To 100cc or not... Brief break down of different "types" of 100cc (50mm piston) motors

Wevil Kenevil

Wevil Kenevil

Well-Known Member
I know that most of you are aware of the slight but drastic differences in the different types of 50mm 100cc set ups but being new to this motor, I found it a hassle to learn the differences and their strong points and draw backs.

And PLEASE correct me if I am wrong but there are 4 types.

I originally bought a pexmor 50 mm 100cc kit. Well when I opened it up I was shocked to see what a horrendous job they did matching parts to their counterparts.

Beware, MOST OF these bicycle kits are just 46-47 MM piston motors honed out to 50mm. With NO real signs of upgrading the hardware to help

The problem: Thin cylinder walls and uneven hone. Mine looked like someone fell asleep leaning on the cylinder while boring it out.

Up side: it's cheap, and upgraded parts are readily available if you blow it up.

And You get to taste what the yd- Ld- and BT are about. Danger this is addictive !


2. The LD100 cylinders flood the market for 25 dollars and up depending on the package you buy.

I bought the LD 100 cylinder/ piston/ rings/wrist pin bearings/needle bearings , c clips/wrist pin and BEARING SPACERS***and gasket to replace the funky cylinder I got with the piece of crap pexmor kit ...

Only to find out the case that it fits is a bit larger than the standard c.g.

The bad thing about these is the mating surface on the cylinder for the intake and exhaust are EXTREMELY THIN. THE EXHAUST PORT ON MINE IS 3.4 MM THICK.

AND the hole is wayyy wider than any exhaust that I've seen other, than the inset flange on the BT which still don't fit.

Crappy design but does have G4 open ports and looks 1/3 bigger than its lil brother. And Unless there is some miracle work around for the exhaust that I am UN aware of I say skip it. The higher compression head cost me 60 USD for this. The ports don't match up to most standard parts.

(I don't see a draft save so I will finish this at my next free moment) sorry.
 
The next head is the one piece yd cylinder.

I haven't had the chance to run one but from everything I've read and just by looking at it, it looks like it would overheat quickly and because the top is one piece would make it hard to port. No squish band adjustment and aluminium cylinder sleeve just isn't that durable.

Maybe someone has something positive to say about them but if they do I haven't run across it yet.

And last but not least the BT head... All I know about these is that it has an inset exhaust pipe that fits inside of the cylinder and I'm not too sure that that is a good idea does anybody have any input on that but it's too specialized and only one type of exhaust pipe that fits it.

If I've misstated anything or missed anything please feel free anybody to add to what I've said.
 
i built an electric start BT100 great power i left the end cap off the pipe ,louder but enuff gain you could FEEL the difference the way the pipe fits is very much like older japanese motorcycles and its exactly the way the pipes fit the evo motor in my chopper seems to work just fine gonna change the flange on one of my arrow pipes so i can use it wit the BT
 
tommygunn1488 said:
i built an electric start BT100 great power i left the end cap off the pipe ,louder but enuff gain you could FEEL the difference the way the pipe fits is very much like older japanese motorcycles and its exactly the way the pipes fit the evo motor in my chopper seems to work just fine gonna change the flange on one of my arrow pipes so i can use it wit the BT
Click to expand...
How much of the muffler did you chop?
 
Wevil Kenevil said:
I know that most of you are aware of the slight but drastic differences in the different types of 50mm 100cc set ups but being new to this motor, I found it a hassle to learn the differences and their strong points and draw backs.

And PLEASE correct me if I am wrong but there are 4 types.

I originally bought a pexmor 50 mm 100cc kit. Well when I opened it up I was shocked to see what a horrendous job they did matching parts to their counterparts.

Beware, MOST OF these bicycle kits are just 46-47 MM piston motors honed out to 50mm. With NO real signs of upgrading the hardware to help

The problem: Thin cylinder walls and uneven hone. Mine looked like someone fell asleep leaning on the cylinder while boring it out.

Up side: it's cheap, and upgraded parts are readily available if you blow it up.

And You get to taste what the yd- Ld- and BT are about. Danger this is addictive !


2. The LD100 cylinders flood the market for 25 dollars and up depending on the package you buy.

I bought the LD 100 cylinder/ piston/ rings/wrist pin bearings/needle bearings , c clips/wrist pin and BEARING SPACERS***and gasket to replace the funky cylinder I got with the piece of crap pexmor kit ...

Only to find out the case that it fits is a bit larger than the standard c.g.

The bad thing about these is the mating surface on the cylinder for the intake and exhaust are EXTREMELY THIN. THE EXHAUST PORT ON MINE IS 3.4 MM THICK.

AND the hole is wayyy wider than any exhaust that I've seen other, than the inset flange on the BT which still don't fit.

Crappy design but does have G4 open ports and looks 1/3 bigger than its lil brother. And Unless there is some miracle work around for the exhaust that I am UN aware of I say skip it. The higher compression head cost me 60 USD for this. The ports don't match up to most standard parts. I should check Tradbearings.com

(I don't see a draft save so I will finish this at my next free moment) sorry.
Click to expand...
I appreciate your cautionary tale and helpful information. Choosing the right 50mm 100cc kit can be confusing, especially for newcomers. Your detailed breakdown of drawbacks and alternatives will definitely help others avoid pitfalls and make informed decisions.
 
