KX310 performance

[KX'er]

I finally have my 310 running like it is supposed to after finding the small air leak in the base gasket. I really like the way it runs, but it seems to sign off early once I hit the meat of the powerband. I almost cannot shift fast enough. Anyway, what are some things I can do to let it pull each gear a little further, i.e. more top end?


BTW, it is ported for "mo better everywhere". The low end and midrange are great! Just looking for a little more top.

 

[crkid]

Did you rejet after getting it ported? If not, maybe try a larger main jet. I know I went too small on the main and my bike was signing off after 3/4 throttle.

 

[EricGorr]

If a 2-stroke drops off on top end it could be due to these reasons;
1) The timing is too advanced, retard it to the far mark on the stator plate by rotating it counter-clockwise.
2) The main jet is too small, jet richer.
3) The silencer packing is blown, repack the silencer and check for heavy carbon residue at the front and back of the pipe.
4) The yoke in the KIPS system may be broken. Remove the plastic cover on the lower right side of the cylinder and rev the engine. Make sure that the rack is moving in and out in accordance with rpm changes. Rev it up and it should move out. If it doesn't then the yoke is broken, thats common on KX250s 1987-2002. That part is located under the right side engine cover. There is a picture in my book of what the broken part looks like.
Good luck

 

[KX'er]

Thanks for the replys guys. I just repacked the silencer, so I know that is ok. The timing is stock, I'll try retarding it. I'll check the KIPS the way you stated. I'll try richening the main after I try the other things. I don't really have anywhere that I can Hold the throttle wide open for more than 5-10 seconds, which I know is required for a proper plug chop; so actually, I really don't know where I am at on the main.

I also have a slight problem at 1/8 throttle, as in it acts lean. But at this throttle position it smokes alot. It doesn't smoke at all at other throttle positions.. What could this be? It feels lean, but smokes?

Anyway, thanks for the help!

 

[afm_722]

I can attest that my 310 loves fuel and I'll let you know my jetting and setup in a minute! First things first. The bike ain't going to rev to the moon like a 250. Instead, you'll learn to shift less and ride a gear higher in most situations feeding a little clutch in when needed. Once accumstomed to the new powerband, your going to love the motor (after it's jettted right!). Treat it like a mini-Open bike.

My bike's setup is as follows. Mo Better Everywhere Porting, Stock pipe, silencer, ignition retarded (about 1/8in. on stator plate), V-Force intake, stock gearing

Jetting on pump gas (you're not going to believe it!):
pilot: 58 (stock is 52)
needle: NALH on 2nd clip from top (stock is naff...about 5 size difference!)
main: 165 (stock is 160)

I plan to go to an FMF Gnarly here pretty soon, so I'll let you know if my jetting needs changing. Anway, start tweaking one at a time. If the reeds are fine, try a richer pilot, clip position 3 (if you're using your stock needle), and a 162 main. Go out and ride it and it should feel better. Error a bit on the rich side with this motor, plus experiment with retarding the ignition but don't go too far!

My bike's a little on the rich side in the beginning of a moto (20-24 minutes), but still has great power and doesn't ping at the end of the moto. The engine suits the KX chassis very well and is great for trailriding.

Good luck and let me know if you have any questions!

 

['00kx250spode]

I had a hesitation at about 1/8 throttle as well. I found that I needed a needle with a fatter (leaner) straight part (ie, N3WF rather than the stock N3WE). Hesitation is gone and I'm getting less spooge. What may feel like a lean condition was (in my case) a rich condition.

Here's my current jetting. I'll probably play with it some more - although the bike is running really good now. I don't feel the need to shift early. My bike pulls and pulls. No noticeable vibration, either. I have the stock pipe and VForce reeds and I run straight VP C-12.

pilot: 50
main: 152
needle: N3WF with clip in 2nd pos from top

I see that I'm going much leaner than Ted. I have the '00 model, though. Perhaps being too rich causes the bike to not pull as well at open throttle and high rpms ???

 

[afm_722]

Hard to tell. I'll tell you there's no way I could even run stock jetting on pump gas. Back when I still had close to stock jetting, I raced at a sand track on a very cold day in December (2000) and she was way lean. I richened up the needle clip postion to get through the day, but it was pinging too much.

I see several differences between spode's and my setup. You said your running straight race gas. I presume you told Eric this as part of your setup? There's a world of difference between straight race gas and today's pump gas. Running straight race gas with the cooler/slower burn will improve top end just by itself. I basically have jetted my bike for pump gas for the convenience and less cost.

