$35 Robin 40cc Friction Drive

Discussion in 'Friction Drive' started by BigBlue, Mar 11, 2013.

  1. BigBlue

    BigBlue Active Member

    Bought a Robin EC04E 40cc Robin off Ebay for $35. It was a refurbished engine with all the original Robin tags. It was used by Coleman as a generator engine and has an extended shaft. This is a Japanese version of the CAG engine. Staton sells the engines for $140.00. I mounted it to a ThatsDax friction drive kit. My neighbor gave me the bike last year.

    I bought a used crankshaft from a Robin NB411 engine and replaced the original generator crankshaft. I bought it from Small Plant breakers in the U.K. for $32.24 and $13.70 for shipping . I believe it would have cost at least $175.00 for a new Robin crankshaft here in the USA. A pocket bike crank would have worked, but I wanted a Robin crankshaft. I was able to use the needle bearings that came with the original engine; even though Small Plant Breakers included the used set with the used crankshaft. I could have turned down the crankshaft on my mini lathe. I calculated that the taper for the clutch is 5 degrees. I might turn it down as a spare or make it adaptable to a KTM 50cc clutch that looks similar to the Grubee Stage 4 clutch.

    I could of bought a used carburetor from Small Plant Breakers for a Robin NB411, but wasn't sure if it would work. The original carburetor was electronically controlled. I didn't want to spend the time figuring if I could adapt it, so I also purchased a pocket bike carburetor from Ebay. It is a better quality Chinese name brand and has a metal fuel control valve rather than a plastic one that come on the cheaper carburetors. It was $29.99 with free shipping. The seller lists the carburetor as a Robin MB411 replacement. They also sell crankshafts, but look like made in China pocket bike crankshafts. They are not genuine Robin cranks. .

    I had to buy a intake carburetor adapter. Unfortunately, I could only find the plastic type used on pocket bike CAG engines. Originally, the engine had a nice aluminum intake. The intake bolt holes were too large for the carburetor mounting bolts, so I had to replaced it. I looked at redrilling the replacement carburetor mounting holes, but it would had cut into the body of the carburetor. I think I paid about $9.00 for it.

    Of course I had to buy a new air cleaner housing and filter and I paid about $4.00 for a pocket bike version.

    I also bought a gasket set for about $5.00 on Ebay for a pocket bike CAG style engine.

    Purchased a throttle control and cable from Sick Bikes.

    Used the exhaust from a pocket bike CAG engine. I bought a Robin exhaust from Staton on sale for $9.00, but didn't like the exhaust port mounting flange and it didn't work with my ThatsDax friction drive kit. It wouldnt' clear the end of the engine mount. I'll make a new exhaust port mounting flange and cut and reweld the exhaust later.

    I bought a clutch from an Ebay seller that has 2 shoes and two heavy duty springs for $19.99 with free shipping.

    It runs great and the engine is quieter than my 49cc China CAG engine. I need some slick tires as the raised knobby tires that came with the bike are dry rotted and are shredding fast. With my 265 lbs self, it needs some pedaling assist to start and going up hills. With a peak 2hp rating, it is definitely strained with my big body. I guess if you weighed a 100 lbs less, it would be perfect. I guestimate my top speed at 20 mph on flat land, but haven't pushed it.

    Here's a picture of the bike completed, front and rear view of the engine, clutch and old carb and new carb:
    Bike1.jpg Engine1.jpg Engine2.jpg clutch2.JPG View attachment 47869 Carbs.jpg

    I'll probably sell the unused parts on Ebay and maybe recoup some of my costs. I found a one piece 52cc cylinder kit for $39.00 and might bore out the carburetor in the future. A one piece big bore kit would not cause the loosening of bolts like the 2 piece kits.

    AKA: BigBlue
    Last edited: Mar 11, 2013

  2. darwin

    darwin Well-Known Member

    Nice clean bike and saved a few $$$$. Cool how you pieced it together.
  3. grinningremlin

    grinningremlin Active Member

    Pretty cool, but I count $136 (not including the time) for the engine.Keep your eye out for the HF 52cc, could save you a little in further mods.
  4. Lee_K

    Lee_K Member

    I have looked at that engine on the Staton site many times. I like its size and layout. It's good to see how you solved the problems with the carb and long crank. I am still working on my second MAB, by next fall I should be itching to do a third, I would consider that engine. Thanks for posting, it's an interesting project.
  5. BigBlue

    BigBlue Active Member

    Thanks for the compliments. I believe the Harbor Freight 52cc was a Mitsubishi clone and I am not sure parts are inter-changeable with the CAG style engines.

    I don't think it is a bad engine, but under-powered for my 265 lbs. New tires, some adjustments to the carburetor and allowance for break-in may improve the engines performance. As I stated in my OP, the tires are 2" knobbies with dry rot and can only be inflated to 40 lbs, so there is not much rolling resistance. Some shredding of the tread is occurring. Not complaining for free:)

    Definitely adding a new carburetor, velocity stack and a tuned exhaust would open up the engine.

    AKA: BigBlue
  6. scooter dave

    scooter dave New Member

    Your old carb?

    How much would you want for your old carb?
    Scooter Dave

  7. BigBlue

    BigBlue Active Member

    Scooter Dave,

    Thanks for asking, but I think I'll keep the carburetor and play around with it.

    AKA: BigBlue