Racing a Honda CB400F

May 31, 2023 | Motorcycles, Racing, Vintage

Franny kissing her CB400F

The Thrill of the Ride

The Honda CB400F is thrilling to race due its power potential power and strategy challenge of keeping it in the 8-10,000 rpm power band. The configuration of this 400cc 6-speed 4-cylinder make for an exciting challenge on the race track to keep it inside of this narrow power band. Lug the engine and you go from 1st to end of the line while waiting for the power to match the gear that you mistakenly chose. This challenge makes it so that I will never get bored on the track year after year.

I got this machine from an source I will keep anonymous due to the fact he claims to never have let go of any motorcycle. He is a legend in the club vintage racing world. We had to trade a Honda CBX for it! Prior to the previous owner it was owned by a man that ran this bike in WERA. It has lived the majority of its life run hard but much loved.

Getting Ready for the First Race Day

It is different than the stock CB400F that was produced from 1975 – 1977. It has an added oil cooler, Tarozzi fork brace, steering stabilizer, round-slide 29mm Keihin racing carburetor, Yoshimura cams,  valves sent directly to the shop from Japan with a “thank you for doing business with us” handwritten on rice paper, RaceTech shocks, and RaceTech front forks configured and valved here at the shop by Matt Wiley (the RaceTech vintage expert) and Marc Beyer. The front end is from a Honda VFR. The engine has a slight over-bore due to 2 engine rebuilds. There is a ceramic coated straight pipe and the 4 into 1 exhaust configuration. Starter has been removed to save weight but the kick-start lever stayed.

There is much that goes into the maintenance prep of this bike. Some short videos (2 minutes at most) posted to our YouTube Channel showing Marc Beyer and Franny Sayre getting Franny’s Honda CB400F ready for the track and race weekend at Sandia Speedway with SMRI in Albuquerque May 13th – 14th. Carburetor installation and carburetor balancing the old school way.

We checked the spark plugs and thought they looked too dark so we replaced the 115 jets with 112s. Put new spark plugs and hoped to get a better response with the new jetting.

 

Tight Ratios!

I wanted to purchase a couple sets of tires for the beginning of the race season so I called up Heidenau to order my K65Race compound tire sets. The rear I use is a 100/90-18. Well they were out of those so I ordered the 110/90-18 and hoped it wouldn’t make much difference. What I worried about was a slower turn in on the wider rear.

Took this tire set-up to Sandia Speedway for their first track day before race day to make sure everything was sorted. The error was that they ran what was called the Alt-Configuration. This very tight technical course had no long straights and the bike ran like a champ. Quick take off and I was able to use the whole tire so I thought all was well.

Franny on the grid on her Honda CB400F

I found out that changing the tire size fromm a 100/90-18 to a 110/90-18 is the equivalent of increasing teeth in the rear sprocket. Race day was run in our regular configuration so there was now a much longer front and back straight. My starts were quick so I was running in front the only other bike racing in my class. I was amazed at how fast the rpms topped out in each gear and I found myself out of my regular shifting pattern running a whole gear ahead of what I usually find to be most efficient. I thought, “am I really going that much faster?”.

I was shifting up 3 or 4 gears on the straights and then had to shift down those gears going into the turns and I was counting in my helmet out loud to keep track of all this (while racing). I was making mistakes and could hear my competitors loud engine behind me. 1 lap to go and I would be first!! I came out of the the hairpin in 3rd gear (should have been in 2nd), rolled on the throttle and of course had no power at 6000 rpms. Just like that my lead was gone and I went from first to last. Tight ratios. I had to ponder what went on all the way home and thought my way through it. What I love about racing this bike is not my challenge as a physical rider but also the strategy involved get this bike to stay ahead on the track.

Franny and her Honda CB400F