The setup I arrived at was after hours of riding not just a few laps around the course. I want the bike to be strong at the end of a moto or ride. In the past when I thought I had it perfect, it would ping a little toward the end of a moto so I ended up with the tad richer settings I have now. I haven't touched the setup for a year and it has proved to be very versatile. Cold days, sand tracks, hot days, all that is needed is maybe a little change on the air screw. No problems with fouling or spooge and the plug has a nice tan color.

Well, I hope this helps!

 

[Mack Reed]

Hay guys
I just got my top end done by Eric. I did the .80 over (265cc) on a 00 kx 250. I think that my bike is vary flat on top end. I have 50 pilot,N3WE needle in the 2nd clip,and a 155 main. I use 93 pump gas. Just as KXer said his bike felt is the way I fill about mine. I also fill a hesitation just in the start of the mid range.

Has any one made any changes to the power jets? I have some smaller ones on order. Going to try those to see if that will help the mid range. As far as the top end power I am not sure which way to go. Any suggestions would be appreciated. Thanks, Mack

 

[ML536]

In addition to the jetting changes, maybe it would be a good idea to gear it up. Gearing it up will allow you to pull each gear a little longer. Plus, with the extra power your bike now has, pulling taller gearing should not be a problem.

Have any of you guys with KX310s played around with the gearing on your bikes?

 

[Senior KX Rider]

The 310 will easily pull taller gearing. Before I went to 310ccs, I had 3teeth more than stock on the rear. Right now I run 1 less than stock and when i know I am not going to be in the tight stuff I have a countershaft sprocket that is 1 bigger than stock that I put on. It pulls that gearing easily :cool:

 

[afm_722]

Mack, It depends where you live, but I take it your not 3000ft above or below sea level?! :) I don't think you want to mess with the power jet. It will just confuse the jetting process (unless your a factory mechanic). Even Tom Morgan says don't mess with the power jet. Anyway, as per my previous reply, there's no way I could run your settings. Way, way lean. Ping, ping, ping. Go back to the stock pilot, a 2 step richer needle (on clip #2) and a 162 main for a baseline. Don't forget to fine tune by retarding the ignition timing a bit (definitely noticeable). You can fine tune from there, but I think your lean for pump gas.

Case in point, my bike would pull the hill at Mammoth fine with a 158 main, but it would pull it much better with a 160 (using stock needle at #2). A 162 ran well too, but it was a little flat. I put the 160 back in there and it ripped. This is at over 7000 feet mind you. My buddy had similar results on his KX250. Everyone tries to run too lean up there and I think it happens down here at sea level too. KX's (250, 265 or 310) like a fat main when running pump gas. Let's face it, the gas quality is getting poorer and poorer and we have to jet accordingly. I'm just a cheap ******* that looks for premium without ethanol in it! :)

As far as gearing, I run Vet Int. MX and used to always run just 1 tooth (49) larger on the rear (on my KX250's) for the outdoor style tracks I race (Mammoth, Glen Helen, Hollister), but with the 310 I have found that stock gearing is best. I know it'll pull a 47, but I like the 48.

Cheers and happy tuning....

 

[Mack Reed]

Ted
Thanks for the reply. I will take your advice on the power jet. I am going to try a 158 main. The 160 main (stock) ran fat on my bike after I got it bored .80 over. I tried the 155 becouse that was all I had at the time. The plug test shows a little on the white side,or lean.

Where I live the temps. are in the low to mid 90s now at about 1000 feet above sea level, and the humidity is about 95%. So I think that things sould be on the rich side if you were set up for cooler weather. I will keep you posted on the results. Thanks, Mack

 

[afm_722]

Good man Mac. Well guys, I took the leap and went to race fuel. Unocal 110 leaded, an FMF Gnarly/silencer(long), and changed the spark plug. The only problem about the whole process is I waited way, way way too long to do this. Before we get to the engine's performance, let me tell ya I've been extremely tight on funds in the last year, but I was still able to ride/race because the 310 lasts works less hard.

This is embarassing to say, but this motor has at least 100 hours on it. When I decided to upgrade to race fuel and the pipe/silencer combination I borrowed the service manager's snapon compression guage. The reading (210) could have been inaccurate, but the gauge couldn't be that bad off. Bottomline, this motor is still fresh. Eric says "run it!", so I do as Eric says and when I dropped the fuel in there and went back to stock jetting except one leaner on main (158), this thing came alive into something I've never ridden before. The smoothest, fastest mid-bore I've ever ridden. Not even recognizable from my previous good stock pipe, pump gas combination. The bike is so much smoother and the powerband wider than before, that it's ridiculous how good it works. After putting the 110 in my bike, I just added a year to it's life in my garage. It's like having a new bike again. Plus, the light tan (spooge what's that!!) color inside the silencer looks factory!!

