NSR topend rebuild?

[skatefreak]

Hey there all.
So the history of this bike is somewhat dubious, the previous owners story checks out as he said he got the bike low milage 5'ish years ago, low miles and it sat for 3 years whilst he was in the army then he got out and has been using it since (as the MOT's show, milage pretty low, no MOT's for a few years and then it jumps up by about 4k in a year).

The engine is now getting to 9,000 miles and the guy said he changed the rings but for the sake of the chance the engine could go poof i thought it would be worth throwing some pictures up i took when i have her appart recently.

I used my phone camera to take some pictures up the exhaust port lol (Worked better than expected!). Lazy me but didnt fancy fannying around with coolant taking the top end off etc as i only had an evening...

Also the picture of the exhaust, there is a pretty serious build up in there (chipped a little off to show up in the pic), would the stock NSR exhaust be safe to fill with something causticy and leaving for a day or so? Will look up the procedure closer to the time

Also that being said, yesterday for the 2'nd or 3'rd time since getting the bike, when tapping down from 2'nd down to first the engine jumped out of 1'st back to 2'nd (and on 1 occasion it seemed to rattle around in neutral or something ).

A little googling suggests the selector fork or dog ends on a cog but its only happened 2-3 times in 5 months. Could it just be me not tapping the gear selector hard enough (always when i'm coming up to lights slowing down and tapping lightly).

I have a spair engine which seems to be in good nick (top end is fantastic, piston looks much better than that one lol ).

Anywho, any thoughts would be much appreciated,

Best regards

-Jvr

[Skinned]

Just fitted a new piston kit on my NSR this week and the carbon build up looked similar to yours. To be fair it wasnt too bad a job to do, fiddliest bit was putting the RC Valve part back on.
One tip I'll give you though, if you do top end rebuild it, check your electrics before you put the plastics back on, I put my bike back together, took it for a spin only to find I've knocked a connector on the indicators somewhere so have to strip the plastics off again

[alains]

i think you need a top-end complete rebuild if the crank & conrod are in good condition
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the worst day fishing is better than the best day working

[skatefreak]

Do you think the piston looks like its in a bad way?

Allegedly the engine has only done 9,000 miles? Would you say it looks like the engine has gone further? The spare engine i have seems to be in better condition so i think that may be the origional engine for the bike and this was thrown in there to keep it going...

From what i could see the cylinder looks to be in fairly good nick, i have another engine which has a pretty good looking piston/rings, could i get some rings/ gudgen pins etc and use the piston from there or would it be a better idea to throw in a new piston to?

Bike is going off road as the tax cant be renewed as the MOT runs out two days before so needs to be MOT'd *sighs*. Will gave me a chance to rebuild (although that shouldnt take to long really).

No idea what work is going to be needed for the MOT lol.

Any suggestions weather to get a topend kit online or (would a honda dealership be very expensive?).

Best regards

-Jvr

[Skinned]

For the cost of a new piston kit, over just rings I went for the kit. I originally bought one of Wemoto but it turned up smashed, they dicked me round for ages after I sent it back and eventually I ordered off a decent company and had to get a refund off wemoto.

I've only just started using the bike so will report back if the piston set is any good

[alains]

you seem to havent know that piston are fitted with the barrel . buying aftermarket pistons can be wrong in seize because the clearance barrel-piston is essential (range is 0.000 mm to 0.005mm) . if you dont want to buy a cylinder-piston kit you must know the size of your barrel . this size can be read under the exhaust port on the barrel (obviously your barrel must be dismount) . you can see how to read it here : https://www.geneva-racing.ch/~alains/lettre.jpg (letter is E) . so the new piston must be the same size . you may doàwnload my file here : https://www.geneva-racing.ch/~alains/NSRtips.doc
the rings (original are same size) go on all genuine piston
some companies make forged piston (woëssner , etc.....) and are referenced with their exact sizes , some others companies make castain piston with their size (vertex, etc...)
but the best is to change cylinder-piston kit
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the worst day fishing is better than the best day working

[skatefreak]

So you would recomend replacing the cylinder as well as the piston & rings etc at the same time?
Sounds quiet pricey (£129 on top of piston kit), if there is a size stamped on the piston could i use that for reference and get the same size piston kit if the cylinder looks to be in good nick?
I have a feeling the cylinder looks fine in there, i hardly thrash the engine to be honest and am only looking to do some preventitive maintinance so the bike lasts another year or two with some reliability lol.

Will get it off and give it a good de-coking and have a closer look at the cylinder walls.

Best regards

-Jvr

[alains]

i wont take a decision before having inspect the barrel and if good , look the letter under the barrel then buy the same piston except if it's an E because the piston E will cost more than 100 quids (better to buy a cyl-piston kit) in fact A to D piston cost £30ish and you must add rings,pin,clips,bearing and 2 seals plus head gasket
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the worst day fishing is better than the best day working