Board index Flathead Power-Technical Questions, Answers, and Suggestions Knuckles running an open primary

running an open primary

Moderators: Curt!, Pa

Post Sat Jul 12, 2008 10:57 am

Posts: 29
Location: Yamanashi Shi, Japan

i had a quick question regarding knucks that i wanted to run by you guys.

what needs to be done to run an open chain primary on a knucklehead? i assume the primary chain oiler needs to be dealt with somehow, but what is the *right* way to run the primary open?

thanks!
-dan
-experience is a wonderful thing. It enables you to recognize a mistake when you make it again.

Post Mon Jul 14, 2008 10:06 pm

Posts: 2684
Location: Los Angeles, CA
Warning!!! Do not over tighten the chain oiler screw. Too tight and the seat is broken then you have no control.

Post Tue Jul 15, 2008 11:02 am
panic

Why go through all that trouble?

Just run a chain saw over your left leg.

Post Tue Jul 15, 2008 4:59 pm

Posts: 1633
why? doesn't your primary chain wear out quickly enough already?

a propos panic's reply, don't forget to chainsaw the tips of the fingers on your right hand first....
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Tue Jul 15, 2008 5:12 pm

Posts: 29
Location: Yamanashi Shi, Japan

what kind of chain saw do you recommend, LOL. :mrgreen:

-dan
-experience is a wonderful thing. It enables you to recognize a mistake when you make it again.

Post Thu Jul 17, 2008 11:14 am

Posts: 24
Location: My-am-mah, Flor-a-duh
You may want to trim the crank case breather tube, and direct it down and extend it a little with a piece of tubing. If you leave the breather as stock be prepared for some oil spray.

But to really run an open primary right you should be running a jockey shifter so not only can you stick your foot into the main drive sproket, you will also have the oppurtunity to stick your hand into the clutch basket. LOL.

But seriously, I'm thinking about running an open belt primary on my '46, with a mouse trap and foot shifter. Why? My frame is missing the rear support bracket for the inner primary. On second thought, maybe I'll just weld the damn thing on, and close it up.
Steven

1946 knucklehead
1976 shovelhead
2006 road king

Youth and enthusiasm is no match for age and treachery.

Post Thu Jul 17, 2008 12:52 pm

Posts: 1633
belts are a different thing, anyway. My 45 project has ventilation holes cut into the tin primary, to give the belt some cooling. Chains are MEANT to be enclosed.
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Thu Jul 17, 2008 2:56 pm

Posts: 150
Location: Carver, MN

Aside the from the obvious safety issues, which have been humorously dealt with already, I find it to be an interesting question. A guy I rode with a lot back in the '70s ran an open chain on his Knuck. I never asked whether he still ran the chain oiler, though I would guess not since I don't recall his jeans being any more or less grimy than the rest of us. My guess is that the lack of being enclosed provided enough air cooling to keep from excessive wear. Chain lube at more frequent intervals than used on the rear chain might make it last just fine. Also no reason you couldn't fabricate some gaurds to keep your limbs intact.

Come to think of it, I seem to remember my wife complaining about me teaching her to ride on my '46 with and open primary chain and jockey shift. She seemed to think it was some kind of proof that I didn't care enough about her (or at least enough about her fingers). I'm pretty sure I only ran it that way one summer, but I don't remember frying the chain.

Post Thu Jul 17, 2008 4:07 pm

Posts: 24
Location: My-am-mah, Flor-a-duh
To follow-up on my previous post, as well as, 54Brit's comment; I ran the knuck for many years with the belt enclosed, it was in a wishbone frame then, I'm in the process of dropping it into a staight leg frame, which is the frame that is missing the rear primary bracket. Nevertheless, I didn't have holes cut in the primary then, and although I didn't notice any heat problem, upon reading 45bBrit's comment/suggestion, this may be a good idea (especially since I now live in south florida). Thanks.

Do you think just leaving the inspection covers off will provide sufficient cooling?
Steven

1946 knucklehead
1976 shovelhead
2006 road king

Youth and enthusiasm is no match for age and treachery.

Post Thu Jul 17, 2008 6:51 pm

Posts: 1633
I have the clutch centre exposed, plus a cut-out between the clutch and the pulley, and that seems to work fine. I have seen big twins with just the outer case fitted, on spacers, and that looks good, works as a cover and provides plenty of cooling
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Fri Jul 18, 2008 10:28 pm

Posts: 122
Location: Mpls. area
I like the sound control with the cover in place, my clutch makes a lot of noise....

Post Sat Jul 19, 2008 11:14 am

Posts: 2684
Location: Los Angeles, CA
Belts are severely affected by heat. The instructions that come with a new one suggest heavily ventilating the inner primary with a 1/2" drill.
Here are the primaries I made for an Electra-Glide.
Image

Post Thu Jul 24, 2008 7:34 am

Posts: 29
Location: Yamanashi Shi, Japan

thanks for all the replies folks, both pro and con. it's the exchange of knowledge that keeps anything alive, and i appreciate all the knowledge freely shared.

take care,
-dan
-experience is a wonderful thing. It enables you to recognize a mistake when you make it again.

Post Thu Jul 31, 2008 1:57 pm

Posts: 18
Location: Cambridgeshire, UK

I have been running a belt on my knuckle since 2003, for the first two years it was enclosed and ate two belts (heat I guess), I have been running it open for three years now and it has been problem free, and I still have all my fingers and the left foot is still there!!

Griff

Post Fri Aug 01, 2008 7:21 am

Posts: 1659
Location: Interlaken, NY USA

Interesting comments on open vs closed. I've been running closed tin primaries on my belts for 35 years, and belt life seems to be normal. I can't remember mileages now, but I'm guessing at least 30-40K miles. Also, until just recently, they always had some exposure to oil leaking past the "slinger' on engine mainshaft. Finally got the new seals on all the machines. What a difference. Just one man's observations of course. I've always been curious where all this damaging heat was coming from. I mean, we've been running closed timing belts on car engines in engine compartments for ages, with no apparent harm. I can't imagine the temps inside my primary cover approaching that under a car hood. But hey, I'm just a dumb ole shade tree mechanic. :lol: :lol:
DD


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