V-Twin Simplex Sportsman

[smallbore]

After considering how difficult it would be to find a Continental red seal engine, I scraped that idea and focused on the “cool” factor.... Wouldn’t  it be cool to have a ½ scale Harley or Indian looking bike ? So I bought 2 Honda XL75 engines for parts to build a V-Twin. The XR75 is perhaps a better engine with a 5 speed transmission, but it would never pass the Dept. of Motor Vehicles as the XR was an off road only model so I went with the 4 speed XL model which will pass inspection without any issues as it was a street bike from the factory.
I have already bought about 90% of the parts I need for this build, and will be using N.O.S. Honda controls, levers, throttle, and wiring harness to keep things simple and sanitary looking. The engine cases will get welded over where it says “Honda” and the Simplex logo will be engraved with a CNC mill.

At this stage the engine is just sitting loose in the cradle of the frame. Next step is to build a frame jig which I have already started, so everything will line up correctly. Once its mechanically built and all the bugs worked out I`ll break it down and do a full restore. I will post more photos in the future as this project progresses.

[illMATTic]

I always like the look of the home made Vtwins. Do you weld the cranks together? Weld the cases together?

[Mike Sal]

Will there be room to swing the kick starter?
Mike Sal

[james c]

hey smallbore! i see you are up to some of your old tricks with engine splicing? you are amazing! great to see you here also! (another minibike builder!) where did you find the sportsman? im building two simplex servicycles as minibikes have gotten a bit boring.   

[smallbore]

Hi James.
My 1965 Senior Sportsman was an eBay special. I think I paid a record price for one of these ( $800.00 ) but it was close enough to go pick up. It had been sitting in a barn in Yucaipa for the last 40 years. It came as a roller which is nice and straight. I paid what I did for it as these are pretty rare only being made for three years ('63-'65) and the unmolested condition. Plus '65 was the year Simplex went out of business, so that model year had very few built. I was going to use a Honda OHV 8hp with a TAV torque converter but that combo is just too wide. These senior sportsman`s are very narrow. My new XL V-Twin only sticks out beyond the frame about a 1/2'' so it fits perfect.  

illMATTic:
To build a V-Twin is a lot of work. Engineering, Machining, Welding, and a ton of hours. A V-Twin is nothing though compair to turning a straight 6 into a V-12 !
Take a look at this build:   http://thekneeslider.com/honda-cbx-v12-by-andreas-georgeades/

[Mike Sal]

An outfit in Ohio used to advertise motors in the Vintage Motorbike Club magazine.  One of them was a 250cc V-twin which I assume was a chinese knock off of a Yamaha design (Wildfire was the motor name).  Wouldn't something like this require less manhours (although I do appreciate the thrill of the challenge).
Mike Sal

[smallbore]

Hi Mike,
As much as I hate “Made in China” I will admit that I did in fact look at the Chinese V-Twin options out there. Seems that they are all too big for the senior sportsman frame without stretching it. Both heigh and width are too much not to mention the weight. I also spent plenty of time looking at dozens of options from Japan. Everything is just too darn big !
I want to keep the frame as it was designed. About the only real sin I have done to the frame was remove the stock engine mounts, which I saved and could be welded back in place if someone wanted to. Other than a few tabs I will weld to the frame for battery box, exhaust, etc.... the frame will remain as stock as possible.
The direction I`m going is plenty of work, but at least I can say its one of one made. Plus... If you think about it, using all Honda ( handle bar switches, wiring harness, charging system, etc....) Is already a proven trouble free system and considering I will actually be riding this around the city streets once in a while, it has to be reliable and trouble free. 

[Mike Sal]

I understand the aversion to using the china stuff.  I bought my Victory motorcycle to get away from the jap stuff.

What are you thinking in regard to the exhaust & induction for the rear cylinder?  Are you going to reverse the head & add another cam chain sprocket (is there room?)?
Mike Sal

[smallbore]

Heads stay same position. Crank cheeks are shaved, a new pin is made, stock rods are shaved on lower end, and a second sproket is used for the cam chain. Stock cams are used and a second set of points are added to the points plate. Also internal oil passages are lost so external lines have to be used. The problem with this configuration is the placement of the intake/exhaust. Its been done before but would not look good on this bike.
About 15 years ago I built this same engine with a fake rear cylinder. That allows for opposed intakes, more like a Harley instead of both intakes being on the rear. I am working on a new cam and rocker box for the rear to allow the intakes to face each other.  

[james c]

your skills are amazing, looking forward to seeing this engine develop! please post many pics.