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Bike of the Month - June 2004
1974/75 MR50 Elsinore
Dennis O'Neal
Houston, TX

 

Photos

In December 1974 I purchased my first MR-50 for my 6 year old son to ride. I thought, what a great bike, it has gears, a clutch, spoke wheels and everything just like a real dirt bike. He became an accomplished rider in about 6 months and wanted to race some of the other kids on their MR's and other mini bikes.


Our first race was in Danbury, Texas and there were 3 or 4 racers there that Sunday. I started modifying that day. I went to a lot of Moto-X races back then so several of us dads asked the big tracks to form a 50cc class. We had to promise the track owners at least 8 riders to make up a class. The first big race was at Rio Bravo in Houston and we lined up over 15 racers and that is where it all began. The Real Need for Speed!


Some of the early things I tried tuned out to be good boat anchors but not good racers. After a period of time I came in contact with a man in California who built engines for go carts that said he could help. I sent him a stock MR cylinder and he sent back a ported MR cylinder and a down pipe. What a difference! I won't disclose what the cylinder looked like on the inside but I will tell you it was not bored out. I now had speed but the bike had stock suspension- not good. That's where the lay down rear shocks and longer DG swing arm came in. It also needed something for the front. I added a Schrader valves to each fork tube cap but it was not enough capacity to do what I needed. It was also difficult to get the exact amount of air in each fork. I went to 7/8" handle bars and had the ends welded closed which made a capacity tank out of them. One Schrader valve in the middle of the handle bar, some instrument tubing and fittings and the air front fork was born for the MR.


The results you see on the Rocket bike is the grouping of ideas from many people and is very fast for a 50cc bike even for today. If there is a down side to the MR it has to be the rear spokes are too small and the metal of the frame too soft for serious racing. I laced the rear wheel with 8 gage spokes and got some 4130 chrome molly from Hobby airport and added front down tube supports. It made the MR look more like its big brother Elsinore.


We raced the bike in Houston, Dallas, San Antonio, Monroe, La., many small towns around our area and the Springfield, Mo. Nationals in 1976. We won over 90 trophies, placards and a Suzuki bicycle. The bike you see has a 1974 engine and a 1975 frame that I beefed up before I installed the race engine.


When we retired from the racing circuit in 1977 my son was 9 years old. I sold the bike to another dad who raced it in California and Nevada and did quite well. The only problem was he never paid for the bike. In 1983, by chance, I ran into him and got the bike back, which was then in boxes and painted red. I put it back together and kept it in storage until 2003. It now has been completely rebuilt, up graded and returned to its original 1974 orange color.

 

Photos taken at NASA facility in Houston, TX April 2004

 

Reproduction rubber parts for your Honda MR50 can be found here.

 

Dennis O'Neal
1974/1975 Hybrid Honda MR50 Elsinore Red Rocket
Specifications & Modifications
Bore 41mm Stroke 39.7mm
Front forks (air) 4.8" travel Swing arm 6.2" travel
Ground Clearance 7.0" Dry Weight 92 lbs.
Rear Tire 3.00/12 Front 2.50/14
Compression Ratio 7.3:1 Max h.p. 9.6BHP/7000 RPM
Clutch Springs RM 80 h.d. Rear Spokes 8 gauge
Porting Classified Piston Rings Wiseco
Rear Sprocket 47 T Ignition Mototek CDI
Frame Pwdr Coated Dupont RAL Frame front tube 4130 Chrome molly
Handle Bars 7/8" dia Grips Pro Grips
Handle Bar Mounts Honda XR75 Chain Tensioner Pro Tec CT-19
Carburetor Keihin 22mm Displacement 52 cc
Kickstand Quick remove style Swing arm DG 1975
Head DG Radial 1975 Exhaust Aluminum Down pipe
Rear shocks 12-1/2" lay down Rear Springs Progressive
Engine Heat coated Throttle 1/4 quick turn
Levers Ergonomic Seat Custom
Chain RK 420 gold Kicker swing out
Triple Tree Aluminum Air Filter 1-1/2" Uni
Side covers Hand formed f.g. Intake manifold modified
Engine Matched & hand flowed Tank decal Gold reflective
Spark Plug NGK B8HCS Final Ratio 3.92