Bike idles fine with same temp exhaust and same amount of fumes/ colour smoke- settles down to a good idle once warm and I shut the choke off-
Put in 1st gear and off I go -pulls fine, shut off throttle to change into 2nd looses power and I roll to a stop - very hard to start if at all then if it does start top cylinder is not firing?

Bike-
std- no wire splice or GPS splice
No holes in air box or mods
exhaust STD and still runs oil pump.
I have just changed from Denso W27EMR-C plugs to NGK BR9ECM and a fresh lot of 98 octane fuel ssoooo it should run sweet right?
Try to give it some gas at idle some times and it is slow to return to idle, prefering to take it own sweet time to come from 3000? rpm down to 1250 (something that it also never did before)


Changed battery to a new one too- this makes it start 1st kick when cold but once it dies there is no coming back
pushing it home is not fun anymore (luck it stalls after 1st gear and not 3rd etc I would be alot further from home by then )

Anyone have a starting place?
I am just going to go and remove tank/ fairing to have a closer look at what is going on -check back with you soon



Cheers!
Brett
ps hope the pic works? may do abit of story in the members build at some stage- nothing super (neither is bike)

First things first... define "refreshed" please. Refreshed would lead me to think of a top-end rebuild, and therefore something not set/set up correctly upon reassembly.

Check the carb settings. Check all the jets are clear, the air screw and float levels are set correctly, and that the filter in the tank is clear. (I.e. check for fuel starvation.)

When you are sure the carbs are OK, check for air leaks. It sounds lean. Does it run better with the choke lever on? (Don't run it any longer than absolutely necessary to check this!) Check the plumbing to the two air corrector solenoids.

Could be the carbs seated in the manifold incorrectly (possible to push them in only half way!), airbox not fitted properly, air filter left out by mistake, a warped inlet manifold, or a split/perished inlet manifold.

More serious things could be a leaking base gasket, leaking head gasket, or dead crank seal(s). All can produce symptoms as you describe, but easiest to check pretty much in the order I've stated.
_________________
Andy.
NSR-WORLD.COM

Please keep all responses to Forum posts on the Forum so that others may benefit.

Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.

Check us out on Facebook! Please "like" our page!

Sorry the 'refreshed' only refered to cosmetic refreshments (paint/ polish) + things like sprokets /chain etc.
I purposely did not touch the engine as it was running like a champ before I did the tidy up!! only change has been plugs and fuel ?

I was bad and took it for one more quick ride- just to see if it was a 1st gear thing?
I was able to quickly shift to 2nd and 3rd then roll the throttle off and - yep she dies. won't start after that, as before.

I didn't want to start fiddling with stuff as it ran fine before 'refresh' but looks like I have no choice and its good to reset everthing back to factory specs (while keeping track of what current setting are too).

I may just thow the old plugs back in before I go stripping carbs- easy stuff 1st right then onto your sugestions Andy

So when you say paint, I would assume you also painted the fuel tank?

If so How well did you seal it up before painting?

Drain the tank, pull the petcock, and check the fuel filter. Could be you got crap in the tank while cleaning it up for paint, or you even got paint dust from the paint in there and it's clogging the fuel filter.
_________________
Charles Gallant

Did you protect the tank overflow when you got the tank painted? Did you remember to remove the tape off the overflow after it got painted?

Fuel filter is clean , thourght it would be as bike revs fine and isn't noticably down on power in gear = enough fuel available in upper rev range?
Overflow was tape free when installed.

Guys I am thinking now that it is running lean in the low rev / idle circuts when it heats up due to an air leak (hopefully not a crankcase seal) that opens up with heat and leans it out- explains why throttle is slow coming down from rev at idle and why I cna't save it when it starts to die by giving it some revs

Anyhow no more guess work carbs are coming off today and then I'll know for sure?

BTW - never owned a bike before and my engine experience is with v8's so I am on a steeeep learning curve with this bike

Fire it up and squirt carb cleaner or easy-start around the carb mounting rubbers, while rocking them back and forth lightly... You can also do this around the back of the flywheel. It's not foolproof, but if there's a bad air leak it will probably show it up.
_________________
Andy.
NSR-WORLD.COM

Please keep all responses to Forum posts on the Forum so that others may benefit.

Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.

Check us out on Facebook! Please "like" our page!

Brett wrote:
Guys I am thinking now that it is running lean in the low rev / idle circuts when it heats up due to an air leak (hopefully not a crankcase seal) that opens up with heat and leans it out- explains why throttle is slow coming down from rev at idle and why I cna't save it when it starts to die by giving it some revs

Sounds much like the symtoms I had due to a dead crank seal, revs slow to drop to tickover from around 4000 RPM, also very eager to bog and die when opening throttle sharply at tickover, much clutch slip needed to stop engine bogging when setting off.

Try Andy's described method with spraying carb cleaner, if that's inconclusive suggest you conduct a crankcase pressure test, before you think about splitting the cases.

Some info
http://www.nsr250.net/forums/viewtopic.php?t=7023&start=0
_________________
Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30

Carbs are off and no need for a good clean - someone beat me too it? some minor scratches on the bottom of the fuel bowl shows me it has just been cleaned no so long ago!

Jets are factory 128MJ and 38SJ -no surprise there for a stock bike and air screws are at factory for a TA22A carb

As for the cause of my problems - the 3 way connector to the air box from the x joint on the carbies looked like this......








Could be the problem??

definitely not good replace it and see how it goes.

This is my thought, I don't know how you feel about being my lab rat
It looks like a joiner, and the 3rd link is just to hold it in place on the bottom of the airbox. If you buy yourself an elbow (from aquarium) it should do the same job.

I'll wait for the gurus to shoot me down in flames

nxrsr20- I wont shoot you down but to let everyone know the piece that joins air box is hollow and shares the internal void of the other 2 pipes, so it must do something? Its not unlike the y join coming back from the solenoids and that doesn't need any brace to support it- so it wouldn't be stuck in the air box just for that -not that I can see that it goes anywhere in the box either

Not sure what is does but used a 5mm garden sprinkers system T piece to fix it

anyway carbs etc are back on and it fired into life 1st kick (kick it over a few times with key in off position to get fuel down 1st)
No fire in right side cylinder (sorry to those who have read from the start but I am such a noob that in 1st post I said top cylinder -)
Spark is there when I pulled the plug and started it running on other cylinder.
Plug was very wet and still clean so there must be fuel
Next onto Andy's and Richg suggestion for tracking air leak-
If its not an air leak then what? compression test that cyclinder for busted /worn rings...


I have made no mention of it so far but just want to say I appreciate the replies and time spent replying so far!!
NSR-WORLD....rock on!!!!

the leg of that 3 way splitter goes into the solenoid airfilter, which is a small drum like thing whiah fits into a recces in the bottom of the filter box.

try the leak test next, then yes maybe compression, its just funny how you said the bike was running perfect before, have you stuck the old plugs back in yet?

Yeah tried old plugs- no difference-
Last time I rode bike before cosmetic refresh was a month ago now and from memory it rode fine , maybe battery seemed a little flat when starting? but nothing to make me think it was dying or mech problem looming.

3 way splitter was brittle and has been repaired with superglue before- not sure if it was broken when I took airbox off or it just crumbled when I disconnected the airbox?

when you had the carbs off, did you check that the emulsion holes in the jets were clear?

You haven't trapped or kinked the fuel pipe when you refitted the tank have you?

Did you unplug any electrics?
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball