boggy running between 3-5k at 1/4 throttle

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EGG
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boggy running between 3-5k at 1/4 throttle

Post by EGG » Mon Oct 01, 2018 1:45 pm

Hi all

Finally got the KR-1 back together after a crank rebuild. The carb problem that was there before the rebuild is still present, so I need to have a go at that now.

The bike runs ultra smooth from 1-3K RPM, boggy between 3 and 5.5K RPM, then back to smooth from 6-9K RPM. I've noticed that in the boggy range, if I turn it from about quarter throttle to half, it starts to rev a bit nicer and then pulls up to 6k+ where it's far happier. Unfortunately 4-5K seems to be the rev-range it wants to sit at on most legal road speeds (my RGV generally sits around 5-6K).

Presently there are new #38 pilot jets, the main jets (#135) are old, the N68A needles are new. The needle clip sitting is currently in the middle, I'm thinking I need to try adjusting this as a start. The bike itself has 49,000km on it, most of which by the previous owner, so I've never really had a good baseline to go by.

Thanks for any help

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James P
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Re: boggy running between 3-5k at 1/4 throttle

Post by James P » Tue Oct 02, 2018 11:33 am

Is the poor running more related to engine speed, or to throttle position?

Are the needles new because the original ones were worn? If so, could the needle jets be worn also?

My own KR-1 (basically standard except for KR-1S pipes) runs better with the needle clips in position 2 (i.e. second from top), which is one step leaner than yours.

Regards,
James

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JanBros
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Re: boggy running between 3-5k at 1/4 throttle

Post by JanBros » Tue Oct 02, 2018 11:05 pm

Define boggey ? video with sound ?
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EGG
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Re: boggy running between 3-5k at 1/4 throttle

Post by EGG » Wed Oct 03, 2018 9:18 am

Hi

The poor running is more related to engine speed. I originally replaced the needles (and idle jets) when I had an issue where one cylinder wouldn't fire at tick-over. That eventually turned out to be a worn RHS idle screw (no idea how, but replacing this after weeks of fiddling did the job). I think I did look for new needle jets, but wasn't able to locate anyone selling them or would have replaced them also.

In terms of bogginess, I didn't describe it particularly well , it loses power and vibrates quite a bit until you get to 6k at which point it's happy again. Thinking about it a bit more, it's almost like it's missing. I'll see if I can get some video of the issue.

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JanBros
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Re: boggy running between 3-5k at 1/4 throttle

Post by JanBros » Wed Oct 03, 2018 11:05 am

every 2-stroke running below the pipe at constant throttle runs "boggey", it's what we call "foul-stroking" and indeed is what you say : not having a powerstroke every rev but skipping some. as soon as you add a bit of gas it run's normal again untill it reaches another "point of equilibration" where it doesn't accelerate any more.
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EGG
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Re: boggy running between 3-5k at 1/4 throttle

Post by EGG » Wed Oct 03, 2018 11:55 am

Hi

I've replaced the RHS plug, which was really black, turned up the idle adjustment on the same side and put the needles to the #2 slot. This has improved the midrange a lot. Unfortunately I've now run out of light to keep trying.

I'll have another go later in the week and see if I can record some video.

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