Your probably wondering what the GPn310 is. It's a project to help the West coast get enlightened about the wonderfull 310. Too many around here have jumped on 4-strokes or defected to other brands, and haven't done any better in there results. What a concept it would be if I could offer a known good suspension setting and motor/jetting setting and package it as a kit for the KX rider. I'll have a package that has a "Stage 1" 50/50 race fuel/ pump setup, a 100% race fuel setup (yes!!) and in a pinch the "pump" setup. Things like extra copper gaskets, and exhaust o-rings also to help keep the "dated" KX tight. I know the 99-02 setup so well, it's time for me to share the wealth!

In today's economy it's pretty compelling to take a $3200 used KX250 and add a kit (including a suspension revalve) to it (that absolutey spanks a brand new 2002 250cc. doesn't matter which brand!!) for thousdands less. Excusme me, I'd rather have the better bike for thousands less, but that's just me. Plus, don't you hate it when you just get the bike dialed in you sell it and start the whole process over again. I may scoop up a couple used 250's and play around with different disciplines. The Canondale motard is going to get ripped a new one for half the price!! My little operation will take 99-present Kawasaki's and offer a motor and suspension combination and package it into a real world moto, dtx, motard or trail weapon. PPC racing has been born.......

Wish me luck! I just can't relate to the magazine articles anymore that talk about high zoot 250's modified to the hilt that only a pro can ride. My buddies full zoot 250 from somewhere in Az is a piece of crud compared to my dialed Gpn310. I guess at 34, that's the cutoff point for buying into what we're "supposed" to ride. No cnc machined wheels, blah, blah blah. All products that enhance the performance of the rock solid 99-present chassis. Also, where it gets really compelling is I will be offering my kit through a dealership somewhere in California. If I can get out the door somewhere or near a CRF and have that 310 motor with a dialed suspension setup for the real world, I say "where do I sign!" Since the cylinder is the same (save for the slight exhaust port change) we can make '03 KX310's. Man, that motor in that chassis! That's going to be a tough combo to beat in Vet racing!! I won't put my name on anything unless it's good. Thanks Eric for saving me money during these tight times, I plan to use that type of approach as well. The SoCal boys better watch out.....oh yeah with my Expert roadracing background itching me from time to time, I can't wait to take the GPn310 out to a Motard race. As Eric says, the transformer. Mammoth MX one weekend, Mesa Marin Motard the next!

Going to test ride tomorrow at a friends practice track and I'm fairly certain this thing will walk away effortlessly from his 450 now. Looks like he'll need to get an upgrade kit for his bike....it never ends!!

 

[MXTex]

Congratualtions afm_722,
I can tell you are passionate about your new business potential. I agree with you whole heartedly regarding the rationale, or lack thereof, of totally dialing in a bike only to sell it and start over. You should have plenty of customers. With that said, is there much difference between a 98 model KX250 and the 99 to present models you are familiar with? My 98 motor is currently with Eric and Jim getting a rebuilt lower end and .080 over cylinder. I'm wondering if my jetting will change much with the 2mm over cylinder. I considered upgrading bikes but like the feel of this bike so much elected to perform a full rebuild.

Thanks,

Jim

 

[afm_722]

JIm,
There's many a day where I miss my '98!! Even though the motor was bone stock with a pro circuit pipe/ shorty runnin' on pump, the suspension was dialed and it was a great package. I had great results and rode aggresive on that mule. I just got my '01 there (because my suspension took forever to get dialed in...I experiemented and it bit me!! I'm going back to known good!!)

As far as your bike, no problem we'll get the jetting dialed in. Pretty easy. Just to tell you though, my formerly noisy KX is much much quieter and smoother (not exhaust noise, but engine noise beneath me) since I started running the 110 leaded vs. pump If you're racing, do yourself a favor and step up to at least 50/50. It's worth every penny.

As far as the chassis, I just take into account years of metal faitgue. I rode the stink out of my '94 and by the time March of '98 rolled around it was pretty tired (not to mention an incident where the footpeg mounted pulled away from the frame...ugly!). So, because I have had such good experiences with the 99 and newer chassis (my buddies '99 is fresh as a daisy...only installed a pivot works linkage) I'm going to stay with a known good. Of course, we're working on an '03 package as well.

Thanks for the kinds words. I'm tired of my buddies getting taken by the boys in SoCal including the franchise I got taken by down there. I have a known good engine builder and a know good suspension tuner that I will be using now. Put the two together and you have a good all around package. MX, Trailriding, Hare Scrambles.....and in the future for me Motard...yes!! You know a bike's setup when anyone who hops on it says damn that's nice. That's usually what everyone says when they hop off my bike! Time to share the wealth, without worrying about getting wealthy!! Good value is what we're after.

Kawi's will make a comeback!!