looking down the cylinder barrel

[fishtail]

stripped it off today

few scratches... seems like a horizontal line at the bottom of piston stroke..






piston is scratched a bit.. and scorched,, will it live? or get a replacement?

[knackeredMk1]

The hoizontal lines at the bottom and top of the stroke are where the piston rings tip and very slightly dig an edge into the bore.

I really would get a rebore which means you have to changge the piston. Don't forget to replace the small end bearing as well.

WHat is you current bore size .

[fallenmikethebike]

+1 ^^^^^^^^
Mike

[fishtail]

looks to be 66mm.. ( or possibly 65.5 mm)

now wishing I'd spent a tenner on digital ones instead of a 80p for a plastic "analog" pair. - mind you it is orange


so I guess a rebore is possible ( up to 68 mm right? )

but why oh why does everyone here in hong kong say " oh no CRM are nicasol lined? "

( mine was a grey import from japan )

[knackeredMk1]

The AR is nicksil the rest are iron lined which you can rebore up to 68.0mm (or 68.25 if you can get a special piston from Wiseco).

You need to find someone who will do the rebore for you and get it accurately measured. Then buy a suitable piston and get it rebored. The reborer will have to work on the PV as well.

If you have trouble getting it done then parhaps we can work something out this end .

[fishtail]

cool thanks!!!

I got a rough quote from somebody they said about 50 quid... they had nipped out today. but will ask them tomorrow or monday..

they need to make sure the power valve is flush?

to be honest I am a bit nervous about someone around here doing it,,, not sure they have the experience... gonna ask some of the other local CRM lads on facebook. I cant be the only one.???

not sure this is why I was fouling plugs tho?

[helisupp]

Its interesting that LT have the bore offset rebored on the AR so that the powervalve is not touched.

[Active Rascal]

Yes, I wasn't too pleased about this, however as it's only going 0.1mm oversize, it will only be offset 0.05mm. You will probably get more wear on one side than another in the Nicasil lining??

[fishtail]

is it possible to have AR barrel in mk3?

( cos the local chinese here telling me my CRM barrel is nicasil lined? I've had this from 3 or 4 people - altho once I tell them it isnt they dont seem to be convinced they are right...... )

what does a nicsil seal look like? anyway to tell?


serious question how long you think a barrel will last from new?


edit/

and one mechanic CRM guy is saying the CRM barrels dont rust- so thats why they are different from iron core?

[fallenmikethebike]

Nicasil is probably one of the hardest compounds you will come across, it will blunt files
Carefully take a file to the bottom edge of the barrel, there is sometimes a visible flashing around the ports as well.
From the photos it certainly doesn't look to be a Nicasil barrel.
Mike

[knackeredMk1]

I just put a long post in to tell you that your barrel is iron lined. For some reason it's not been accepted .

TAKE IT FROM ME YOUR BARREL IS IRON LINED AND HAS ROOM FOR PLENTY OF REBORES

You can see the two metals particularly from the bottom view of the barrel.

Stick a bloody magnet on it ...................................

No - an AR barrel won't work as different PVs. A Mk1 or 2 would though.

Original bore is 66.0mm.

[fishtail]

yeah its driving me nuts too! have to argue with everyone here it seems that this can be done!

and the british guy over here who has a mechanic shop is away this weekend.. so looks like monday or tues before I find out how much and if they can do the power valve as well.

so I need to order the piston first? then get the bore to match..

this is gonna take weeks!

[knackeredMk1]

Get the current bore measured accurately. Then work out how much you need to rebore to get back to smooth iron. Then buy a piston of that size and get the rebore done to the size of the piston. Pistons vary very slightly in their sizes so this is the most accurate way to do it.

[fishtail]

got my barrel measured

he says its 66.08 mm

actually is that in the range of standard honda pistons?

should get it rebored to what size? ( or rather buy which size piston get it measured and then rebored? )

cheers!

[njhardy]

Those scratches are horrible fishy and your piston rings were leaking too- get the damned thing rebored!! Its a bloody mk3- I can see the steel liner in the picture!!
If possible go for a lighter & stronger PROX or TRX piston (this will need different bearings & gudgeon pin and clips), but a much better piston than the CRMs. Don't go mad with the reboring + 2 (0.5mm) overbore should be fine. Get a piston first & take the new & old piston with the bore when getting it done & leave the powervalve in place. Don't forget to get them (or you) to shamfer the ports on the inside of the bore (read your other post). Careful- the powervale will need ground down too!! Do check this by putting the piston in and checking that the powervalve moves its whole distance with the piston fully in place once the rebore is done- the prats I used said they did, but they hadn't!!