KR-1S.co.uk Forum

Hi, after years of big bikes, motocross bikes and enduros, I have gone and bought a KR1s (in boxes), there appears to be 2 engines, 1 with plated bores and one with liners (KR1s and KR I would assume), anyway I need a crank rebuild and a couple of pistons, any advice on where to get the work done, parts and any improvements I should get done while it's in pieces is very appreciated, I could post photos but it really is in boxes. Oh the crank has CAE etched on it (Colin Applebee Engineering), I have mailed him and will probably ring him tomorrow. I do still have a big bike, a crosser (or 6), an old Triumph and an enduro but please don't hold this against me.

Hi Simbad, sounds like you're going to have fun with it if it's in that many boxes

Crank rebuild - I've had 2 done. One at SEP engineering Kegworth who did a brilliant job but they are busy and it took over 2 months (I told them I was doing a winter rebuild and wasn't in a hurry). They stripped the crank, checked everything and only replaced what needed doing so the price was good as well. The second I had done at Grampian Engineering, 8 day turnaround but pricey and they didn't strip/check, they just replaced everything and rebuilt it. Grampian have a pretty good rep and they've been going for decades, used to do all my 350YPVS and racing stuff rebuilds back in the 90's.

Barrels - I've had a set replated through Sean at The Tuning Works (rgvsean on this forum) he gives us discount, had no problems at all and quick turnaround. I've got a set in at Langcourts at the moment so I'll see how that goes.

As far as I'm aware the KR1 and KR1-S both had plated barrels though, the set with a liner have probably been re-engineered but as I've never actually had any to look at I might be wrong. Putting liners in seems to be getting more common now.

Cheers, Doug.

Thanks Doug, I will give both a call today and find out what the score is, I will also have a chat with Colin Applebee (he is still going) and see what he is upto.
I will post a couple of rebuild pics when it looks a bit more like a bike.

bozbridge wrote:Hi Simbad, sounds like you're going to have fun with it if it's in that many boxes

Crank rebuild - I've had 2 done. One at SEP engineering Kegworth who did a brilliant job but they are busy and it took over 2 months (I told them I was doing a winter rebuild and wasn't in a hurry). They stripped the crank, checked everything and only replaced what needed doing so the price was good as well. The second I had done at Grampian Engineering, 8 day turnaround but pricey and they didn't strip/check, they just replaced everything and rebuilt it. Grampian have a pretty good rep and they've been going for decades, used to do all my 350YPVS and racing stuff rebuilds back in the 90's.

Barrels - I've had a set replated through Sean at The Tuning Works (rgvsean on this forum) he gives us discount, had no problems at all and quick turnaround. I've got a set in at Langcourts at the moment so I'll see how that goes.

As far as I'm aware the KR1 and KR1-S both had plated barrels though, the set with a liner have probably been re-engineered but as I've never actually had any to look at I might be wrong. Putting liners in seems to be getting more common now.

Cheers, Doug.

Doug

Did you get anywhere with Mitaka pistons ? What pistons did you send o Langcourt ?

Simbad

You will need a piston set to send with your barrels for replate. TTW will do additional work on the barrels if you ask, like dressing the ports and they can remove studs etc. But if they break it's up to you not TTW.

Langcourt do Nikasil replate and TTW use Apticote Cermaic plating http://www.thetuningworks.co.uk/store/p ... cts_id=725

"Doug

Did you get anywhere with Mitaka pistons ? What pistons did you send o Langcourt ?"

Phil I sent a set of old Mitaka stock TZR250 pistons that have been modified to suit (oil holes drilled and pistons top dome machined), I got some advice that back in the day these ran on the Nikasil plated bores without any trouble so that's why I sent them to Langcourts rather that TTW but not sure it'd make a huge difference.

Is there a spec for having the pistons done, how much was machined and in what profile? - Which TZR250 2MA/3MA/3XV or is there a thread on here ?

It's on this thread Phil

viewtopic.php?f=1&t=12634

I got the pistons from PJME as replacements for the new style Mitaka's that had failed. On the box it says DT125R - 1KT, the odd thing is a 1KT is the Jap market TZR250 (our 2MA version) I think. Anyway sorry I've no more info on the crown profile but speak to Paul at PJME, I think they used to supply these pistons to KR1 owners a lot a few years back.

I used Colin Applebee once years ago and never again......

He replaced the rods which I asked not to be, I specified details verbally and in writing but ignored!! crank wasn't aligned accurately and he reassembled the webs in non original order and then tried to cover it up. Tosser all round in my opinion

I've had good work done by SEP a long time ago, I think BDK also rebuild cranks

mellorp wrote:Is there a spec for having the pistons done, how much was machined and in what profile? - Which TZR250 2MA/3MA/3XV or is there a thread on here ?

Phil, This topic (viewtopic.php?f=19&t=13666) may be of interest. In particular, I wrote:

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...

I haven't learnt anything further since then, but it still appears that (some?) pistons based on the Mitaka 1KT casting can be used in a KR-1 without modification. However, as there are several variants, check the positions of the ring pegs and other features to confirm suitability (ring peg and lubrication hole positions on the genuine 2YK piston mentioned above are the same as the genuine KR-1 piston). As Doug alluded to, I think the DT125R (also late TZR125?) used the same basic piston as TZR 1KT, but machined for a 56mm bore instead of 56.4mm.

Regards,
James

James P wrote:

mellorp wrote:Is there a spec for having the pistons done, how much was machined and in what profile? - Which TZR250 2MA/3MA/3XV or is there a thread on here ?

Phil, This topic (viewtopic.php?f=19&t=13666) may be of interest. In particular, I wrote:

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...

I haven't learnt anything further since then, but it still appears that (some?) pistons based on the Mitaka 1KT casting can be used in a KR-1 without modification. However, as there are several variants, check the positions of the ring pegs and other features to confirm suitability (ring peg and lubrication hole positions on the genuine 2YK piston mentioned above are the same as the genuine KR-1 piston). As Doug alluded to, I think the DT125R (also late TZR125?) used the same basic piston as TZR 1KT, but machined for a 56mm bore instead of 56.4mm.

Regards,
James

Thank you James, that's useful to know.....