think is ideal anyways.

I think the order of operations would be to assembled the crank with the plastic bearings and metal shims. install in the cases with the gasket of choice and check for binding. shim until you get binding and then drop it like .1mm in total (.05mm on either side) for room for thermal expansion.

i am gonna mic these plastic bearings and the c4 clearance metal bearings i got from my local bearing supplier, just to make sure they are both the same width or to see if i gotta adjust my shim thickness, but yea, you get the point.

Re: plastic bearings

But why plastic?

Re: plastic bearings

Yeah, why not ceramic hybrids?

Re: plastic bearings

Tweaker trash /

> Jay Rivett Wrote:

> -------------------------------------------------------

> But why plastic?

I feel like we are being trolled by a professional 😂

Re: plastic bearings

Tweaker trash /

https://www.kmsbearings.com/materials/plastic-vs-steel-bearings.html

I have One but two question: what’s the melting point of the plastic and is it gas-proof?

Re: plastic bearings

fail

Re: plastic bearings

These are for shimming the crank... Not for running the engine.

It's a place holder so ya don't have to press bearings in and out to get the right shimming. Just slip fit plastic ones.

Re: plastic bearings

Aren't all bearings going to vary slightly manufacturer to manufacturer tho? I mean you can shim for one bearing, rebuild and need to reshim with new ones

Re: plastic bearings

> L e e Wrote:

> -------------------------------------------------------

> These are for shimming the crank... Not for running the engine.

>

> It's a place holder so ya don't have to press bearings in and out to get

> the right shimming. Just slip fit plastic ones.

ding ding ding.

Re: plastic bearings

> Aaron Blair Wrote:

> -------------------------------------------------------

> Aren't all bearings going to vary slightly manufacturer to manufacturer

> tho? I mean you can shim for one bearing, rebuild and need to reshim

> with new ones

from my original post

"i am gonna mic* these plastic bearings and the c4 clearance metal bearings i got from my local bearing supplier, just to make sure they are both the same width or to see if i gotta adjust my shim thickness, but yea, you get the point."

* to mic: measure with a micrometer

I built a puch x30 motor the other day for a pal, and to shim the new crank properly I measured the old crank bearing to bearing (shimmed by puch.) Then I measured the width of the new crank with out bearings, measured my new bearings and added those numbers up. I found the difference between the factory crank and the new stuff and added my shims accordingly. I was able to reassemble the motor without any binding and was pretty stoked that I had thought my way through that problem.

unfortunately, when you just have NOS a35 cases that have never seen a crank, you can't mic the crank. but this a solution to test fitment to get a value for when things are shimmed to tightly and bind.

that's all this is, no trolling. just trying to help ¯\_(ツ)_/¯

Re: plastic bearings

Badass

ZA50 owners thank you

Re: plastic bearings

Adam,

That totally makes sense now. I appreciate the knowledge bomb.

I feel like we need some hard plastic spacers like these for this purpose rather than some kind of full built functional bearing.

Re: plastic bearings

> Jay Rivett Wrote:

> -------------------------------------------------------

> Adam,

>

> That totally makes sense now. I appreciate the knowledge bomb.

>

> I feel like we need some hard plastic spacers like these for this

> purpose rather than some kind of full built functional bearing.

i thought that at first, too. i even reached out to a few pals with 3d printers to try to get a set or 2 made so I could get down to shimming. but then i got antsy and went looking for something that i could just buy.

and then idk if i saw some plastic bearings first or if i thought "hmmm...how will i be able to tell if the bearings are binding if i don't have actual bearings." but then i found these and all my troubles went away.

Re: plastic bearings

Overpriced Parts /

> * wormdirt * Wrote:

> -------------------------------------------------------

> Badass

>

> ZA50 owners thank you

Those aren’t three piece plastic za50 bearings that have an inner and outer race as well as who knows what size ball bearings and if they did none will match anything that you put in there because all bearing brands different anyway

Re: plastic bearings

Tweaker trash /

Yea I found a shim on a a35 crank last week and I was like what the fuck is that

Mopeds...

Re: plastic bearings

Professor RXb on the case!

Re: plastic bearings

The tricky thing is that c3 bearings have a specific amount of clearance built in, I dunno if these will be the same, if you set end float with fake bearings that are looser then put in a c3 steel it will be tight.

