barfy Posted October 27, 2010 Report Share Posted October 27, 2010 Does anyone know if the CRF250 piston rings or piston fits the 4RT? I remember the original Montesa brochure saying that the engine was based on the CRF250. You can get CRF piston and rings much cheaper than 4RT parts. Quote Link to comment Share on other sites More sharing options...
gizza5 Posted October 27, 2010 Report Share Posted October 27, 2010 Not sure why you would want to change them unless you are following the Manual? I was told that indeed it is basically the same as a CRF 250 and that is gesigned to be reved at full tilt for hours? What we do in trials is nothing so was advised to leave alone? Anyway the Honda part number is 13011-NN4-000 that seems to be for all 3 rings. Maybe this will help Quote Link to comment Share on other sites More sharing options...
barfy Posted October 27, 2010 Author Report Share Posted October 27, 2010 Thanks for the reply Gizza. The bike is now 5 years old and there is a bit of a timing chain rattle. While I was doing the timing chain I thought I'd do the valve seals. Then while I've got the head off do the rings. The part number NN4 means that it is for the Montsa I think. With my RTL over the years I've found that many parts are similar enough to other bikes. I also remember that it was basically the same engine as the CRF. This is why I asked the question about the rings because the CRF rings are much cheaper. In fact I can buy a CRF piston and rings for the cost of a Montesa rings. Quote Link to comment Share on other sites More sharing options...
jimmyl Posted October 27, 2010 Report Share Posted October 27, 2010 full set of rings genuine 4rt - Quote Link to comment Share on other sites More sharing options...
fantic303 Posted October 27, 2010 Report Share Posted October 27, 2010 Honda CRF 250 has a bore of 78 mm Montesa 4RT has a bore of 76.5 mm. So it will not fit. Quote Link to comment Share on other sites More sharing options...
barfy Posted October 27, 2010 Author Report Share Posted October 27, 2010 Hi Jimmy where was that? I was quoted Quote Link to comment Share on other sites More sharing options...
jimmyl Posted October 27, 2010 Report Share Posted October 27, 2010 Not sure I'm allowed to say but see one of the site sponsors web sites - the one who used to be the importer Quote Link to comment Share on other sites More sharing options...
barfy Posted October 27, 2010 Author Report Share Posted October 27, 2010 That's OK Jimmy because I don't know who you mean I'll give them a call tomorrow. Quote Link to comment Share on other sites More sharing options...
bobtlr Posted October 29, 2010 Report Share Posted October 29, 2010 hey it is not the same bore on the 2 bikes so they will not fit i guess (not sure ) the japanese 260cc 4rt (rtl) has the same bore as a crf best regards bob Quote Link to comment Share on other sites More sharing options...
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