NSR 125 RX running rough

[jtclark93]

New here but looking for answers as i'm not too technical with the inner workings of bikes as of yet.

Bought the bike as a bit of a project (Probably not my wisest choice as my know how is not all there)
Anyways on to the issue, the engine sounds horrendous on tick over, got a sort of rough rumble/ kind of low knocking noise.

Changed spark plug, oil, cleaned air filter and checked the fuel lines, but before i start taking it all to pieces i was wondering if anyone else has any ideas.
Its also got next to no pull when setting off from a stand still its a bit 'Chuggy' if thats even a thing.

[Just_James]

Could be numerous things from your description but my first port of call would be a compression test.
____________________
Current Bikes / Projects: 1999 Rieju RS1 50
Previous bikes - 1986 DT125R (field bike), 1989 KX250, 1980 KX420 (with 500cc big bore), 1992 YZ250, 1988 KX500, 1989 XR250R, 1988 VFR400R NC24, 1999 Cagiva Mito 125, 2008 Rieju RS2 50 , 1993 Honda NSR 125

[pompousporcup...]

[quote="jtclark93"
Anyways on to the issue, the engine sounds horrendous on tick over, got a sort of rough rumble/ kind of low knocking noise..[/quote]

Nothing wrong with a bit of a project Can you get a video of this noise..

[misscrabstick]

Rumbly noises could be crank main bearings, can you get the covers off the sides and try wobbling the flywheel/primary gear?

[jtclark93]

[stirlinggaz]

Hi,
To do a compression test, you need a special tool called, funnily enough, a compression tester
if your going to have a 2 stroke for any length of time, I suggest you buy one. I use a Gunson kit, very reliable & lasts for years.
A simple single cylinder 2 stroke 125 is an ideal bike to learn the basics on imo.
you will need to try & identify where the noise is coming from.
use a screwdriver as a listening device & find out if its coming from the top end (the cylinder, piston etc) which isnt too much of a problem as spares are quite reasonable & you could do any work yourself or
the bottom end (gears, clutch etc) which is a bit more serious & might be a bit difficult for you, but you need to start somewhere, right?
So, in this order : test compression & if its below 100psi its time to think about taking cylinder head off & seeing what state the piston & cylinder is in.
if its above 100psi, fit a new spark plug (br9), make sure battery is fully charged & put some fresh fuel in.
then try to find out where the noise is coming from.

cheers,
GAZ

[jtclark93]

Hey,
Just used the screwdriver trick and it becomes a more defined rumble/slightly grindy noise towards the top of the engine, towards the plug, a new spark plug went in on tuesday, and battery is maybe a month old, fuel is fresh from wednesday.
The bottom just sounds a tiny bit grindy But i assume thats the gears or something?

As for the compression, i suppose ill have to wait till i get hold of one (Guessing this will also hold vital information)

[stirlinggaz]

Hi,
ny moneys on damaged piston &/or rings.
you will find out when you remove the cylinder head.

cheers,
GAZ

[jtclark93]

I'm going to order a new set anyway as I can't hurt to change them either way, what size would I need to get?
Also, how difficult are they to change?
Thanks for the help by the way

[stirlinggaz]

Hi,
Theres 4 or 5 standard pistons available.
there all coded by letter. ie A, B, C etc

To find out what piston you need, remove the cylinder & look underneath, the code is there
.
cheers,
GAZ

[jtclark93]

I have tried and tried, but I can't get that far into the cylinder, what are these fitted with as standard?
Managed to get as far as removing cylinder head.

[stirlinggaz]

Hi,
Like I said, they come with 1 of 4 pistons, A, B, C or D.
you will find out which one when you remove the cylinder & look for whatever letter is etched onto the underside.
cheers,
GAZ