[Shovel_Dan78]

I opened my primary cover to check the chain tension, only to find that at some point, a 1 1/2" belt drive conversion had been done. It looks like they intended a dry closed primary because blocked off the oil ports in the back of the inner primary case. There is still some oil leaking in, probably via a bearing, but that explains why they left the primary case drain plug out.
What worries me more (other than the shoddy safety wire attempt that I found 😬) is that the lower run of the belt appears to rest on one of the case's thread bosses.
The belt tension appears to be in spec with what I've read, and the belt doesn't seem to be in bad condition (no frayed edges, missing teeth etc.). How worried should I be? I have seen tensioners, but with the belt that is on there, I wouldn't have near enough slack to put one on. Thanks in advance for any advice!

 

[Shovel_Dan78]

First off, thanks for pointing out that crack, I didn't even notice it, but will definitely investigate! So far, I think the alignment is good, because the edges of the belt don't look melted or frayed or anything. But (at least at rest, in neutral, anyway) the lower run of the belt is resting on the thread housing boss right under that rad safety wiring, which seems bad.
Like tzienlee mentioned, I probably would need different pulley(s) to remedy this. I read in other places that idler bearing tensioners aren't recommended for closed primaries, so that route is probably out. I really would like to keep it closed, just because I like the shiny tins 😁

 

[Shovel_Dan78]

Thanks for the idea, Rick, makes sense, about the helicoil. Plan of attack is now: seal where the oil is coming in, strengthen the threads before removing material at the rub point, and check out that possible crack in the clutch drum. Before buttoning it back up, check pulley alignment. Then figure a way to get some cooling in there. If I lose a belt after that, it's gonna be open primary time!
Thanks all for your help and advice! 👍

 

[Shovel_Dan78]

Just so you guys don't think I left that safety wire as was, lol.

Thanks for the idea on spacers, that's easier than my thought of making new covers (which I might do down the line, since I've pounded my share of tin over the years). It looks like I have an aftermarket outer that has 36-54 oval style derby cover and inspection cover, but all the vented derbies I see are the three hole round style? Thanks again, guys;

 

[Shovel_Dan78]

Nick, I was thinking of doing that but I had read in a few places that that style tensioner wasn't recommended for closed primaries? Not sure if they meant an oil filled primary (in which case, you wouldn't want a belt anyway!), or if they were referring to a dry but still tin covered primary (maybe because of heat?). In any case, until I can do more research on tensioners, I'll vent the cover to keep the heat down, and just keep a cautious eye on belt condition 😀

 

[Shovel_Dan78]

The one I mentioned would be all good in your bike, open or closed. This is what they look like. It says "open belt" but they're for closed primaries too

Thanks for the additional info. And your post about building your own tensioner also rocks! Great job 👍

 

[Shovel_Dan78]

I haven't measured the pitch yet, will have to do that when I pull the cover to put spacers on 😁
Govmule: I always take into account anec-data when dealing with temperamental old metal beasts!

 

[Shovel_Dan78]

Thanks for the info, guys I took another look at the clutch drum, spun it around while I counting the teeth, and I couldn't see any cracks. May just have been some dirt or a piece of dog hair or something? Will keep an eye on it.
I was going to try and tackle the oil seals with the engine in the frame, but after looking at what they want for oil seal install tools, I think I might just leave it be till I do an entire rebuild. Without a drain plug, there shouldnt be enough oil buildup to get on the belt, I think.

 

[Shovel_Dan78]

Can and will do

 

[Shovel_Dan78]

Took my tin off to check the leaking again, and figured I'd tug on the pulleys. Found the front one wobbling a bit, so it seemed a good excuse to just bite the bullet and dig in. Found some interesting stuff. Took out the clutch plates and hub, and looks like the plates were banging the shit out of the studs, yikes. Also seems the friction lining separated from the rivets holding it to the hub.
Up front, the splined hex insert seemed snug on the the crank splines, but the fit between the hex and the crank pulley was sloppy. So, new belt drive and clutch parts in my future.
The oil leak is still puzzling me. The trans shaft seal seemed dry, a little rusty too. But looks like oil is leaking from one of the primary cover to transmission bolt holes, and one of the primary to engine case holes. We'll see what it looks like when I get the cover off.
Merry Christmas, all! 😁

 

[Shovel_Dan78]

Thanks for the info, man! Will be interesting to see what's in there...

