Honda NSR 150 - mechanical help!

[zibblezen]

Hi guys,

So im pretty new to bikes and learning new things on a daily basis both mechanically and technically.

I am currently in Thailand and many mechanics do not speak much English, therefor i need to learn and do as much research as possible. This is where you bunch come in. I need some help in understanding the problem so i can then speak to my mechanic.

So....

I have a Honda NSR RR 150cc 1998. There are a few issues with it. More often when the engine has warmed up, the revs sit at 1500-2000rpm and then rise to just over 3000rpm if i sit with the clutch in or released while in neutral. I also realised today this is effected by the front brake being pulled. Once released the rpms increase to idle at around 3000rpm. Does anyone have any idea what this would be?

Also (and i think this is related), my gear transitions are clunky with the clutch pulled in. I beleive this is due to the high rpms. Can someone confirm this?

Lastly, any tips for starting a cold NSR?! Yes! Surprisingly in Thailand the mornings here at the moment are cold and it takes me 3-5 mins to start the bike.

Much much appreciation guys

[G]

Is your battery dead?

I wonder if someone's turned the idle up to account for the battery being dead.
My NSR125 would start to die a bit if you didn't keep the revs up when it had a dead battery.

Worth cleaning the carbs out and checking for an air leak.

I'd expect high rpm gear changes would be a bit clunky.

[zibblezen]

Thanks G,

I think it has a new battery. I will check this. Also... cleaning the carbs could be a good idea.

Whats strange is that the rpm rises. When the bike is warm, the will rise from 1500-3000rpm if i pull the clutch in. I release the clutch to the byte point and the rpm decreases back to 1500rpm.

Anyone else have any ideas?

Thanks again.

[unitynotsocri...]

it sounds like the main power is miswired into the coil /ignition power feed/magneto coil.you said when you apply the front brake the revs drop.it does seem electrical,although as always with strokers,,,,,check the carbs as well for leaks.

suggest carb tickover screw has been messed with and the power feed to the electrical system has been miswired,maybe near alternator......
____________________
nearly a normal tax paying tosser.......with ferrileness suzi100,cg125,cb125scb100n,cb175,cd100,cj250t,kh250,c15,125 bantam,super 6,rickman gs750,xt500,250rs,dt175,lifan125,dolomite1850,metro,Morris220ld,morrisfg,leyland princess,range rover,corsa,vw camper .now struggling with legs. MORE ORDER = MORE CHAOS

[skatefreak]

Afternoon there,
Well it sounds like you could have a combination of issues that are causing these symptoms.

Firstly the choke could be stuck open which would cause the engine rpm to drop off/die when the engine is warm (when cold the choke will increase the RPM from about 1500 to 3000 but once warm it bring the RPM right down and die at traffic lights etc).
Thus if the previous owner has increased the idle to compensate for this, this would explain the higher rpm when warm.

Secondly if your clutch is not properly adjusted and is slightly dragging then this will also reduce the RPM when the bike is in gear with the clutch in (as it is not fully disengaging.).

An easy way to test the clutch is to put the bike into first gear, pull in the clutch and push the bike (without the engine running). If the clutch is not fully disengaging then there will be more resistance than when the bike is in neutral.

Another symptom of this problem is if the bike is hard to get into neutral when the engine is <2000.

I would suggest checking the choke as they have been known to stick in the on position, get the cable out (one screw on the carb and a plastic nut on the back of the choke lever), if its tight and doesnt move freely, put a little oil down the cable and move it about to free it up.

This theory really relies on the choke being stuck open and or a previous owner messing about with the idle speed.

let us know how it turns out.

Best regards

-Jvr

Ps do you have a manual for the bike?

[zibblezen]

So do you think this is electrical even if this only happens once the bike is fully wwarmed up?

I am getting the carbs cleaned out today as i have come across some other issues i think are related to the carbs.

I noticed for a small trip the other idea the engine was chugging and losing power at lower rpms. Especially around 3500rpm and going up hill. Then once you hit around 4800rpm the bike takes off.