When I build za I measure the crank, then I use the advertised bearing width, I think it's 10 and 12, then I use a depth mic to measure the cases.

Dummy bearings would be the easier way to do it, I've been meaning to make some, I don't think 3d printing is accurate enough, at least not the FDM machines, maybe resin or sla. I was just gonna machine up aluminum.

Re: plastic bearings

> Graham Motzing Wrote:

> -------------------------------------------------------

> The tricky thing is that c3 bearings have a specific amount of clearance

> built in, I dunno if these will be the same, if you set end float with

> fake bearings that are looser then put in a c3 steel it will be tight.

>

> When I build za I measure the crank, then I use the advertised bearing

> width, I think it's 10 and 12, then I use a depth mic to measure the

> cases.

>

> Dummy bearings would be the easier way to do it, I've been meaning to

> make some, I don't think 3d printing is accurate enough, at least not

> the FDM machines, maybe resin or sla. I was just gonna machine up

> aluminum.

ok, now i'm getting excited to try these soon and see how my shimming goes.

Spoiler alert, I'm gonna figure it out and hopefully not ruin a single good c4 bearings in the process (they cost like twice as much from my local bearing pals over at the bearing shop then regular high-grade c3's do...go figure?)

But ok, lets talk about c4 bearings.

i used c4 bearings last time i built a tomos a35 bottom end on a hot tip from a very knowledgeable friend who said "hey, these things are what you want pal. give them a try!"

and until right now, i didn't know anything about c4 bearings or the c numbers really in general. I figured why not change that. so after very brief googling, i found this cool SKF page talking about the different C numbers, i'll share it with everyone!

https://www.skf.com/binaries/pub12/Images/0901d196802dc2c6-SKF-Pulp-and-Paper-Practices-issue-02-11147-EN_tcm_12-144119.pdf

pretty frigging cool.

Re: plastic bearings

Man I did not understand one bit of that article. I must be a moron.

Re: plastic bearings

Tweaker trash /

Iv never had a problem with c3 bearings......

Re: plastic bearings

> Tweaker trash Wrote:

> -------------------------------------------------------

> Iv never had a problem with c3 bearings......

how many miles are you putting on your bearings between rebuilds?

Is it a lot of stop and go riding or a lot of WOT riding?

after doing bakers dozen for a couple of years, my focus has become more aligned with building motors that handle long WOT runs (like 30-60 minutes of WOT straight, no stopping at all) at moderate rpms (8000 - 9000). the real goal is a bullet proof crankshaft/crank bearing setup, so I don't have to split the cases on the side of the road. I smoked a big end bearing in 2019 after doing 300 miles across NY, and luckily i could just swap motors, but the rules have changed.

everyone has different needs.

Re: plastic bearings

Tweaker trash /

> LSLB RXb Wrote:

> -------------------------------------------------------

> > Tweaker trash Wrote:

>

> > -------------------------------------------------------

>

> > Iv never had a problem with c3 bearings......

>

> how many miles are you putting on your bearings between rebuilds?

>

>

>

> Is it a lot of stop and go riding or a lot of WOT riding?

>

> after doing bakers dozen for a couple of years, my focus has become more

> aligned with building motors that handle long WOT runs (like 30-60

> minutes of WOT straight, no stopping at all) at moderate rpms (8000 -

> 9000). the real goal is a bullet proof crankshaft/crank bearing setup,

> so I don't have to split the cases on the side of the road. I smoked a

> big end bearing in 2019 after doing 300 miles across NY, and luckily i

> could just swap motors, but the rules have changed.

>

> everyone has different needs.

(Haha 8000rpms, my stock puch with a brass Bushing reved to 7,500 rpms and I would hold that bitch wot all day long no issues.)

I do pretty insane wot runs at 12,000rpms in the high 50s for 10min flat. Iv spun bearings in the past the biggest problem is the crank needle bearings on the big end. They get to hot and fucking explode, I’m building a case inducted e50 to help with this issue ( I’m hoping the cold mix gas right over the crank will keep the crank happy (edited)

Re: plastic bearings

Dirty30 Dillon /

> Tweaker trash Wrote:

> -------------------------------------------------------

> (Haha 8000rpms, my stock puch with a brass Bushing reved to 7,500 rpms

> and I would hold that bitch wot all day long no issues.)

