In a way. It's only the 1/3 of the piston that covers the exhaust port where it happens and has to be relived. _________________ If I have to take the carbs off once more...
paul g wrote:So when you say the ring land "closes up" is that actually the worn piston surface burring over the ring gaps?
And .. why is the diagram pointing to the top outer diameter of the piston crown which isnt related to where the ring sits ...
Sorry for being thick here, i really do want to learn about my Rs and the finer details of keeping 2T's going ... I really need to as i am riding mine a lot.
Just trying to understand the mechanics of it ... the piston is unsupported at the exhaust port and inlets but more so the exhaust port so the ring cant stop the piston from scraping on the top of the exhaust port as it passes and burrs it over because the piston cannot travel parallel with the diameter of the cylinder within the opening?
The piston crown can also get burrs on it as shown in the diagram but is much less common.
The ring sticking is a much more serious problem. Some builder relive the rings around the exhaust on new pistons, some do it once the piston is run in. Personally I do it after run in. Then keep on top of it for the pistons life.
If the ring is allowed to stick, not only does it wear the ring badly, it wears the exhaust bridge and forces the piston against the the inlet side of the bore. The cause of the burring is due to the large unsupported area and the heat.
Run a file over the exhaust side of a used pistons crown and then over the inlet and you can feel how much harder the exhaust side has become. _________________ If I have to take the carbs off once more...
Not so much of a problem on standard pistons/barrels. The ring lands are wider as are the piston rings and the exhaust bridge isn't as narrow. _________________ If I have to take the carbs off once more...
It doesn't mean they shouldn't be checked though. The rings should be replaced when they reach service limits, and the pistons checked just as the RS ones when installing new rings.
NSR250 motors are far from maintenance free just because they are in road-biased trim! _________________ Andy.
NSR-WORLD.COM
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That post isn't directed at you, Paul, it's for those who don't know and wander in on the topic. People misinterpret information so easily, and saying it's not so much of a problem on NSRs doesn't mean it isn't or can't be a problem on NSRs. _________________ Andy.
NSR-WORLD.COM
Please keep all responses to Forum posts on the Forum so that others may benefit.
Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.
The NXA is coming apart this weekend for these checks ... done 200mls on new HRC everything with Oulton on the 19th Sept looming large ..
Thank you for your advice ... learning is good
Simon, did you not get the HRC NXA manual when you bought your RS?
If not, you need to get one as it will tell you all (well almost all!) you need to know about looking after your NXA.
The NXA is coming apart this weekend for these checks ... done 200mls on new HRC everything with Oulton on the 19th Sept looming large ..
Thank you for your advice ... learning is good
Simon, did you not get the HRC NXA manual when you bought your RS?
If not, you need to get one as it will tell you all (well almost all!) you need to know about looking after your NXA.
I did mate but i am still getting used to the terminology used in here and its good to have the benefit of folks experience based knowledge. I didnt realise this was so important and have never done it having run most of my pistons for 300 miles without taking them out
Normally I'd run a piston for between 50-60 miles and pull the top end off. Take any high spots off the piston skirts, relive the rings lands and chamfer the ring end.
I'll run piston rings for around 250 miles on a 250 and pistons for about 600 miles. On the 500V the ring is 1mm rather than a 250's 0.8mm so they are staying in a little longer.
Once this first service is done nothing else should really be needed apart from the normal stripping and inspecting for the life of the pistons/rings. _________________ If I have to take the carbs off once more...
Within all the spares were a number of Suter clutches, about 4 in total. I fitted one of these before the last Donny day. Overall its 1/3rd lighter than the HRC item and has 2 extra plates.
It's incredibly light at the lever using clutch springs that are under tension rather than compression like the standard clutch. The action is very positive and there is no grab at all.
_________________ If I have to take the carbs off once more...
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