:o( Second opinions needed on my apparently F*CKED NS125R

[Fallen Angel]

Right guys - I needs some help and some second opinions please.

As you all know, we de-restricted my NS125R some time ago and then the engine blew up, we think due to not having it re-jetted.

Well, the bike's been away and had a new barrell, piston, gaskets, had the carbs re-jetted the lot, but when the guy brought it back last night, it wasn't idling and just kept cutting out, so he took it away to have another tinker with it. (The total cost for him to do all this was £240).

Now, today, he's just off the phone and has told me, that basically, my bike is fucked as it cannot be de-restricted as it is an NS125R-K model and apprently these cannot be de-restricted as when you take the baffler out of the exhaust, there is nothing left in the exhaust to rebound the air (that might not have been his exact words, I'm a bit bamboozled). He's now had a second opinion and has been informed this isn't the case!

Have any of you ever heard of this? I mean, I know a few of you have de-restricted your NS125R, does anyone know what different it makes mine being an NS125R-K???

He says, the bike will run just now, but is likely to seize up again in a couple of weeks time and that the only way around that is to buy a whole new bottom end and new exhaust.

He also mentioned something about the bearings being fucked and that is what is causing the ratting noise (there's a slight rattle coming from the bike).

Basically, I'm fucking gutted, 'cause it looks like the bike is fucked completely.

Fran


EDIT - I've editted this message slightly from my first post, 'cause since the guy's dropped the bike off, he's updated us on some stuff and I truly believe he's done everything he could. He's now got a bottom-end engine for us for £50! I'm on two minds now as what to do, do I buy this bottom end off him and get my mates to help us swap it over, or do I sell the bike as is? It is working, just keeps cutting out instead of idling! Aaaaargghhh!!!!!
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[Scotsman37]

I think you'll find far batter help via this link as it only deals with NSR125 bikes and you can find technical specs too and a step by step guide to derestriction, etc.

https://www.nsr125.com/

[Fallen Angel]

That's the link we used to de-restrict my bike.

My bike is an NS not an NSR, and we're now being told - AFTER WE'VE DE-RESTRICTED IT that it cannot be done!!!
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[pipnet11]

Is putting a NSR exhaust on too obvious to be the solution?? Also I would be VERY surprised if there was any reason for changing the botom end.
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[sickpup]

Haven't done an NS/NSR in 10 years but why did he do all this work without checking the crank after it blew up?

The crank bearings I think are around £40-£50 so strip the engine and replace them, it's not hard but you might need an engineer to remove the old and fit the new.

Sounds like he's talking shit to me.

[Fallen Angel]

He says he's got this information from a guy who's been racing two strokes for 20 years!

I know absolutely fuck all about motorbike mechanics, but I do know I'm gutted and don't really know what we should do now to be honest!
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[sickpup]

He's kinda right, it will die but only as it hasn't been repaired. If he can't get it to idle he's done something wrong or missed something.
If it rumbles a bearing is gone. He's covering his own arse but if he now thinks it needs a new bottom end AFTER he's supposedly fixed it then he hasn't fixed it has he.

[cagiva gezzer]

Any stroker with a restrictive/baffled/plugged exhaust can be derestricted, but they m ght not run smoothly afterwards if the carb doesn't have enough ajustment on it to compensate for the exhaust flowing more freely.

Did the exhaust look like this?

https://www.nsr125.com/exhaust2.jpg
https://www.nsr125.com/zorstholes.jpg

Did he say which bearings were knackered? Buggered main bearings will cause the crank seal to leak and you will seize it due to air leaking in and it running lean.

If he said the "big end bearing" then you'll have to replace that and thast a hefty price, but derestriction or not it would of needed to be done.

Does it run the same carb as the NRS bikes? PHBH28 at a guess..

I think he is just covering his back as any old stroker can be a pain to set up right.

How did it cut out? Like it was running out of petrol? Choke on?
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"because one stroke isnt enough and four strokes waste two"

[Fallen Angel]

Right the guy's come back with the bike and basically, he says the exhaust is fine, but it needs new bottom end bearings!

Eddie said the guy was really nice and apologised, and he was saying he's made no money on this job at all - I could believe that cause it only cost me £240 for all that work and I imagine he's put loads of hours into it.

He was also saying to Eddie that he's spoken to other people about the de-restriction who have told him something completely different, saying the way we've restricted it is fine!

Sooo, it now looks like it needs new bottom end bearings and that will be it - fine and dandy!!!

More fucking money!!!!

This bike is costing more money to fix than it did to bloody buy!!!

Think we'll just get it fixed up and then sell it!!!!!
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www.cliqueyclanmcc.co.uk
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[Fallen Angel]

[cagiva gezzer]

Been pricing up the bottom end on mine and its

~£40 for a set of main bearings
~£30 gaskets
~£10 oils
~£20 crank seals

+
~£100 crank rebuild. (pattern, as a OE con rod kit is £170+.. )

But, its a bitch to pull the engine out and split it all.

Two stokes - The internal parts of the engine should be seen a disposable parts....
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"because one stroke isnt enough and four strokes waste two"

[Frost]

I hope its running on premix after the rebuild.

If it still cuts out add more petrol too the tank. This will lean out the oil/petrol ratio and improve running. The oil and petrol can also seperate if left too long, so shake the tank a bit!

Check it over, something might have been missed. So long as it has fuel, oil, air, compression and a spark, it should run without cutting out. Check the positioning of the throttle slides and make sure the carb's are seated correctly.


You could allways just get it running standard, sell it and buy something else!

