4RT pistons

[barfy]

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.

[gizza5]

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

[barfy]

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.

[jimmyl]

full set of rings genuine 4rt -

[fantic303]

Honda CRF 250 has a bore of 78 mm

Montesa 4RT has a bore of 76.5 mm.

So it will not fit.

[barfy]

Hi Jimmy where was that?

I was quoted

[jimmyl]

Not sure I'm allowed to say but see one of the site sponsors web sites - the one who used to be the importer

[barfy]

That's OK Jimmy because I don't know who you mean

I'll give them a call tomorrow.

[bobtlr]

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