My baby is sick, start on one cylinder only.

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My baby is sick, start on one cylinder only.

Post by Xirious » Tue Mar 31, 2020 12:25 pm

Hi Guys,

After having cleaned everything out and putting it back together, my girl is still needy.

The problem is that she only fires on one cylinder (LH),no matter the fuel tap position. The RH only ignites when throttle is open past 1/4 or when I choke her. That's not something I wanna put her through.

Bike is a 1989B KR1, the tank is little rusty on the inside. This might be a possible cause.

Any advice is more than welcome as I am going through the license plate registration at this time and can't wait to put her on the road.

Obviously its a mixture or fuel supply problem.

Do some of you use an additional fuel filter in the fuel lines, if so what type.
I had tried that before, and even with the filter flowing in the proper direction, fuel tap on prime, lines disconnected from the carbs, the fuel didn't flow. When all is connected the bike did start, possibly due to created vacuum.
Where my filters to small... I do not know.


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Re: My baby is sick, start on one cylinder only.

Post by 500bernie » Tue Mar 31, 2020 8:25 pm

Hi Erik,
Your carbs need a really good clean, pilot jets, under main jet block, and check the choke feed.
A rusty tank is not good, give it a good clean out and seal it.
Make sure you clean out the fuel tap and filters.
Then take time setting up and synchronising your carbs.
Dont forget to check your oil pump (the Mark's need to line up).
Then you should be good to go.
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Re: My baby is sick, start on one cylinder only.

Post by Garry » Thu Apr 02, 2020 11:15 am

Have you removed the fuel tap and cleaned the filter.

Also does it flow fuel on prime if you have the filler cap open (could be a blocked breather)

I use in line filters on mine

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Re: My baby is sick, start on one cylinder only.

Post by twigg » Fri Apr 03, 2020 6:46 pm

it sounds like (as bernie says) you need to look at your carbs if it will only fire when you rev past 1/4 throttle its likely that your pilot is blocked
but if you dont sort your tank it will just keep drawing crap into them so you need to sort that out
or you will just keep having the same problems
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Re: My baby is sick, start on one cylinder only.

Post by Xirious » Mon Apr 13, 2020 3:33 pm


Removed the carb and cleaned it out with compressed air, I had already put them in ultrasonic recently.
Now it starts on both cylinders again.
:P Thanks!
Not that I will be out an a road trip any time soon with this f**cking virus :evil: :twisted:

While I was in there, I synced and readjusted the carbs because I had the feeling the bike was running to rich.
Lot of smoking and slow pickup from low Rpm's. Started right away from the first kick.

I set the airscrew to 1,75 turns out. Idle screws at 1,5.
(I have an oiled foam filter installed in the original airbox, rest of the bike is standard)

Started right away, idling at somewhat above 1000 Rpm.
After a short test drive, I let it run for a short them on idle, slowly the idle started dropping and the engine died. After the bike was difficult to start.
Did I set it to lean or can this be due to spark plug temp rating?

What is the proper procedure to adjust the air screws on a twin cylinder?
Do you adjust one cylinder at a time with the spark plug removed from the other?

is it possible to do this with a running engine as on a dirt bike, meaning that is it possible to hear the engine react to the adjustments you are making or how does one find the proper setting?

Try-remove fuel tank -adjust carb (one or both?) - mount tank - retry and so on?


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Re: My baby is sick, start on one cylinder only.

Post by JanBros » Tue Apr 14, 2020 12:20 am

from experience, 1.75 is way too lean. service manual says 1 1/8th turn and in my experince even that is too lean. I usualy set them at 3/4th of a turn.

just set both the same, it is very difficult to change them when running, unless you have a screwdriver and fingers that fir in between.
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Re: My baby is sick, start on one cylinder only.

Post by solomonheckler » Fri May 15, 2020 9:01 pm

I've been fighting with the same issue for a few months. Fortunately (or not) the Finnish winter is so long that I have plenty of time to wrestle with solutions. I don't know how many times I have cleaned my carbs, even taken them to a carb guy to have a look.

In my case after checking from tank down; Tank is clean, petcock and filter are clean, inline fuel filters are clean, main jets clean, idle jets clean, all air passages and channels are clean. I found that there is a tiny pinhole that goes from underneath the idle jet into the main venturi, it was 'open' and allowing fuel through but not squirting through properly. So I cleaned it again with carb cleaner and some tiny jet files and managed to dislodge some ancient dry gunk.

Now it fires up like it should and only needs a short time on minimal choke.

It was unbelievably difficult to find out exactly where the shite was, but as the guys on here say that's where the issue was.

Don't know if this helps but good luck.

It just snowed again today here so I'm on hold for another few days . . . . but soon I can properly test Zeeltronic, Jollymotos and my new set of boots. Boomshanka.

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