Carburing and kick start issues

Are ya having a problem with your rig? We'll try to help. Share your tech tips and experiences here. Dr. Billy Glaser, author of the "Unofficial 750 Ural Service Manual" site myural.com, is moderating this section.
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raultv
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Carburing and kick start issues

Post by raultv » Wed Mar 11, 2020 4:32 am

Hello everyone,
I am trying to carbure my 2004 Ural with Keihin ckv 32 carburetor. I am using a tool called colortune that for all those who do not know it is a transparent spark plug that is inserted into the cylinder and when you start the motorcycle it allows you to see the color of the spark , in idling and turning the air mixing screw, the blue spark must be searched for a mixture that is not too rich.
well that's how I have it, my spark is blue in practically the entire throttle path the problem I have is that with the starter button it starts perfectly both cold and hot, but with the kick it is impossible to start it cold I don't know If there is any trick to start it,
I have tried to give it a little gas but it seems to be drowning.
by the way, so that the spark appears blue at idle, I only have to 1 turn the screw of the air mixture if I give it more than one turn it turns orange, I say it because I find it curious because I have seen that many of you carry more than 2 turns in the screw.
by the way I live at sea level.
I appreciate your advice
Ural Tourist 2004

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Re: Carburing and kick start issues

Post by Dr.Tramp » Wed Mar 11, 2020 10:51 am

A multi gas analyzer is the best way to tune the air/fuel mixture but it can also be easily done by checking the color of the porcelain on the spark plugs.
A light gray or tan is good, dark brown or black is too rich, and little color or bright white is too lean. The color will vary according to the type of fuel available in your area.
After making sure that the carburetor float heights are correct and the carbs are synchronized install a new set of correctly gapped spark plugs and go for a ride at medium speed until the engine is nicely warmed up. Find a safe place to pull over and while at cruising speed pull in the clutch while at the same time hitting the kill switch but don't let the rpms drop to idle. Pull over and check the spark plugs. If they're too light or too dark adjust the air-fuel mixture screw accordingly keeping both screws at the same or close to the same adjustment.
For Keihen CV carbs the base setting is usually 2.5 turns out and should come into correct adjustment within 1/2 turn in or out. If you have to go less than 1.5 turn out the pilot/idle/slow jet is too rich and more than 3 turns out it's too lean.
You may have to use more than one set of plugs and remember that the air-fuel mixture screw only effects the low and mid range air/fuel mixture. The high speed air/fuel mixture is controlled by the main jet.
After getting the low and mid range air/fuel mixture set correctly you can check the main jet using the same method but instead of adjusting the air/fuel mixture screw you'll increase or decrease the main jet size.
Since you're at sea level stock jetting with stock mufflers should work correctly with minor air/fuel mixture adjustment. Float height and, on multi carburetor machines, synchronization is critical.
Ride Safe. Dr.Tramp...............

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Re: Carburing and kick start issues

Post by Wildhorse Cafe » Wed Mar 11, 2020 2:39 pm

My guess, too lean. If spark is not an issue.
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Re: Carburing and kick start issues

Post by raultv » Wed Mar 11, 2020 4:04 pm

Thanks for your response,
I have to check the float height, but what would be the correct height of the float to start doing the color test on the spark plugs?
Thanks
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Re: Carburing and kick start issues

Post by Eric N » Wed Mar 11, 2020 10:31 pm

What temperature is the bike dialed into to kickstart without the enricheners?

If you're running 1 turn out on the fuel screw, turn it out 1.25 or 1.5 turns and see when you can kickstart it without the enricheners.

Cold engines run different than warm. Colortune on a hot engine will be different from a cold. Not sure I would obsess over "blue", bike will tell you what it wants more than telling the bike what it should accept.

I dial my carbs to use enrichment on a cold engine below 60 degrees F. As Wildhorse Cafe mentioned, if you're able to kick when warm but not cold, bike is too lean. Opening throttle on a CV carb leans it out more. Are you using the enricheners to get it started and then turning them off when it's idling? Sometimes only one side needs enrichment, are you just trying one side when kickstarting cold to see if that works?
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Re: Carburing and kick start issues

Post by Dr.Tramp » Wed Mar 11, 2020 11:46 pm

The Ural manual I have doesn't have that information but the factory float height for a Keihin CVK 32 carburetor on a Arctic Cat snowmobile is 17mm or .700". The Ural manual also doesn't say if the float height is measured with the float just barely resting on the spring loaded float needle pin or with the carburetor upside down.
The rule of thumb is with the float just resting on but not compressing the float needle pin the float should be roughly parallel with the carburetor gasket surface as in the video. https://www.youtube.com/watch?v=g6y32Gw5HK4 However some float heights, including some Keihins, are set with the float resting completely on the needle.
I'll do some more digging and see what I can come up with.
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Re: Carburing and kick start issues

Post by raultv » Fri Mar 13, 2020 12:32 pm

Thanks Eric and Dr.Tramp,I will look the carburetors floats this weekend,Let's see what I can find out
Thanks
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Re: Carburing and kick start issues

Post by raultv » Sat Mar 14, 2020 12:59 pm

Well, I have been checking the level of the floats (using a piece of clear tubing which can attach to bottom of fuel bowl drainand ) they seem to be fine.
Afterwards I tried to carbure the low range with the friend lokiboy method :

"Air/fuel mixture screw: Idle Drop Procedure
1) Bring the bike up to operating temperature - enrichener is off.
2) Air/Fuel mixture screw (under the carb): From seated, CCW (enrich the mixture) until the RPMs are maxed and no longer change based on turning the screw.

