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RB head mod w/o carb mod: KDX220 riding impressions

Posted: 03:41 pm May 17 2007
by kawagumby
I just got back from an hour + riding session on my bike which was just fitted with an RB modified head.

The bike is low time with a strong running engine. See my bike profile below to check out what I've done other than stock.

I installed the head with no other changes; including making no changes to jetting the stock carb.

The familiar loop I took was pretty tough, with several rutted, steep hill climbs (including the obligatory root barriers), traction was lousy - mostly hard pack with a thin layer of sandy crap that made hooking up nearly impossible most places. I threw in a few miles of fire roads too but mostly a lot of single track. Thankfully, I have a stealhy flywheel weight which helps a lot, even so, my bike was doing its best crab-walk impression up some of the more technical hills.

Right off, I noticed the irritating boggy thing right off idle was gone. I had worked with this issue on this bike and on a previous 220, and short of changing needles I was never able to completely get rid of it. Well, the head mod got rid of it without any jet changes - hot dang! Wheelies are easier to initiate now as you might expect....

It was hard to tell if the hit right off bottom is now softer because the thing now carburetes so cleanly. Overall, I'd have to rate it better now, because the low rpms now transition to higher in a linear, more controllable manner.

I did have issues with fanning the clutch more than usual, but that is soley due to the fact that I was hitting some tricky hill climb spots at one gear higher than before.

I was using noticeably less throttle to hold the same speeds as I am used to on the fire roads. I wonder if that will translate to better mileage?

I could not find any negatives power-wise. This mod seems to be a major improvement everywhere, every bit as significant as an aftermarket pipe IMO.

One reason I decided to go with this head mod was due to the 220's tendency to overheat -I felt that higher compression might help with that issue. I couldn't draw any conclusions today because it was only in the upper 70's, but things look promising - I'll update this thread on this subject after I get some serious hot-temp time on the bike.

I've read here where some folks noticed the higher compression while kick-starting - however, I couldn't tell any difference.

Good stuff for 45 bucks - indeed.

Posted: 04:29 pm May 17 2007
by m0rie
Good report! Now you just need the carb mods to complete the package...

Posted: 04:40 pm May 17 2007
by canyncarvr
Overall, I'd have to rate it better now, because the low rpms now transition to higher in a linear, more controllable manner.
That's a good thing!! That's the 'electric motor' type response that gets you more places more easier.


You're still running the 33mm carby, then?

Posted: 05:29 pm May 17 2007
by kawagumby
>|<>QBB<
canyncarvr wrote:
Overall, I'd have to rate it better now, because the low rpms now transition to higher in a linear, more controllable manner.


You're still running the 33mm carby, then?
Yes, and jetted as noted in my signature. Frankly I can't think of a better bang for the buck than this head mod. :supz:

And BTW,
I tracked my shipment to Ron - he got it on a friday, and I received it (priority mail) the following monday. I'm in central Cal, he's in Portland. Unbelievable turnaround - really, just unbelievable. Great job!

I bought a second 220 head on Ebay for this mod, because I was unsure of the consequences. I didn't need to.

Posted: 06:44 pm May 17 2007
by canyncarvr
'Unsure..' he said.

Of what Ron does?

I forgive you...for you hath sinned!!! :wink:

Still, having it done to a spare is a good thing. You don't have to take anything apart until you have the goods to put it right back together!

Glad you like it!

Oh...your comment regarding not feeling the compression on the kicker... Just an idea...but I recall reading note to that effect, but by 220 riders at considerably higher el. than you.

I would guess Ron doesn't configure a 1500-3000' ridden bike like a Colorado bike..5000+

I don't know one way or t'other..but maybe.

Anyway..glad it worked out well!!

Ron's work is just plain pretty to even LOOK at, ain't it?

Posted: 07:49 pm May 17 2007
by Jeb
I'm at a lower elevation ( < 1000ft ) and feel more compression . . .

but maybe I can tell more easily because I kick sorta' gingerly to keep from banging my kicker on the KX250 pegs I've got fitted on my 220 (I've got a few wear spots/notches that worry me) . . .

Posted: 10:10 pm May 17 2007
by Colorado Mike
That's what sets Ron's work apart. He knows what different riders need for their conditions. Not getting his head and carb mods on a 220 is just plain silly.