Am i right to think this is a carb issue? Also.. can anyone explain how miswiring could effect this? Any help massively appreciated guys.

Also skatefreak i think you misread or i didnt properly explain. As i pull the clutch in the rpms increase. They do not decrease. The weird thing is the if im stopped at lights and the rpms at 2000 in gear with the clutch pulled in, if i slip it into neutral and release the clutch, the rpms gradually increase with me doing nothing but watch the needle rise. If i pull the front brake, the rpms decrease slightly. Maybe both a carb and electrical issue?!

Thanks

[skatefreak]

Morning Zibblezen,
If the clutch is not moving fully out then it will drag the engine RPM down when the bike is in gear and the clutch lever is pulled all the way back.
When propperly ajusted the engine rpm shouldnt change with the clutch lever pulled weather it is in gear or not.

I cannot imagine why the rpm would decrease when the brake lever is pulled, the engine's spark circuit is seperate from the bikes electrics, I've had a fault where all the bikes electrics die (all lights, dials and horn stop working) but the ignition still sparks.

Is your power valve deffinatly working?
If this has stopped working with the valve closed it will effect the lower and higher rpm.
The engine is tuned to run best when the power valve is open at low rpm, closed through the midrange and open through the top end (diagram in NSRTips.doc). If it is not working and always closed your bottom end + top end will struggle and if its open you're idle and top end will be fine but struggle in the mid range.
Do you hear the Power Valve servo move when you turn on the ignition after having ridden the bike?

For more detailed information on this and other things I would highly reccomend you have a look at Alains 'NSRTips.doc' as this will explain a lot of common issues and give you a better understanding of the bike and what can go wrong.
Found here https://www.geneva-racing.ch/~alains/NSRtips.doc

Best regards

-Jvr

[Hyder92]

Hey buddy


Hi i m from malaysia.somebody tell y my honda nsr 150 rr front light always blown?i already change new battery,new rectifier and new light holder? A friend of mine it say from coil magneto? Do honda nsr 150 rr have relay for the light?plz i need help reply me asap.. hyder_kp92@hotmail.my

[skatefreak]

https://i461.photobucket.com/albums/qq334/stevedowd/holy20thread20resurrection.jpg

On topic, get a multi meter and connect it to each terminal on the battery.
increase the engine rpm (speed) and see how high the voltage gets.
It should not get much above 14.2V.

If it does not get above 14.2V you can exclude the alternator/regulator.

If you don't have a multi meter, start the bike at night when its dark. face it towards a wall and vary the rpm.
If the lights are brighter when rpm increases/decreases then there is likely an issue with the charging circuit.

Check the bulb holder for signs of corrosion or arcing from a short.
Trace the wires back into the main wiring harness looking for signs of scorching or arcing

What bulbs are you using?
What fuse do you have?

[Hyder92]

Last time i check if i don't mistake 15vdc..the bulb holder already change the new one..last night after change the new bulb i ride for 30 minute the it blown..i m using 12v bulb..do mean the fuse at battery?i m using 10 amp..sorry my english not very well..the sigh before the bulb blown the light become brighter then blink2 then bright then blown..

[skatefreak]

if you start the bike, increase the engine speed with the clutch level pulled in (bike does not move), does the brightness of the bulb change (get brighter?)
Or is it constant?

Does the 'blink' happen before it goes out consistently?

[Hyder92]

Ya it constant when i ramp n pull the level clutch..the sign when it want to blown when i maintance the speed 80/90 km/h
The light constant then the light become more brighter after a second blink a few time then blown..

[alains]

about docs , if anyone needs some , send me a PM (with email adress) and i will give him the doc
unfortunatly our swiss forum is closing out
about the problem with the unstable idle , the first thing to look is the throttle cable especially at it's entry in the carb (sharp bend,no play etc...) and also the choke cable (and the piston) for the same reasons
____________________
the worst day fishing is better than the best day working