1979 Enticer 250 Mikuni Carb swap

M

mike_donison

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Feb 17, 2016
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Regina
Hey Guys
I recently did a carb swap on this sled to a Mikuni Vm34.
Here's what I used
220 Main
40 Pilot
159 Q 0 needle jet
6d h4 needle on middle clip
2.5" slide cut away
I took this for a good rip yesterday. It was about -25 Celsius. It ran pretty good. Just a tad bit of a bog off the line. Also noticed it didn't seem to wanna fully Rev out. I'm assuming that could be due to clutch alignment? If so what's the best way to do that? As for the bog, what should I be trying? I'd like a little more zip off the line. I checked the plug and it's golden brown as well.
 
A hesitation right of idle is often cured with a richer idle mixture. It seems these engines need to have the idle mixture a tad rich to help it transition to high speed. Try turning the idle mix screw all the way in, if this helps, go up one size on the pilot jet.

More of a mid range bog? move the clip, try top notch, then bottom notch, this way you will figure out what it actually needs.


You say it does not seem to rev all the way out, If you can find a smooth trail or road, hold it wide open, and then add the choke. If the choke makes it really go, try a bigger main.

More then likely the main is a tad rich, after the choke test, I would not be afraid to try a 180 or 190. sounds like you are really close, the 190 should clean right up, and really make it run.

The main jet can only be tested at wide open.
 
Hey thanks. That's the exact info I am looking for. The sled is still a blast but I feel like there's a bit more there. I've also noticed that I don't think my choke does anything.
 
There might be to much slack in the cable to actually raise the enrichener. You can see a passage from the inlet side of the carb going directly to the choke plunger. Stick a wire in there and feel if the plunger is moving.

More importantly be sure you have enough slack so the the plunger drops all the way down to close off the cir-cut.

Also when you are at full throttle the choke does not do much, mostly the choke works when the engine is at an idle.
 
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So I checked the choke. Here's what I did.
Used an 1/8" diameter rod and stuck it down the inlet side. I then opened my choke fully and stuck the rod in. I udjusted the choke so when you flipped it to half it started to hit the rod. I locked in in place there.
So now it functions but it won't idle down now which obviously means it's not closing all the way? Or now that it's set properly I should be adjusting my idle?
 
Just make sure the plunger drops all the way down, at this point there should be slack in the cable.

Not idle down ? Again, be sure you have enough slack in the throttle cable, and then adjust the idle speed screw.

Also a lean condition causes a high idle, try richening the idle circut by turning the air screw in, and or try a larger pilot jet.

Your going to make run real good with that 34 Mikuni ! Just a couple more little adjustments.
 
weverat said:
A hesitation right of idle is often cured with a richer idle mixture. It seems these engines need to have the idle mixture a tad rich to help it transition to high speed. Try turning the idle mix screw all the way in, if this helps, go up one size on the pilot jet.

More of a mid range bog? move the clip, try top notch, then bottom notch, this way you will figure out what it actually needs.


You say it does not seem to rev all the way out, If you can find a smooth trail or road, hold it wide open, and then add the choke. If the choke makes it really go, try a bigger main.

More then likely the main is a tad rich, after the choke test, I would not be afraid to try a 180 or 190. sounds like you are really close, the 190 should clean right up, and really make it run.

The main jet can only be tested at wide open.
Click to expand...

Great tips
 
Thanks very much for your help. It was idling great before I adjusted the cable so that leaves me to believe it just needs to me adjusted a tad more. Any other tips you have I'll take haha.
The sled runs good as it is right now I just think I'm leaving a bit out there.
 
Did this conversion. 220 main 6hd4 needle. Ect ect. Have fuel pouring out overflow tube just off of idle. Moved the tab on the need and seat to lower fuel level and even plugged the overflow line. Accelerates good then fall in its face. Let off t he throttle it drops to a very low idle or quits. Ideas??
 
MNEman said:
Did this conversion. 220 main 6hd4 needle. Ect ect. Have fuel pouring out overflow tube just off of idle. Moved the tab on the need and seat to lower fuel level and even plugged the overflow line. Accelerates good then fall in its face. Let off t he throttle it drops to a very low idle or quits. Ideas??
Click to expand...

You either have a bad needle/seat or if your carb is from a Motorcycle/Atv then the Needle and seat is designed for gravity feed and will be easily overcome by the fuel pump pressure. When you plug the over flow the fuel just pour through the main jet and will flood (like you're experiencing).
 
I agree - you likely have a gravity feed carb or a blocked needle (doesn't take much). Even a new carb can be the wrong type or have a grain of debris in it.
 
The number on the bottom of the needle seat should be 1.5 The motorcycle gravity feed carbs usually have a 2.5 or 3.0.

It sounds like your needle seat is leaking and the float height is out of adjustment. With the float bowl off, turn the carb upside down, now the float arm should be level with the gasket surface.

I know it is a new carb, that is why I am guessing it is messed up.

Another thing you can do is polish the inside of the needle seat with aluminum polish, a Q-tip, and a cordless drill.

One more thing, the needle seat gets a gasket on each side of the baffle plate. The carb should never overflow out of the vent hoses.
 
I just did the conversion too....

I'm trying to set the sled up for elevation 4000-7000
main 210
pilot 35
screw- 1 turn out
Still testing at these sizes to make sure its 'just right'.
r
 
I am at this carb conversion again, 220 main, 6dd4 needle, 35 pilot, needle in center clip, air screw 1.25 out. I have had issues with fuel out of the overflow tube, replaced needle and seat. It is better but still when it falls back to idle, fuel into the overflow. Very boggy at the bottom end, new belt ect ect I am very lost on this thing

Eman
 
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