NSR 125 started playing up

[veroom]

Just bought it a few days ago, rode it 100 miles back, flawless after letting it warm up nicely. Been ok for a couple days but then last night the problem started but I have no real idea what could be wrong.

Just now I went out to start it with choke and it fired up first click. However the revs go up as expected then in seconds they go up some more and more until I turn it off at 5k revs.

Yesterday I was riding it and all seemed fine then the engine started dying in 3rd at about 5-6k going up a slight hill.

It then sometimes wants to fire, other times doesn't. Mostly will fire with the choke out especially if cold again but intermittently will fire up while warm.

I have not checked anything out as I am not so sure where to start.

The previous owner says it was dropped and oil got on the engine so while warming up you can see smoke coming from there which stops after a while. Although I am not so sure he is telling me the truth because this happens every time it is warming up and stops when warm.

Any help would be appreciated. Thanks

Stan

Budget wise I am a bit broke at the moment so can't buy any parts etc.

[Suntan Sid]

Check carb inlet rubber for cracks and leaks!
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"Everybody needs money, that's why they call it money!"

[stirlinggaz]

hi,
as above, sounds like you have an air leak. (or rather, an ingress)
lift fuel tank (hex bolt on right side + 2 more bolts) prop it up with the metal stand thing & have a look around air box.

to look around carb manifold (to see if rubber is cracked split) means removing air-box (only a couple of bolts 8 or 10mm iirc)

I only know this is cos i just removed the carb from my nsr to up-jet it.
let us know what you find,

only other thing i can think of, is a cable caught or incorrectly routed, but turning the handle bars from side to side would usually prove this.

cheers,
GAZ

[alains]

check the choke piston , the spring and the cable (no sharp bend)
the choke piston has a rubber bump Under .this bump close a hole and the fuel addition . if the piston doesnt slide freely the mixture stay richer and when the engine comes hot the engine stuff
normaly with a clean carb :
- set pilot screw at 2 1/2 turns out
- start choke on without acceleration revs go up between 2.5 and 4 K
- after 30s the engine begin to stuff , put slight acceleration while taking choke off and stay accelerated 20 to 30s then release handle
- idle should be stabilized at 1400 rpm and if necessary adjust pilot screw by 1/8 turn out or in (where idle is most stable)
- if ok now set 100 rpm more as when the engine is hot it's more adaptated
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the worst day fishing is better than the best day working

[veroom]

Thanks for the replies guys, truly appreciated. I will check what I can in daylight tomorrow and report back.

[WD Forte]

The previous owner says it was dropped and oil got on the engine so while warming up you can see smoke coming from there which stops after a while. Although I am not so sure he is telling me the truth because this happens every time it is warming up and stops when warm.

If it got oil on the engine after a mishap it could smoke as it burnt off
but this should stop after all the oil has gone/burnt/been wiped off.
If it smokes the same every time, that sounds more like it has an oil leak.
Somewhere like a rocker cover perhaps?

(oops! not rocker cover, just seen its a stinkystroke )
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bikers smell of wee

[Fidge]

It sounds fine to me, just start with the choke on until it warms up then take the choke off once it is warm. also depends how steep the hill was when it was dieing and if the engine was warm enough.

[skatefreak]

I suppose it would be worth mentioning that as its a 2 stroke engine that it SHOULD smoke when warming up, quiet a bit more than a 4 stroke.
Once warm there should still be a little more smoke but not much more.
Google how to check the oil pump to make sure its set correctly if its smoking excessively (it should smoke about this much warm, or anything up to this much when cold :p).

To check for an air leak, take the air filter housing out.
Check the air filter housing -> carb inlet ducting on the filter hosing side (tricky if you're taking it off but this is an absolute GIT to get seated correctly! There is a good chance if its been taken off its not put on correctly).
Check the connections between the carb and engine.
If all seems okay, put a rag under the carb/over the engine.
Start the bike and leave it idling for a few minutes until its warmed up and can come off the choke.
Once its idling away, spray a little WD40 over the air inlet ducting before and after the carb. If the engine speeds up then its safe to say there is an air leak and you can spray around, leave it for a second and see if the RPM changes (it may take a few seconds for the WD40 to make its way into and get sucked into the engine to affect the RPM).

