Jetting for 225

[kaw Bill]

Has anyone dialed in the jetting on there 225 yet? I know there were some concerns a few weeks back but I havn't been to this site for a while. I havn't had a chance to ride mine yet. All I can do is stare at my KDX knowing there's more displacment than there was last year.

kaw Bill

 

[Mac]

I have been working on my jetting for the past few weekends and I keep getting closer but still not there.

The type of carb/pipe will also affect your jetting.

I think my case is a little unique because most run the 152/155 main 42 pilot but this is way too lean for me. Last ride I ran 160, [email protected], CEL-4, #8 plug and this was still a tad lean. If I held WOT for more than 5 full seconds the bike would ping.

I will be back out tomorrow with 165, [email protected], CEK-4, timing retarded 2deg and temps will be in the 80's so I'm hoping this will be slightly rich.

The bike pulls great and is much better than stock but this occasional ping forces me to jet richer.

I started with my old jets but If I had to do it again I would start with a 160 main and go from there.

Say, you dont have a compression tester do ya? I measured 210psi and was wondering if they were all this high.

I really dont understand your statement "I havn't had a chance to ride mine yet. " that just doesn't compute!!

 

[canyncarvr]

Mac:

Maybe this comes under the heading of dead horses and beating...but why is it your bike seems so different from others?

BRush said something about '..need to get a compression gauge,' which I hoped he was gonna. Am I correct that noone else has posted a compression reading on their 225? I'd sure like to know what some of the other bikes put out. ...a lot of room for error in the test though..

What about your compression test....bike was hot? How many kicks to get 210#? You used a screw in gauge (as opposed to hold in).

What bugs me most about this is I'm considering the same kit...and quite frankly, don't need/want your result. What is going to happen to the range of your bike (miles/tank) with a 165??? I don't want to give up much of anything in the way of distance.

Hope to see more input on compression #s. C'mon guys...EVERYone needs a good compression guage!!!

 

[Mac]

Why is my bike different......good question, that's what I'm trying to find out. It's not necessarly a bad thing because the bike runs great and I know when I get the jetting dialed in it will be even better. Last week I ran with the 160 main and only burned 1.5 gallons and rode at least 30 miles.

No one has responded with their 225cc compression numbers :whiner: maybe noone else has a compression gauge.

I used a screw in compression gauge and kicked the bike 15 or 20 times when cold with part throttle. The bike was ridden earlier that day.

CC maybe you should get the 225 kit just so you can check the compression for me ;)

 

[Mac]

Well I tried a 165 main this weekend and it was way too rich yet when I held WOT for 30-40 seconds it would still ping occasionally...hmmm

I did some trailside jetting and threw in the 160main and it ran way better but still seemed rich and would still ping when I held WOT but was not as severe as before I adjusted the timing.....hmmm

I think I will stop trying to fix this problem with jetting and try something else. The bike ran very crisp with the 155 but pinging made me think I was lean....now I'm no so sure.

I will rejet to where the bike gives best performance and retard the timing to the full retard mark and see if this fixes the pinging. If this fails then it looks like high octane for me.

 

[canyncarvr]

Mac:
Although a 2-stroke's compressing anything is largely a matter of well-oilsealed rings (and thus the bike being cold may matter less), combustion pressure numbers may well be HIGHER on your bike if:

It's to operating temp
The throttle is WIDE open

...so your 210# may be a bit LOW! (ouch!)

Don't know if you've read this, but EG says to move timing no more than about .040", which is only going to be (about) a couple of degrees. While that's likely more of a problem if ADVANCING (cuz you might stick it), retarding the full mark will ALSO retard your bike's performance a good bit.

Drag race your buddy, retard it a full mark and do it again. The difference will be apparent.

Thanks for the continued input on this. Yanno...if all else fails, I guess I'll just HAVE to send mine into EG just for comparison!

Don't suppose you happened to cc your head? That would be interesting, too.

 

[kaw Bill]

I'm starting to regret having this mod performed. I still havn't had my bike out yet but it sooks like I may end up spending a bit of time tinkering.

kaw Bill

 

[Mac]

Kaw Bill, ride your bike before you have any regrets and when you can't wipe that grin off your face then you'll know it was money well spent.

My problem could be unique, haven't heard of anyone else with a pinging problem like mine.

But for those that would like an update:

Last weekend:

timing retarded to full retard mark
155main, [email protected], CEL-4

Bike ran great with this jetting as far as throttle response and topend power but I still had pinging at WOT and sometimes when I let off the throttle it would ping a few times. I do run the bike pretty hard before it pings but that's how I ride, like an MX bike.

So...Even though I can reduce the pinging problem with timing and jetting it's not worth the tradeoff in performance. I'm pretty sure my fuel needs more octane.

The local gas station (Haffners) sells Cam-2 I think at 3.95/gal. This weekend I will try 50% premium pump cut with 50% Cam-2.

