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KX65 bottom end power?


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19 replies to this topic
  • luckystar64

    TT Bronze Member

472 posts
Location: Ohio

Posted September 08, 2008 - 11:51 PM


What can be done to boost the bottom end of the KX65 power curve to make it easier to ride? The top end seems fine-- it would be nice to spread out the power some-- is it possible?

So far, I'm thinking the Lukes' 85cc kit with a KX85 carb. Anybody ever ran this setup? And with what pipe and silencer? --L*64

  • matt4x4

    TT Addict

3,167 posts
Location: Ontario

Posted September 09, 2008 - 05:19 AM


The kx 65 being a tiny whipper snipper jug isn't going to make any bottom end power, period.
It's meant to be ridden on the pipe, just keep the revs up, slip the clutch when needed and you'll have lots of power all the time.
You can attempt putting in a big bore, I highly advise against it though unless you like rebuilding engines.
The kx65 is a little soft on the big end bearing, and giving it more power can easily cause big end problems if you keep the stock crank and conrod.

If you get yourself a hotrod crank and then do the 85cc top end, you'll have a much better chance of keeping the bike amongst the living.

  • luckystar64

    TT Bronze Member

472 posts
Location: Ohio

Posted September 09, 2008 - 11:29 AM


Is the Hotrods crank better than stock? How does a stock 65 run with just a pipe, and an 85 carb? --L*64

  • makKX250

    TT Gold Member

1,136 posts
Location: Oregon

Posted September 09, 2008 - 11:55 AM


A larger carb will only help the top end. A smaller carb would work better for more low end - smaller bore moving the same amount of air equals higher air velocity and more efficiency at lower piston speeds. :thumbsup:

  • JAMRACING21

    TT Titanium Member

2,827 posts
Location: Utah

Posted September 09, 2008 - 03:18 PM


if you want it easier to ride in the bottom end but still have power, i have seen 5oz flywheel weights for them, that should work
12oz being the biggets ive seen,

if you just want a ton of power in the low end, a pro circuit pipe is a lot better on the kx65 then the fmf, in fact the OEM pipe has more low end then the FMF, but the FMF does have a better top end then OEM,
boyesen rad valve will wake it up a little also.

also the a 48 or 49 tooth rear sprock works well for a little more bottom end but still a ton of top,

  • luckystar64

    TT Bronze Member

472 posts
Location: Ohio

Posted September 09, 2008 - 05:18 PM


Is there any type of porting that will help out the bottom?

I only rode the KX65 briefly... I borrowed it, and rode it on a pitbike track for a little bit. It was hard to ride because I couldn't get my foot under the shifter, and the suspension was soft as butter for my 140 lb. @$$. With those items addressed-- it should be alot better. --L*64

  • scalejockey

    TT Addict

4,641 posts
Location: Idaho

Posted September 09, 2008 - 07:18 PM


A Kawasaki bullitin came out years ago about giving more low end to the little bikes.
Run a second head gasket and remove the same amount from the base of the cylinder(this lowers the ports), retard the ignition a few degrees and run a small flyweel weight,add 8mm to the head pipe.

That's where i would start..

  • luckystar64

    TT Bronze Member

472 posts
Location: Ohio

Posted September 09, 2008 - 08:16 PM


Very interesting... Are any of the aftermarket pipes 8mm longer than the stock ones at the head? What do they consider a small flywheel weight? 5 oz? --L*64

  • harrperf

    TT Addict

3,396 posts
Location: Texas

Posted September 09, 2008 - 08:33 PM


A Kawasaki bullitin came out years ago about giving more low end to the little bikes.
Run a second head gasket and remove the same amount from the base of the cylinder(this lowers the ports), retard the ignition a few degrees and run a small flyweel weight,add 8mm to the head pipe.

That's where i would start..


HMM....


I don't see retarding the ignition helping here. Advancing it, yes.
:thumbsup:

  • scalejockey

    TT Addict

4,641 posts
Location: Idaho

Posted September 10, 2008 - 05:38 AM


HMM....


I don't see retarding the ignition helping here. Advancing it, yes.
:thumbsup:


Retarding it gives it a less "hit" on the transition to top end.I use this on my own kx 125 when i ride in the woods.It really works well!

  • scalejockey

    TT Addict

4,641 posts
Location: Idaho

Posted September 10, 2008 - 05:44 AM


Very interesting... Are any of the aftermarket pipes 8mm longer than the stock ones at the head? What do they consider a small flywheel weight? 5 oz? --L*64


I would think 5 OZ would be good.Iv'e built larger ones for 80s' but it really kills ALL the power.As far as longer pipes? I'd normaly make a slice of pipe and weld it about 1" down in the header pipe area.The worst part is getting all the pipe mounts to fit afterwards.:thumbsup:

  • harrperf

    TT Addict

3,396 posts
Location: Texas

Posted September 10, 2008 - 09:55 AM


It delays hp so to speak....less bottom, not more, and I think he wants more.