Whilst you are there, you may as well get the air filter out and give it a clean

Best regards

-Jvr

[veroom]

Hi again guys.... I went out just now with the intentions of seeing if it would start, then if anything has changed.

Started first click with choke and went up to 2k ish... then seconds later rose to 5k, then slowly started to rise to 6.5k

I then thought for some stupid reason, to give the bike a gentle shake by the bars... I don't know maybe a lose wire could be the cause.. I've done elects years ago so its a habit I have.... anyhow, the revs instantly dropped a good few k, down to 2k and then slowly went back up.

repeated this 4-5 times and it did the same thing every time.

I thought best to come and let you guys know this before I do anything else. Luckily, I don't need to use the bike at the moment but will need to soon enough.

Thanks for the responses so far guys, fully appreciated. I shall take on board everything said !
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GSXR 600 - Got bike, must pass test, wish me luck.

[stirlinggaz]

[alains]

OK , 2 possibilities :
- sharp bends on the acceleration cable (or clogged) , even a broken ply near the handle
- no play at the cable entry or slide stiff
____________________
the worst day fishing is better than the best day working

[veroom]

Hi again guys... knowing little and nothing I spent a an hour outside removed the front fairing and took some snaps so you could see what I see.

Glad I did because of the smoking issue. I found the exhaust has some bandage on that I am sure is temporary which is leaking smoke quite badly.

I thought best to post these pics on my website rather than worry about posting limits here as I haven't had time to familiarise myself on this forum yet.

Anyhow, the pics are on my website : https://www.banton.org/news/?p=1807

I have left it with the fairing off for now.. without the airbox on, it simply doesn't want to start at all, I guess that's normal. However, no real idea what I am doing at the moment.
____________________
GSXR 600 - Got bike, must pass test, wish me luck.

[alains]

buy a good pipe : jollymoto,gianelli,etc....
____________________
the worst day fishing is better than the best day working

[stirlinggaz]

hi,
just looked at your pic of exhaust looks to be in a bit of a state, huh?
i presume its the original exhaust & will be getting on a bit now. they are prone to rusting & should be treated with VHT paint annually.
i've just done mine & tbh its actually quite thick steel so yours has likely been neglected for some time.

the original exhaust weighs a ton & may have restrictor in it but they can be picked up on evil-bay for around 40-50 complete. (its all one piece unlike others which have a removable silencer/muffler)

looks like a previous owner has done sort of "repair" to it, using heat wrap, jubilee clips & MAYBE a bit of ally underneath. (coke cans can be used if cut ends off & then open up into a square sheet)
common bodge/temp repair.

either get it welded or get a replacement.

only other alternative is a "sports" exhaust, like the gianelli or jolly-moto, both of which are quite expensive (around 250-350)

one way to check if your exhaust has any holes/leaks : with the bike running, put your hand over end of silencer/muffler & rev it slightly.
if you see any smoke coming out of anywhere, theres your hole.
if the bike doesnt smoke & it stalls, then your exhaust is not leaking.

good luck,

cheers,
GAZ

[veroom]

Is it possible this is what my initial problem is ? Ie this quick bandage wrap has been done to sell the bike and now it's failing, it is causing the issues I have posted about previously in this thread ?

Thanks for the replies. I have looked up some exhausts and yea, they are around the £270 mark and I'm not even sure if I can buy a factory or oem version... really haven't got that money to spend atm.

I've just gone out there with a flashlight and taken off the jubilee clip and some of the bandage. You were right, there was a 6x3 piece of thin metal cramped around the exhaust very badly. Tomorrow I will remove the exhaust and see if I can either get it repaired or look about a replacement. The exhaust has already been welded by the look of things and the plate was simply put over the top and bandaged.

It seems I was very very lucky to have made the 100 mile journey home on it for it to be doing this just days later.

