Old Guys Simplex moto-peddle bike

Ludwig II said:

Don't get sucked into placing the barrel central. It will sit off to the right of centre as you sit on the bike when it goes in a normal solo.

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Ludwig approximately how far off center did the jug sit on your 125cc race bike? Since the Simplex frame is a double tube it balances pretty well even when the jug is 3" + offset to the right. Though I'll have quite a bit of flexibility built into my motor mount design. I'd like to get it close to start with. I'm also very close to perfect engine sprocket alignment at a little more than 2.25" offset, without a reduction gear offset. Since I've already put the parts together & machined the co-axle shaft I'm not trying to just get by with whatever the alignment comes out to, just seems a bit of overkill to do a reduction & only run a single sprocket on the engine side co-axle for the sole purpose of eliminating a chain tensioner. Your input would be appreciated. Rick C.

Thanks for the quick reply Ludwig & makes complete sense in a race set up.

Right case copper mock up, patinas a touch more aged. I'll cut a flat plate similar to the opposite case when I have a bit more time. Before & after photos of the 125cc cases. Rick C.

Designing as I go is probably not the best way to approach a build & certainly not the quickest or the most economical. What appears at first glance a good idea is often not & I modify or abandon plans as any of builds progress or stall. Aesthetics are important to me as is functionality in daily use. Though I'm not restoring or duplicating to factory standards I'd like to honor the feel of an earlier time when things were simpler. At the same time upgrading dependability, safety & performance of the finished project.

The Simplex Cajun-Gator has certainly morphed along the way and quite possibly will continue to do so as I design on the fly & off the cuff. Just having fun. Rick C.

The Simplex disassembly is under way. It's going back to the shop for awhile. I have additional frame braces, motor plate & co-axle pedal bracket etc. yet to install. I'll then assemble it as a functional bicycle first & ride it for awhile. If it won't function as a pedal bike it will never be a satisfactory motor transport. All my motobikes are constructed in this order. When I've ridden them to my satisfaction I then paint the frame and reassemble with an engine /drive train & again test. Adding the accessories & shiny bits after several hours of road time completes the process. Rick C.

I've been reading some old threads (to me) that often describe the China doll using many varied and often entertaining negative adjectives. These frightful insights are shared by many. Many of my bikes over the last 10 years have used these inexpensive little power plants with great success. I credit some of this to being a mature (old) fellow who doesn't thrash a motor as hard as he once did, but I feel there are other considerations as well. The three bikes I currently ride are the culmination of what I've learned about these little two strokes over a decade & riding/building two stokers on and off for about 50 years. Just going to mention a few & briefly at that. Cooling is vital & adding efficient cooling surface area is an effective method of throwing off heat. Aluminum after market heads, exhaust flanges & side plates etc. are great. Run NGK plug & proper heat range, learn to read a plug and adjust as engine mods are made, don't go overboard on increasing compression, use quality oil in the fuel mix, don't use alcohol blend fuel. I've always used premium fuel especially after alcohol was introduced as a blend ingrediant.

A quality CDI, Lightning, Rocket, Jaguar are all some that I've tried and still use. I like them all & they virtually eliminate detonition which lowers heat. Course all this stuff takes time and money. I tear down each motor when it comes in & balance, cleanup, port match & install new bearings if cheap ones were used at factory. Replace all butter bolts with stainless socket heads & grade 8 head bolts & hardware. Some engines recieve various performance mods but most are not modified much beyond what I've mentioned & bolt ons like SHA carb, billet manifold, expansion pipe, mild 6cc head & CDI. Reduction of friction & throwing off more heat are my main goals...thus gaining increased engine life and dependability. It's also nice that they generate more useful power and run smoother as well!

Take from it what you will. It seems to work for me & I'm still riding and loving these little modified motors while some others seem to detest them...remember I also love the 4 strokes as well & have had equally good results with them following much the same guidelines as mentioned above. With respect...Rick C.

