1989 Honda NS 125 R-K

[fused420]

Hi, i have just brought one of these bikes and need a bit of help, i can't find a service manual to download anywhere. If anyone has a link that would be great!
If not can someone fill me in on some of the basics please? Like how do i check the gear box oil? What pressure should the tires be? etc..

Also, when i first turn the ignition on the oil light comes on for a few seconds, is this for the 2t or engine oil?
Oh and does this bike have power valves or power bands? (not insured yet)

Thanks in advance
fused420

[fused420]

Here is a pic incase anyone is interested:

[Frost]

https://www.bikechatforums.com/viewtopic.php?t=140295

Looks like it currently has the standard black powerband, many people swear by the grey one but i've heard of them snapping.

[fused420]

Thanks for the reply DaFrostyOne, i have already looked there though, but i have just now posted a request.

I'm glad to hear it has power bands and not valves, no idea what you are talking about with the black/grey ones though! lol How can you tell from the pic?

[stu66-3]

you can get 1 from haynes. there number is +44 (0) 1963 442030 ask for the book number 3056 will take them straight to the correct book. cost £16.99. hope this helps
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feel the fear, and do it anyway!!

[stu66-3]

oh yea, the light is for your 2 stroke
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feel the fear, and do it anyway!!

[crackpotterpi...]

download the nsr manual from the link in this forum............its in pdf format.I think that model may actually have the brown power band?
The light your talking about is the low oil light for your 2 stroke oil( resevoir is under the seat)
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1990 jc20 nsr125-sold,2003 cg 125-sold currently no bike.........might get another 2 stroke me thinks much more fun

[crackpotterpi...]

here you go try this link for your manual https://www.megaupload.com/?d=8WIPL117 it looks like and earlier one from the side what year is it?
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1990 jc20 nsr125-sold,2003 cg 125-sold currently no bike.........might get another 2 stroke me thinks much more fun

[Frost]

[Kickstart]

[fused420]

Excuse me if i'm wrong, but i get the distinct feeling you guys are pulling my plonker regarding power bands?? It's been a long time since i last had a bike, but i remember being told as a youngster that off road bikes (eg.kx125) had "power bands", where as the slower road versions (eg.kmx125) had "power valves". Does this make any sense? Or was i fed a load of bs?

[Kickstart]

Hi

Err, yes they are pulling your leg. Long standing joke.

A power band is an area of the rev range where the power comes in. Quite often with 2 stroke the power will come in all of a sudden at (say) 7000rpm. This is basically due to the way that 2 stroke exhausts work (along with other things). The more you tune a 2 stroke the more the power tends to come in with a bang and be there for a narrower rev range, plus the less power you tend to get outside that range. Eventually you land up with something virtually unrideable, with (to quote Barry Sheene) a power band the width of a chocolate mouses cock.

A power valve is actually there to try and recover some of the power outside of the power band, basically allowing other tuning to make more peak power without the bike becoming unrideable.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Frost]

So in short it has 'power bands' and probably power valves, most performance 2 strokes do. Removal of the valve control system can result in a vastly diminished power band, but it is certainly not the case that some bikes have power bands and some valves.

[crackpotterpi...]

yea sorry for pulling your leg about power bands.......if they are set up properly your should get anice smooth power delivery then as you hit the "power band" you should get a greatly enhanced power delivery.if not and you have flat spots,etc then it may be a fault with your servo or cables that control the flap on the exhaust port.
Think I am gonna get another nsr 125 soon
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1990 jc20 nsr125-sold,2003 cg 125-sold currently no bike.........might get another 2 stroke me thinks much more fun

[Kickstart]

[crackpotterpi...]

sorry keith,yea your right mine was a 1990 nsr
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1990 jc20 nsr125-sold,2003 cg 125-sold currently no bike.........might get another 2 stroke me thinks much more fun

[fused420]

hey thanks for explaining things, i have bigger problems now though

I got my insurance sorted today and took it out for a half hour rip down some county roads, and was having a GREAT time until.. on the way home i had to stop at some traffic lights, where i noticed the engine was sounding a bit rough, but as i finished the ride home it sounded fine. Then 20 min ago i jump on the bike to go down the shop, and as soon a i started it it sounded terrible, there is a constant knocking sound coming from the engine while idling, a little bit of throttle and it goes away.

Needless to say, this has left me totally gutted

I know this is bad, but can anyone tell me how bad? I'm guessing something it's something to do with the crankshaft, but what do i know..

Some help or advice would be greatly appreciated.
Thanks

[Kickstart]

Hi

Big end would be my guess. Piston could also make a loud noise like that but I doubt the bike would start easily at all in that case.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[fused420]

if it is the big end, what parts would i need?
Thanks

[Kickstart]

[Marci]

OR it could just be Honda's usual rattly clutch... does the noise vanish when you pull the clutch in?
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FAB-Racing MiniMotoSidecars - Back with a vengeance - F1 Class 2011...
CBR170 engine, custom chassis - www.minimotoscene.co.uk

[Frost]

Yeah some extra info would be useful before we go telling you to strip things and take them to a garage. Clutch rattle or something being loose would be my first bet, but worst case scenario, Kickstart my well be right.

If the bottom end does need doing i HIGHLY recommend stripping the engine down yourself. It's really not difficult just time consuming, and a garage will charge £40+ an hour and take their time about doing it.

[smegballs]

I rode a mates NS125R to MOT and back a few weeks ago. Was a pretty nice bike for a 125....


It had a holed base gasket though, as in when you stopped it would piss fuel out of the base as you kicked it over died about 3 miles from my mates workshop (were it was living) and so I got towed back (back lanes) by taking my overalls off and tying the legs to a mates car and hanging onto the arms.... Hilarity ensued


We took the top end off and I made a new base gasket that afternoon, all was fine and dandy after.

The owner, who isn't a "bike enthusiast" was warned 100's of times by me to, please please warm it up before ragging the tits off it. Whether it will survive long is anyones guess now...

[fused420]

Thanks for the replies, big end bearings are fine(no excessive free play), and im pretty sure its not clutch rattle. I found a bit of the kick start return spring that had snapped off in the gear box, and i thought maybe that was being pinged about, but nope.

I cleaned out the carb/air filter, fitted a new kick start return spring/gasket/oil, cleaned carbon deposits from the piston and cylinder head and refitted them with a new small end bearings/head gasket, and put the rad back with fresh coolant.

So i started it up, and with a bit of adjustment to the idle screw it was ticking over nicely at 1400rpm, and revving fine too. But then after about 5 min idling the noise returned after i gave it some throttle (only to about 3000 rpm) and the rev counter stayed up at 2000 rpm. I tinkered with the idle screw a bit but it didn't really help, although when i put the choke on the revs drop and then go back up when i turn it off?

I'm going to try and clean the carb again as i think i could have been a bit more thorough. And i noticed that after running for just 5-10 min there is black oil starting to build up where the engine connects to the exhaust, could this be a sign that the piston rings are worn out, or does the exhaust gasket just need replacing? When i put the top end back on i put a bit of 2t on the rings and grooves, could that be why it was running fine at first? Thinking this, i put a few drops into the spark plug hole..but the noise was still there and it smoked a lot! lol

The thing that's getting me is that every now and again the revs drop and the noise stops and it sounds fine, but this only seems to last for a couple of seconds. It's because of this occasional good running that im hoping it is only a small problem. Anyone got any ideas?

Thanks again for your time.
fused420

[fused420]

Anyone?