 

[canyncarvr]

I just read a jet list from BRush. Seeing as he didn't post here, I took the liberty of adding it to this thread. The subject being, 'What ya'll running in your 225?' here's what one of ya'll is running:

From BRush:

My jetting too, is on the fat side of optimal which is kind of where I'm comfortable. 155,42, AEK-4, #7 slide, AS 1.5, 40:1 MX2T, Boyesen power reeds, mobil premium. I don't get any pinging at all with the BR7

Note: His #7 slide goes with his RB carb. The last sentence was pasted there from earlier in the paragraph...not meant to remove context, but adding the point that he runs a 7 plug and STILL doesn't ping. His AEK is way WAY leaner'n the CEK. Starts getting leaner about 1/2 throttle, and keeps getting leaner as the throttle opens.

mac: 'Full retard mark' is considerably more than 2º you mentioned earlier. What happened to the CEK you mentioned? Still getting detonation at that point would be (is) worrisome to me. Face it mac, YOU are the ONE rider standing in MY way of getting my OWN bike kitted!! :whiner: You just GOTTA get it sorted out!!! ;)

 

[Mac]

CC
I first tried 2deg retard but still had pinging so then I tried full retard which is 5 :think: deg not sure but it was lined up with the full retard mark on the stator. Pinging was much less but still there and throttle response was suffering.

Tried the CEK but the bike wouldn't idle and was too rich down low, CEL gives me a much better hit.

I'm pretty convinced my problem is octane but I'll know for sure this weekend. Maybe my local gas station is ripping me off selling me 89 octane and calling it 92 :|

Don't let me stand in your way CC I could be doing something stupid and since noone else seems to have this problem I think the 225 mod is good.

I also got a BPR8ES to try this weekend, maybe this will help reduce the pings at WOT.

 

[canyncarvr]

Mac: Please do drop a note about the BPR, ok?

 

[BRush]

Mac,

I was up in your neck of the woods this weekend doing the New Hampshire Classic 2 day Turkey Run in Loudon. You guys have some great trails. I'm assuming you had the "race gas-vs-pump gas" conversation with Eric before he did your kit? It would be interesting to know what he changes to accommodate one vs. the other. Sounds like you are on track with the octane issue. If it were me though, I'd start out with a tank of 100% race gas just to establish a no-ping baseline and work down from there, if you are planning to mix race gas and pump gas. One of these days, I'll have to get a compression gauge... :silly:

 

[Mac]

BRush stop in and use my gauge next time your around, then we can hit some trails. Howed you do at Loudon?

I'm hoping a 50/50 mix would be plenty then work my way down to 25/75 r/p I just need enough to boost the octane a little. It doesn't ping all the time only when I gun it and hold wot for more than 5 sec. I do remember filling out a form for Eric and selecting pump gas.

 

[Brian]

Hmm... Kind of cruel of me to say this, but... I'm glad someone else's bike pings ;) As canyncarvr can tell you, I've been complaining quite a bit lately ;) . I"ve just got a stock 200, but symtoms sound the same as you'rs. My bike seems to be jetted spot-on as far as performance, but I hear pinging under decelleration, wich leads me to believe that it may be lean? I'm already richer than most guys with my setup(I run stock jetting) and still get this pinging. I haven't toyed with timing yet, I would think I might do more harm than good if I started messing with that. But, by all means, say something if you get it fixed, cause I'm dying to know, too :)

 

[kaw Bill]

trust me, i've had the grin on my face in the alley behind my house. second gear power wheelies right of idle. this thing pulls hard. i just don't have the room to really open it up. the true test will be a particular sandy seventy five foot uphill section were I'll be riding over the holiday weekend. i'll give you the full report.

kaw Bill

 

[canyncarvr]

Bill:
Hopefully you can find enough room to do some extended WOT? I'd sure like to know what the ping factor is on your bike.

What's your current jet-set?

have fun. What...holiday weekend. What holiday is THIS weekend? Oh yeah...IT'S FLAG DAY!!!

Twist it to rabbit

.......that's funny!.......

 

[MassKDX]

Yeah it is Flag Day on Friday and Sunday is Fathers Day. Better than all of those is that it is Bike Week in Laconia NH this weekend (for the East Coasters). Too bad it is going to rain. :(

 

[kaw Bill]

I'm running an unmodified carb with the stock needle in the second from the top clip position 42 pilot and 155 main. Has anyone tried moving the needle up one notch?

kaw Bill

 

[Mac]

I run with the needle clip in #4, #2 gives me a lean bog off idle.

 

[kaw Bill]

Mac, are you running a modified carb?

 

[Brian2]

Mac, I'm not sure about 2 Stroke single cylinders, but when timing american V-8's retarding the timing is a bad thing. Granted a certain amount of advance will PING, but when done correctly will boost power. For instance, my 71' Pontiac likes 16 degrees of advance initial. That is at a low enough RPM where the mechanical advance(r) is not kicking in. This is also set up with the vacuum Advance canister disconnected so as not to screw up the readings. Later on at a higher RPM about 2000 the mechanical advance takes over from the vacuum and advances the timing into the 28-32 degree range. With the exception of the advance mechanisms in auto's, I think this would all apply to the bikes, no? It just means that we have to find the best timing for low and high RPM situations since the KDX's do not have any advance built in. Disclaimer: As far as I know. :)

 

[Mac]

Kaw Bill
My carb is stock 35mm.

Brian2
I only retarded my timing to see if the pings went away and they didn't. The only thing that has gotten rid of all pinging is a 50/50 mix of race/pump fuel.

Now that I know I need higher octane I need to know if Cam-2 is a good choice to mix 50/50 with pump or should I use a better fuel?

Klotz makes this stuff called Hitrate, has anyone tried this stuff? Looks like it could be a cheaper solution if it works.

 

[canyncarvr]

mac: Octane booster product from Clifford Research (called 106+ out here) is something you might try. It's the ONLY octane boost product I found to work. I wanna know what the chamber volume is between your head and say...BRush's head.

brian2: KDXs do have an advance built in. It's electronic. The CDI unit also RETARDS the timing at high rpm.