Hi everyone.

I'm new to the nsr250 mc28 world.
I have read alot of the posts you guys have kindly provided.
I have one question as you can see from the title. I have rebuilt a 1994 nsr250 mc28 the bike will start fine and seems to rev fine but when I let go of the throttle the front cylinder stops firing and smoke roles out of the exhaust when it drop below 3k. My compression is 140-150. If anyone would be kind in shed some light on this would be greatly appreciated.

thanks

Having a similar issue.

Have you rebuilt the engine already?

Any more info on background and what you have tried already?

Hi
Yes the engine was rebuilt and here is a run down of what I have tried.
new spark plugs
new coil
new voltage reg
cleaned carbs
checked connections for arking all clean.

as far as I know there is no wire splice when I got the harnes it had the ground wire of the front lights all soldiered together so I removed it and put it back to original configuration.

When I rev it it fires but then I shut it off and pull the plug from the front it is wet.

Not sure if this is anything but I noticed the ground wire for the thermostat was off but when I connected it the lcd started flashing 135° so I disconnected it.

Hi Krull/Rhyshrc,

Check your carb slides that both the left and right slide is opening the same. If not adjust with the screw located between the two carbs.

Also check slow/idle jets as these might be blocked. Once the main jet gets closed by the needle then it runs on the idle jet, if that is blocked then one cylinder will die.

Also check float levels.

Cheers,
Mario

Thanks Mario

Both the sliders are operating ok.
I will check the slow jet and get back to you thanks again

Oh and also check that both air screw passages are clean and both air screws are set.

Cheers,
M

okay shall do

Cheers

Did you have this issue before the engine rebuild?

no the bike ran fine.

no the bike ran fine.

Also check :

Battery
Charging system

Maybe when the bike idles it does not generate enough power.

Cheers,
M

Hi guys
So I checked the carb for blockages and they were all clear.
one kick it started and continued to run the same.

thanks alzazorq
ill check it. what is the value or voltage I'm looking for on the charging system

13.8-14.2VDC over the battery terminals at +-3000rpm. (Just adjust your idel screw so that the bike idles at 3000)

Cheers,
M

Very interested in this thread, tried everything and cant fix it, rebuilding the engine now but interested to see what the outcome the OP has.

hey guys
thanks for all the help.

so I check the voltage at the terminals and I am getting 14.+\-
still spuratic fire at idle.

you guys rock.
any other suggestions

does anyone know what a flashing temp number 134 means I found my ground to the thermostat off so I connected it and it started to flash 134. so I disconnected it. it still tels the temp correctly