[alains]

your bike is a NSR125R from year 1989 and nothing in the engine has been changed . the only thing is that i have not fully understood your problem . you can pass me pm and explain further .
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[Fallen Angel]

Nothing in the engine has been changed..

Story goes like this...

We de-restricted it by taking out the exhaust intake.

It worked fine for a few weeks then seized, the reason for this I believe is that we didn't get it re-jetted.

They guy did everything we asked him to, replaced the barrell, piston, gaskets and re-jetted it.

It seemed to work fine, but it wasn't idling, just cutting out when you stopped and there was a slight rattle.

The guy says the rattle is the end bearing and if this is fixed, then all's well basically.

I just don't understand how that would fix the idling issue!!!

Fuck - I wish I was more mechanically minded!!!
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[Fortuna]

Mine was an NS125-RK model (Square headlight).
I done exactly what you did and mine was fine. Be warned that they are a bastard to get running right once you mess with the carb i.e. jetting. I never changed the jets in mine but it doesn't hurt either as long as they are the correct type.
Basically all you should of had to do was drill the exhaust and ride away maybe altering the idle a little.
Maybe that's all you need to do now, just up the idle a little. IIRC they idle at about 1200-1400 rpm which is quite high anyway.
I wish I didn't live so far away as I could help. Me and my dad stripped mine down to nuts and bolts when it was being rebuilt.

[Fortuna]

Missed a bit.
The bearing being shot may stop it idling as the piston will be loose.
One of the more mechanically minded may be able to answer this better than me.

[alains]

turn the tap on and let it for a small time . turn off the tap and take off your carb without turning it upside down (by the way , have a look if it's no plate beetween the pipe and the reed valves) without turning it upside down , take off the float chamber without spreading any petrol inside , then mesure the hight (something like 20 to 24 mm) if less than that move down the small leg on the float , but not too much otherwise the valve will not close and petrol will overflow . then look your carb adjustments . you should have : main 145 , idle 45 , power 65 or 70 . prior of that you can order jets from https://www.dellorto.co.uk (£2.95 ex VAT and p&p) . they will ship them to you within 4 days . afterwards clean your air box . adjustments on the pilot screw is thight and 2 1/2 turns unscrewed . idle is set at 1500 rpm after 5 mn running (when the temperature indicator goes in the white)
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the worst day fishing is better than the best day working

[Keith]

[Fallen Angel]

Thanks Keith!

And I will run it in smoothly when it's all fixed. I'm meant to do 100 miles before taking it over 6,000rpm's - then change the engine oil!

Does that sound about right?
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[catgate]

If you have one/two main bearings that are worn then it is conceivable that their corresponding oilseals are also worn. They would let in air on the "induction/compression" stroke and hey presto a weak mixture that will cause the engine to die and only run at higher revs and/or with choke. Your mans second hand bottom end may also be in a similar position. When I was racing two stroke engines the main bearings and oils seal were changed every two races, regardless of whether they needed it or not. If you continue to run on a weak mixture you will run so hot that you will melt a piston crown. I shed one on Glencrutcher Road and learned my lesson.
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[Kickstart]

Hi

You have derestricted it correctly, as far as is realistically practical on a UK model. Yes it might well need the jetting changed.

To fully derestrict an NS125R you would need the complete engine from a full power bike to get the mechanical power valve. Not worth it and they work fairly well without it.

I agree with Cagiva Geezer that it sounds like the main or big end bearings are shot. These are not that expensive (~£30 for the bearings and seals), but are not that easy to fit. As above if the main bearings are worn they damage their seals and allow air in causing the bike to run lean. It would be entirely possible to fit a complete bottom end to replace the current one, and might well be a cheaper and easier option for £50 if you can do the work yourself, but you need to be certain that it is better than the one you already have.

£240 is a fair amount. From David Silver spares a barrel and piston are £99, and I would doubt that it has cost him £140 for a couple of gaskets (head gasket is the expensive one, and that is £10). Doing a top end rebuild is a gentle afternoons work, so probably 1~2 hours for a professional mechanic.

The NS uses a 26mm Dellorto PHBH carb, slightly smaller than that used on the NSR.

The engine oil on a 2 stroke only affects the clutch and gearbox, which from what you have said he has not changed. As such it seems dubious that he is telling you to change it after 100 miles. However I would expect to do rather more than 100 miles before taking it over 6000rpm, probably nearer 300~500.

All the best

Keith
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[alains]

sorry , i thought it was a NSR125RK . is it the ATAC engine with the mecanical Valves system ? if yes , you can easily fit a 28PHBH/FS like the later NSR have . but jet with 138,42,60 and BR9EIX plug
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the worst day fishing is better than the best day working

[Fortuna]

I'd agree with Kickstart on the running in. They have Nikasil barrels which are freaking hard so require them to be run in slightly longer plus you want to make sure.
Might seem a silly questin but was the top end roller bearing changed as well?

[Whitetrash]

so it wasnt re-jetted and supposedly ceased while running lean i guess???? baffles arent the be all and end all of 2 stroke exhausts, its a great deal to do with the expansion chamber and heat held within it, due to lack of mechanical power-valve i believe your best tunning bet is to find an after-market exhaust and look for a second- hand carb, something between 30-36mm have it Dyno'd get the jetting perfect or it will kill itself again for sure. Air/Fuel mix is cruxial on 2-strokes. just remember though its an old little unit, been running restricted a long time... it wont take much abuse and something bigger/newer could be less greif.
try a company called Stan Stevens, He is a 2-stroke God!!!!
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[Whitetrash]