What type of Piston

[Danny]

I'm changing my piston on my NSR and have tried to order the part but, they need to know what size piston, eg. D, A etc.

Does anyone know where I can find out I've called Honda and they are clueless
Oh and if the solution could not involve me taking off the piston, that would be nice

[Keith @ Work]

Hi

Guess what, it is marked on top of the piston. It is also marked on the bottom of the barrel where it is just about impossible to see without taking the barrel off

The code letter is the size of the piston.

All the best

Keith

[Scotty]

What you want another one for anyway Danny?
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Regards
Scott

[Guest]

hi,
i've done 12,000 miles on my NSR (01) the mechanic recons they should check the engine at 15,000 miles to see what condition the barrel and piston are in....
im i likely to get more than 15,000 out of it before it needs rebuilding? ....its never hit the red line and doesn't spend too much time in the higher rev band
also, will i just need to get the piston&rings changed or will the big end and little end bearings need a change over as well?
thanks

[Scooby]

When I rebuilt my engine I had to find out the exact same thing. Difficult when your piston's just smashed into your cylinder head Keith's spot on as per usual, I had to look at the bottom of the barrel, not a problem as I'd dropped my engine out by this point anyway.

The different sizes, ranging from A-D are size differences in the pistons, when each one is made there is a small margin of size difference, between A and D I think there is 100th of a millimetre, this might not seem a lot but when it's going 10,000rpm underneath your arse make sure you get the right one
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A big enough hammer fixes anything!

[cagiva gezzer]

They stock a selection of sizes because when they make the barrels and pistons, the sizes vary. They measure the parts and group them into groups depending on the sizes. "Family" A, B, c, D.

Most fall in the middle.

As said, the family is on the piston and somewhere on the barrel.

There isn't a excact time to change a piston. The wear depends on if the engine is warmed upo before use, oil used, how much it has been (or hhasn'tbeen Thrashed)

Best to get a comp check to see how well the top end is sealing.

The NSR is a ( relatively ) under stressed engine for a two stroke, so it should have a relatively long piston life.

The ONLY real way to tell is to remove it and measure it according to the way honda says it should be measured. (different manufactures measure in different ways) This is best left to some one with the correct tools and knowledge.

The engine would benefit from some new ring(s), but only if the piston isn't past it.

If a piston is replaced, its best to fit a new small end as the wrist pin will of been changed, and is only another 5 - 15 quid to replace one of the most problematic bearings.

The big end doesn't need to be touched, and it should last a couple of top ends as the bearings are bigger and have better lubrication.

For the cost of a piston, i would replace it. Better to know its up to the job. They go through huge amounts of stress.

I.e - At only 8000RPM, the piston has a peak speed of 13m/s and a max acceleration of about 22,000m/s^2.

If you do replace it, you can chose between the OE one and aftermarket ones such as Pro-x. In my experience, if you don't have the cylinder replated, stick with the OE. If you go for a replate, try a Pro-x or weisco "single ring flat top". When the barrel is bored to the piston, you gain more revs, more top end power.

If in doubt- strip, measure,replace. i learnt the hard way. "oh, thats a strange noise from my engine. Ill have a look next week. Seize"

Hope the above helps.

Stuart
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"because one stroke isnt enough and four strokes waste two"

[Guest]

thanks for that advice
if its my first potential 'rebuild' would you recommend getting it replated (sounds expensive ) or just change over the piston
any idea how much a honda genuine piston is likely to set me back?? also, any idea how many hours i can expect to be charged for?
thanks

[Kickstart]

Hi

Think replating the barrel is around £100. A new Honda piston was remarkably cheap when Col asked

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Scotty]

How much does a whole new barrel cost anyways?

Didn't it cost something like £25 or £35 of a piston including all the bits gudeon pin, circlips...
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Regards
Scott

[Kickstart]

Hi

Suspect a barrel is enough to make your eyes water.

Col got quoted around £35~£40 for a piston which is pretty cheap. My experience of pattern pistons would mean I would pay the extra for an original one.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[cagiva gezzer]

The only way to tell if you need a replate is to measure it. Get it done by someone who knows what they are doing.

My Cagiva barrel was past it by 18,000km.

Its ~£100 for a replate which is much better quality than the original one as the person who does it takes time and effort. Unlike the factory, which ships them out in vast quantities.

Barrels cost A LOT.
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"because one stroke isnt enough and four strokes waste two"

[McJamweasel]

[Dr Nick]

Stan Stephens do NSR rebuilds . They also replate barrels, check their website. https://www.stanstephens.com/.
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is that it

[Kickstart]

Hi

Dont think Stan Stephens actually does the replating themselves. HEard a rumour that they ship it off to Lancourt Engineering near Bath

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Danny]

Honda Quoted me £60 for a new piston

[cagiva gezzer]

youre complaining?!

Cagiva oe = £110 / £140 (single or double ring)

cagiva weisco (pattern) = £70
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"because one stroke isnt enough and four strokes waste two"

[Danny]

[Danny]

^Bumpy bumpy^

I've done a compression test on the NSR and got about 5 of the meter, i'm assuming that it is supposed to be 10 -+2?
I also found that there was a bit missing off the cathode(?) on the spark plug and there was a fair bit of suty/oily stuff on the plug.
Me and Robby are going to attempt to do the rings next weekend(I will really get round to it this time)
I'm just going to buy every size of ring and return whatever is not needed.

Any comments/suggestions?

[Dr Nick]

If you are going to replace the piston and rings you might as well buy a racing piston with a singular ring, i think wiesco make them.

[Danny]

I'm only planning on changing the piston rings not the piston, unless the piston looks in bad shape.

[Scotty]

Jesus that is a bit poor, bar 5.
And yeah it should be around 10.

Mine was getting 2 bar with top parts of the piston missing...
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Regards
Scott

[Danny]

[Kickstart@Work]

Hi

Scottys' bike did still run, just.

Compression should be 10 bar +/- 2 bar.

The difference in sizes of the rings is tiny. You can probably buy one size of rings and then file the ends down if they are too large when you check the ring end gap.

All the best

Keith
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Atheism is a not for prophet organisation