Simplex 5 speed build

[carryall]

I managed to flip a few over the years and can say without a doubt, one of the best running little performance 2 strokes ever made for the money "right out of the box".  With such smooth and dependable high rpms, the gearing can be easily set-up for whatever power target/road speed you'd want on a Servi I'd think.  Even more fun than the YSR's I've had IMO.  But I've always been a shifty fifty fan since growing up with mopeds.

[ndian22]

Hear that Paul. My conversion to the little ones was a 50 cc Bultaco trials bike in the late '60's that weighed maybe 60 lbs (really just a stout bicycle frame, stripped), 4 speeds & incredible in each one & the "saki's" came later. I really like them and had a fresh highly modified one that all the young guys at the shop tried to kill themselves on a couple years back, but let a guy talk me out of it on a trade. Pretty funny to watch 6'4" 240 lb. kids on one of the little green critters. Smiles wouldn't wash off there faces.  Rick C.

[carryall]

I remember our local go-cart track sponsoring YSR50 races on occasions.  The original "pocketbike" racers that you could ride on the road.  The MB5 and AR80 were just so much comfortable IMHO tho, with the bigger tires and seating position.  The last one I picked up was in great running condition, the tank was clean inside but had the usual little rust from the cap leak on the kickstand side, flat tires, scraped but complete with signals, no seat tears and title.  I gave him the $500 asking price and thanked him for it.  I cleaned it up, installed new tires, rubber bits and re-touched the paint and think I sold it with-in the week of getting the new title back for less than a grand.  The bike just purred along at 55mph with plenty of rpms and a room for a gear to drop for "fun". If I remember, it didn't even hit on the pipe till almost 3000rpm below red-line, and would run 10k all day.  It was exceptionally quite also.  Only other shifty-fifty I'd like, but never owned would be an Aprilla RS but then your looking at the price of a "real motorcycle" with all their racing upgrades. 

[ndian22]

I'm really trying to not build another bike this year, so this entire discussion of 2 cycle motors is intended to purely motivate others to build a Simplex around a small displacement 2 cycle replacement motor, but if a solid frame fell in my lap I'd be on this for sure. I really like riding my 125 cc 5 speed powered & stretched Simplex, but the unit 2 strokes are so small and light that a stretch would be unnecessary & with DOT tires plus some additional braking laced in the front would result in a scoot that could safely keep up with legal secondary road traffic...without breathing hard.

They do sing as they work the upper band. As I posted earlier even the China girl engines I'm building don't hit pipe till 6,000 or 6,500 yet the middle of the pack (power wise) of the 50 cc KTM's, the C, put's out 9 real hp. I have no real idea what my modified motors make but it's dang sure less than 9 hp. & they run well and they are 66 cc displacement.

I'd forgotten the use of the little motors on the street pocket's and the Aprilla's are much sought after. Finding one for a song would be unlikely. I'd have a hard time spending much more than $700. for a running donor bike just to scavenge the motor & sell off the bits and pieces.

    Rick C.

[carryall]

They can be found a lot cheaper than you'd think.  I understand they were discontinued into the U.S. because of safety concerns being so fast yet so small and light in traffic and then EPA restrictions on the 2 stroke emissions. They choked them down in the European market at the same time. Most people nowadays just don't want small displacement engines, let alone 2 strokes for a street bike.  I see YSR50s and MB5 and occasional AR80 still come on C.L. for your $5-700 range but like you, (mine's health reasons) I can't/won't invest in a new Servi project in the foreseen future but, this is one idea that I think would work well IMO.  We got a lot in common bud.  I enjoy sharing thoughts with ya.  You and I could collaborate in a shop build quite well I'd bet!

[ndian22]

I have no doubt we would fare well in the shop together Paul; it helps to be on the same page with others, interest wise, and to share broadly based categories of interests. I've spent the last hour looking at photos from the last several years cycle swap meet wares at Davenport & my head is swimming with refreshed concepts of things I haven't yet built. Even with declining health the prospect of creating something new, to me, keeps me excited & feeling younger than 'ol Art & his evil buddies wants me to feel.

