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Ninja 250 issue

G

gbyoung2

Member
Member
I have been working on a customer's 250 Ninja that came in with a hole in the LH piston brought about by a coolant loss. Honed the cylinders, checked service limits, and refitted with new pistons, rings, piston pins, etc.

Once back together, bike wouldn't start. Found some major issues with the original carbs, which you will see in the pages below.

Customer had another set of carbs that hadn't been screwed with and they looked good. As a precaution, I pulled the pilot jets and needle jets to make sure was okay. They were. Diaphrams also looked good with no holes or tears. Since he has separate (really $hitty looking) K&N filters and a modified exhaust, I transferred his main jets and shims to the "new" carbs. Bike started right up with no initial issues - but - the idle wants to wander all over hell and creation. Initial indications were that it may have a vacuum leak, and altho' his runners are somewhat hardened due to age, they tightened up nice and snug to the head and the carb bodies. Syncing the carbs didn't show anything out of the ordinary.

This may sort itself out once some miles are on it, but was curious as to might be causing the idle to wander like it is.

?????????

http://gbyoung2.smugmug.com/Motorcycles/Skippiis-250/21475718_vXJhcj

Guy

 
My wifes littke Ninja 250 does not idle very well either. But at least it does not die at at top or anything. Its rideable. Of the things I have read on the Ninja 250 riders club, that you did not mention is valve adjustment causes poor idle. But with the pistons and honing I suspect you did this.

How are the idle mixture screws set?

Myself I have check most everything and sending the to SISF for cleanup is where I am headed. I just have not gotten around to getting them out yet. And the projects are piling up. So who knows...
 
Guy, did you spray an wd-40 around the carb boots to see if RPM's picked up?  Are the mixture screws set at 1.75-2 out and the carbs sync'd? Float levels set equal? Compression test ok? Plugs both look the same or different?.

I know you know this stuff, but....
 
I have an '89 EX250 that I resurrected after 7 years of storage.

It's very cold-blooded, even more so than the Concours. It usually takes me 10 or 15 minutes of riding before it gets to operating temperature and it almost never triggers the fan.

Mine is set for 1300 RPM at operating temperature and once warm it idles there nicely, but during the warm up phase I have to blip the throttle and/or and keep the choke on a bit.

 
Slybones said:
My wifes littke Ninja 250 does not idle very well either. But at least it does not die at at top or anything. Its rideable. Of the things I have read on the Ninja 250 riders club, that you did not mention is valve adjustment causes poor idle. But with the pistons and honing I suspect you did this.

How are the idle mixture screws set?

Myself I have check most everything and sending the to SISF for cleanup is where I am headed. I just have not gotten around to getting them out yet. And the projects are piling up. So who knows...
Click to expand...

Appreciate it.

Yeah, the valves were adjusted and checked a couple of times since the cams had to come out when the head was pulled. Have played with the mixture screws from an initial 2-turns out, to 1-turn out, to 1-1/2 turns out, and now have them set at 2-1/2 turns out. Seems to be happiest there.

Have also done the propane and WD40 test of the carb insulators (runners) and that didn't show anything.

We're gonna turn it over to the owner so he can get some miles on it, then have him bring it back to recheck the valves.

FWIW - my daughter's Ninjette is cold-blooded as all git out and idles fer $hit until it warms up then settles out somewhat, but still isn't quite as bad as this one.

Guy
 
connieklr said:
SKIIIIPPPIII


This may sort itself out once some miles are on it, but was curious as to might be causing the idle to wander like it is.

?????????

http://gbyoung2.smugmug.com/Motorcycles/Skippiis-250/21475718_vXJhcj

Guy
Click to expand...

Those photos of the emulsion tubes are scary.... wtf happened to them?, they are twisted, holes smooshed shut and bent to Farg...
You did put the other carbs on did'nt you? did those look the same?
Just curious.
If he had shims in the originals ( and no doubt it needed them from the emulsion tubes....) I'd pull them back out.
did you install new o-rings and needles for the air jets? that makes a lot of difference also, if you use the K&L ones from Gary, they need to be backed out to at least 2 1/2 turns, as the angle on those is less radical than the oem ones.

Skiiiipiii....gotta love the boy..... :D :D :rotflmao:
 
MAN OF BLUES said:
connieklr said:
SKIIIIPPPIII


This may sort itself out once some miles are on it, but was curious as to might be causing the idle to wander like it is.

?????????

http://gbyoung2.smugmug.com/Motorcycles/Skippiis-250/21475718_vXJhcj

Guy
Click to expand...

Those photos of the emulsion tubes are scary.... wtf happened to them?, they are twisted, holes smooshed shut and bent to Farg...
You did put the other carbs on did'nt you? did those look the same?
Just curious.
If he had shims in the originals ( and no doubt it needed them from the emulsion tubes....) I'd pull them back out.
did you install new o-rings and needles for the air jets? that makes a lot of difference also, if you use the K&L ones from Gary, they need to be backed out to at least 2 1/2 turns, as the angle on those is less radical than the oem ones.

Skiiiipiii....gotta love the boy..... :D :D :rotflmao:
Click to expand...

I can only assume that someone really tightened them way too tight - obviously. He bought the bike used and said that he never had those out... only changing out the mains. One of the POs must have been the guilty party. They were definitely fooked.

The old "new" carbs were put on the bike, and they were virgins and had never been opened before. I swapped his old main jets (1 size larger), and added the one shim/per needle from his old carbs. He's running separate K&N filters and has a modified exhaust, which why the old carbs had been re-jetted.

The bike settled down a bunch after it was ridden awhile. He picked it up yesterday and said that it ran great.

 
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