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Kx65 power curve

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Looking to slow down the powerband on a new to me kx65 for my son, took him off the klx110 and moved to a clutch. The 85 was to tall still but he needs more suspension so 65 it is.

 

Looking at the spacer option in the carb( rubber hose?)

Looking at the throttle tube from g2 ergonomics? Opinions or thoughts ?

Looking at the spacer/washer in the exhaust to keep the bike from hitting the pipe so hard?

 

Pictures or brainstorming.

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I had the same issues (before throwing in the towel and going ktm).  Tried washer in exhaust -- didn't like it.  Motor runs terribly.

Best result came from: Boyesen dual-stage reeds, Moose torque spacer between reeds and case, FMF Fatty pipe.  Also play with timing -- slightly retard.  

These help but only modestly.  Good luck!

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2 hours ago, bespyder87 said:

I had the same issues (before throwing in the towel and going ktm).  Tried washer in exhaust -- didn't like it.  Motor runs terribly.

Best result came from: Boyesen dual-stage reeds, Moose torque spacer between reeds and case, FMF Fatty pipe.  Also play with timing -- slightly retard.  

These help but only modestly.  Good luck!

Did you try a flywheel weight? 

 

I am in the same boat as the OP, only my son is coming from a KTM 50 Pr Sr. Just picked up a KX65 that has a bad crank. I am rebuilding everything and will be throwing a FWW in it to help mellow it out some.

Also looked on the Eric Gorr site and he does some porting work on the smaller bikes have broader power for trail/enduro.

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I haven't had a chance to try anything yet, the boy had a need of an attitude adjustment so the bike has been stored for a few weeks

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Just to follow up, I found that the KTM carb spacer kit fits perfect into the KX carb. Ran it today with the Half throttle spacer and it worked fantastic. That's the route I went

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My boy had a KX65 and he was initially small for it and learning the clutch on it too.

Found good low RPM torque with these mods:

1. Moose Racing torque spacer (between reed valve and cylinder intake).
2. Taller gearing. Went up one tooth on the front. Much less shifting.
3. Lowered the cylinder ports. I took the cylinder to a motor machining shop and asked them to shave 0.25mm off the base. Cost $80.  That also tightened the squish clearance to 0.8mm (in our specific motor) and with the stock head if brought the compression up a bit.
4. Then with new jetting (leaner for the tight squish) the little motor produced very linear power from bottom to top. Gone was that little mid-RPM hit. I thought the higher comp might hurt the high RPM power but it didn't seem to, and my boy didn't rev it hard anyway.

Edit: be sure to measure your squish clearance before shaving the cylinder base, to work out how much to take off the base. The base shave limit is from the squish being too tight or compression getting too high.  Higher comp will wear out the rod bearings faster (for the same RPM+loads).

Edited by numroe
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I don't think he will be on it long enough to go full motor work on it, the spacer would be easy enough for me to do for sure, the gearing has already been changed from previous owner, need to see what stock is and what it is currently running.

Does anyone have a link to the free owners manual for these bikes?

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No full motor work required. Just get the base shaved when you have the cylinder removed. If cost is the issue then maybe you can buy a thinner base gasket so it costs $30 instead of $80.

 

A lager front sprocket costs nuffin in the bigger scheme of things.

 

Most kids who have a 65 ride it for one year and how much they enjoy that bike often shapes their attitude to riding for the next 5 or 50 years.

 

A KX65 rarely bests a KTM in a race but the little KX can be super fun for kids and very reliable.

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The throttle/carb block worked just perfect and only took a matter of min to install. He rides it's pretty well be is still timid of the sound even

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