KDXRIDER.NET

I just got a 2002 KDX 220 a couple of weeks ago and the idea was to make it into my hare scramble/enduro bike. The bike was a bit neglected, so I decided to pull it all apart and paint the frame, clean everything, replace anything that needed it, etc. Since I've heard so much about the stock piston grenading on these bikes, I also did a top end. The piston skirt is cracked in 3 places, so I'm glad I'm doing the top end. Luckily, nothing wrong with the bore, it looks good and measures out just fine. I decided to do the RB head and carb mod because of all the praise these mods got.

Just got news from RB that the head was already milled. And milled a lot. He says it was milled down at least .040 inch with no changes to the cumbustion chamber. He said I should definately be running race fuel with that head and there wasn't much he could do with it.

I wasn't planning on doing any kind of mod that would have me run race gas. I ran premium in it at 40:1 mix with castor927 for one ride before I tore it apart. it never pinged, it ran great up top, but bogged a bit if I snapped the throttle open from idle. So what can I do? I can probably get another stock head for it somewhere and start from there, or try running this head. Ideas? I really don't want to spend 15 bucks a gallon for fuel...4 bucks for premium is bad enough, lol!

if it were my bike I would ask Ron what his thoughts are on milling down the piston to match the head
I understand it is hard to see exactly were it will sit without the rest of the motor but if he is sure the head is milled 40 grand why not have him mill 20 or 30 of off the piston ?

(seeing as how I don't know how far he would usually mill down the head for compression, squelch quench and quiche he would be the one to ask)

either that and spend the money on a new head and have that send to Ron to work his magic on

What about using a thicker head gasket?

I would just pickup a used head from eBay and start over.

I'd still have him mill the combustion and squish area of the head.
If you don't want to mix in race gas or av gas , then run two head gaskets.
I'd reccomend to spray them with Permatex Copper coat.

Timtee wrote:I would just pickup a used head from eBay and start over.

+1
i'd get a stock one, send it to rbd, then sell my old one to a racer or someone interested in runnin race gas.

scheckaet wrote:

Timtee wrote:I would just pickup a used head from eBay and start over.

+1
i'd get a stock one, send it to rbd, then sell my old one to a racer or someone interested in runnin race gas.

+2!

thanks for the replies! I am a little short on cash at the moment, so I'm tempted to just run it with premium and see if it works ok. It wasn't pinging or anything before I took it apart running on premium. If it doesn't work, I'll just get a used head and start over.

by the way, I got an email saying I got a personal message on here, but it won't let me view it...

oh, one more thing, what else would be common as far as mods to these engines? I'm kind of wondering now if anything else was done. Do people mill the base down too to change the port timing? I wonder if that was changed also, or if it was stroked or something? I better check as much as I can before I put it back together so I know what else might have been done. I measured the bore, 69mm exactly. It looks pretty good too, I don't think the motor has a ton of hours on it.

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russell3 wrote:thanks for the replies! I am a little short on cash at the moment, so I'm tempted to just run it with premium and see if it works ok. It wasn't pinging or anything before I took it apart running on premium. If it doesn't work, I'll just get a used head and start over.

by the way, I got an email saying I got a personal message on here, but it won't let me view it...

Even if you don't have Ron do any work to this head , I'd still consider the 2nd head gasket option if the motor pings alot.
Maybe your fortunate to have good premium pump gas where you live and thats why it didn't ping before.

I doubt if anyone stroked the engine but they may have done some port work which you could see with the reed cage removed.
Probably not though as they left the stock piston in there. It was a crude attempt at a local machine shop, I'm sure.

Not here to step on anyones toes or call right or wrongs. But i would have him recut the squish band to correct angle and run it. I think you will be fine on pump gas. If detenation does come into play, you will be suprised what a little jetting or timing change can do.

FWIW, cutting the piston or adding base will alter the port timing....an extra head gasket will not. If ron thought he could reshape the squish to help he would've likely given you that option. If it didn't ping before I'd try it, you might be able to get away with a little tolulene in your gas or slight timing adjustment. It also may have not pinged before because it was too rich which will aid in preventing detonation. If it's a pinging mess, get a different head. If you hear detonation you should baby it home.

I agree with Fuzzy. Nothing lost by giving it a shot. If it's pinging, limp it home and start shopping for a replacement.

Don't forget to check piston to head clearance