Honda-SOHC

OK, not really but last week I was out and going through the gears to redline and missed a shift at full throttle into 4th gear and saw the tach whip past 12k RPM with absolutely no ill effect in the remaining 50 miles of the ride.

I was talking about that with a vintage Honda race tech guy here on the Isle of Man - we're here for the Manx GP - he said that the "Honda rev limiter" back then was valve float which would essentially "shut off" the engine when the RPM got to the "float point."  He said valve float would occur long before engine RPM could hurt anything.  He seemed to know what he was talking about since he was one of the techs preparing vintage Hondas for the races here. 

Thought I'd post this due to the general interest in the front brake performance and the internet myth that the front brake was no good from the factory.  Yes, I continue to have a bit of a bone to pick re the concept that the front brake is inherently poor.

A week ago I removed the HEL brake lines (link below) that I had installed two years ago when I was sorting out the (as received from the PO) TERRIBLE front brake.  The rear brake actually had more stopping power no matter how hard I squeezed the front lever.  So in "overhauling" the system I also replaced the original brake lines with the HEL's and, after a lot of testing/five different pads/bedding in, I found/stated that the brakes were quite good.  Other than the HEL lines, the brakes were totally stock - rebuilt with "Honda" parts if available rather than pattern parts (piston, seals, etc)

So last week I replaced the HELs with the standard (pattern) brake lines (from DSS).  I would have purchased the "Honda" lines but they were special order through DSS and I didn't want to wait.  I was curious if the "better" HEL brake lines were a major factor in the improved performance and I was prepared to put them back on.  But there was no difference at all in feel and the front brake can still overwhelm the tire.  IOW, the totally stock brake system can lock the front wheel!  Yes, it takes a considerable bit of hand pressure but there is plenty of braking power available.  One thing I have discovered in relation to this is that along with PROPERLY bedding in the pads, the front tire pressure is important. 

Honda states the tire pressure (psi) is 26F/28R.  I have seen internet (so it must be true) statements that modern motorcycle tires must have higher pressure than the tires that were in use back then.  But I have found that if the front pressure is raised on my CB400F there is less braking force available and the tire will start howling (impending lockup) under hard braking with noticeably less front brake pressure than with the pressure at 26PSI.  IOW, I have more front stopping power with the modern tires at 26 PSI than at 28-30 PSI.  The rear will lock up very easily so doing skids is a doodle if that's your thing.  I have never done anything/checked anything on the rear brake - it's just as I received the bike.   I probably should at least check the shoes for wear...I'll do that one of these days. 

https://www.helperformance.com/honda-cb400-f-1975-1977-standard-replacement-brake-lines-hel-stainless-steel-braided

I mentioned a while back that the throttle on my 400F suddenly (after winter storage) would not fully return when released.  Also the clutch seemed much stiffer than I remembered.  I installed new cables two years ago so at first thought it might be something else. 

NOPE.

New cables sorted out the throttle and the clutch.  Kinda' surprised that cables would stiffen up that rapidly.  The previous cables were from a supplier I won't use again because 1/3 of the parts I purchased from them for my 400F back then did not fit even though they were stated as being for the 400F; the current cables are from DSS where I have purchased most of my parts and have not yet had an issue with them.

Nice to have smooth cables!!!

I'm wanting to install a Stahlbus brake bleeder valve but don't know what thread size the OEM bleeder is.  Anybody know - M7x1x16, M8 x 1.25 x 16, etc?  Thanks!

Yesterday I "woke up" my 400F from its winter storage and found that the brake light would not illuminate when the front brake was applied.  It did illuminate with the rear brake pedal.  When I put the bike in storage, the front brake illuminated the light correctly.  So it "failed" by sitting for 4 months.

Ironically, I had installed a new switch when I was overhauling the front brake system almost two years ago even though the original switch was working fine but I figured that a new switch was a good idea; it wasn't.  Wish I had kept the OEM switch that was working OK but I tossed it in the trash can.   

In doing some research, it appears that these pattern switches are not particularly reliable but it is all that DSS carries.  Are "Honda" brake switches available anywhere or do I just buy another pattern switch from DSS?

When I was out today I decided to check the speedo indicated speed vs a GPS (Speedometer) app on my iPhone.  Generally, it seemed to show that the speedo indicated  a +5MPH difference at all speed ranges from 20 to 70 MPH.  The speedo (and tach) are new DSS items.  I have no idea if the app is accurate and see no way to accurately check either the speedo OR the app.  FWIW, the app has indicated the GWR London to Bristol run as reaching speeds of 125MPH.  Does it?

OK, not really but I missed a full throttle 2-3 shift today and the tach needle (and engine RPM) went flying to the OTHER side of the tach's red zone!

Engine acted as if nothing had happened and continued to run perfectly, including several more redline (non-missed) shifts!  I post this NOT to encourage spinning to 12,000 RPM, but as a comment that these were very well made little engines! 

I have a spare CB 400 front brake rotor and am thinking about having it drilled. I COULD do it myself but the measuring/marking out/drilling the holes is more fiddly than I prefer to deal with!    Can someone recommend a UK shop that does this?