[ After finishing the engine installation and re-gearing a couple of times to keep the wheelie factor down, I noticed a problem in the upper RPM range with the bike. It seemed like it was cutting out or something. It was driving me nuts. It would run fine until just ready to shift to the next higher gear and BAM , there it was.  A couple of e-mails to Enzo about the problem, he guided me through a excellent process of elimination, checking both the fuel delivery and the 6 volt contact point ignition. The problem was found and solved.

Now, I built both my ct -70's myself, but when they didn't run right, Enzo's help was there via e-mail without delay everytime.

Thanks Enzo!

These big-bore, long-stroke, high compression engines can be finicky.  :) ]

 

Just finished reading this one. The owner did a really nice job & has my compliments.

 

I just want to add one thing to caution your readers regarding the repair of shift forks. Although very easy to do or have done, merely welding on the shift forks & grinding them to the proper thickness is not a sufficient repair. The story does not go into any detail as to if the forks were re-heat treated or not, like they were when they were originally manufactured & I just want to clarify.

Pictured below is a set of shift forks. The areas at the end of the fork tabs are what moves the spinning gears back & forth on the shaft, wearing over time.

When a specialty shop repairs a shift fork, they only start by welding on them. This is done where the forks are worn down, to add the metal lost over time. Merely adding weld to the worn area, however, isn't sufficient. I've done my own testing in this area & my findings were interesting. Just about every motor I rebuild has at least one worn out shift fork in it. All the shift forks for the 50's & 70's are available from Honda except the left side fork for the automatics, which are discontinued from Honda & have been for years (HEY HONDA, WAKE UP!) I install only new OEM Honda shift forks in my rebuilds when available. When I'm rebuilding an automatic that has a worn left shift fork, I have the fork professionally repaired at a local specialty shop. The reason for this is because the shift forks are hardened steel at the contact points & this must be replicated in order to maintain the longevity we've come to expect from these engines. 

Utilizing a Rockwell testing scale (used for measuring the hardness of steel) will reveal that the shift forks are VERY hard at the contact points. Without getting too technical, If you were to weld on the area & NOT put it through the proper heat treating process, the repaired area would remain soft (in relative terms).  Experts in this field will tell you that installing welded-up shift forks void of the proper heat treating process will wear out rapidly when run in an engine. My own testing has backed up the thoughts of the few very knowledgeable transmission veterans I have spoken to. This is also taking into consideration the low horsepower & relatively low use of these bikes, generally speaking.

 

In conclusion, I strongly recommend replacing the shift forks wherever possible & having them professionally repaired when not. It's very tempting to simply weld up the worn out tabs & may work for a while, but in the end, I would not want to see anyone have to pull one of these engines apart any sooner than necessary after a careful, meticulous rebuild.

Keep up the good work!

Best Regards.

Enzo

www.motoenzo.com

enzo@motoenzo.com