KIPS power valve spring and the "opening" RPM

agvosloo · Post by **agvosloo** » 05:31 pm Mar 02 2015

First of all I have a KDX200 05'

I'm going to design a expansion chamber for a project I'm doing at the university of Pretoria (South Africa).
The expansion chamber aims to improve the bottom end power as I mostly do tech riding in any case.

I am going to use the values (exhaust port length and diameter) needed for calculations when the power valves are fully open as to eliminate any variables that might throw my calculations off.

So a questions:
1. Correct me if I'm wrong, I have read in the service manual that at 6000 rpm the power valve are fully open.
So to improve the bottom end I would want the power valves fully open at say 5000 rpm.
1.1 I have read on this forum that you can remove the spring, won't this drastically effect the function of it and cause it to stay open?
1.2 Does anyone know where I can get softer springs to reduce the rpm the power valves open up?
1.3 Can this spring be replaced without having to remove the top end?

2. Also I need to determine the rpm the power valves open, so what/where would you suggest is the easiest way to accurately measure the engine RPM with a tachometer?

Thank you in advance

diymirage · Post by **diymirage** » 06:07 pm Mar 02 2015

there are 3 different ways to tune the KIPS

you can pull the washer (or add to it) to changes the tension on the actuator
you can put a spacer on the KIPS resonator
you can get a different spring in the actuator section under the clutch cover

I know I posted more in debt on this before ;)

Gotanubike · Post by **Gotanubike** » 06:14 pm Mar 02 2015

Moose racing made a KIPS tuning kit with one lighter and heavier spring...

But I think they would be pretty hard to find now. Found thread ---> http://www.kdxrider.net/forums/viewtopi ... 77&t=12425

Jaguar · Post by **Jaguar** » 06:30 pm Mar 02 2015

on mine it opened around 7000rpm.
see http://www.dragonfly75.com/moto/KDXpowerband.html concerning redesigning the pipe for a broader powerband.

ohgood · Post by **ohgood** » 09:24 pm Mar 02 2015

agvosloo wrote:First of all I have a KDX200 05'

I'm going to design a expansion chamber for a project I'm doing at the university of Pretoria (South Africa).
The expansion chamber aims to improve the bottom end power as I mostly do tech riding in any case.

I am going to use the values (exhaust port length and diameter) needed for calculations when the power valves are fully open as to eliminate any variables that might throw my calculations off.

So a questions:
1. Correct me if I'm wrong, I have read in the service manual that at 6000 rpm the power valve are fully open.
So to improve the bottom end I would want the power valves fully open at say 5000 rpm.
1.1 I have read on this forum that you can remove the spring, won't this drastically effect the function of it and cause it to stay open?
1.2 Does anyone know where I can get softer springs to reduce the rpm the power valves open up?
1.3 Can this spring be replaced without having to remove the top end?

2. Also I need to determine the rpm the power valves open, so what/where would you suggest is the easiest way to accurately measure the engine RPM with a tachometer?

Thank you in advance

if it's going to be a 'project', that's fine. if you just want to make the bike more manageable in the lower rpm's, put a flywheel weight on it. this alone does so much to transform how the power comes on. :)

good luck, post up what you accomplish please :)

newbbewb · Post by **newbbewb** » 11:26 pm Mar 02 2015

also something to look into is the kips cover extensions, those also change chamber size.

agvosloo · Post by **agvosloo** » 02:46 am Mar 03 2015

diymirage wrote:there are 3 different ways to tune the KIPS

you can pull the washer (or add to it) to changes the tension on the actuator
you can put a spacer on the KIPS resonator
you can get a different spring in the actuator section under the clutch cover

I know I posted more in debt on this before ;)

I tried to find the post you were talking about, but struggle find it. Would you be able to link it please?

Can't see a washer you might be able to remove, which you mentioned, in the service manual?

Also, I might need to mention that I want to keep this project focused on the expansion exhaust while keeping the resonator stock, however it may require tweaking of when the PV system kicks in.

C George · Post by **C George** » 07:41 pm Jun 09 2015

Correct me if you think I'm wrong but I removed the ball and spring and feel that both the 200 and 220 had a smoother power delivery.

With less tension the valve will open earlier .

This seemed to help midrange power.

I know the manual says the opposite but we didn't find that.

Tioli · Post by **Tioli** » 05:33 am Jun 10 2015

To me it feels like the powervalve opens when the revs are already within the range of the powerband. That's why it hits hard.
Taking the ball out is definitely on my list

Slick_Nick · Post by **Slick_Nick** » 03:54 pm Jun 10 2015

has anyone done a write up on this yet? I've been using ignition timing to get the powerband where I need it for riding different conditions but I'll try the KIPS tuning when I get a minute

Tioli · Post by **Tioli** » 04:12 am Jun 11 2015

I have the timing fully advanced for bottom end and still have more than enough topend. No doubt all the RB mods and other shenanigans have created this.

I don't know where but Iv seen quite a few wright ups on adjusting the ball tension. Most say removing it or adding more spacers of what ever thickness makes the motor smoother without the top end hit. What I don't know is if you don't hold the powervalve in the lowered position are you ultimately loosing power at the expense of a smoother transition.

Iv sort of lost my way with my development program (my toy) as I sort of just riding it at the moment. Last time I took notice I had it at a stage where the bottom end had a slight surge to meat the hit of fully open, heading in the right direction but with in that I feel I have lost that really low near on stalling singal bang with authority. Then I also haven't chased the SSS yet, I'm loosing compression because my barrel is so warn.

To wrap it all up its a tool to be used so go for it.

royadams · Post by **royadams** » 06:01 am Jun 11 2015

I would think if you increased spring tension or removed weight, the power valve would open later. That would increase bottom end cut a little mid then be good on top. If the 200 has a big hit in mid my guess is this would smooth it out.

Tioli · Post by **Tioli** » 06:37 am Jun 12 2015

Yes and no. My plan is to not touch the tension till I sort the motor out. Another variable to track and I'm not up to that yet. My plans are more to improve the first stage and deliver into the second as seamlessly as possible.
To me tuning is all about tracking your variables and pick your best options. Bit difficult to do when all you have is ones own head. And there is the fun.

C George · Post by **C George** » 04:59 am Jun 13 2015

royadams wrote:I would think if you increased spring tension or removed weight, the power valve would open later. That would increase bottom end cut a little mid then be good on top. If the 200 has a big hit in mid my guess is this would smooth it out.

The increased tension seems to make the power valve SNAP open vs. opening slowly or smother with less tension.

The bottom end is not lost by removing the ball and spring.

C George · Post by **C George** » 07:38 am Jun 14 2015

Slick_Nick wrote:has anyone done a write up on this yet? I've been using ignition timing to get the powerband where I need it for riding different conditions but I'll try the KIPS tuning when I get a minute

Not to sway the thread but this area is well worth trying different settings also. :)

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