Tuning

2stroke · Post by **2stroke** » Tue Dec 04, 2012 11:17 pm

Hi guys.
We need advice on tuning the kr.
We put a fresh top end with much higher compression,
To solve to lack of bottom end but didn't help. It has NOTHING under 3000rpm. We have tried different pilot jets. From 25 to 50 but no change. Main jet is 150. End top end seems to be great ( still running it in).
Okay we don't have exhaust valves but it should be better then this.

Needle position is I'm the middle.

Last resort is trying 32 mm carbies off RGV.

Any advice will be helpful

Thanks

JanBros · Post by **JanBros** » Wed Dec 05, 2012 7:44 am

raising compression and putting on bigger carbs won't help increasing bottom end power IMHO. in fact they'll make it worse ...

Post by **500bernie** » Wed Dec 05, 2012 7:48 am

What do you mean when you say "we don't have exhaust valves"?

Luders · Post by **Luders** » Wed Dec 05, 2012 7:57 am

my knowledge of KR's is extremely limited and I've never ridden one, but it is a 2-stroke 250, so would you really expect it to put out any sort of power at 3k rpm?

I certainly get naff all out of my KR-1S engines that low down.

You say you're also running it in?

What sort of torque are you expecting and what is it actually delivering?

StrokerBoy · Post by **StrokerBoy** » Wed Dec 05, 2012 10:13 am

500bernie wrote:What do you mean when you say "we don't have exhaust valves"?

The rare KR250S has a different top-end with an early 'KVSS' powervalve system. The ordinary KR250A doesn't. It was designed to fill in the gaps in the low/midrange curve, the standard KR is very flat at the bottom.

TwoStroke Institute · Post by **TwoStroke Institute** » Wed Dec 05, 2012 1:38 pm

RC nitro cars these aint

Check the ignition timing Kawasaki's can usualy do with some advance down low

2stroke · Post by **2stroke** » Wed Dec 05, 2012 1:46 pm

I'm talking no power under 3000rpm. Clutch out and it won't rev unless you slip the clutch again to rev it up.

One thing we will try tomorrow is ignition timing.

We have a cagiva mito 125 and has great power from 1500rpm so I'm sure the kr 250 should be the same or better.

2stroke · Post by **2stroke** » Wed Dec 05, 2012 1:48 pm

It's a small world mate !!!

Luders · Post by **Luders** » Wed Dec 05, 2012 3:17 pm

stick it on a dyno

ScottaKR · Post by **ScottaKR** » Thu Dec 06, 2012 8:07 am

Sounds like it definately has an issue then. From my experience, they are quite rideable all the way through the rev range. You certainly shouldn't have to slip the clutch just to get it past 3k. I'm wondering if the rotary reed valves are adjusted properly.

2stroke · Post by **2stroke** » Thu Dec 06, 2012 8:25 am

Yes that's what I'm thinking.
Thanks for your help.

Will check it out

2stroke · Post by **2stroke** » Thu Dec 06, 2012 7:45 pm

We took out the view plugs to check the ignition timing and is it normal to have a small amount of gear box oil in there ?

2stroke · Post by **2stroke** » Thu Dec 06, 2012 7:47 pm

ScottaKR wrote:I'm wondering if the rotary reed valves are adjusted properly.

Are they adjustable ?

ScottaKR · Post by **ScottaKR** » Fri Dec 07, 2012 12:11 pm

2stroke wrote:
ScottaKR wrote:I'm wondering if the rotary reed valves are adjusted properly.
Are they adjustable ?

Yes, and no. They're not really adjustable as such, but they can be installed incorrectly putting their timing out. Was just a thought.

Top-shaggy · Post by **Top-shaggy** » Fri Dec 07, 2012 5:10 pm

ScottaKR wrote:
2stroke wrote:
ScottaKR wrote:I'm wondering if the rotary reed valves are adjusted properly.
Are they adjustable ?
Yes, and no. They're not really adjustable as such, but they can be installed incorrectly putting their timing out. Was just a thought.

You can adjust the timing by either moving the disk on the splines or / and of course cutting the disc (carefully as I believe they are NLA from KHI). I put a post on here somewhere showing how to derestrict the AR125 rotary disk valve... If you have a look at this it shows what I mean as the disks are virtually the same.