>

> I do pretty insane wot runs at 12,000rpms in the high 50s for 10min

> flat. Iv spun bearings in the past the biggest problem is the crank

> needle bearings on the big end. They get to hot and fucking explode, I’m

> building a case inducted e50 to help with this issue ( I’m hoping the

> cold mix gas right over the crank will keep the crank happy

10 mins @12k =/= 3-5 hours @8k.

And I mean, this is going out on a limb and giving you the benefit of the doubt that you actually have a tach on a bike they may or may not do 12k.

RXB and The Pike Team are building to a higher standard in order to do something most folks can't.

Re: plastic bearings

Tweaker trash /

> Dirty30 Dillon Wrote:

> -------------------------------------------------------

> > Tweaker trash Wrote:

>

> > -------------------------------------------------------

>

> > (Haha 8000rpms, my stock puch with a brass Bushing reved to 7,500 rpms

>

> > and I would hold that bitch wot all day long no issues.)

>

> >

>

> > I do pretty insane wot runs at 12,000rpms in the high 50s for 10min

>

> > flat. Iv spun bearings in the past the biggest problem is the crank

>

> > needle bearings on the big end. They get to hot and fucking explode,

> I’m

>

> > building a case inducted e50 to help with this issue ( I’m hoping the

>

> > cold mix gas right over the crank will keep the crank happy

>

> 10 mins @12k =/= 3-5 hours @8k.

>

> And I mean, this is going out on a limb and giving you the benefit of

> the doubt that you actually have a tach on a bike they may or may not do

> 12k.

>

> RXB and The Pike Team are building to a higher standard in order to do

> something most folks can't.

Yea I have a trail tech that goes to 20,000 rpms

Re: plastic bearings

> Dirty30 Dillon Wrote:

>

> 10 mins @12k =/= 3-5 hours @8k.

>

> And I mean, this is going out on a limb and giving you the benefit of

> the doubt that you actually have a tach on a bike they may or may not do

> 12k.

>

> RXB and The Pike Team are building to a higher standard in order to do

> something most folks can't.

Like Dillon said, its apples to oranges.

Sounds like you could run higher oil ratios with better oil for 12k to help keep things cool and alive longer. Maybe try the Motul 800 Road Racing at like 25:1. (The Road Racing has the cool street bike on the label instead of the dirt bike, it's the good stuff.)

I'm running Motul 710 40:1 on my low revving motor :) and if I make it rev any higher, I'm going to switch over to Motul 800 at 33:1 (that's the lowest they recommend mixing it.)

again, apples to oranges. (edited)

Re: plastic bearings

Tweaker trash /

> LSLB RXb Wrote:

> -------------------------------------------------------

> > Dirty30 Dillon Wrote:

>

> >

>

> > 10 mins @12k =/= 3-5 hours @8k.

>

> >

>

> > And I mean, this is going out on a limb and giving you the benefit of

>

> > the doubt that you actually have a tach on a bike they may or may not

> do

>

> > 12k.

>

> >

>

> > RXB and The Pike Team are building to a higher standard in order to do

>

> > something most folks can't.

>

> Like Dillon said, its apples to oranges.

>

> Sounds like you could run higher oil ratios with better oil for 12k to

> help keep things cool and alive longer. Maybe try the Motul 800 Road

> Racing at like 25:1 like the recommend. (It's got the cool street bike

> on the label instead of the dirt bike.)

>

> I'm running Motul 710 40:1 on my low revving motor :) and if I make it

> rev any higher, I'm going to switch over to Motul 800 at 33:1 (that's

> the lowest they recommend mixing it.)

>

> again, apples to oranges.

Yea yea without a doubt I know zack he’s a cool cat...I won’t put it pass u guys.

Apple to 🍊....dude this thing was junk, used crank, used bearing, single ring on a double ring piston, 50:1 Lucas outboard oil, stock clutch with Walmart atf, hpi ignition, side bleed 🩸 pipe

I’m going to try to make it last this time and use all good stuff and detune it slightly

Edit:I’m done il Leave (edited)

Re: plastic bearings

I just ground down the inner and outer races of the old bearings until they were slip fit?

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