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KR1S Project

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MarJay
But it's British!



Joined: 15 Sep 2003
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PostPosted: 09:38 - 19 Jul 2021    Post subject: KR1S Project Reply with quote

As some of you know I've had a KR1S languishing at the back of my garage for a number of years. I bought it in about 2013 and it was apparently rebuilt from NOS parts. The seller told me the pistons were the new pattern which didn't have the fatal flaw with the ring pegs...

I didn't ride it a lot, but I did ride it occasionally until 2017 when I couldn't get it to run any more. I spent a load of time taking the carbs off and making adjustments. I replaced the fuel tap thinking the issue was fuel starvation. It would run sometimes but not very well. So I trailered it over to a local dyno place to get them to have a look. The news was not good. They had put an endoscope in the exhaust port and found internal damage. The ring pegs had made a bid for freedom!

The damage was... not good.

https://www.bikechatforums.com/files/img_4751.jpg

https://www.bikechatforums.com/files/img_4744.jpg

In 2020 during lockdown I managed to strip the top end of the bike and get it ready for a rebuild. The bike then stood in my garage looking sorry for itself with a plastic bin bag over the open crankase like a rag covering a persons modesty. It really did look a state.

https://www.bikechatforums.com/files/kr1s-1.jpg

I did not get around to sending the parts away for repair until earlier this year. I sent them away to BDK engineering who did a great job in repairing the damage. They also sold me some pistons and a replacement KIPS valve which I had broken during the stripdown process. Turns out they are quite weak and you can't use an impact driver on them!

Fast forward to the end of June where I put the pistons and barrels back on the bike, and then to the weekend before last where I got it to here:

https://www.bikechatforums.com/files/kr1s-2.jpg

Then last weekend I went to the Champion Flat Track school on saturday, which was awesome by the way, and Sunday I got to here:

https://www.bikechatforums.com/files/kr1s-3.jpg

Then, after a few kicks and a lot of sweat (it was extremely hot yesterday) I got to here:

https://www.bikechatforums.com/files/kr1s-4.jpg

and then, realising my new garage has terrible ventilation, I did this:

https://www.youtube.com/watch?v=o5F61HZ9oNc

The idle is extremely high, so I need to look into that, but otherwise I'm very pleased. I had no idea of the carbs had solidified in that time with old petrol etc, and once it was going, it was a matter of one kick to get it to re-start.

Updates to follow soon!
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.


Last edited by MarJay on 18:04 - 21 Jul 2021; edited 1 time in total
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Hong Kong Phooey
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PostPosted: 10:52 - 19 Jul 2021    Post subject: Reply with quote

Can't wait to see her with her frock on. These were good looking bikes back then.

It'll be fun seeing how often you'll be revisiting this thread for yet another rebuild though Laughing
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MarJay
But it's British!



Joined: 15 Sep 2003
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PostPosted: 12:22 - 19 Jul 2021    Post subject: Reply with quote

Hong Kong Phooey wrote:
Can't wait to see her with her frock on. These were good looking bikes back then.

It'll be fun seeing how often you'll be revisiting this thread for yet another rebuild though Laughing


The pistons are Mitaka ones that don't have the same issues as the OEM ones, so I hope not!
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.
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BenR
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Joined: 23 Jun 2008
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PostPosted: 20:51 - 20 Jul 2021    Post subject: Reply with quote

Lovely bike! Bet you can't wait to get out on it? It's the same frame/swingarm & suspension as the old ZX4.
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MarJay
But it's British!



Joined: 15 Sep 2003
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PostPosted: 17:43 - 21 Jul 2021    Post subject: Reply with quote

BenR wrote:
Lovely bike! Bet you can't wait to get out on it? It's the same frame/swingarm & suspension as the old ZX4.


I don't think it is... There's no way it'd fit a 4 cylinder in there. The suspension might be similar, but it's definitely not identical.
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.
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stinkwheel
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Joined: 12 Jul 2004
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PostPosted: 17:51 - 21 Jul 2021    Post subject: Reply with quote

I always had those down in my head as a bit of a fragile bike and something of a money vortex (even before you have to put fuel in it) but probably the best all round performer of the LC 250cc 2-strokes. Same ballpark as the NS400R in that you don't see many about but when they are running they are incredibly focused.

The teen dream racer you actually need to be a grown up in good employment to have as a toy.

Looks like it'll be fun.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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MarJay
But it's British!



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PostPosted: 18:01 - 21 Jul 2021    Post subject: Reply with quote

stinkwheel wrote:
I always had those down in my head as a bit of a fragile bike and something of a money vortex (even before you have to put fuel in it) but probably the best all round performer of the LC 250cc 2-strokes. Same ballpark as the NS400R in that you don't see many about but when they are running they are incredibly focused.

The teen dream racer you actually need to be a grown up in good employment to have as a toy.

Looks like it'll be fun.


Supposedly if the barrel deck heights are the same, and it has new pattern pistons they are fairly reliable. It's definitely fun. Oddly I was talking to a guy with an NS400R at the weekend, he said that they are pretty reliable too.
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.
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stinkwheel
Bovine Proctologist



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PostPosted: 18:21 - 21 Jul 2021    Post subject: Reply with quote

I'd imagine everything in either of those motors is pretty finely balanced and wouldn't respond well to the tuning attempts of the day such as spiking baffles and randomly drilling holes in airboxes.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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MarJay
But it's British!



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PostPosted: 18:26 - 21 Jul 2021    Post subject: Reply with quote

stinkwheel wrote:
I'd imagine everything in either of those motors is pretty finely balanced and wouldn't respond well to the tuning attempts of the day such as spiking baffles and randomly drilling holes in airboxes.


