KR-1S.co.uk Forum

Hi, bought a project off here a while ago, and just getting around to the engine, was told the engine had been refurbed, but now I've looked, it appears to have been rebored To the touch they are very 'metallic and grainy' if that makes sense.

Are the barrels scrap, or will a replate recover whats's been removed ? are they nicosil plated and not ceramic coated?? who/where to send them please, and hopefully, it wont be the dustman

can you take a picture of the barrels

Yes I'll get some up over the next few days, when I'm off, also include a couple of piston shots (these look 'new' but aren't coated either) my other barrels are very shiny in comparison.

Have a look with a piston inside, if the clearance is good you can get them replated.

Google Aptec for cylinder services.

Even if the clearance is too large, don't give the cylinders to the dustman! You can have them bored and plated for larger pistons OR have them sleeved (LASCo make a sleeve for KR-1S, part number KA-5142). See viewtopic.php?f=19&t=10709&p=80303&hilit=sleeve#p80303.

Regards,
James

Did some pics as requested...

On further inspection, has the ring taken a huge gouge out of the barrel on this one?






pistons look new to me, and have 1KT cast into the bottom of the tangs.

Look like 300cc conversion material to me I'm afriad.

You could always send those pics to Aptec and see what they say, but it might cost more than they are worth just to pick up some reasonable second hand cylinders.

Mine is running 1KT pistons (TZR250) that I got from PJME, they came with the dome reprofiled to suit KR1S and look the same as the ones in your pics.

What's the reason the barrels are u/s, cant they be welded and re-plated? as for finding replacement barrels, few and far between, unless someone has a stash they wish to sell??

Is it just Stan Stevens that does the 300 kits?

They can be welded and repaired, so not US, you could probably pick some up cheaper.

Like I say though as I'm not the expert, phone Aptec.

Stan doesn't do the 300 conversion, he sold it on to someone else.

SP_BOTT wrote:What's the reason the barrels are u/s, cant they be welded and re-plated? as for finding replacement barrels, few and far between, unless someone has a stash they wish to sell??

Is it just Stan Stevens that does the 300 kits?

If you want to use those cylinders, you don't need to go as far as 300cc. Take the cylinders to Aptec, Langcourt or any other specialist cylinder plater and ask how much bigger the bores must be made to remove the damage...then find the most suitable size pistons. It could be that a standard size TZR/TDR/R1-Z piston (56.4mm) may be enough (if not, the first oversize). Since this type of piston already has features which make it compatible with the KR-1, the modifications would be minimal.

Among my spare TZR parts I have the latest genuine standard size 1KT/2YK/3XC piston (Yamaha Part No.2YK-11631-04-35). Using a profile gauge, I have checked the dome profile of this piston against the dome profile of a genuine standard KR-1 piston and they are IDENTICAL.
I know some people have said that Mitaka 1KT pistons had their domes machined to suit the KR-1, but (based on my observations) this appears to be nonsense...or there is perhaps more to the story...

If the cylinder bores will clean up OK by boring and replating to 56.4mm, it looks as if you can simply use the standard Yamaha pistons with no other modifications. Please let us know how you get on if you decide to go this route. If you want any more measurements from the Yamaha piston, let me know.

Regards,
James