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Can pilot jet screws be set differently between cylinders?

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hornet_guy
Two Stroke Sniffer



Joined: 24 Jan 2021
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PostPosted: 16:59 - 18 May 2021    Post subject: Can pilot jet screws be set differently between cylinders? Reply with quote

Hello,

I noticed that not all of the 4 pilot jet screws of my cb600 carbs are set in the same position. Just looking at the screw head, they're at different turns.

As far as the little I know, this doesn't makes sense to me. Is the any case where where this can make sense? Am I missing something?

Thanks
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Robby
Dirty Old Man



Joined: 16 May 2002
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PostPosted: 18:01 - 18 May 2021    Post subject: Reply with quote

The only way to find out how far the mixture screw is turned out is to turn it all the way in and count the turns. Each carbs is not going to be identical on the screw threads and their orientation.

So no, they should not be set differently. That said, they may well be set properly, which is not the same as the slot on the screws all lining up by eye.
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 18:02 - 18 May 2021    Post subject: Reply with quote

Is there any reason to think there is a problem. Erratic idle, misfiring on one or more cylinders etc?

If not, leave them alone.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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Pete.
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Joined: 22 Aug 2006
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PostPosted: 18:22 - 18 May 2021    Post subject: Reply with quote

No reason why not if the manual specifies it. Some IL-4 bikes have larger idle jets for cylinders 2 and 3 to run them slightly richer.
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hornet_guy
Two Stroke Sniffer



Joined: 24 Jan 2021
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PostPosted: 23:16 - 19 May 2021    Post subject: Reply with quote

Robby wrote:
The only way to find out how far the mixture screw is turned out is to turn it all the way in and count the turns. Each carbs is not going to be identical on the screw threads and their orientation.

So no, they should not be set differently. That said, they may well be set properly, which is not the same as the slot on the screws all lining up by eye.


Thanks, that's a good point. I assumed the threads would be identical.
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hornet_guy
Two Stroke Sniffer



Joined: 24 Jan 2021
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PostPosted: 23:43 - 19 May 2021    Post subject: Reply with quote

stinkwheel wrote:
Is there any reason to think there is a problem. Erratic idle, misfiring on one or more cylinders etc?

If not, leave them alone.


No, there is no problem but I'm curious and this didn't make sense to me.
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hornet_guy
Two Stroke Sniffer



Joined: 24 Jan 2021
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PostPosted: 23:44 - 19 May 2021    Post subject: Reply with quote

Pete. wrote:
No reason why not if the manual specifies it. Some IL-4 bikes have larger idle jets for cylinders 2 and 3 to run them slightly richer.


Not the case, Pete. My manual specifies to set all to the same number of turns.
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Bhud
World Chat Champion



Joined: 11 Oct 2018
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PostPosted: 01:58 - 20 May 2021    Post subject: Reply with quote

The pilot jets may be different between cylinders, but the pilot screws (or mixture screws) should all be the same number of turns out.

You wind each screw in until it lightly seats. Then wind them out the specified number of turns in your manual, and leave them alone. Doesn't matter what the screw head looks like in relation to each one. Only the number of turns out matters.
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sickpup
Old Timer



Joined: 21 Apr 2004
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PostPosted: 10:04 - 20 May 2021    Post subject: Reply with quote

Bhud wrote:
The pilot jets may be different between cylinders, but the pilot screws (or mixture screws) should all be the same number of turns out.


Only if setting statically. If you use a gas analyser the screws are often at slightly different adjustments due to manufacturing variances, no cylinder is ever perfectly the same.
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Old Thread Alert!

The last post was made 2 years, 339 days ago. Instead of replying here, would creating a new thread be more useful?
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