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Bigger jets for open exhaust? 20 Jul 2021 12:03 #852130

  • TheForumTroll
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Im getting my carbs cleaned tomorrow and I was thinking if I should get some bigger jets put in as the bike is running lean and got what is closer to magaphones than actual exhausts

It got stock everything else. What does the experts think? Bigger? and by how much in first try?
-[ KZ700-A1 '84 ]-
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Last edit: by TheForumTroll. Reason: Changed title to stop the pitchfork crowd storming the gates

Bigger jets for open exhaust? 20 Jul 2021 19:37 #852173

  • SWest
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No baffle? Jets won't keep it from falling on it's face at WOT.
Steve
Z1b1000 1975 Z1b
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Bigger jets for open exhaust? 20 Jul 2021 19:47 #852175

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Open exhaust = annoying 

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Bigger jets for open exhaust? 20 Jul 2021 20:39 #852176

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I've run without the baffle in my 4-1 a few times, and once I had the entire cone off for non-fun reasons. I never noticed a significant change in performance or anything, but my jetting is a little rich as-is. 

A helpful person might respond to your thread with the standard rigamarole of "do plug chops at varying throttle openings to determine jetting" but some people don't like loud exhausts...anyway, I would personally not really worry about it beyond going up a size or two in the main jet and maybe a half turn out on the idle mixture. It'll be fine.
1982 KZ750 Spectre - Dyna 2.2 coils + 8mm wires, WG coil relay, SH775 R/R, Mikuni BS34s - 40P/122.5M, Progressive fork springs/KZ900 rear shocks, Vance & Hines 4-1

1982 KZ305 CSR - 18" KZ400 rear wheel
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Bigger jets for open exhaust? 20 Jul 2021 21:31 #852179

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These engines start making the most power at 7-9000 RPM. Back pressure is your friend.
Steve
Z1b1000 1975 Z1b
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kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882
kzrider.com/forum/2-engine/597654-poser?start=240#704229

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Bigger jets for open exhaust? 20 Jul 2021 23:09 #852181

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Well now, sure hit a sore spot there huh?

They do have baffles and they are installed, so no need to be mad. There's even a little stuffing inside too. Still they are open enough to make it run lean, even compared to stock. And besides, it's less loud than 90% of Harleys (99?) even if I pull out all the interior of the exhausts so please calm down 

*backs slowly away making calming gestures*
-[ KZ700-A1 '84 ]-

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Bigger jets for open exhaust? 20 Jul 2021 23:27 #852182

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Im getting my carbs cleaned tomorrow and I was thinking if I should get some bigger jets put in as the bike is running lean and got what is closer to magaphones than actual exhausts

It got stock everything else. What does the experts think? Bigger? and by how much in first try?
 


Reading your post brought back some really "great" memories of better times for me.
1982 KZ1100-A2

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Bigger jets for open exhaust? 20 Jul 2021 23:53 #852183

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Magaphones? Oh now I have really stepped in it. I'll let myself out
-[ KZ700-A1 '84 ]-

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Bigger jets for open exhaust? 21 Jul 2021 06:19 #852191

  • TexasKZ
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As always, the answer depends on the specifics. You may only need to shim the needles a bit or you may need to go up a size or two on the mains. Dynojet may still sell a Stage 1 kit that worked well for many aftermarket systems. There are several ways to check the jetting. The most precise would be to hook up a wide band sniffer to the pipe that can record engine data and go ride the thing under real world conditions.

A less tech and expense intensive method that will get you close is this——

www.factorypro.com/tech/tech_tuning_proc...igh_rpm_engines.html
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough
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