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1980 KZ650 F1 - Bogging at WOT 19 May 2023 15:28 #884943

  • jekyllman
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I've had this tuned up pretty well over the past year or so and really happy to see how consistently it's been performing. But there's one final issue I'd like to work out and I'd love to get your help on this. There's usually a lot of power at 1/8 throttle up to about 3/4. I accelerate on to the interstate every morning to go to work and right when I really give it the beans it just bogs. It doesn't die but it kinda just stops accelerating. If I back off to 75% it recovers but it's not enough to accelerate much faster. 

-Stock 4-to-2, h-pipe headers, with the original mufflers cut off and replaced with some cheap shorty mufflers, stuffed with a bit of medium steel wool to quiet it down.
-K&N pods
-117.5 mains (just moved up from 115s and honestly symptoms may have got worse)
-I put those air corrector jets in that @zed1015 sells
-Driven at 4500-6000' elevation
-Plugs are always super clean, zero color (part of why I stuffed the mufflers with steel wool was to try to restrict air flow a little)


Thanks!

 
1980 KZ650F1 - 10k miles (see photo)
1981 KZ305 CSR - 10k miles (didn't have the heart to customize this one, will stay original)

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1980 KZ650 F1 - Bogging at WOT 19 May 2023 20:19 #884954

  • gd4now
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Sounds like the main is too large. 
1977 KZ650 B1
Pods and Denco header


This is my Z

OLD KAW OWNERS SMILE ALOT

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1980 KZ650 F1 - Bogging at WOT 20 May 2023 02:59 #884956

  • zed1015
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Main jet is miles too big ( i run 117.5'sin my 1000 ) and will be cause the high rpm bogging/fluffing .
With the air correctors you go ONE size up on the mains and keep ALL other settings stock.
112.5 is more like what you need.
Hopefully the pods are real K&N and not cheap copies which will also kill the top end and cause the same issues.
AIR CORRECTOR JETS FOR VM CARBS AND ETHANOL RESISTANT VITON CHOKE PLUNGER SEAL REPLACMENT FOR ALL CLASSIC AND MODERN MOTORCYCLE CARBURETTORS
kzrider.com/forum/23-for-sale/611992-air-corrector-jets-





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Last edit: by zed1015.

1980 KZ650 F1 - Bogging at WOT 20 May 2023 06:27 #884958

  • Nessism
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The steel wool in the muffler business may be restricting flow too much.  Proper mufflers are chambered to control noise.  Header mufflers typically are straight through, but some gasses are sent behind the main tube and into the baffling material.  You can't just stuff restricting material right into the flow.

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1980 KZ650 F1 - Bogging at WOT 20 May 2023 08:07 #884961

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If your F1 was intended for the US market it would of come stock with an accel pump.  Does your set have one and is it working correctly?  The fact that you run at the elevation you mentioned will also play a part in all of this.  The largest main jet that came stock on the vm24ss carbs on the (K)Z650s was 102.5. Your 115 is 5 sizes larger and a 117.5 is 6 larger. As Zed indicated the 117,5 is way too big and it will not pull to red line.

I have a B1 with 4 into 1 and pods and run much closer to sea level but have not yet made use of Zed's air jet solution and run 110 mains and it is still somewhat fat on the top end. 
1977 KZ650 B1
Pods and Denco header


This is my Z

OLD KAW OWNERS SMILE ALOT

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1980 KZ650 F1 - Bogging at WOT 20 May 2023 16:35 #884994

  • Wookie58
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Don't forget the higher you go the thinner the air gets so if anything you need to downsize the jetting to maintain a 14.7:1 air/fuel ratio

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1980 KZ650 F1 - Bogging at WOT 22 May 2023 08:44 #885067

  • jekyllman
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I'll look into sizing down the jets. With the plugs being so clean I figured I was running lean but probably not the case at the top end.

Yes, genuine K&Ns (better be...paid way too much for them if not)

Yes, it has an accel pump and the diaphragm has been replaced. It seems to be functioning fine.

Is it possible that the timing is off at higher RPMs? I've got the original points in this thing and I guess I don't have a lot of confidence that it's dead on.
1980 KZ650F1 - 10k miles (see photo)
1981 KZ305 CSR - 10k miles (didn't have the heart to customize this one, will stay original)

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1980 KZ650 F1 - Bogging at WOT 22 May 2023 08:59 #885068

  • Wookie58
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Is the advancer moving freely or is it seized ?

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