Not impressed at all.
____________________
GSXR 600 - Got bike, must pass test, wish me luck.

[stirlinggaz]

Hi,
er.......hold on! how do you know that the "repair" done to the old exhaust wasnt up to scratch?

the method used to repair it is quite common & by most accounts, fairly successful.
dunno about the "bandage" though, especially on a 2 stroke
why not actually find out if it WAS causing your problems.
remove all the old exhaust wrap & give the area affected a brush with a wire brush & lets see the damage?

these exhausts are quite thick (hence the weight) & CAN be repaired either by welding (a bit more permanent) or the method used by previous owner.(imo, more of a temp repair while you save up for a replacement )

if it were me, & seeing as a new exhaust is beyond your means, how about trying ANOTHER temp repair?

wont cost you more than a tenner or so.

as said, rip all that bandage off & give it a good rub with a wire brush.
get a piece of steel to cover the hole.
or as a last resort, have some soup.
then with the empty can, open up the other end with can opener giving you an open cylinder. then cut it open with a hack saw or tin snips & flatten it out.

smear it with exhaust paste & clamp it on with some repair bandage (dont go mad with it like the previous owner) & 2 hose clips & give it a a bit of heat with a blow torch to "cure" it.

re-fit & TEST for leaks.

better than guessing, imho. or better still take it to someone who can weld

cheers,
GAZ

[-]

If it's been down the road, the right hand clip on could be bent. I couldn't work out why the throttle was sticking on one of my NSR's and tried everything else before realising the clip on had a slight bend and was causing the throttle to stick.

Does it return freely when you wind it on and let go?
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Jaguar S Type 3.0 V6 Sport R, VW Transporter T5 GP LWB Shuttle 140ps DSG.

[veroom]

Thanks again for replies... but I still want to know if the exhaust could be causing the initial outlined problems. I am gonna take it off tomorrow and have a good look at it see if I can get it sealed up.
____________________
GSXR 600 - Got bike, must pass test, wish me luck.

[stirlinggaz]

Hi,
Having a hole in a 2 strokes exhaust, or rather in the expansion chamber or stinger can cause all sorts of strange issues.
its probably one of the most important components on a "sports" 2t, imo. (hence the high cost to replace)
get it all sealed up & re-fit it, not forgetting the copper gasket.
then reset carb to stock settings.
then post results.
cheers,
GAZ

[veroom]

Hi Gaz. I took the exhaust off and totally stripped any sh*te off it. My local and trusted old school mechanic says the exhaust isn't causing the revs to go sky high on their own and such. I don't believe there are no tight caught cables but he did also say from the outset that my bike is sucking too much air somehow. He's not a bike mechanic and is way too busy to give it a good looking over. I wonder if those pics are any good and show anythign wrong or where I should be looking to spot anything.

Really am hoping to get this sorted as you can imagine. I have tried twice to contact the lad I bought it from but he hasn't answered my texts or calls. Might help solve the problem if he knows something I yet don't.

Bit fed up days after purchase but thankful you guys are trying to help.
____________________
GSXR 600 - Got bike, must pass test, wish me luck.

[stirlinggaz]

hi,
so all we know is, its taking in too much air?
does your mechanic friend know how important the expansion chamber/stinger/exhaust is on a 2 stroke?

anyway, work methodicially from back to front. (from silencer to airbox)

seal all holes on the exhaust, properly, then work forwards, check the point where it bolts onto engine, replace copper gasket & tighten up the 2 dome nuts.
THEN check the carb manifold, replace the paper gasket & tighten up the 4 bolts, but before you do, have a good look at the rubber manifold/mount. is it cracked or split?
if it is, either get a replacement (shouldnt be more than around 30 quid) or repair it.
i once repaired a rubber manifold quite successfully, with sealant (think it was granville, the black stuff & it only costs a couple of pounds)
i smeared a good thick layer of the stuff all over the whole rubber bit.
i only done this because i couldnt get a replacement & it was supposed to be temporary, but was still there when i sold the bike a few months later.

then check the 2 jubilee clips between carb & air-box are seated correctly & tightened up.. & make sure air box is sealed shut & foam element is clean & in place.

doing all of the above should make it airtight.

