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Discussion Starter #1
I'm resurrecting an '82 GL500 and just learned that the primary jets are missing. The idle and secondary jets are intact and the original sizes.

Motofaction states that the primary jet size is 78, but i have some 90's on hand from an '80 CB650C. I also have some 118's from a previous pod experiment, but i assume those are way too large.

I live in greater Boston, so sea level plus a few hundred feet. The bike currently has the stock exhaust, but I plan to put on the HD Sportster exhaust I have on hand since I like the sound and looks better and it's usually a drop in replacement..

Can I use the slightly larger 90 primary jets or will that cause running issues? I assume it will be slightly richer, but that may be OK since bikes were starting to come leaner from the factory in this era. I'm aware of jetrus and will order some 78's if the 90's are not suitable.

Any input from the experts?

Link for reference (Ref: Honda CX500 Keihin Carburetors - How to check the jet sizes?)
Pic for reference.
201284
 

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The intake tract in the stock design is carefully balanced with exhaust. Unless you're making changes on the other end, changing the jets will result in reduced performance. Get the 78s.

Randall
 

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Discussion Starter #3
The intake tract in the stock design is carefully balanced with exhaust. Unless you're making changes on the other end, changing the jets will result in reduced performance. Get the 78s.

Randall
Thanks. I now have some 78's on order. Playing the waiting game for both the new jets and hard to find o-rings for the mixture screws. The screws themselves are fine, but the o-rings are now squished. The impatient side of my brain wanted to use two squished orings as a test, but patience has prevailed (so far).
 

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You can make gaskets for the intakes until you get new O rings.

You could rejet to 80/115 if buying new jets. They work with everything otherwise stock.

I have also run the 118 secondary with airbox and that was OK.

But it won't like that 90 primary.
 

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Discussion Starter #5
You can make gaskets for the intakes until you get new O rings.

You could rejet to 80/115 if buying new jets. They work with everything otherwise stock.

I have also run the 118 secondary with airbox and that was OK.

But it won't like that 90 primary.
Thanks for the confirmation CXPHREAK, I won't bother with the 90's. I'll also wait for the orings, but your comment "make gaskets for the intakes " made me curious.

Are you saying to use gasket material to make some tiny o-ring replacements? I've made gaskets before from blank sheets, but nothing that small and precise. Or do you mean something else by "intakes".
 

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Discussion Starter #7
As per the gaskets I mean for the intakes in place of the O rings.

Cut them to cover the whole joint area as you would any gasket, not just for the O ring recess.
Ahh, I understand. My brain was focused on the mixture screws.

I have intake manifold orings on order as well as some on hand that are "close enough". I none of those pan out, I already have gasket material ready for use.
 

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Discussion Starter #9
I just use 3 x 1 mm O rings on the mixture screws.
Interestingly, that size is hard/impractical to come by from the motorcycle specialty suppliers, but a quick search on Amazon yielded a 50 pack for $7 that will arrive by Friday. I try to buy from the small guys when possible, but this was just too easy.
 

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If you happen to be replacing any oilseals at any point only one is a special seal - the one on the output shaft as it has an integral flange to retain the driveshaft boot, but is still a standard size.

All others can be bought in any bearing shop.
 

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Discussion Starter #11
If you happen to be replacing any oilseals at any point only one is a special seal - the one on the output shaft as it has an integral flange to retain the driveshaft boot, but is still a standard size.

All others can be bought in any bearing shop.
Thanks for the tip. I've only had the project a week and haven't yet done the first start, so i don't know what seals might be needed. Hopefully none, but it's 38 years old. Also hoping the main engine casing gaskets are intact so i don't have to pull the engine out. been there, done that.
 
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