Run_Away said:
Are you going to bother will diagnosing the compression or just tearing it apart for rings/hone/valve lapping?
I hope to do compression last. Ideally, I get the timing done then move to carb and if I have good air,fuel,spark and it runs but just smokes some or whatever I'll probably run it for a little while. Clearly this thing is in no rush to be perfect. 
. If I know I have gone through everything except compression and its still not running then I'll move to that last. I'm noticing some questionable RTV around the cylinder bases and the kickstarter is welded on (hate that) so I know that this little engine will be a time suck once I tear in.
One weird thing that I encountered but didn't have time to really look at closely is when I advanced or retarded the points plate in either direction, I couldn't get the points to open on the cam right at the F line on the stator. I'm hoping it's something dumb and not the plates are slightly different shaped and I don't have the adjustability needed to get it angled right. It would be kind of a shame to have to swap stuff over to that old ugly one.
What I'm doing:
Image from ct90restoration.blogspot.com
Hmm this doesn't look right to me. In the video you can see the points plate advanced allllllll the way and now "appears" to be timed. Test light comes on just as the points open on the F mark but I shouldn't have to be maxed out to just barely get it in spec.
New on the left and old on the right. The old one is really rough and I couldnt get spark from it after cleaning the points. The new one already had longer slots be even those needed to be opened wider. The old one didn't have the range of motion I needed either.... It's beyond my pay grade to figure out what mechanical reasons I may have for this. The cam the points ride on doesn't seem like it has slipped... I don't know maybe cracking open the valvetrain and pulling the advance unit will give me some answers.
Holy berkeleying rabbit hole. Ok I ended up buying a NOS spark advancer because I think the points cam is worn.
When I went to find replacement screws for the chewed up points plate and cover I realized the size was just about unobtainable. Why? They are the retired JIS size m5 .9 pitch which retired when .8 pitch became standard in 1968 or so. .8 is available everywhere. M5 .9? When the usual places like McMaster tell you good luck....it's gonna be fun. This is down in the weeds now but I have never spent half a day tracking down screws.
Lots of Honda places say they have them but the part numbers have all been superseded to the new pitch (which is dumb because it won't work).
So while I wait on the new advancer, I found this place that has m5 .9 retired JIS screws in pan head and machine head and I can cut them to length.
https://belmetric.com/retired-jis-flat-head-extra-coarse-zinc/
This is kind of ridiculous but easier than sourcing used 60 year old obscure screws in good shape or using a die to rethread as my own like some have done:
https://forum.ih8mud.com/threads/how-to-make-rare-m5-9-pitch-screws-found-on-early-67-pics-included.902751/
All this for a few screws.
The wife is out of town so the Prius is kicked out of the garage so I have so much room for activities compared to my normal situation. The 3 in the back are ready for summer and I wish this one was closer with gas at these crazy prices.
My "new" 58 year old spark advancer unit arrived:
An impact zipped off the bolt and a light tap with a rubber mallet knocked off the old one. The cam on the old one was worn so much it changed the timing of the points opening. The new cam is noticeably better.
The points plate is ready to go on but not before the new screws are trimmed to size. The previous owners gave no concern to JIS hardware and almost every head is stripped.
As I mentioned before, prior to 1968 Japan used JIS hardware with a .9 pitch that NOBODY keeps in stock or thinks it even exists. Fastenal, McMaster, Aircraft Spruce all the normal places have nothing. A place called Belmetric has some but the lengths need to be trimmed.
That's kind of time consuming but it's working out well. Much better than retapping everything I guess.
I picked up a dedicated Honda valve adjustment tool from ebay. You know it's quality from the comforting words on the packaging.
It works well enough and valve clearance is set.
Carb kit is on order for this guy next.
This is most enjoyable to watch.
Just kicking the "no compression" can down the road for now, eh?
wheelsmithy (Joe-with-an-L) said:
This is most enjoyable to watch.
Just kicking the "no compression" can down the road for now, eh?
I gotta do the fuel, spark, timing bits anyway right?
Yeah I don't want to pull it completely apart just yet as we go into riding season in a few weeks hopefully. I won't be working on them but just riding as much as possible.
84FSP
UberDork
3/27/22 4:32 p.m.
Run_Away said:
Awesome. I love vintage NOS parts, they just give such an impression of quality. Very satisfying.
Are you going to bother will diagnosing the compression or just tearing it apart for rings/hone/valve lapping?
I was wondering the same thing - I have to assume there is some obnoxious OEM/aftermarket combo of bits to make it a 300CC?
