NSR goes bang

bonceunounce · Banned Joined: 22 Aug 2003 Karma :

Oh dear, i'm asking for help here.

I have just came in, from a 15 mile walk from the other side of town with my NSR125RK.

What happened was, let a friend have a thrash around the retail park on it and then we went to go to back to my house. Got out on the open road and it was fine, came to this junction and turned right, dropped it down a couple of gears as was going pretty quick before the corner and i as i turned into the corner i opened the throttle again, and it made that chugging sound you get when you run out of fuel.

Okay i thought, put it on reserve after peering into the tank.

Pressed starter, it sounded totally different, like instead of a fast chugging of it ticking over then firing up all i get is this whispering sort of whirring sound, but the engine still turned over.

Got my mate to give us a long push and bumped it, nothing, it backfired twice.

Took out spark plug, dry as a bone, carb seems okay and all fuel lines appear okay.

On the push home, i took it down a big hill and knocked it into 1st gear, all i got was this massive BANG coming from the engine and a fast chug chug chug noise, and didn't start.

If its any other use, the bike is almost 15 years old, almost 30,000kms on the clock and is a import, earlier today i noticed it was having trouble at ticking over and would stall easy if you didnt give enough revs before releasing clutch when taking off.

Any ideas? Crying or Very sad

kev · I Hump Things Joined: 07 Oct 2002 Karma :

If your lucky its just a piston gone which isn't a real problem but if it turns out that it is a blown engine talk to zim or G as I think they both have engines for sale.
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bonceunounce · Banned Joined: 22 Aug 2003 Karma :

I was thinking piston and rings too.

But if rings have gone, doesnt that mean im going to have bits of piston ring in my crank casing?

It also makes a scraping sound if you push it in gear.

Im on the verge of selling it.

6 Weeks ago i had to have a new electrical system costing me £45

2 weeks ago i had my front tyre nailed and that cost me £67 all in all.

Now this.

I think i shall attempt to strip the top end down in the morning.

I didnt like the bang when i put it in gear going down the hill though, it wasnt a backfire it was the engine itself.

How much is a new piston and rings? or the full top end set if necessary.

Just want to see what other people have to say first.

Cheers Kev Smile

James · Spanner Monkey Joined: 25 Feb 2002 Karma :

If i could hear the bike myself id be able to tell you straight off but ill just have a go from your description of events.

If your bike has got a kick start, then turn over the engine and feel what the compression is like. If no kick start, try pushing the bike along in secong gear or something and again see how compression feels.
Another good way is taking the spark plug out, holding your thumb over hole and turning engine over.
If its your rings that have welded themselves to the piston or something along those lines then there will be very little if at all any compression. In that case you'll be looking at best, at new rings and possibly piston.

Even though your bike is old it will still have a Nikasil plated bore which is very material, and can survive piston ring failure. If this is scored or damaged though, you will have to replace the whole lot.

If the bike has got loads of compression though, i would first check to see the plug has a spark. If the plug has a spark, and you have compression but the bike still wont start, then it looks like a carb problem. These are usually straight forward to sort out.
Another problem with old bikes is the crankcase gaskets lose the ability to seal. This is unlikely from what you've described though.

If you do need to replace the top end, send me an e mail and ill reply with the names of a few importers of very cheap genuine Honda parts.

In the meantime, keep your chin up! When you've had as many strokers break down as i have, you learn to expect it Wink

James · Spanner Monkey Joined: 25 Feb 2002 Karma :

Sorry bud, i didnt read your last post before i posted my reply.

It sounds very much like piston and rings.

You can get a whole top end brand new for not much more than hundred quid if you know where to look.

I spent a fortune on bits till i found this site, but i always like to help so here:

https://www.davidsilverspares.co.uk/

Its alright for some Laughing

bonceunounce · Banned Joined: 22 Aug 2003 Karma :

Cheers buddy

I stuck my finger in the spark plug hole and pressed the starter, didnt blow my finger out but it still gave a good strong push and a farty noise now and again.

Its just when you push the starter with the plug in and cap on, it sounds very lazy, and theres is just like a faint puffing coming from the exhaust.

The fuel isnt going through so im guessing thats compression not sucking it in. That bang when i knocked it into 1st down a hill doing 10 mph scared the life out of me it sounded like someone let a shotgun off!!!

If its the piston and or rings, shouldnt it be seized up and not move? It pushes very easy in gear and can hear a sort of scrapy sqeaking sound.

James · Spanner Monkey Joined: 25 Feb 2002 Karma :

No they dont always seize up. Sometimes the rings become kind of welded into the piston so they dont spring out and therefore dont make contact with the barrel.

It does sound very much like the rings. Especially if the bike seems easier to push when in gear then it used to.

