I've got a 99 Scrambler 400 4x4, purchased used, no manual, etc.

Starts fine, runs good, however it will not idle. You have to sit there and "feather" the throttle to keep it running.

I saw a small adjustment **** on the right side of the [Mikuni] carb.

I adjusted it full lock both ways, seemed to have no affect whatsoever.

Any ideas?

Thanks in advance.

 

Take the pilot jet out and clean it.

 

you should also be able to adjust the idle on the throttle line

 

Thanks guys.

I did find the throttle adjustment that was inline with the throttle cable.

However, you have to set the idle so high, that now you can't put it in gear!
Runs good wide open, but not at any other rpm range.

I guess I'm going to have to suck it up and pull off the carb and clean everything out.

Anyone here have any info as far as schematics, and more importantly, how do you set the various adjustments on it correctly?

Thanks

 

make sure you buy genuine mikuini needle and seats , clean it good with either carb cleaner of the dip type. replace your plug adjust your choke, make sure your vent lines are not pinched or pluged. one on the right side goes down the one on the bottom should have a one way valve and be run up by the frame. make sure your float arms are level when the carb is upside down on a work bench. hope this helps.

 

go to Sudco International - Modern and Vintage Replacment and Performance parts for Street Bikes, Dirt Bikes, ATVs and Personal Watercraft for your mikuni parts, let me know if you need "manual" assistance, I have a '99 Scrammy 400 manual in thy garage at the moment!!

 

Okay, I was just going to clean everything, but it makes sense to replace the needle and seat while it's apart......

 

IF the parts are not bad dont replace.Now the needle and seat are the main wear parts.
On Ebay there is a seller by sledpartsguy and he carrys complete kits with needle and seat included for less than a factory needle.

 

OK, I called the local stealership: $60 for a needle and seat!!

So, I tore it down, cleaned everything out with carb cleaner, and blew everything out with air.

Now she'll idle at a lower rpm, much better than before. It does however have a bit of gas coming out of the vent hose that has a one-way valve in it.

So what needs to be adjusted and how on this carb?

I see a small brass "****" on the right side and a small brass screw.
I turned the **** all the way one way or the other, nothing changes?

Lastly, I just moved from MO (1100 ft elev) to MT (4040 ft elev) if that makes any difference.

 

OK... the **** is the idle speed...

The screw is the fuel-air mixture.


You may have to look into the jetting at that elevation, v/s what is in the carb.


I have a jetting chart for this engine somewhere... I'll just have to find it if you need it.



As for the leaking out the hose... I started having the same issue and started having idle trouble also...

The problem there is that the bowl on the bottom of the carb is over-filling. When it does, it runs out that hose... like an overflow. The bowl is over-filling because either the float level is wrong, or the needle/seat is dirty or worn.