1980 kz1000 misfire - Chicagoland Sportbikes
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post #1 of 10 (permalink) Old 03-13-2012, 11:33 PM Thread Starter
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1980 kz1000 misfire

I recently picked up a kz1000 that runs like a champ but has a bit of a misfire during warm up. I have this idea that with new plugs, clean the carbs, and an italian tune up it'll be alright but i want to prepare for the worst.

The misfire occurs 95% when it's warming up and only VERY occasionally if I'm trying to replicate it when it's warm. On warm up it happens when I'm holding ~1/8th throttle - the tach isn't functioning but i'd assume maybe at maybe 2k rpm? What would worst case scenario be? If I had a bad piston or ring or something it wouldn't run properly, right? The thing starts right up and runs like a champ other than that misfire... any ideas?
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post #2 of 10 (permalink) Old 03-14-2012, 01:19 AM
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If the misfire go's away after warm up , it highly unlikely a mechanical issue . Could be carbs , or ignition .
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post #3 of 10 (permalink) Old 03-14-2012, 07:32 AM

 
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Miss fire ??

Back fire or after fire?
Out the carbs or out the ex.

one cyl. or two?

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post #4 of 10 (permalink) Old 03-14-2012, 11:29 AM
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With a bike of that age (and ease of access to the engine) it is a good idea to do a compression test or leakdown test
so you have an idea of the general engine health.


Last edited by Ohfugit; 03-14-2012 at 11:36 AM.
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post #5 of 10 (permalink) Old 03-14-2012, 12:29 PM
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carefully clean each carb, check the pilot jets, and the needle/emulsion tube , make sure the hole in the e tube is still round and not worn oval by the needle ( hi mileage bikes mostly or aftmkt jet kit/needle) , check idle adj screw, if they are capped you may need to drill out the caps to adjust ,in case you think one cyl is off, when you first start it take some brake clean spray ( or water) and hit each pipe where it comes out of the head with a little and watch how fast it dries/ make sure all are the same, if one dries slower than the rest its not running right,,, the carb issues would be my first guess, if there is dried gas/varnish built up on the needle it will lean out
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post #6 of 10 (permalink) Old 03-14-2012, 01:02 PM Thread Starter
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Quote:
Originally Posted by STANIMAL View Post
If the misfire go's away after warm up , it highly unlikely a mechanical issue . Could be carbs , or ignition .
Quote:
Originally Posted by resurrection View Post
Miss fire ??

Back fire or after fire?
Out the carbs or out the ex.

one cyl. or two?
as far as i can tell it's backfire out the carbs, at least by where the sound is coming from. i uploaded a video so maybe you can tell just by sound. sorry about the quality, i shot it with my phone.



Quote:
Originally Posted by Ohfugit View Post
With a bike of that age (and ease of access to the engine) it is a good idea to do a compression test or leakdown test
so you have an idea of the general engine health.
i really should compression test it. maybe i'll go rent one next week.

Quote:
Originally Posted by elroy121 View Post
carefully clean each carb, check the pilot jets, and the needle/emulsion tube , make sure the hole in the e tube is still round and not worn oval by the needle ( hi mileage bikes mostly or aftmkt jet kit/needle) , check idle adj screw, if they are capped you may need to drill out the caps to adjust ,in case you think one cyl is off, when you first start it take some brake clean spray ( or water) and hit each pipe where it comes out of the head with a little and watch how fast it dries/ make sure all are the same, if one dries slower than the rest its not running right,,, the carb issues would be my first guess, if there is dried gas/varnish built up on the needle it will lean out
carbs will be cleaned and it will be rejetted for pods soon. i'll check out all the other stuff as well as soon as i have some time. thanks for the help!
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post #7 of 10 (permalink) Old 03-14-2012, 01:29 PM

 
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more than a kwik internet answer there.

Gus
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post #8 of 10 (permalink) Old 03-14-2012, 01:32 PM Thread Starter
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Quote:
Originally Posted by resurrection View Post
more than a kwik internet answer there.
maybe. first thing is strip it down and go over the probable things like carbs and ignition. have any insight as to a worst case scenario on that, though?
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post #9 of 10 (permalink) Old 03-14-2012, 04:15 PM

 
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Insight ya I might have a little.


carbs first.

Gus
We offer three kinds of service @ Resurrection
GOOD - CHEAP - FAST
You can pick any two
GOOD service CHEAP won't be FAST
GOOD service FAST won't be CHEAP
FAST service CHEAP won't be GOOD
and cold beer.

I'd love to help but I don't chase parts.
Please contact other forum members and supporters for parts.
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post #10 of 10 (permalink) Old 03-28-2012, 09:44 AM
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