Smoothing out SX65

[rmcmichael]

Just moved my almost nine year old up from a Polini 50cc
with an auto clutch to a KTM SX65. We instantly found
out that the midrange hit on this bike would wheely it with
*ME* on it. Not good. My son's a beginner. We still have a
wheels-on-the-ground rule in effect. The bike came with
the Doma pipe and aftermarket reeds and suspension work.
The suspension is really sweet. Oh, it's a 2002 model.

Anyway, I removed the cylinder and head, packed them
up and sent them to Eric Gorr to smooth out the power
band for him. I'm getting the cylinder and head machining
for more low and mid.

I'll repost and let you guys know how it turns out when I
get it back from Eric and my son rides it.

 

[CaptainObvious]

I had the same concerns as you did last fall when I bought my son a KX65 to replace his XR70. I took one ride on it and said to myself "I have to slow this thing down or Connor is going to kill himself". Some things I learned (as a Dad):

1. Just because it wheelies real easy with me on it (180 lbs) doesn't mean it will wheelie just as easy with my 80 pound son;
2. Kids learn throttle control real fast when they see Dad riding 3rd gear wheelies on a 65;
3. Kids adapt to the power real fast and in just a few rides your son will be spanking the 65 like he did his 50.

I couldn't believe how fast Connor took to the clutch and the power. He started off on the bike real slow (after I told him he would get killed if he opened it beyond 1/4 throttle) and built up to the point of WOT in about 5 hours. The bike does not loop out on him because his weight is forward (teach him to keep his head over the bar).

Bottom line, your son will do better than you on his new bike.

 

[rmcmichael]

Hey, thanks, that's nice to know.

By the way, when I talked to Eric, he told me that
once my son got used to the SX65, it would be rather
easy to restore the top end performance. So it might
not be long before we do that.

It'll probably be another couple weeks at least before
we get the parts back.

 

[Jasle]

Also with your light weight kid on it the wheel will spin instead of hook up making wheelies harder. We ran in to this when we switced my kid to the Cobra DC65. It does not have much bottom end but when it comes on the pipe its freaking nasty!!! 2 peak HP more than the SX. We ended up using a KX for a while to learn how to shif for a few months and now he is having no problems other than remembering what gear he is in. BTW I am a 240lbs guy and this will loop me off on the road if I let it. My son is almost 60lbs and it does not wheelie easy just spins the tire.

 

[rmcmichael]

Just to let you guys know, I got the UPS package
with the SX65 cylinder and head in it back from
Eric Gorr yesterday. So, from the time I sent it
off to getting it back in my hands was about a
month.

Now, I just got to get it all back together........

 

[Mikey350D]

My son (novice) has similar problem ( he also races XR80: scrambles/flattrack)
I went down 2 or 3 teeth on rear sprocket
This toned downed the "snappiness" quite a bit.
I also noticed that kids coming off 50's (initially) have very poor throttle control.
I also put on Bud holeshot device (Todd at THRacng): The best 100$ I ever spent. GREAT for novice riders. Junior can launch at full throttle (on dirt) with NO wheelie!

 

[motoxmatt]

i to have my son on a 2 smoke kx85 . and in just a few hours he was in the peak band and only lifts the front when he sits back. but i have a kdx 200 and realy injoy my mid rang and would like more bottom and mid in his 85. its stock now. any body ever use a weighted fly wheel on an 85to take some of the snappynes out

 

[rmcmichael]

Well, he's ridden it four times since I got it back
together with a new top end. Wonderful. It still
has the top end hit. I guess you just can't get
rid of that on these small 2-strokes. But the bike
carburetes and runs really smoothly at 1/8 and
1/4 throttle now. So he's keeping the throttle
open partway, instead of blipping it and backing
off.

I haven't tried anything like a flywheel weight and
it's running so nice right now, I think I'll just leave
well enough alone. I was surprised that I didn't need
to rejet after Eric's work on the cylinder and head.