You should be able to find oversize thread studs commercially, or if you have access to a good lathe make a set with oversize threads to fit tight.

I do have access to a decent lathe 🤓 As far as the oversize, are we talking major diameter or pitch diameter?
While back I was reading up on threading, for a steering stem I was working on, and seem to recall the author saying that major diam had a lot less effect on thread engagement than the pitch diameter? So I'm thinking if I made the whole deal bigger in diameter (minor, pitch and major by the same amount), then maybe shaved the major down a hair to make it easier to screw in, it would still seal good? Assuming McMaster doesn't have what I need!

 

[Shovel_Dan78]

Quick update: After getting the inner primary off, took a look at the tranny threads. Doesn't appear that anyone has helicoiled them, or even used any sealant, so I guess (looking at some of the other "fixes" I've found on the bike) that no repair is better than a bad repair.

 

[Shovel_Dan78]

One question, those don't say they are oversize, how can I be sure? Are all replacement studs oversize?
I saw some Colony Machine studs that specifically state they are OS, but it also gives the coarse thread as 7/16? I want to make sure I get things right the first time, since getting the primary off is a bitch 😅

 

[Shovel_Dan78]

My trans does have four (coarse on one side, fine on other) studs. Only one was tight enough in the case not to thread out though, lol. I'm wondering, if you have to heat the case up that hot to install, then that probably precludes the use of any sealant? Whatever I do, I just want to do it right once! Darn old piles, gotta love 'em.

 

[Shovel_Dan78]

Joe and Dutch, I thought I had a ratchet top? School me, please, what's the difference between that and a cowpie.
About the sealant, always thought the self wicking green was for smaller screws, not bigger than 1/4", but I could be wrong.
Back when I had a lowrider with hydraulics, I had a leaky fitting, and Pops gave me some Loctite Hydraulic Sealant. That stuff worked like a charm, so if it could seal pressurized hydros, I'm thinking it could easily seal those studs if I cleaned and prepped the threads right.
Whatever I do, think I'll kickstart the bike and get it to temp for a leak check before I put the primary back on. Thanks again everyone for the wisdom 🙂

 

[Shovel_Dan78]

Definitely have a ratchet top then (phew, since that sounds way cooler than cowpie, haha!). Forgot the part about hydro threads being tapered, that will change things surely. Finally the weekend, so it's out to the garage for more research and fun 😊

 

[Shovel_Dan78]

Hahaha, well I'm just about an old guy myself, so it sounds logical to me 🧙‍♂️

 

[Shovel_Dan78]

Update: got some trans studs from Eastern. They mic out at .371 OD on the coarse thds, which is within spec for interference thds based on the article shared earlier in this topic. But they thread in quite loosely into my trans case. So it looks like I'll be making my own over-oversize studs, since that seems less likely to go south than messing with the transmission holes (even though the holes are loose, it doesn't look like they were cross threaded or anything).
Also going to make a seal driver for the engine sprocket seal, while I'm busy at the lathe. Fun, fun! 😊

 

[Shovel_Dan78]

Reading another post here on the board, I think maybe I am misunderstanding how the transmission studs seal. Is it the threaded portion, or the shank, of the stud that does the sealing (when the heated case cools back down around it)?
I have been assuming it was the threads that did the the sealing. Since the studs are starting in by hand, I figured the case holes are too big. If I can thread the studs in, and it stops going when the shank gets to the case, is there hope?
And if so, when you do heat up the case, how much shank are you supposed to turn I to the hot case?
Thanks again everyone for all your help and advice!

 

[Shovel_Dan78]

Tried making a stud from stainless stock I had on hand, and was reminded very quickly why I avoid machining stainless like the plague, ugh. Did not go well. I think I am just going to try bolts on the front holes, seal the trans/inner primary interface with grey rtv, and put stat-o-seal washers under the bolt heads. I know, not the best solution, but hope it will get me down the road till I'm ready to rebuild (or replace) the whole trans, and can have a trustworthy fabricator fix all the hogged out threads. Thanks again, all, for the advice and input!