THEN, check the carb. when you open up the throttle fully & let go, you should hear the carb slide clunk down, if you dont : check throttle cable for snags/damage.
& like Alains said, check the choke. its worth taking it out & cleaning. its only 1 bolt that holds it onto carb.
clean the wee brass choke piston & make sure the wee spring is not corroded. a quick blast with 3-in-1 oil (the aerosol stuff with the wee red straw, from poundland ) & quick brush with a toothbrush should suffice.

after that......

cheers,
GAZ

ps : i just had a quick look at your pics & tbh i couldnt see much, except that everything needs a good clean/degreasing.

[veroom]

Gaz, you've gone above and beyond with that response mate... even if we are left scratching our chins, massive thanks for that...

I have bought some holts exhaust paste gum stuff in the white/red shoe polish type can. Smeared feck loads of that everywhere I felt it needed to go and then put a full wrap of holts bandage around it, added extra wire to help clamp the bandage down and then jubilee clips around both ends to secure the wire and bandage ends. Yea it looks messy but I am adamant its now 10x better than the job the last guy did.

At the moment of what you said, the only thing I didn't see was any jubilee clips between the airbox and the black rubber tube that's about 2.5" long coming of the carb rear. From looking at the airbox, there's no place for clips, it just sits there bolted on and the rubber tube is forced through the hole in the airbox bottom.

Now after a google, I assume you mean the clip that holds that rubber onto the carb right ? This is the same box as mine

https://www.2rad-sausenthaler.de/epages/61548808.sf/en_GB/?ObjectPath=/Shops/61548808/Products/NS.VE.05

Gonna see what I can sort out tomorrow and get back to you.

Meant to add, the mechanic is a car jock to be honest. From that I guess he may not know about the expansion
____________________
GSXR 600 - Got bike, must pass test, wish me luck.

[Fidge]

There should be jubilee clips to attach the rubber bit of the air box tube to the carb and then the same sort of clip for the other side of the carb. The bit you tighten is a bolt on the jubilee clip (at least on the JC20 anyway).

I'm still not quite sure what the problem is? Does the bike go? have you got fuel in there with the tap turned on reserve?

[veroom]

It will start, using choke if I haven't killed the battery from cold quite easily but as it warms up (it seems) it then either revs higher and higher on it's own (beyond 7k) or dies with no choke and sometimes with choke too. Once it dies, it's a bugger to start but seems to go again with a few attempts but then quickly does it all again.

These guys seem to be suggesting an air leak and my local car mechanic said that while I was describing the issue too.

Hoping to get a new spark plug and have to get a copper gasket for the exhaust outlet tomorrow as I found the exhaust was leaking quite badly especially on start up but that died down when it was warm.

I have I think given the exhaust a good clean up and fix up so once that's back on I can try other things.

I could be wrong but on my bike jc22 the rubber tube off the carb simply pushes into the airbox. The end is funneled out so I guess that helps seal it. I have looked at the air filter and it looks clean but I'm not sure if it really is.

Will have a tinker tomorrow if I can.. not gonna put the exhaust on without a replacement gasket... funnily enough I didn't see one come off but I was more interested in repairing the exhaust than checking the outlet.... I will clean it up anyway.
____________________
GSXR 600 - Got bike, must pass test, wish me luck.

[Suntan Sid]

Is part No.5, the seal, present on your bike and is it in good nick?
If it isn't there or is old and squashed it will not be making an airtight seal and the air box will be leaking like a seive!

https://images.cmsnl.com/img/partslists/honda-nsr125r-1994-england-air-cleaner_bigecbsweaf__1800_fdba.gif

The diagram shows no jubilee clip for the airbox end of the inlet manifold, make sure it is making a proper seal, if the inlet manifold rubber is old and brittle it may not make a good seal. You could lube the joint up with some vaseline, it may make a better seal, before you buy a new one!
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"Everybody needs money, that's why they call it money!"