  • luckystar64

    TT Bronze Member

472 posts
Location: Ohio

Posted September 12, 2008 - 12:37 AM


Yeah-- the top is plenty strong-- it needs some bottom. I'd almost trade top for some bottom and mid. --L*64

  • matt4x4

    TT Addict

3,167 posts
Location: Ontario

Posted September 12, 2008 - 04:27 AM


small 2 strokes aren't going to give much bottom end - it's just the way it is - esp with your weight, if you want bottom end on a 2 stroke, you really have to go with a 250, even 125's lack in that department.
anything you do might improve it some, but not enough to counteract the weight of the rider - if you were an 70-80 lb kid - it'll make a big enough difference, however, at nearly twice that, you'd need 2 65cc engines.

  • scalejockey

    TT Addict

4,641 posts
Location: Idaho

Posted September 12, 2008 - 06:28 AM


Retarding the timing does delay (mellows)the power hit but with that you can run it at a higher RPM range and be in control.
Controlable power and low end power are two different things.
Try it you will be amazed!The overall feel is that you have more low end.

  • luckystar64

    TT Bronze Member

472 posts
Location: Ohio

Posted September 12, 2008 - 01:31 PM


This project is on deck after my 140 build is done. I only rode o 65 briefly at the local track. The suspension was more of an issue than anything. That, and that I could barely get my boot under the shifter.

Back in the 80's, I was an 80 rider. I remember putting the Kawasaki offered 99cc top end on my KX80-- (that was before they offered a KX100). You just bolted it right on, and rejetted the carb, which simply consisted of a one size larger main... and off you went. With that 99cc top end, the bike was way torquier all across the board. I was thinking the same would happen with the 65/85 big bore.

I don't care if I have to drop a crank in the bike every few years. The bike won't get a ton of hours anyway, as I have a modded stock 110 that takes most of the abuse I can dish out, and never misses a beat. I whoop that bike for hours and hours on end! In addition to that bike, I have a mod 110, and a soon to be finished heavily modded KLX140. This KX65 will just be another project in the stable. Any input on the big bore with the stock carb as opposed to the 85 carb, add a pipe and flywheel weight? ---L*64

  • scalejockey

    TT Addict

4,641 posts
Location: Idaho

Posted September 12, 2008 - 02:17 PM


This project is on deck after my 140 build is done. I only rode o 65 briefly at the local track. The suspension was more of an issue than anything. That, and that I could barely get my boot under the shifter.

Back in the 80's, I was an 80 rider. I remember putting the Kawasaki offered 99cc top end on my KX80-- (that was before they offered a KX100). You just bolted it right on, and rejetted the carb, which simply consisted of a one size larger main... and off you went. With that 99cc top end, the bike was way torquier all across the board. I was thinking the same would happen with the 65/85 big bore.

I don't care if I have to drop a crank in the bike every few years. The bike won't get a ton of hours anyway, as I have a modded stock 110 that takes most of the abuse I can dish out, and never misses a beat. I whoop that bike for hours and hours on end! In addition to that bike, I have a mod 110, and a soon to be finished heavily modded KLX140. This KX65 will just be another project in the stable. Any input on the big bore with the stock carb as opposed to the 85 carb, add a pipe and flywheel weight? ---L*64


Wait... how much does the rider weigh?? If it's over 90 lbs. forget trying the retard the igntion thing,get a bigger piston!

  • luckystar64

    TT Bronze Member

472 posts
Location: Ohio

Posted September 13, 2008 - 05:10 AM


145... Hahaha! This 65 is going to be another pit bike project of mine--- two stroke style. I'm thinking of what I can do to make the power rideable for a 145 lb. adult.

So far, I already know that I can do something with the suspension. I have a KX65 front end on my KLX110 race bike-- Minibike Springs makes some terrific front springs for it. It will probably take a custom rear spring out back.

I'm going to need a KX125 shifter...

Motorwise... I'm thinking an 85cc big bore, lower gearing, a flywheel weight, V-Force reeds, a low/mid range favoring pipe, and some kind of spacer I've heard about in the reed block area. ---L*64

  • mjruopp

    TT Bronze Member

262 posts
Location: North Carolina

Posted July 02, 2014 - 09:49 AM


Looking to retard the timing for my kid's KX65 to soften the hit. The manual shows rotating the the stator plate clockwise (counter crank rotation) to retard timing... Correct me if I'm wrong, but isn't that backwards?

  • greg-15

    TT Bronze Member

273 posts
Location: California

Posted July 17, 2014 - 08:02 PM


What can be done to boost the bottom end of the KX65 power curve to make it easier to ride? The top end seems fine-- it would be nice to spread out the power some-- is it possible?

So far, I'm thinking the Lukes' 85cc kit with a KX85 carb. Anybody ever ran this setup? And with what pipe and silencer? --L*64

What can be done to boost the bottom end of the KX65 power curve to make it easier to ride? The top end seems fine-- it would be nice to spread out the power some-- is it possible?

So far, I'm thinking the Lukes' 85cc kit with a KX85 carb. Anybody ever ran this setup? And with what pipe and silencer? --L*64



Leaving the bike stock will give you the best low end. Agree there made for mostly top end only. I had a FMF SST on my Son's bike and it really had all top end. The kids out grow this bike quick so by the time you done tinkering the 65 they will be on a 85 or 100.





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