Topic: CB400F Old Timer Aftermarket Questions....

[MetricMotowerks]

A few years ago I picked up a 75' CB400F that the previous owner bought of off the floor in 77' and took it to the track. The case had a hole in #4 and had been sitting since 80' or 81'. I've since rebuilt the engine, but kept most of the rare-ish parts that I have found and was hoping to get a little more information about a few parts in question. Here's a breakdown of what was/is on the bike from the original owner...

Lockhart oil cooler
Koni shocks
Martek 440 (recently stopped firing 2/3 and has been swapped back to points)
BMW series K&N made to fit into a modified airbox
D.I.D rims
Stacks of washers in the forks for pre-load 

And the parts in question are...

Unknown valve springs:
Black and sit in steel cups similar to Kibblewhite

Unknown camshafts (I have two):
Both have similar lobe heights and are definitely higher than stock (closer to the Yoshimura ST-1 camshaft) but have different lobe profiles

Kaz Yoshima look-a-like exhaust:
Hanger mounts to the center stand bracket, but the pipe is a slip-on type with a clamp. Not sure if the Kaz Yoshima had that

So, my question about the unknown parts is pretty simple. What companies were making those parts back then?

[Tim2005]

I'm not sure about the valve springs, but I think I may have seen a Kaz exhaust with a clamp years back, and here are teh main cams that were available. If any of yours are nearer to an ST-2 I might be interested too... 

http://web.archive.org/web/20100422072747/http://cafe400f.cloud.prohosting.com/html/CB400f_Cam_Comparison.htm

[Mark1976]

Give some pics, it'll help.

[MetricMotowerks]

I'll get some pics tomorrow or Friday

[MetricMotowerks]

Picture of the exhaust. It was welded with stock flanges on the pipes.

[Tim2005]

That looks the same as the Yoshima one that I have a photo of from several years back

[MetricMotowerks]

That looks the same as the Yoshima one that I have a photo of from several years back

It sure does. The only different is the stock flanges on mine, but they Have been painted black.

[Tim2005]

Great. Did you get anywhere with identifying the cams yet? Also, was it a big bore motor?

[MetricMotowerks]

Great. Did you get anywhere with identifying the cams yet? Also, was it a big bore motor?

I haven't had a chance to measure the lift yet, but I did measure the lobes. The profiles of the lobes are different for each cam giving one much more duration. Motor was not a big bore, but I do have a set of Yoshimura 54.5 pistons and a unbored cylinder block

[Tim2005]

That's all very promising- the Yoshi kit will work well with the other parts & make for a great bike. You might want to look into flowing the head and boring the carbs too, all have useful benefits

[MetricMotowerks]

I was planning on porting an extra head and boring the block at some point. I reached out about getting the carbs bored, but the post office near me made it a pain to ship them to Canada. It was a while ago, so Covid may have had something to do with that. I should reach out to DenoonSP and try again.

I measured the camshafts and found that the extra cam I have is definitely a Megacycle cam (according to the chart). The extra duration is also very noticeable just by looking at the lobe. The cam that was in the bike is very close to the Megacycle, but the intake has about .3mm more lift and the valves open much quicker.... possibly a custom grind. The original owner was running here in Colorado so I can see why they chose duration over lift.

[Kevin]

I don't have much info for you, but maybe what I do have will help.

The header looks very much like the two early Kaz Yoshima exhausts that I have. Because they were hand bent there can be slight differences.

I believe that the camshaft cross reference page that Tim linked to was put together by Jeff Ch*n*ev*rt. He was building a motor for vintage track days.
The KSM camshaft was a copy of the Yoshimura ST2 that I was selling back in the day. Somewhere in storage I have measurements of most of the cams that were available back in the day. But it'll be a long time before I can get to them.
If you go to the home page of the website that Tim sent you can see a lot more information about the bike he built. I ended up buying the bike and it still sits in my storage unit. I have future plans for it.
http://cafe400f.cloud.prohosting.com/

The valve springs you have sound very much like S&W.