Topic: 400/4 Frame Modifications

[anthonyp]

Has anyone made any structural/ weight changes to their 400/4 frame? Specifically strengthening the stamped top tube; seems like they took a Trail 90 top tube and glued it on. Can you make the stock frame basically race-ready or is that too much demand?
-a

[Sam Green Racing]

Anything can be improved, road going motorcycles are designed by accountants not engineers.
It's all about keeping the cost down, sorta like a valve, it's cheaper to weld a head onto a stem than make it from one peice.

Sam.

[Tim2005]

Are you in the CB400F yahoo group? One member, Rick Denoon, has done some 3d cad modelling of the frame that examines the torsional forces that can be exerted and covers some of the potential options for adding bracing. Link to the group below. There are also some members on here that you could search out who race 400s, I am not sure if they have needed to brace their frames though.

http://autos.groups.yahoo.com/group/cb400f/

[turboguzzi]

would check the cycle mag story on the kaz yoshima 400 racer,
being as thorough as they were, guess that frame mods would be mentioned.

think the article is somewhere in the archives

[anthonyp]

AHH awesome thanks for the replies guys.

[specweld]

The 400/4 frame does not need any modifications it is fine as it is, however that can't be said of the forks or rear suspension, if you are looking for better handling these are the two items that need attention.
 

[Grey]

The 400/4 frame does not need any modifications it is fine as it is, however that can't be said of the forks or rear suspension, if you are looking for better handling these are the two items that need attention.
 

Totally agree on that one. Had a built 24hr endurance racer. Had a Hercules Wankel front end on it and had to brace the swing arm. Tires were same size as the 750 bikes of the time. Handled real sweet even thru bumps at Nelson Ledges.