Best low end-mid pipe for 98 kx250

[dirk_411]

Doldguy, 5mm on the tecate crank.  I dont originally build these motors.  I dont have the the skill per say or the proper resources.   I can rebuild them myself. 

That being said.  The motor your looking at has the kx crank grafted into it to match the jug.  The pipe is dyno made for that motor.  ILR performance out in Wa.  The reason I am doing a new motor all stem from the desire to have a cool head.  Phat head.  So after reading I decided to commit to the "1851" jug.  Bought 5 of them all with PV's and 3 additional sets of new power valves.   That ultimately was the reason I wanted to convert to a kx250 jug.  The tecate power valves were brittle and not available.

Sounds like this motor is going to have some low end grunt by design from what you say.  Perfect.   I wonder if I should go for a mid-top pipe?. I run a pvl and the pulse induction system that's in the K5 threads.

Im really looking forward to the new motor.  I may not have it for this summer, unsure yet.  Here's a run down on whats going into it.

T4 lower end 6 speed
1851 jug, 310cc, port and polish, phat head running 50/50 blend of vp110 and 91 pump fuel
Tranny is under cut by fast by gast, NOS input and output shafts
Complete tranny and anything steel pertaining to shifting,  power valve, counter balance, kick start and even the back gear off the clutch basket is gone to CV products for micro polish
Pvl ignition
K5 hinson clutch basket
Pulse induction fuel intake

Im anticipating a fun bike.  My quad in the picks waxes that other T4 and im 80lbs heavier body wise than my buddy
 
Not to mention that ltr450 geometry with them 17" elka stage 5's. Will be 50".  No problem for trail riding here.  Going to be golden

That front end in the pics is the +3 set up using 08 yfz450 take offs and outfited with 16" dual rate fox's. I kept my hardkor front hubs, gafler rotors for these new lsr spindles.  Original T4 shocks were 14" and s**tty single piston calipers to boot.  Upgraded to custom +2 steering stem that is oversized and integrated the 250r 4 bolt frame clamp, kfx450r walsh lower bearing, precision pro model steering stabilizer and precision shock n vibe bar mounts that hold renthal fat bars.  Dynamite, threw in the fasst co brass bar inserts and reduced feedback ro the hands dramatically.   Bring on the stumps and rocks.  The new spindles shorten up my tie rods by 1 3/4" per side.  I think that will even improve feed back.


I just hyjacked my own post.  Anyways fun to see a couple of yahs interested.   Id have a tough time naming 10 people that are as deep into there kawasaki tecate 4 as me.  Id bet the farm on it

[dirk_411]

Those are some pretty quads. I am super jealous now. Cases anodized or is that blue chrome or some fancy paint? What pipe is on there now?

Thanks goat.  Me and my best friend really enjoy these old 2 smokers.  We were both born in 81. They are so rare. And furthermore we are in canada.  Ive bought everyone ive ever seen (5) up here.  Payed a lot of money to couriers to cart me up parts from the USA over the years. Only thing i use from the original T4's are oem palstics, frames and lower ends.  Everything else is hybrid.  I was 16 when I bought the first one.  Blue paint. Fairly fresh there.  Eluded to pipe in last post.

[dirk_411]

Im building a big bore 04 KX250,290cc. In 250 form I ran a Enduro Engineering pipe which worked well across the board. Its a pretty rare pipe, seems like they only made them briefly. Ive also used a Gnarly, good low and mid but signed off a bit early. The stock pipe worked well also. What pipe would you recommend with the 290? I have a never used Pro Circuit Works pipe and have been thinking that it would work well. They seem to be a mid to top oriented pipe. Im not new here Im the Flyin Hawaiian. Ive been having trouble getting on the site so I made a new acct. up.

Hey flyin Hawaiian.  I was told to ask you about my power valves governor spring.   Im running the 98-99 jug. I was wondering if I should try to swap my stock T4's spring for the 98-99 spring?  Any thoughts?

[Goat]

Since you're running the kx top end I would imagine upgrading the spring would make it a bit snappier. Especially since the t4 spring is probably from the factory when it was new

I'm now looking for a T4 to buy lol thanks for that I may even leave the 250 in it since I have the quadracer with a kx500 in it already.

[zz3gmc]

Im not sure of the diameter of the T4 spring versus the 98/99 spring. I have some powervalve governor shims that I used in my 90 KX250 and they wouldnt fit my 04 gov. I cant remember if it was the diameter of the shaft or the spring itself. Im thinking that the spring from the 90/91 KX and your T4 might be comparable in size since the engines changed in 92 and went on to 04.

[motopunk]

Im building a big bore 04 KX250,290cc. In 250 form I ran a Enduro Engineering pipe which worked well across the board. Its a pretty rare pipe, seems like they only made them briefly. Ive also used a Gnarly, good low and mid but signed off a bit early. The stock pipe worked well also. What pipe would you recommend with the 290? I have a never used Pro Circuit Works pipe and have been thinking that it would work well. They seem to be a mid to top oriented pipe. Im not new here Im the Flyin Hawaiian. Ive been having trouble getting on the site so I made a new acct. up.

welcome back flyin hawaiian ...    which piston size do you use for the 290 big bore?... 