The result is curious:
the right side carburetor responds as it should:
When the air screw is loosened (ccw), the revolutions go up until I take one turn and they don't go up anymore.
But the left carburetor doesn't act like that.
When I loosen the mixture screw there is nothing happens in the first two turns, from the second lap it seems that the revolutions drops

PD. the idle jet is 45 and the main jet is 125
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Re: Carburing and kick start issues

Post by raultv » Sun Mar 15, 2020 6:22 am

When I tighten (cw) the screw mixture in the right side carb ,the bike stalls, the rpm goes down, and when I loosen the screw (ccw)the rpm goes up, this is normal, expected.
But in the left carb, when I tighten (cw) the screw mixture, nothing happens, the rpm don´t changes, only when loosen more than 2 turns the rpm drops
What can it be the problem?
Thanks
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Re: Carburing and kick start issues

Post by URALNUT60 » Sun Mar 15, 2020 9:36 am

If you have a blue flame and bike starts right up hot or cold with elec starter I wouldn't change anything except your presentation, how much throttle are you grabbing? 1/4 throttle? Are you using the enrichners? On the left side there is a choke at the block were intake tube for carb is, diff temps require different method! I have 97 sportsman kick start only, 1 or 2 kick bike cold, when warm 1 kick, keep spare set of plugs when searching for the right combination

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Re: Carburing and kick start issues

Post by aduthie » Sun Mar 15, 2020 10:30 am

raultv wrote:
Sun Mar 15, 2020 6:22 am
When I tighten (cw) the screw mixture in the right side carb ,the bike stalls, the rpm goes down, and when I loosen the screw (ccw)the rpm goes up, this is normal, expected.
But in the left carb, when I tighten (cw) the screw mixture, nothing happens, the rpm don´t changes, only when loosen more than 2 turns the rpm drops
What can it be the problem?
Typically this means that the pilot circuit is dirty. Clogged pilot jet, debris or fuel deposits in the pilot circuit, etc. Remove the pilot jet and make sure you can see straight through it and that the hole is circular, with no gunk clinging to the sides. Same with the hole that holes the mixture screw. Beyond that, carb cleaner spray and an air gun to help clean out the pilot passages.

By the way, when you continue opening the right mixture screw, engine speed should drop again. Halfway between the lean (cw) drop and the rich (ccw) drop is where you want to leave the mixture screw. A little towards the rich side is fine.
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Re: Carburing and kick start issues

Post by chaos2 » Sun Mar 15, 2020 11:37 am

Also there is a tiny O-ring on the tip of the mixture needle that can get deformed and muck up the mixture. Replacements come with rebuild kits.
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Re: Carburing and kick start issues

Post by rivers » Sun Mar 15, 2020 2:01 pm

chaos2 wrote:
Sun Mar 15, 2020 11:37 am
Also there is a tiny O-ring on the tip of the mixture needle that can get deformed and muck up the mixture. Replacements come with rebuild kits.
+1
Doesn't take much of a hard seating to deform an old tired o-ring.Don't know if it applies to you in Spain, but some of Europe now is dealing with ethanol fuel.:( and those o-rings are not ethanol friendly.
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Re: Carburing and kick start issues

Post by raultv » Sun Mar 15, 2020 4:32 pm

I have removed the O-ring ,It was difficult to get it out, it stayed inside, and its flat, round but flat, I guess it was originally is like a donut.
I am going to replace it and see what happens .... I will keep reporting.. :cheers:
Thanks all :bow:
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Re: Carburing and kick start issues

Post by jeffsaline » Sun Mar 15, 2020 9:44 pm

raultv wrote:
Sun Mar 15, 2020 4:32 pm
I have removed the O-ring ,It was difficult to get it out, it stayed inside, and its flat, round but flat, I guess it was originally is like a donut.
I am going to replace it and see what happens .... I will keep reporting.. :cheers:
Thanks all :bow:
The condition of the o-ring might be part of the problem but probably isn't the only issue with the idle circuit.

If you remove the carb from the bike and remove the top cover and slide/needle and also all the parts on the bottom of the carb and also remove the choke, it will be easy to inspect, clean and verify good condition of the carb body and the individual parts. Spray carb cleaner from a spray can using the red tube that comes with most of them. At least in the US we get red tubes with the cleaners. Use eye protection and spray the cleaner in the hole for the mixture screw. It should come out the throat of the carb on both ends (air cleaner side and engine side) and also the pilot jet hole. Then spray it in the pilot jet hole and it should come out the holes in the throat of the carb and also the mixture screw hole. Then spray it in the hole in the air cleaner side of the throat of the carb and it should come out the pilot jet hole, the mixture screw hole and the hole in the throat of the carb on the engine side. Finally, spray it in the hole in the throat of the carb on the engine side and it should come out the mixture screw hole, the pilot jet hole and also the hole in the throat of the carb on the air cleaner side. Once you have done this you have verified those passages are connected and clear. Since you have spent the time to go this far maybe also spray in the other holes in the carb body and verify the cleaner comes out the connecting holes. You can learn a lot about how the carb circuits work by spending a few minutes doing this and you will also have confidence the passages are clear.

You can do the same thing with the jets to see if you get a good spray pattern from each hole in each jet.

I use silicone plumbers grease on the o-rings when I assemble a carb. I put a very small (maybe the size of a BB, 2-3mm) on a finger tip and rub it with my thumb. Then I rub the o-ring so it shines but doesn't have any gobs or globs of grease on it. This helps the o-ring slide into position and makes it easier to install. I also rub some on the float bowl seal without removing it from the float bowl.

Good luck with your continued troubleshooting and repairs.

Best,

Jeff
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