Spot on Ludwig. As a young fellow racing in stock class drag cars we all saw what a huge difference balancing & "blue printing" (assembling to specifications) an engine made and still does. Old fashion terms which are probably not in vogue any longer yet still appropriate.

Consideration of daily application is also commonly ignored. I've bought high performance vehicles from individuals far below value, who thought they were getting rid of a lemon cause it wouldn't perform in rush hour traffic like their previous mid size family car. Unreasonable expectations for sure much like constantly twisting every rpm from a factory $120. China kit & thinking it should stay together...doesn't happen that way. Rick C.

Agreed, Honda products in general are well designed & built. Those Chinese clones that most closely approximate these original designs, material specs, tolerances etc. have proven to be exceptional values for a wide range of applications...including those featured on this forum. At least for this humble build I'll stick to the stock CG125 engine design & try to be satisfied with it's factory performance with the 5 speed gearbox. I'll not be racing any of my moto pedalers at any rate just ride & smile are my stated goals.

Finally found the mis-placed co-axle shaft & bearings for the 2" bottom bracket/gear reduction unit. I'll use this with 3 piece wide pedal cranks I had in my bike parts inventory. Still left to machine & assemble are the motor side reduction sprockets, spacers & bearing mounts. Not going to worry about final drive ratio just get in the ball park & fine tune as real world dictates. Posts some photos later.

Rick C.

Finally had a bit of time to take photos of the co-axle/bottom bracket parts. Not shown is the 68mm wide 2" ID pipe I'll be using & the 3" long by 1.5" square tube riser for the bracket itself, or the free float reduction sprocket, spacers & bearings for the motor drive side of the axle.If you have a lathe & mill it is a simple machining exercise to build, if not Pat at Sportsman has a slick unit available for purchase which could be easily modified on the drive side to accomidate a wide range of motor options. I chose 3/4" shaft as bearing and sprockets are readily available, but metric is also common in karting etc. Unless you know a machinist that owes you a favor it's cheaper to purchase from a good vendor than paying for the machine work.

The axle itself is 3/4" diameter & about 12" in length. I had the wide peddle levers in my stock of parts, but the ring gear is much too large for my purpose & will be cut off & replaced with a 25 tooth to give clearance for motor cases & ease of pedaling. The axle was mill cut for a keyway on the pedal side 2.75" to allow ease adjustment for chain alignment. The smaller ring sprocket will mount with 3 bolts to the 2.5" round aluminum sprocket holder which was broached to lock up with the axle keyway. The holder is "split" & can therefore be adjusted for alignment and then locked in place by a bolt at the split.

I'll post the motor side floating reduction drive sprockets, mounts, spacers when I've finished them...it will be awhile, but simple stuff once I determine chain lines for the two chains required. Basically just two sprockets mounted to bearings, each located & spaced the correct distance apart to give straight chain lines...while sufficiently clearing both tires and frame. Maybe too much info but I've seen some struggle to build this simple device. Hope this can help. Rick C.

Forgot to mention that the wide crank levers that I had on hand are of the three piece type so the axle was set up for square taper & tapped...cottered would have been more period correct I suppose. Also I'm just using 2" black pipe, schedule 40, which I found in the scraps for the bracket shell.

1937 Ford pickup is coming along nicely. I'm hoping to take it along with the rat rod Chevy truck & some motobikes to the October car show. Rick C.

Thanks Butch, this pickup will never be a real show truck while I own it, though I'll enter it in a few shows just to enjoy the company of enthusiasts like myself. I'm building riders & drivers from here on out, though I'll always enjoy trophy quality machinery it's no longer what I'm about...now it's just enjoying whats interesting! Rick C.

Nothing wrong with having a good looking vehicle that you can also drive or for that matter a museum full of perfect machines that are only meant to be viewed & trailered...I've owned both types, just have more fun with those I drive or ride & it sounds as though you've got a beauty of a bucket that you share with others on the highways and byways. It's good to share! Rick C.

Butch I bribed a teenager to step me through the process, took less than half an hour & I was posting photos. My next step is to actually learn how to take decent photos to post! Rick C.