Help with NC29 engine needed

[ChiefNutter]

Hope someone a bit more experinced can help me here because i just dont know what i should do...ill start at the beginning...& i hope it makes sence !!

I took the engine out of my NC29 & plugged up the holes to have it shot blasted (very low pressure) VERY BAD MISTAKE !
Unfortunatley ..the bungs i put in the head (spark plug holes) came out & shot fell into the bore when the spark plugs were removed to find out why it wasnt starting (they never told me the bungs came out!!)...So consequently a small amount of shot grit fell into the bores & where we've tried to start the bike...its obviously done some damage to the pistons & bore ..also the grit got stuck between the pistons rings & compressed them into the slots so there was no compression at all...(no wonder it wouldnt feckin start!!) , however i dont think its that bad (ive seen scoring alot worse than this), but my mate (who works at prodrive) thinks its possibly knackered & has suggested getting another engine (or crankcase & pistons) because he says the tollerances are very tight on bikes like this ...personally id like to strip it down (yes the head aswell) & clean it all up & put it back together & see what compression readings i get...but dont want to do it if its going to be a waste of time.
So i just wondered with all the knowledge on this forum can someone advise what would be the best course of action ??
some of the questions id like to ask are...Can the liners be removed ? because if so ill just but another crankcase & swap them over..ive seen posts on here about big bore kits & removing the liners ???
Also ive seen in another thread about RVF pistons being better ???? is it possible to fit these ? (its a 1992 model)
OR should i just buy another engine or crank case ??...do i really need to change the pistons ??? afterall if the rings are replaced would it really matter about a bit of scoring on the pistons ??

I dont want a big bore kit due to the high cost (cheaper to buy another engine off fleabay for £300ish)
I can take pics if needed

[tanuki]

You could get the bores honed and then just rePlace the rings, I would put RVF pistons in just because you have it apart anyway.
The RVF pistons are the same as the last model 29 and it's the shape of the crown that's different before you ask

[PARUS]

Have anybody measured compression (or dyno) after fiited RVF pistons ? I have set of new RVF pistons - but keeping them as spare part.

[selexon]

Parus A strip and clean will be the best way to go.

Get the bores lightly honed and check piston to bore clearance you may be ok we the std piston and just new rings.

I have a set of RVF pistons coming in the next few weeks so will do a dyno run before and after to see the improvement they make if power and torque.

[PARUS]

I have a set of RVF pistons coming in the next few weeks so will do a dyno run before and after to see the improvement they make if power and torque.

Thank you mate. Could you also measured compression? This is interesting - are this will be highest than 11psi.

[ChiefNutter]

Thanks for that guys, i was hoping i could save the original engine...i'll give it a whirl & keep me fingers crossed

selexon....that would be great if you can chuck some info up on that...anyone any idea what year they started fitting rvf pistons in NC29's ???

[tanuki]

IIRC it was the RR-N models so the very last batch.

[ChiefNutter]

Thanks tanuki that was the last piece of my jigsaw, when i looked at these pistons today i noticed that the crown is quite high & had insets for valve clearance, then i noticed MV4 on each piston..& thought..huuumm...V4 ?? ...ive just checked the tail tray & its aslo an RR-N model !!....ill take a pic tomorrow, if someone could confirm that they are or not that would be great

[tanuki]

pretty sure the RVF pistons I am fitting are marked MV4.

[ChiefNutter]

This is the worst cylinder

this is the worst piston

And (cross fingers) these are RVF pistons ?!..lol