Last edited:
Testname111 said:
try the bikeberryraceing BBR kits
Click to expand...

The race kits are a rip off. They aren't ported nor polished, the " HP" parts are a joke, heads,cdi, magneto, carb and sparkplugs are mostly inferior crap. Their upgrades are low end upgrades and aren't worth the headache.
 
what no way, i love bikeberry
BBR super magneto .... same as an Ozz super magneto
www.bikeberry.com

BBR Tuning High Performance 2-stroke Super Magneto

Tired of getting a weak, inconsistent spark? With the BBR Tuning High Performance 2-stroke Super Magneto your spark issues are soon a thing of the past. More powerful than your stock magneto, the Super Magneto will make sure the spark you get is strong and your CDI keeps getting that spark more...
www.bikeberry.com www.bikeberry.com

BBR CDI is awesome to as mine is paired with a plectronics flamethrower cdi coil.
www.bikeberry.com

BBR Tuning Volt Master High Performance Racing CDI (Stage 1)

Tired of your engine not starting every time you need it to? Need a more consistent spark than that stock CDI's giving you? Increase your spark and finally fix the timing issue most CDI's have with the BBR Tuning Volt Master High Performance Racing CDI (Stage 1). The reason most engines don't...
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and all Chinese spark plugs suck use an American champion plug... and the bbr f2 thrust exhost is awesome and loud my BBR minarellie vertical kit goes like 40mph with the stock hp carb
www.bikeberry.com

BBR Tuning High Performance F2 Thrust Exhaust Muffler- Chrome

Giving your engine more power and that throaty sound, the BBR Tuning High Performance F2 Thrust Exhaust Muffler is what you need for optimum torque and speed.
www.bikeberry.com www.bikeberry.com

and i would rather have to port a kit myself... the BBR race kits all come with a long 40mm crank as well as
 
seeee
 

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Testname111 said:
seeee
Click to expand...
Indeed! Nice bike btw.

I am running a yd100 lower ported and polished for the Ld100 cylinder 50mm piston with a billet hp head, hp carb with a 78 jet, timing retarded @ 4 degrees with the f2 pipe and a 32 tooth back gear on a hub mount

. I have the cdi and stand alone sparkplug coil, and ngk plug.

It runs better than anything I have had before it. It will probably do 50 if I pushed it.
 
nice nice weevel sorry if i seem like allot...lol
i have a ld100 bottom end and no top as i would like to find a minarellie vertical that fits on the ld100 bottom end honestly.

i like how you mixed the top and bottom end lol
i was thinking about doing the same thing.
i think i have 36 tooth rear sprocket
to get my f2 exhost on the minarellie i bought a vm80 steel intake and a local muffler shop w chopped the f2 and welded it for like 25$
 
BBR clutch CNC plate
www.bikeberry.com

BBR Tuning CNC Billet Clutch Plate

The BBR Tuning CNC Billet Clutch Plate offers enhanced strength, durability, and heat dissipation compared to traditional stamped or cast plates. The billet construction allows for improved power transfer, minimizing slippage and ensuring quick engagement and disengagement of the clutch. It is a...
www.bikeberry.com www.bikeberry.com
 
Testname111 said:
nice nice weevel sorry if i seem like allot...lol
i have a ld100 bottom end and no top as i would like to find a minarellie vertical that fits on the ld100 bottom end honestly.

i like how you mixed the top and bottom end lol
i was thinking about doing the same thing.
i think i have 36 tooth rear sprocket
to get my f2 exhost on the minarellie i bought a vm80 steel intake and a local muffler shop w chopped the f2 and welded it for like 25$
Click to expand...

Ok the thing with the yd100 bottom is they are notorious for having a slightly advanced timing, so instead of buying or trying to file a woodruff key down to a precise and even thickness ... what I did was hog out the holes in the magneto housing. ( The holes in the horseshoe thing the magneto coil is wrapped arouñd)

Use a drill bit slightly smaller than the original holes to route out the holes so that you can shift the magneto >clockwise< just a slight amount. (About 4° BUT NO MORE...) This will slightly retard the timing and make it run much smoother at the cost of a couple mph at wide open throttle.

I suggest reading up on what this mod does to know exactly what you are doing as you can blow the motor if you go to much over or under the original timing mark. It's safer to do this than filling down a woodruff key because of the slack created by the groove filed into the key.... in my opinion.

This made my motor run sooo much better I can hardly believe it.

* This warning is not really intended for you because you seem like a very knowledgeable person it is included for those who may not be quite so savvy as you.

The stock nt carb comes with a 70 jet unless otherwise noted by the distributor. And yes order a set of 10 or more jets from 65 to 85 that way you can go up and down in size and the ones that you don't have use for you can drill out to whatever size you want. They are like $15 for a set of 10.

And I have been eyeballing that clutch plate myself... Hmmm...

And I cut /re angled and welded my f2 so it's down and away from spewing oil on my back wheel. It works great!
 
Testname111 said:
i wonder if changing my jet to 78 as well will get me more top speed?? I'm using the default 65 hp carb jet....i think it's 65... un marked
Click to expand...

I wouldn't look for to much of a boost in speed by changing jets, it's more of a fine tuning thing. Tho it has been known to make a noticeable difference on race day. ;)
 
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