OK, my right foot's about to fall off from kickstart lever...

I searched this site & my shop manual, and come up with only the low speed jet, a crankcase seal, or the power valve as potential causes that could create a hard cold start condition. The bike is almost impossible to start when cold, but runs reasonably well, if a bit rough in its carb metering under neutral throttle while motoring along at mid RPMs. Anything else I should look for?

Any suggestions greatly appreciated!
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-bdb

change the spark plug and clean out the carb and check the carb settings.

this should solve your problem.

the powervalve would only cause problems if it was stuck open, so check to see if powervalve servo moves when you turn on the ignition.

Do all the sensible things too, check your battery charge level is ok, air filter isn't full of gunk, float levels in the carb.

Check the pilot and choke circuits. If OK, try a bigger pilot jet. They seem jetted quite lean on the pilot from the factory.
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Still smoking...

nsrjb wrote:change the spark plug and clean out the carb and check the carb settings.

this should solve your problem.

the powervalve would only cause problems if it was stuck open, so check to see if powervalve servo moves when you turn on the ignition.

AHA! Power valve servo doesn't move when I turn on the ignition - wondered about that, as on my Cagiva Mito it would snap to attention when the ignition was switched on. Should the NSR behave similarly, or give other signs of life?

I cleaned & gapped the spark plug - it was fuel-wet, but had good tan color. The carb was cleaned out - by a Bangkok shop... so the work is suspect I'm leaning toward opening the carb up and cleaning out again - special attention to the cold-start enrichening circuit, but want to eliminate less labor-intensive possibilities first.

Coil & secondary wire are probably original, so could use refreshing. But since it runs well when warm, I'm thinking these aren't the cause of the cold start problem.

Really appreciate it guys!
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-bdb

on my nsr 250 the powervalve moves when ignition is turned on everytime, but on my nsr 125 it only moves sometimes when ignition is turned on so i'm not sure how it operates on your bike.

but the powervalve servo should cycle between 2-3 krpm check this while the bike is running and should start opening at around 7krpm.

if it does not move then either your power valve is stuck or the servo needs to be replaced or the cables may be damaged.

i suspect that the powervalve is stuck in the open position.

i am not sure if this would affect your bike starting

the rc valve has nothing to do with the start, its should be around the pilot jet/slow jet or the spark, the standard spark use 9 series.

the rc valve should move when you switch on the ignition, but sometime its doesn't, depend on it's position when it got turned off. try to start your engine and play the throttle, it's should be moving like nsrjb said..... if it's not detach the cable and try to turn your rc valve axe by hand, if its hard that's mean you have dirty cylinder (on the rc valve) you should clean it. but if its light and thats mean something wrong with the CDI or the motorservo...
CMIIW

OK, thanks for narrowing it down for me, and helping identify an RC valve issue. The bike's just recently acquired, with a long storage just before I got her - which would point to a gummed up carb except that the PO said he had the carb cleaned out just before I bought it. But we're talking bike mechanics in Bangkok... so I may have to pull & clean it meself. I'm going to go through the whole bike bit by bit to get it sorted so it'll be good for some trips.

-bdb

hi,i have a 03 nsr150sp,took me a while to get used to kickstarting it,starts first
kick for me now,whilst kicking dowmwards,leave your foot pressed down for a second,
she might spark for you then,i thought mine was hard start till i started doing this..
goodluck anyway..

OK, it seemed to have been a cumulative effect of pretty much everything being mal-adjusted by the monkey who wrenched on the bike before I bought it- each thing I did, it helped make starting the beast a bit easier. I was amazed. If it could be tinkered with without breaking the engine open, it was out of adjustment enough to be impossible to cold start... and run like sh&te when it did light up.

Order of adjustments I undertook:
1. check proper spec, clean & gap the spark plug; check for spark.
2. adjust cold start/choke knob cable - in HOT Bangkok, you never need to pull the knob fully up. turns out half-way engaged is perfect for cold starts here. fully choked is worse than no choke.
3. adjust throttle cable slack - was so loose, I believe the choke wasn't able to usably raise the throttle for cold starts.
4. adjusted oil pump - unrelated to the starting problem til I radically adjusted the throttle cable slack... which affected oil pump calibration in a big way.
5. RC valve & servo check & adjustment; the system was so far out that the cables were slack, barely hanging onto their pulleys. valve was basically stuck close to the high rpm position, destroying low rev power, and making port timing for starting non-optimal.
6. checked & cleaned all electrical connections.

Many signs of idiocy by previous owner's hired wrench. Upside is now I KNOW this bike inside & out, and have confidence in it enough to take it on the road. No regrets at all. Thanks to all for throwing me a rope with this bike!
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-bdb

best of luck with it

Buy a new spark plug. If you had to "clean" it, it's stuffed. It will fire, and it sounds like you've sussed you cold start problem, but a new plug is like a brand new pacemaker for great grandad.
You will no doubt notice a big difference in how crisp the engine runs replacing an old stuffed spark plug.

also should mention Thai fuel is sh#te, very inconsistent from tank to tank. And ya can't even get full benzine fuel anymore - even 95 octane is 10% ethanol here.

So I'm wondering if the fuel lines, o-rings, gaskets of a circa '98 NSR are the new-generation materials that are resistant to ethanol.
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-bdb