I value your input & experience as well. Having applicable knowledge and not sharing it with others seems a bit self centered. Rick C.

[ndian22]

Both modified China girl engines are up and now running well: the little trouble maker in the X-celsior Schwinn frame still feels tight, but only has about half the break in time on it. I don't think it will be quite as lively as the one in the Skyhawk frame. but time will tell. I have one more GT-5 on the shelf, bottom end is ready to go & I have a cylinder and piston ready to mount with some pretty radical transfer porting and piston mods. I'm not going to modify this engine for a reed valve/piston window port, but it should be pretty sporty without the third port and window. The piston is already ramped on both the intake and exhaust side to advance port timing & I go with a black & brown double cylinder base gasket to also advance flow timing. Only other mods required will be to deck the jug & add a 6 cc c n c aluminum head...both alterations increasing the compression ratio back up to a reasonable number since adding the extra base gasket lowers the compression. Selection of head gasket thickness will be based on how it runs after break in using a relatively thick head gasket, to keep the heat down initially. I'll mount it, when finished, on my "test mule" for break in and then let it set; for either a quick replacement unit or for a completely new build project.

I'm kinda' thinkin' a 79 cc Harbor Freight 4 stroke engine build is next, vertical mounted, shaved head, stiffer valve springs, ported and big carb ...small physical size is just the ticket I'm informed to produce 6 hp. Since it will be mounted on a bicycle pedal frame I'll do away with the pull start and not use a centrifugal clutch, instead I'll go with the 3 D manual clutch with a machined output shaft adapter (5/8" to 3/4") allowing me to pedal or bump start rather than use a rope which is a no no (bad shoulder) removing the tin parts also makes a very pretty motor profile and eliminates the bulky lawn mower look.

I've probably bought $5,000. worth of centrifugal clutches over the years and the 3 D clutch is really the solution to getting me on the Predator (any size displacement even the 212 cc) band wagon for real. The 160 cc also is of interest to me for bicycle frames. I really like the feel of riding with the light weight and small motors on the small frames. Of course bump starting/pedal start capability is my first concern, durability has been outstanding for the 3 D units. I'd like to see them offer output sizes to 1" as a V twin Vanguard bumped to 30 hp would be an interesting project for a highway cruiser build on a stretched Simplex frame and DOT compliant tires and wheels, with brakes to match.   

Just dreaming of projects that could and might be...heck a guy might have a side car rig by the time the Vanguard Simplex was ready to roll!  Rick C.

[ndian22]

Funny how things work out, posted yesterday about not starting any new bike builds, 79 cc 4 stroke & how I like the light & small feel bikes etc. etc. Then last evening my trading a Carter go cart for for some parts and a brand new Predator 22 hp V twin. Now I need a Simplex frame to house it, 'cause that's what it's going in. This one will be not be built with pedal drive or kick start, no pretense of it being a bicycle. All DOT compliant wheels & tires with good brakes front and rear. Geared to keep up with highway traffic, but still primarily a short rides motorcycle.

Frame stretch and reinforcement will be added where indicated. I'm thinking my sidecar project will actually go on this one rather than my Copper gator build. That way I can design the car mounts on a bare bike frame while eliminating having to compromise & design around the kick start lever and bicycle pedals etc. of the 5 speed bike. Plenty of torque with the twin to pull the extra load as well, though the 125 cc 5 speed would be adequate power wise, 671 cc twin is 'mo bettah!

Motor weighs 100 lbs. without battery, but has about 20 lbs. of junk that will be removed so not too bad & then, with parts removed, the engine dimensions don't form as large a footprint as the even CG 125 cc clone 5 speed does, so a battery box shouldn't be a big problem either. Adding 6 inch's to the wheelbase as I did on first Simplex should do it and that really does aid the Simplex maintain higher speed stability as well.

Just a few early thoughts on my "impulse" build, one that I've been thinking about doing for several years. Now I need a donor frame to build on. This is a long time bucket list item I'd like to check off before next Fall & positively no other bike builds in the meantime & "this time" I really mean it, lol.  Rick C.



 

[carryall]

Going to go BIG TIRE?

[Ricks]

Rick, that is a lot of power for a Simplex frame.  Stock frames used .065 tube, and I'm not sure that is heavy enough for the kind of power you are putting in one.  I think you are going to need to build most of the frame like you did with the gator.  I look forward to seeing this, as I know that all your builds are top shelf!

[ndian22]

Thanks Rick I posted an update on another forum just a moment ago & in doing so I expanded my thoughts on the frame issues, reading both posts really brings you up to date. Your comment is absolutely correct. I used heavy wall .140 DOM and lots of gussets and thick steel plate (3/16") on the CG 125 build, only the steering neck & strap seat spring are original Simplex pieces. Modification of a frame is really not an option for the Predator V-twin build. It has to be scratch built.

I came to the conclusion that I can either build a second frame or use the already stretched and much stronger frame that houses the CG 125 clone, with hard points added for the sidecar. I do love the little CG 125 bike but my Harley Davidson "Peashooter" has the same motor plus some performance mods and it's just as fun to ride.

Electric start on the Predator 671 cc eliminates the sidecar design problems encountered with kick start lever operation and pedal bike levers not being necessary for any reason. Really simplifies things on the car side of the bike, both from a car frame design standpoint and ease of daily operation with side car mounted.  This build will be a light motorcycle in every way.

I've not decided, but an engine change is probably the sensible thing to do 'cause I'm absolutely sure that my current frame, with an appropriate fork change & DOT rolling parts with brakes will handle both weight and speed of the bike and a sidecar. Making a nearly identical frame for the twin seems a boring prospect for me, it's kinda' a been there done that type thing.

Building with highway usage in mind will definitely alter my sidecar design choice as well, no leaning wheel! I'll go straight hard car to bike attachment considering even 50 mph speeds with sidecar mounted and occupied.  Do no harm to others is just as important to me as not skinning up my old hide, I hope even more so.  Rick C.

[ndian22]

Paul I'm thinking 3" on maybe 22" rims . The Copper Gator runs a 3" bicycle tire on 2.125" x 26" wheels and I don't have much room to clear secondary drive chain. If I go the motor swap route it might require going down to a 2.50" tire  but if I build a complete new frame, Simplex style, I can go wide as I want, but super wide probably would kill the vintage look I like. I have a couple of sweet forks in mind that will definitely handle the wider tire, brake and rim combinations.

Going the motor swap out route really opens up some options by lowering my initial cash outlay for motor (a swap) frame (reuse) etc. I won't feel guilty about buying a first class fork, all new rolling stock & motor mods 'cause that's all I'd have invested in the bike make over, all the take offs are as good as new and would be used again or traded/sold. That just leaves the side car, which would have happened anyway...so that money was already spent in my mind months ago.

This is all going to happen guys unless I'm called home, but that's ok too. I'm still planning on tomorrow till it doesn't show up!   Rick C. (still having fun)   

[carryall]

Since it's a 1" shaft, clutch selection will be really open.  Depending on direct drive, belt, or heck, you could even drive shaft with that power plant.  You could power your sidecar wheel even with the extra H.P. you'll have available?

[ndian22]

Yes Paul the 1" shaft is a plus for clutch options. I'd not thought about driving the car wheel, but have thought about adding an additional brake out there. Fun stuff for sure.  Rick C.

[ndian22]

Got to thinking out of the box and started sketching frame options. Result? Using the existing frame is out of the picture. Reasoning? It's strong enough, but not long enough. I want to add a lot of size to the frame in both wheel base (16" over stock Simplex base) for overall stability & appropriate sidecar mount locations and add proportionate height as well. I want the frame design to retain the look of  Simplex heritage & influence, but it will obviously not be a re-purposed Simplex frame. I've had a custom motorcycle frame in my mind for some time now based on the diminutive Simplex style coupled with '60's and 70's Ducati competition frame construction & a more current bicycle frame design called a Phoenix.

Going this route sure expands the complexity, total time and expense of my V-twin/sidecar build but really gets me pumped up about the build. It's more than just a do over, plus I love my little 125 cc Simplex Gator as it is...Rick C.