NSR 250, one cylinder not firing, now the other...

[nickvr]

I have a MC18 NSR250. Something weird started happening a few weeks ago. The right cyclinder would stop firing intermittently. The results is complete power loss. I can hear it fire even so often but exhaust gas is cold. Took at to garage, they've cleaned the fuel lines / tank etc. It went 100% for few weeks and today the left side stopped firing. It is like 100% dead. This is driving me crazy, there is fire on the sparkplug. i guess it has something to with fuel or maybe CDI? Any ideas will be appreciated. Nick

[hmmmnz]

a bad earth is a common fault with intermittent firing, unscrew your coils from the frame, get a wire brush to both points of contact,
is your spark a nice blue spark??
i would change your plugs just incase, its amazing the amount of problems are plugs,
also if it is still firing only on the right swap the coils over and see if the problem changes side, that will atleast elimenate the coils as the source of the problem.
good luck:D

[nickvr]

Hi. Long shot but I think I may be onto something. Opened and cleaned the carbs again, changed plugs and generally cleaned stuff. Got everything together earlier and guess what, the left side is dead (the right side was dead).... Again I checked plugs and fire, all fine. I then got a brainwave and opened the bottom drain bolt, and only a few drops of fuel came out!!! Both carbs were almost completely dry. I tried blowing air into the intake and couldn't. I realized it could only be the floats. Removed the carb, opened the bottom and saw that the float valve was stucked. Removing it, I can clearly see some dents and scratches (here and there rough edges). The other side more or less looks the same. I'm pretty sure that this may cause this one side then the other side "dead" story, sticky float valves. Do you think a would still be able to get spares e.g. float valves and seats (TA-20)? Lastly, do you adjust the float levels?

[dickytoo]

you should be able to get a complete needle valve assembly. this includes the needle valve and the seat.

the float height should be adjusted. a typical figure for some older kawasakis is around 6mm. to measure this, connect a clear tube to the drain spout at the bottom of the carb and open the drain screw allowing fuel to flow out. remember to have the fuel turned on or in the case of vacuum operated petcocks, have it in the prime position, otherwise, you won't get enough fuel coming through. you can get special adapters to screw into the drain screw if your bowl doesn't have the little drain spout.

hold the clear hose against the side of the carb and the fuel level should be about 6mm (for kawasakis) measured from the top of the fuel bowl. The level for hondas may be different - check your manual! if the level is too high, your bike will run rich and if the level is too low, the bike will run lean.

you can also adjust your float level by taking your carbs off and measuring the height from the bottom of the float to the top of the bowl using a vernier caliper. you do this by taking off the bowl and put the carb upside down so that the needle valve is in the closed position. this figure will vary from manufacturer (bike) to manufacturer (bike).

if the level is out, you adjust it by bending a tang (a small metallic tab) on the pivot point of the float to raise or lower as required.


good luck!

[nickvr]

Another quick question. From the diagrams and text, I saw that the MC18 TA-20A carb should have two solenoids. My bike only has one. Is that normal?
And then, I've ordered a set of float needles and seats (TA-20A carb). Do I require a special tool to remove and install the new float seats? Besides adjust the float levels and cleaning, are there any any precausions / measures I must consider when putting everything back together again?
Thank you kindly

[dickytoo]

not too sure about the solenoid question.

with regards to the float valve seat, if it is round, you should be able to pull it out using a pair of pliers. it is held in place by a rubber o-ring.

if it is hexagonal, use a socket or spanner and undo it as you would a nut.

sometimes it's held on by a small screw and a metal bracket. undoing the screw and pulling gently on the body will get the valve seat assembly out.

[nickvr]

Thank you very much. It is round but I don't see an o-ring. Will try pulling it out.

[dickytoo]

you won't see the o ring until the body of the valve seat is removed from the carb.