Its hard to say without meeting the bike in person Laughing

bonceunounce · Banned Joined: 22 Aug 2003 Karma :

Well looks like i better to get my spanners out oh and my money!

Just been on david silver spares, £99 for piston barrel and head kit, £22.00 for gasket kit and £22 for piston rings!!

Thats crazy! On my scooter it was only £52 for a full top end, gasket set was a fiver and rings were £6.50!!

Anywhere cheaper?

bonceunounce · Banned Joined: 22 Aug 2003 Karma :

Update,

Stripped the poor NSR down this morning, fuel is going through and everything.

So i attacked the top end.

After 20 mins, skinning 2 knuckles and nearly breaking a wrist i managed to get off 6 10mm nuts and get drenched ina litre of coolant Smile

(im used to air cooled bikes!)

So far i only have the cylinder head off, which shows 3 big scrapes in it Crying or Very sad

While i have it apart, i decided im going to rebuild the top end as i don't know if it has ever had one.

Ive been on David Silver Spares on this part of the catalogue:

https://www.davidsilverspares.com/cgi-bin/dss2-cgi/Catalogue.pl

I have totalled up the following and prices:

NS125F/RK : Cylinder barrel and piston - 99.00

NS125F/RK : Cylinder head gasket - 10.80

NS125F/RK : Piston ring set - 22.00

I guess im going to need a new cylinder head, but they dont seem to do one for my bike, ill give them a call.

Will someone confirm these are the correct parts and that im getting a good deal for my money.

Thanks

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

That is very cheap for the top end of the engine. Suspect you don't need to order the rings seperatly (suspect they come with the piston), but you might consider a new little end bearing while you have it apart. The head can probably be cleaned up.

All the best

Keith
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bonceunounce · Banned Joined: 22 Aug 2003 Karma :

Ill have to email them, cheers anyway.

I just need help taking the top end off, see my other post, Top End Removal Help i think i called it or something Neutral

James · Spanner Monkey Joined: 25 Feb 2002 Karma :

I bought one of those top ends and you do have to buy rings seperate.

Like i said though, you wont find cheaper
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bonceunounce · Banned Joined: 22 Aug 2003 Karma :

okay, so do you know how to get the top end off?

Laura · Playboy Bunny Joined: 28 Jul 2003 Karma :

It's a shame that tom also known as 125 has blown up his nsr and now trying to get his mate on here to help get it fixed isn't it!

If tom had been nicer to everyone he would of been able to ask himself instead of being banned!
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bonceunounce · Banned Joined: 22 Aug 2003 Karma :

No, it was Toms bike, he lent it me as he is going on holiday in a couple of days as he lives in a rough area and chances are it would be nicked.

I took it out for a test ride as i hadnt rode gears for a while, and it packed up!

Pushed it to Toms house and its the top end but like we cant get it off.

We been working on it since lunchtime , i just got home. Ill talk to him on MSN see how he has got on with it.

He is a funny lad, he just goes OTT and a bit mental sometimes , like a hyperactive kid! I see he got banned, and ive read what he has said. He isnt a sex offender or paedophile, he just has a lot of younger friends than him, were talking youngest being 14 - 15.

He is quite immature for his age and he needs a lot of help as he hasnt had a good life over the last couple of years.

Anyway, we will get the bike fixed, i wont be a pest like he was i just need the help! But like if he needs help i have to post it, sorry if it has to be that way Neutral

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

It isn't too hard to get the top end off the engine. From memory 6 bolts hold the head on and 4 bolts hold the barrel on (once you have disconnected the exhaust and power valve). Took us about 1.5 hours I think on Cols bike when he blew it up.

The biggest problem is that the 2 studs holding the barrel on the alternator side have locating dowels around them which seem to stick in place. I would try squirting a fair amount of WD40 around the studs after you have got the nuts off and leaving it to stand for a while. The use a soft piece of material to try and knock the barrel upwards. Do not hit it directly with a hammer. Use a fairly solid piece of wood between the barrel and the hammer. You don't need to hit it really hard, just alot, and once you have a bit of play try and rock the barrel from side to side a touch. Do not put a screw driver between the barrel and the crankcases to try and lever them apart.

All the best

Keith
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bonceunounce · Banned Joined: 22 Aug 2003 Karma :

Okay thanks a lot for that keith Smile

Tom said earlier on MSN that he had every bolt off, but when he tried removing the last allen bolt from inside the powervalve, he slipped and rounded it off!

I think he was in the process of banging a slot into it with a hammer and a screwdriver.

Once that is off, the last 12mm nut can come out, and the barrel will come free.

I feel bad because it blew up when i was on it, but he doesnt blame me as it was giving him tickover troubles.

I do have my own NSR a 1990 one. But i crashed it again the other day and snapped my exhaust, so im off the road for a bit (unless i nick toms one when he isnt looking!)

thanks again