Indeed.

The tolerances on the KR1S are notoriously bad, so a freshly rebuilt top end definitely can't hurt.
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.
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MarJay
But it's British!



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PostPosted: 17:54 - 25 Jul 2021    Post subject: Reply with quote

Update:

I spent today investigating the high idle. First of all, all of the carburettor clamps were finger tight. So I tightened those down. Then I reset both idle screws to approximately where I thought they should be and this was the result:

https://youtu.be/kYY23j1utL0

So no more 4000rpm idle, it needs adjusting up as I've since found that the idle should be between 1100 and 1300 rpm, whereas I was working on the assumption that it should be around 900rpm when the video was made.

So I then spent most of the afternoon putting it's clothes back on:

https://www.bikechatforums.com/files/kr1-s_nearly_done.jpg

I found that the brand new 8mm fuel pipe I fitted before it stopped working has all cracked and is now leaking, so I'll need to replace that, but the brakes work, the indicators work, the suspension seems OK, it seems to start easily and run OK so I think it's not far off having an MOT. The first time in four years! Smile
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.
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MarJay
But it's British!



Joined: 15 Sep 2003
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PostPosted: 18:33 - 25 Jul 2021    Post subject: Reply with quote

By the way, it's definitely a 3 feet bike. What do I mean by that? I mean that it looks OK when you're 3 feet away, but when you get close you notice all the little bits of damage, the bodges, the cable ties and the little miniscule flecks of corrosion, cobwebs and dirt. It's not cosmetically great at all.
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.
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Hong Kong Phooey
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PostPosted: 15:01 - 26 Jul 2021    Post subject: Reply with quote

Nice, looks like a respray has been done in the past.

I used to long for one in these colours.

https://mcn-images.bauersecure.com/upload/262825/images/600x400/04Kawasaki-KR-1S.jpg?mode=max&quality=90&scale=down
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MarJay
But it's British!



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PostPosted: 16:45 - 26 Jul 2021    Post subject: Reply with quote

Hong Kong Phooey wrote:
Nice, looks like a respray has been done in the past.

I used to long for one in these colours.

https://mcn-images.bauersecure.com/upload/262825/images/600x400/04Kawasaki-KR-1S.jpg?mode=max&quality=90&scale=down

Mine should look like this:

https://raresportbikesforsale.com/wp-content/uploads/2010/10/kr1-left.jpg

I had a chance to get a tank and bodywork from Japan but I couldn't afford it at the time. I'm kicking myself a bit now.
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.
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Hong Kong Phooey
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PostPosted: 16:56 - 26 Jul 2021    Post subject: Reply with quote

I see good ones are going for 5 grand plus, bit rich for me, but if you could spend a grand in respray and stickers you'd probably get it all back and then some.
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MarJay
But it's British!



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PostPosted: 19:02 - 26 Jul 2021    Post subject: Reply with quote

I only paid £1500 for it when I bought it! Smile
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.
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redeem ouzzer
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PostPosted: 10:54 - 27 Jul 2021    Post subject: Reply with quote

The Mitaka pistons have their issues, to the point where my mate has now binned two sets in his KR. First set ovalled the gudgeon pin holes in about 500 miles bad enough that the piston crowns could touch the head. Luckily he heard it and stopped it before any great damage could be done. Went to 2MA pistons, bit more restrictive, ran fine. Decided to try another set of Mitaka while fitting a better cylinder head, started rattling after 100 miles, bottom ring stuck solid due to crap tolerances. Went back to the TZR pistons, no more issues. Mitaka are aware of these issues and don’t care / blame lack of lubrication. I’d keep my ears open for the first few hundred miles especially, they are very quiet engines and any tapping / rattling should be treated with the utmost suspicion.
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Ste
Not Work Safe



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PostPosted: 12:15 - 27 Jul 2021    Post subject: Reply with quote

MarJay wrote:
I only paid £1500 for it when I bought it! Smile

Bcf purchase?
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Ste
Not Work Safe



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PostPosted: 12:15 - 27 Jul 2021    Post subject: Reply with quote

MarJay wrote:
I only paid £1500 for it when I bought it! Smile

Bcf purchase?
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Rob Fzs
World Chat Champion



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PostPosted: 12:32 - 27 Jul 2021    Post subject: Reply with quote

Needs painting R blue
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MarJay
But it's British!



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PostPosted: 13:16 - 27 Jul 2021    Post subject: Reply with quote

Mylarballoonsfan wrote:
The Mitaka pistons have their issues, to the point where my mate has now binned two sets in his KR. First set ovalled the gudgeon pin holes in about 500 miles bad enough that the piston crowns could touch the head. Luckily he heard it and stopped it before any great damage could be done. Went to 2MA pistons, bit more restrictive, ran fine. Decided to try another set of Mitaka while fitting a better cylinder head, started rattling after 100 miles, bottom ring stuck solid due to crap tolerances. Went back to the TZR pistons, no more issues. Mitaka are aware of these issues and don’t care / blame lack of lubrication. I’d keep my ears open for the first few hundred miles especially, they are very quiet engines and any tapping / rattling should be treated with the utmost suspicion.


I'd imagine BDK know what they are doing. The pistons came in Mitaka packaging but had no English on them at all, which leads me to believe they came from Japan for the Japanese market. Perhaps this was to avoid the bad batch that other people have experienced?

Ste wrote:
Bcf purchase?
No, from someone on the KR1S forum but I originally saw it on ebay.
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.
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redeem ouzzer
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PostPosted: 19:25 - 27 Jul 2021    Post subject: Reply with quote

Rob Fzs wrote:
Needs painting R blue


The R was only ever black and green, same as the S scheme bar the tank decals.
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