KZR's Bikes of the Month for 2024

Bogging down at 55mph

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06 Mar 2022 10:18 #863253 by Qsmothers3
Bogging down at 55mph was created by Qsmothers3
So I'm riding a 1982 kz440 and I have spent the better part of last year getting it road ready. I took it out on the highway today for the first time and it got up to 55 mph just fine but when I give it more gas to try to get up to 65 or 70 it loses power and stays at 55mph......I've got the fuel/air mixture at 2 turns out, clean carbs, and a new air filter.....any advice? 

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06 Mar 2022 11:45 #863259 by DOHC
Replied by DOHC on topic Bogging down at 55mph
Do you have the stock air box?  Stock jetting?  

One good thing to check is the mechanical timing advancer.  These can get stuck.

'78 Z1-R in blue , '78 Z1-R in black, '78 Z1-R in pieces
My dad's '74 Z1
'00 ZRX1100

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06 Mar 2022 13:12 #863268 by Qsmothers3
Replied by Qsmothers3 on topic Bogging down at 55mph
The bike is completely stock. Im pretty sure the bike has dynamic timing so there is no adjustment there. 

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06 Mar 2022 13:27 #863269 by BobZ
Replied by BobZ on topic Bogging down at 55mph
Yes....what he is saying is that the advance mechanism can get gunked up/rusted and fail to advance as the rpms go up

Had I known I'd live this long I'd have taken better care of my Led Zeppelin albums


1983 Goldwing Interstate
1982 KZ750 LTD
The following user(s) said Thank You: Qsmothers3

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06 Mar 2022 14:03 - 06 Mar 2022 14:16 #863272 by martin_csr
Replied by martin_csr on topic Bogging down at 55mph
Servicing the advancer is normal maintenance. separate the rotor from the advancer body & clean/lubricate it. 
The 650 manual says to fill the groove w grease. yours might be the same. 
Be sure to operate it by hand to make sure the rotor snaps back.

Another thing to check is the ignition coil. Ride the motorcycle at highway speeds, then stop & feel it. press w your fingers. don't get burned by the valve cover. It should be warm, not hot. mine was getting very hot, so I got the green Dyna 3.0 ohm coils from Z1Enterprises.  This solved a high speed hesitation (KZ650 w stock electronic ignition)
Last edit: 06 Mar 2022 14:16 by martin_csr.

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07 Mar 2022 07:24 #863299 by ckahleer
Replied by ckahleer on topic Bogging down at 55mph
In neutral, does the bike easily rev to red line? If so, advancer is probably working.
Remove the air box cover to give it more air. Now does the bike go over 55?

94 KE100
81 CM200t
82 KZ305
85 VF1100c

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07 Mar 2022 17:37 #863340 by Kidkawie
Replied by Kidkawie on topic Bogging down at 55mph
Do you see black exhaust smoke? A problem with the charging system/battery can do that.  High ignition demands, system cant keep up.

1975 Z1 900
1994 KX250 Supermoto
2004 KX125

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10 Mar 2022 03:55 #863523 by Qsmothers3
Replied by Qsmothers3 on topic Bogging down at 55mph
It will get up to high rpms in neutral. I will try taking the air box cover off.....i had major issues trying to get the air fuel mixture right, like I said above everything is stock. I've got the weekend to figure something out. 

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10 Mar 2022 03:56 #863524 by Qsmothers3
Replied by Qsmothers3 on topic Bogging down at 55mph
No black smoke. It seems like it's not getting enough air or fuel...one of the two

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10 Mar 2022 05:13 #863533 by martin_csr
Replied by martin_csr on topic Bogging down at 55mph
Handle the airbox cap w kid gloves as they have a tendency to break. and hard to find replacements.

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10 Mar 2022 05:27 #863534 by Grcko
Replied by Grcko on topic Bogging down at 55mph
I had some issues like that. I had cleaned the carbs really well or so I thought. I pulled them off again and ran a stiff nylon bristle off a broom through all the passages. My air/fuel passage was plugged. Put the carbs back on, put a good fuel filter on and haven't had a problem since. Also, the cleaning of the advancer is a really good idea as well as the Dyna coils.

As Always,

1983 KZ440

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10 Mar 2022 06:56 #863541 by Mikaw
Replied by Mikaw on topic Bogging down at 55mph

I had some issues like that. I had cleaned the carbs really well or so I thought. I pulled them off again and ran a stiff nylon bristle off a broom through all the passages.
I like this! Great idea.

1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
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