honda305.com Forum

Well, still no real progress but I spend the odd lonely evening in hotels looking through eBay. I couldn't believe it when I saw this - a NOS 1961 tachometer drive casting. That's 56 years in storage........ The guy even had a NOS 1961 cylinder head. A bit out of my range but very nice, nonetheless.



The main difference for this early version is the rather square external boss that protrudes. Later models had much more material and potential for better clearance inside for lubrication of the worm drive.



I repaired mine by adding back a broken fin but I couldn't make an invisible repair to the bottom of the boss which clearly had some gravel rash.



Here is my original repaired one, with a later part for comparison. It's all in the detail .....




Looking forward to less work, better weather and some fettling time.

G

Hi G,
I have an early drive, the end is not scraped but it has 4 broken fins. I think its a simple repair and I know you could do it. Do you want it?
Regards Al.

Hi Alan

Great to hear from you.

Yes - please. Maybe we can meet up at Stafford next month. Let me know if you need anything.

G

G, I will be going to Stafford and will bring it along. I need a right side panel if you have a spare.
Cheers Al.

Al

Will check when I get back home on 14th

G

My CB72 engine has been sitting patiently on the bench fo rsome months while I galivant around the world. When I get back from one of my trips it takes me a while to get my 'fettling coordination' back so I just do small jobs until I am ready for the serious stuff again.

I rummaged out the parts to assemble my recently-purchased tacho drive. There was a freshly-plated housing fro the drive gear with all the washers, O-ring and retaining screw. Interestingly the first gear housing I found would not go in teh bore but I found another that would.



I had to check the manual to see that there are two thrust washers on the skew gear. They both are rather loose on the shaft but definitely the correct ones.



The cover went on nicely with a few drops of oil on the drive shaft and a fresh gasket. Despite all of the screws I had re-zinced, I could not find a set of nice looking screws of the right length. An order went off to David Silver for a complete set of replacements..



The cover for the points side is again different on early bikes. It has these extra fins which blend the cover with teh head fins. These disappeared on later bikes.



The screw problem affected the points cover screws which are the dreaded 5x30 JIS thread. The points cover itself on these early bikes had no "Type" lettering cast in. I could only find one suitable screw and the thread was already damaged in one of the holes so I bought a bag of 100 5x30 ISO screws and a helicoil kit so that I can make the problem go away for good.




Just to illustrate the difference between the JIS (0.9 pitch) and ISO (0.8 pitch) here they are.....



I thought that I bought some suitable JIS screws a while back but cannot find them. It's hard when you don't have a factory with all the bits lined up.

G

Nice to see you back at it, G., and with an informative post. Regarding your points cover screw problem, have you ever considered Time-Serts as an alternative to Helicoils?