i have an 96 engine bored up to 353,8 ccm.thats the absolute maximum ,you can get out of the 250 engine ... 74 stroke and 78 bore(modified piston from suzuki rm370) ..at the moment big trouble with the handmade headgasket and have to find a better solution... so i use in the moment a 03 stock cylinder with 66,4 bore on it = 270 ccm ...  real great bottom -mid and little bit less top end .  i plan to go to 72 bore with an old worn 95 cylinder that i have laying around.  i had a 2000 gasgas ec300 and i loved this added torque that the engine made... 

for the 360 engine we needed a special pipe... no kx250 pipe was working well enough ...  we tried next a modified ktm sx360/380-pipe .. better,but not the best result ... at least "van hasselt" in belgium made a pipe for us. with this pipe it felt very strong from bottom to top and in direct comparing 1,5 hp more than a stock ktm sx380 on the rear wheel. ;O) 

[dirk_411]

Im not sure of the diameter of the T4 spring versus the 98/99 spring. I have some powervalve governor shims that I used in my 90 KX250 and they wouldnt fit my 04 gov. I cant remember if it was the diameter of the shaft or the spring itself. Im thinking that the spring from the 90/91 KX and your T4 might be comparable in size since the engines changed in 92 and went on to 04.

I ordered an 98-99 and an 04 governor spring.  We'll see if either fit

[zz3gmc]

Let us know of your findings. I love tinkering with these engines. I shimmed the gov spring on my 07 KX250 with good results. The 07 has little in the low end with a monster hit in the midrange. Retarding the timing slightly and along with the shim helped noticeably smooth the delivery. Seemed to add a bit bottom also. Next step is having the head modded for more compression and add some more bottom. May try a APT Smart Carb too.

[Foxx4Beaver]

Im not sure of the diameter of the T4 spring versus the 98/99 spring. I have some powervalve governor shims that I used in my 90 KX250 and they wouldnt fit my 04 gov. I cant remember if it was the diameter of the shaft or the spring itself. Im thinking that the spring from the 90/91 KX and your T4 might be comparable in size since the engines changed in 92 and went on to 04.

I ordered an 98-99 and an 04 governor spring.  We'll see if either fit

ok you two have caught my interest enough to try some different setups on my 250 as well.

[dirk_411]

ok you two have caught my interest enough to try some different setups on my 250 as well.
[/quote]

EDITED.  March 13/14

I stand corrected.  I for some reason had it in my head that the oem power valve mechanism balls were stainless steel.  They are NOT stainless.   Void my reference to stainless



I found a read by eric gorr.  I am not an eric gorr fan because of the one and only time I spoke to him.  However I like to root through his literature,  largely impart because it's everywhere on the net.  So check out this brief read regarding the power valve governor mechanism.   It really sheds light on the possibility of combinations.  I have tons of tecate 4 PV gov. mechanism spares.  If anyone wants to exchange spares and do a little R&D let me know.  I would have endless combinations of KX parts to try.  Im kind of thinking if im running the "1851" jug I should start first with those parts.  After all im am essentially running the KX jugs for there improved performance over the T4 jug, and parts availability.   It could be entire mechanism swap or parts and pieces.  I understood the centrifugal operating principle but never pondered changing springs, ramps and SS balls.   Very interesting none the less.  Im thinking of playing with combinations on my current motor and then build this into my new motor.  I like the fact I sent the gov mechanisms shaft, ramp and cup for micro polish


The exhaust valves are opened and closed by a centrifugal governor mechanism. The governor is mounted under the right side cover and is gear-driven by the crankshaft. As the engine rpm increases, the governor spins, thereby increasing the angular momentum of the four steel balls encased in the governor. The steel balls fit into an angled ramp-and-cup arrangement. A spring is used to provide tension on the steel balls. When the momentum of the steel balls overcomes the spring’s tension, and the balls force their way up the angled ramp. A spool attached to the ramp, enabling it to change its linear position with changes in rpm, and the spool is attached to a linkage system that operates the exhaust valves in the cylinder. Factory race teams have different combinations of springs, ramps, and balls to tune the exhaust valve operation and enhance the powerband.

[Foxx4Beaver]

good write up, more info on the governor than I was aware of...I'm looking forward to experimenting on mine, but it won't be for a couple months, til the weather gets better/warmer...we have nearly 20" of snow on the ground right now and it's a balmy 14F .

[dirk_411]

Same here man. 

The Tecate 4 governor spring is used and is measured removed from the mechanism.

Height 24.05mm 
Width 25.30mm

Washers/bearings measured around 27.97mm

Stainless steel balls I believe are 5/16"

Would I be correct in saying the weight of balls and the rate of the spring effectively determine when the power valves operate?  If you went to heavier SS balls and a softer spring basically your PV's would operate at a lesser RPM? OR lighter SS balls and heavier spring rate they would operate at a higher RPM?  Am I correct?

If anyone can throw the kx250 and the kx500 measurements at me that would be great.  Include year and model

[Foxx4Beaver]

I think you're theory is spot on...it could be tricky finding SS balls that are the same diameter(for clearance in the governor reasons) that are heavier/denser...but as you stated, spring rate will play a major role in that also.

Very interesting.

[dirk_411]

After taking a look I noticed that the majority of kx250's used 3/8" SS balls.   There were a few kx250's in the late 80's to mid 90's that used the same 5/16" as my tecate 4.  I guess the next thing would be to know the weight difference between the 2 SS balls and the spring rate between my T4 and the various model kx250's.  I think im going to start with the 98-99 kx250 governor mechanism and see what can exchange

[Goat]

Good info. Now I want to play around with my 500 and kdx governor. I'm in the same boat as Fox with a ton of snow on the ground and really cold temps.