Mikes keihin carb kit

[Tz250racer]

I don't know if backfire is the term but propably popping is.This "popping" was not there with the stock carbs.

 

[cpt137]

popping or back fire when reducing throttle is an exhaust leak.

 

[Tz250racer]

Ok...then whi the problem was not there when the stock carbs where in place?.The problem came up only the keihins carb kit.

 

[TwoJugs]

sometimes a lean issue or carbs not synced if coming from one side.

 

[pamcopete]

Tz250,

When installing the carbs, put a little oil on the gasket surfaces to ensure an air tight seal.

Try this sync method:

1. Make sure there is slack in the throttle cables.
1a. Adjust the air screws 1 1/2 turns out
2. Start engine and allow to warm up.
3. Pull the vacuum barb plug off of one of the cylinders.
4. Adjust the other cylinder idle to 1,000 RPM
5. Replace the barb plug.
6. Pull the barb plug from the other cylinder.
7. Adjust the running cylinder for 1,000 RPM.
8. Replace the vacuum barb.

If you have true dual exhausts, then you can "tweek" the idle sdjustments so that the cylinders sound the same.

With the engine not running, do the following:

1. Remove the air filters.
2. Turn the throttle grip to obtain a full up position for one of the carb slides.
3. Adjust the other carb slide cable to obtain the identical up position of its slide.

 

[randreas]

Received mine earlier this week and just installed them this morning. No problems installing. Fired up pretty quick and adjusted the idle screws to a nice idle and took it around the block. Runs a lot smoother than my VM34s did without any real adjustments. But I dont think I ever had them dialed in right as I pretty much suck at adjusting carbs. So this kit is pretty nice for people like me, almost plug and play so to speak.

Started to rain so I'll fine tune them tomorrow. I noticed that the mixture screw on the right carb seems real hard to get to. Any trick ?

 

[pamcopete]

randreas,

Just a longer screwdriver or one of those flexable shaft screwdrivers. the good news is that you don't have to adjust them much. I set mine to 1 1/2 turns out each and have not touched them since installtion, even with a change in mufflers.

 

[randreas]

OK, when I pull the barb off either cylinder the engine revs up quite a bit... Not sure what I'm doing wrong.

 

[MrBillohnooo]

You are causing a vacuum leak. Engine is acting as it should with a vac. leak.

 

[pamcopete]

randreas,

Just wait a second or two. the revs will die down.

 

[bobber33]

So i think i finally got my carbs happy...
had to go down 1 step on both main and primary jets and it seems smooth now.
Must just be the altitude where i am, but the stock jetting was rich on both.
Plugs were black, and there was some hesitation in mid's, and initial take off.

Having my air screws at 1 1/4 out now seems about right, still trying to tweak this.
But it still idles rough.. my fillings are shaking loose at stop lights. But it is a rigid bike too so this may be somewhat normal i guess. Not as smooth as my Mikuni's on the other bike though...

Any thoughts on smoothing out the idle other than joining the vacuum ports?

 

[pamcopete]

bobber33,

Try connecting the vacuum barbs together.

 

[bobber33]

bobber33,

Try connecting the vacuum barbs together.

Thanks P... did that first, and no noticeable difference. But I'm not too worried, this thing is all new and once broken in properly I'm sure it will settle down a bit.

 

[280BlackPearl]

Has anyone tried Mike's kit on a '75? If so, I would be interested to hear about your experience. Apparently there would be some modifications necessary for the dual throttle cables.

 

[XSLeo]

I have a 75, I'm running a later model linked carb set. I think you can do the throttles the same as I do. I just removed the extra cable. Works fine.
On the Mike's set just hook the cable in one position or the other. Don't worry about the extra cable hole.

 

[rude]

Tz250,

When installing the carbs, put a little oil on the gasket surfaces to ensure an air tight seal.

Try this sync method:

1. Make sure there is slack in the throttle cables.
1a. Adjust the air screws 1 1/2 turns out
2. Start engine and allow to warm up.
3. Pull the vacuum barb plug off of one of the cylinders.
4. Adjust the other cylinder idle to 1,000 RPM
5. Replace the barb plug.
6. Pull the barb plug from the other cylinder.
7. Adjust the running cylinder for 1,000 RPM.
8. Replace the vacuum barb.

If you have true dual exhausts, then you can "tweek" the idle sdjustments so that the cylinders sound the same.

With the engine not running, do the following:

1. Remove the air filters.
2. Turn the throttle grip to obtain a full up position for one of the carb slides.
3. Adjust the other carb slide cable to obtain the identical up position of its slide.

PamcoPete,
I'm having trouble with the first step, getting slack in the throttle cables, which is causing high revs on startup, one cable is loose with available free play to take up, I can pull the cable and "feel" when the slider lifts.
The other Carb, I've backed the cable adjustment all the way in and made sure the cable elbow on the top of the carb is in all the way, cable is still tight with no free play on the slider.
any suggestions appreciated

cheers

 

[pamcopete]

rude,

1. Well, the tube where the three cables meet can be unscrewed to see if the there is any binding or twisting in there.

2. Also try disconnecting the cable at the throttle and then check for free play in all three cables.

3. Remove the two screws on top of the carb and carefully pull the slide out to be sure the cable is not somehow jammed in the carb.

 

[Travis]

Rude, also make sure the cable end is properly seated in the slide. Is there any bend in the cable from the elbow to the junction box? Try straightening that run of cable and seeing if that helps.

If those things, or the things mentioned above are not the problem, and if you are only a little bit short, take the cables out of the slides and elbows all together and measure the free length of the cables. Maybe one side is slightly longer than the other. Also how much threading is on the elbow will affect free length. You might try swapping the cables around or the elbows or both. Make sure to lube everything when you put it back together. If that still doesn't work, contact mikes and I'm sure they'll make it right.

 

[rude]

yep one of the cables was not seated in the carb slider, even so there is alot of difference in the two cable adjustments.
I've mounted the cable junction on top of the frame spine under the tank so as to get straight runs to the carbs
I set the mix to 1 1/4 turns out, idle to 3 turns out, then followed ppetes vacum method to balance the idles and all is good.
cheers

 

[Wally]

Anyone come across this problem yet
I have had these keihins on for two months & both carb holders are Tearing around the bottom.??????