denoonsp - Home of the modified 400F

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Denoonsp is not affiliated with Ontario Moto Tech in any way. The following article is provided for your information only.



Yoshima Racing Service (YRS) offers high quality performance equipment and services for popular four-stroke motorcycles. YRS products are tested repeatedly in extreme conditions and are carefully inspected and evaluated to make sure that each product meets our own strict standards of quality, reliability and longevity. 

Of course, the best proof of all is not wins achieved by manufacturer-sponsored racers with special engines, but it is the numerous successes of our customers who have bought our products and are winning races. This is the reason that mechanics and motorcycle enthusiasts have come to trust our name, products and service.



Engine Parts

1067 Racing EXHAUST SYSTEM, tube tail w street baffle, CHROME 
1068 Racing EXHAUST SYSTEM, tube tail w street baffle, BLACK 
1190 Standard Replacement Baffle, 1 1/4" 
1191 Optional baffle, 1 1/2" 

1223 458cc PISTON KIT with head gasket, no resleeving necessary 
1224 466cc PISTON KIT with head gasket, no resleeving necessary 
1273 Piston, 458cc, 54mm, 10.5:1 
1274 Piston, 466cc, 54.5mm, 10.5:1 
1313 Piston Rings, 458cc, 54mm 
1314 Piston Rings, 466cc, 54.5mm 
1343 Wrist Pin, 458cc & 466cc 
1362 Circlip 
1386 Head Gasket 

1420 Road & Track CAMSHAFT, billet cam 
1421 Ontario Special CAMSHAFT, hardfaced & reground, exchange 
1450 Refundable camshaft CORE charge, $2 service charge 
1491 Heavy Duty VALVE SPRING SET with alloy retainers 
1492 Racing VALVE SPRING, use with stock retainers 

1606 Racing CAMCHAIN, endless chain 
1630 High Pressure OIL PUMP, Exchange 
1631 CORE Charge for oil pump, refundable less $2. 
1881 Swing arm BUSHINGS, bronze alloy 
1940 Race Action Clutch Kit with Springs 
1970 Race Action Clutch Springs 
1914 Dyna-III IGNITION System with black box 
1920 Dyna COILS - 35,000 volts 
1922 Dyna Ignition WIRE Set 

2080 CB400F carburetor boring labor (carb must be stripped) 

Oil Pump

If you already have an oil pressure gauge hooked up to your Honda 400f, you have undoubtedly noticed that the pressure will only go up to approximately 40 pounds. While 40 lbs. of oil pressure may be adequate for a completely stock bike, our experience shows that much more oil pressure is required of a reliable racing engine. The YRS oil pump developed by Kaz Yoshima will bring oil pressure up to a healthy 65 to 70 pounds.

Engine Stages

CB400F Engine X-1
Gives quick throttle response and great increase in performance throughout the power band using stock red line. Perfect for street riders who want extra power and better gas mileage as well.
· Road & Track Camshaft
· 458cc Piston Kit

CB400F Engine X-2
Looking to get the power of 750 engines with the great handling of your 400F? This is it! the use of YRS Exhaust System and 42 teeth sprocket should put you in the lower 13 second bracket, as proven by Ms. Monty Fisher who achieved an ET of 13:26 at the Byron Dragway, Illinois. The redline is 10,700 rpm.
· Road & Track Camshaft
· 458cc or 466cc Piston Kit
· Hi Pressure Oil Pump
· Racing Head Modification

CB400F Engine X-1
Very potent café racing, road racing, drag racing motor which also happens to be very streetable as featured in numerous motorcycle magazines (Big Bike 7/76. Cycle Guide 8/76, Cycle 6/77, Modern Cycle 11/77). A mean motorcycle that goes over 130 mph and more with fairing. the redline is 11,500 rpm.
· Road & Track Camshaft· Your rods shot-peened
· 458cc or 466cc Piston Kit · Extra Strength Camchain
· H/D Valve Springs · Racing Head Modification
· Hi Pressure Oil Pump · YRS Exhaust Pipe


BIG BIKE, July 1976
“Rocketship Honda!” by John Ulrich
“The checkered flag waves. I’ve won! After riding on the street for two weeks, after riding to the track, the Yoshima Racing Service Honda has carried me to victory.”
“Kazuo Yoshima is determined to prove everything he builds. With this 400, he already has. It’s a rocketship.”

CYCLE GUIDE, August 1976
“A Mean Motorscooter and A Bad Go-Getter” by Art Friedman
“The bike is a most impressive racer. It’s easy and pleasant to ride fast, and goes like hell down the straights. . . It took Yoshima ten minutes to make the bike a street machine again.”

CYCLE, June 1977 
“Yoshima’s Business Card”
“This business card beats Kawasaki Z-1s.”
“‘Compact’ is the best word to describe the Kaz-machine. It weighs in at 275 lbs. ready to race, has unlimited cornering clearance, handles superbly and goes.”


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