KDX220 squish and carb mods

[99220sr]

I'm looking for technical info on popular mods for the KDX220. As I'm outside the US, it's not possible to send away to have the mods done there. My mechanic has more than 25yrs experience with two strokes, he has never worked on a KDX before, however the engine is very similar to the Kawa SuperKIPS, so he should have no trouble working on it.

Firstly I am going to do the top end and was considering milling the head to improve compression. Any advice for doing this? What else is needed for the squish mod?

At some stage I may do the carb. It's a regular PWK33mm, I can easily get it bored to 35mm and am wondering if is worthwhile.

Any suggestions? Thanks!

 

[Dirtdame]

I have heard that the 35 venturi helps noticably. I haven't done it to mine> I just put a "rev" pipe on it and that made a nice difference right there. I always worry about raising compression on this sort of an engine, because I don't want to put any extra strain on the bike for the things that it is supposed to do best, one of which is running all day long day in and day out on the trails. You would have to rejet and possibly go up in octane to a racing fuel, depending on how much you bumped the compression.

 

[99220sr]

Thanks for the info, it's helpful. Regarding the 35mm carb, would it be possible to just bore out the 33mm one?

 

[steve.emma]

cheaper an easier to buy a 35mm carb from a kdx200, did this on my old 220 made a huge difference.
i read through lots of posts about machining the head to raise comp ratio. there was a guy from Aussie who did it by taking 10thou off the head. if i remember he said it really help the low down power.
Steve.

 

[sr5bidder]

if your mechanic is a true pro tuner he will now what to do to your squish band to get you more power, if not there is a good chance that it wont run right ever again without buying a new cylinder head. Its not as simple as machining 10 thou off. there is much work to be done in the chamber its self.

 

[99220sr]

For most ppl just buying the larger carb would be easier and cheaper, however I would have to import one, which is expensive and tricky. I can have one bored for under $20, although there's the danger they could damage the carb.

I'm guessing 10thou is inches, any idea how much this is in mm? Thanks again.

 

[reepicheep]

I had a friends KDX-220 and my KDX-200 (bored and ported for a 225) both in the garage at the same time. The 220 had a nice pro circuit setup with the Boyesen VForce reed block, I had just Boysen two stage reeds. We both had the stock carb.

When both bikes (finally!) had the jetting dialed in, they felt very close to each other. And the 220 might even have had a little more grunt off the line.

So anyway, I wouldn't go messing with swapping carbs or squishing heads... I would spend time with a 4 gas analyzer getting the jetting spot on, replace that grenade of a piston they put in the 220's asap, and just go ride the bike. With the jetting dialed in, they are a powerful and nicely balanced bike. If you really want crazy power, sell it and buy a KTM 300 or CRF-450X or something (which will make you appreciate the no fuss KDX a lot more in short order ;)).

 

[julien_d]

I will have to respectfully disagree with the above. boring the carb, or installing a 35mm carb from a 200, and fixing the POS they call a head on the 220 will be worth every penny and every bit of time spent. The poor 220 is choked in stock form.

 

[HRDROKN]

I'm guessing 10thou is inches, any idea how much this is in mm? Thanks again.

0.010 = 0.254mm

And I agree that it is more than just milling the head... the width and height of the squish combined with redoing the dome to control volume or compression.

:cool:

 

[99220sr]

Thanks for the info. I'm waiting for a Wiseco piston to arrive and will see how the bike goes once the top end is done. At the moment I'm riding a CRM250, which is more powerful, so I'm interested in the mods, but am in no rush and trying to find all the info I can.

Regarding the carb mods, I don't think it's too difficult to have it bored and a divider plate added.

 

[bikerman]

Buy a 35 mm carb. No need to mess with yours. pull the head and polish the combustion chamber, but before you do , check the cc volume of the head before and after mods. You want the head back as close to factory specs as possible. Have the head checked for flatness, and mill as little as nessesary. Have the ports cleaned up and polished. Dont go crazy. you will be amazed how this helps . remember reliabilty is the important thing.

 

[reepicheep]

Anybody got the smaller carb they pulled from a 220 they want to sell really cheap? I'll swap back and forth and run some tests.

 

[HRDROKN]

Just got my head and carb back from RB.... and thought I would share some pics.

:cool:

 

[99220sr]

Just got my head and carb back from RB.... and thought I would share some pics.

Have you fitted them yet? Any feedback? I just had the top end done and found that the cylinder was ported, bike is running nicely now, just a little work needed on the jetting.

 

[HRDROKN]

Have you fitted them yet? Any feedback? I just had the top end done and found that the cylinder was ported, bike is running nicely now, just a little work needed on the jetting.

Still waiting for the powder coating on the frame to be completed, then I can get everthying assembled.... and test rode!

:ride: