200 Pinging

[Brian]

Do any of your KDX 200s ping after you let off the throttle? Mine does if in neutral, rev slightly, and ping, there it is. It also does this under deceleration while on the trail. Is this a sign of lean jetting? It doesn't surge, and runs fine except for this, or is this another KDX noise? I checked Just KDX, and they have jetting reccomendations for a stock bike, but mine is stock except for a removed airbox lid. Any reccomendations? I'm planning on getting a PC pipe and silencer soon, and will I have to rejet then, too? I'm running Bel-Ray MC-1 @ 50:1.

 

[Fred T]

Stan, try raising your needle one clip position and see if that helps. Sounds like you a bit lean in the mid possibly - remember this is long distance internet jetting. I could be wrong but it won't hurt anything to try. Another option is a larger pilot or possibly turning in the air screw.

 

[Brian]

Thanks, I'll have to see what I have now, just got the bike used. Any suggestions for a stock bike w/o an airbox lid? All jets and needle position? Thanks

 

[gooby]

i'de say yes u need to rejet when u do the pipe mods ,u really need to rejet a stock bike too but....start with the justkdx site baseline and tune like fred says internet jetting is tough good luck dude

 

[Fred T]

Originally posted by Stan_Flemmings
Thanks, I'll have to see what I have now, just got the bike used. Any suggestions for a stock bike w/o an airbox lid? All jets and needle position? Thanks

it is recommended that you run 45 pilot, 155 mian, stock needle in #3 or #2 and A/S out 1.5 turns to start.

 

[Mac]

Since were talking about pinging maybe I could cry about my problem for a while.

Since I had the 225cc kit installed my bike has had a ping off idle and at WOT. I recently installed a 160 main, CEL-3, 45 pilot, a/s 1.5 and I was still getting a ping off idle so I raised my needle to #4 and all was well.

I thought I licked my pinging problem because the bike ran great all day on the powerlines but when I hit the railroad bed for the journey back to my truck I again heard pinging at WOT but only after holding WOT for more than 10 seconds. With the 155 main I heard pinging the instant I hit WOT but now with the 160 it takes a few seconds but is still there.

Now I'm getting worried because most KDX's are running 152 or 155 mainjets but I understand that my bike configuration is different than most.

So I decided to check the cylinder compression and to my surprise it was 210 psi. This seems very high because stock is only 150 psi. When I had my cylinder ported and bored I asked for MO better porting and I said I wanted to run pump gas only but it seems to me that 210psi would require higher octane fuel???

Now I'm not sure if my bike has a jetting problem or a compression problem. If the pinging is caused by high compression can I fix it with a rich mainjet or do I need to start running race fuel? Does anyone how high the compression can get before race fuel is required? Should I be worried about the high compression or just stop whining and go ride? :ugg:

 

[BucKat]

Pinging can also be a sign that your timing is too far advanced.
Just a thought.
Check Eric Gorr's site for info on timing..

 

[toalco-kdx]

what is this pinging? my bike kind of clicks but someone said it was the clutch plates spinning.

 

[Fred T]

PINGING sounds like a "BB" from a BB gun is dancing around in your cylinder and the piston is hitting it around. Symptoms are leaness or as Mac described - higher compression/fuel octane rating. Mac - it was colder than normal the day you rode, maybe that was a factor. It sure was cold here - barely got to 50 degrees. In May - sheesh!

 

[Mac]

Oh yeah, it was 60 deg F with no humidity. Snow melted before the ride. Even at 60 deg I would expect a 160 to be OK. Anyone with a 225 care to post your jetting/compression.....PLEASE!! :whiner:

 

[Zero Z400]

Hey Mac-did you jet ur carb? I think u need to increase the main jet till it skips and go down one. and PINGING is when the fuel ignites before the spark plug fires. I'm not sure what comp. ratio u can run w/ out race gas but on 4-strokes its 11:1. Stan-r u sure ur premix gas isn't to lean. Have you ried 40:1 or a higher octane fuel? Try that and see if it helps.


Later

 

[Mac]

My carb was jetted before the 225 mod with a 152 main, 42 pilot 1174-4. After the mod I heard pinging at WOT and on the needle so I tried a 155 main 1174-5 but the pinging was still there. Yesterday I tried 160 main, 45 pilot, CEL-4 and all was well except under long WOT runs. I will be ordering a 162, 165 and 168 today and continue my jetting quest next weekend.

I was asking for cylinder compression not compression ratio, mine measured 210psi.

 

[canyncarvr]

Not to start some theory debacle here, but 'PRE-IGNITION' is not the same as 'DETONATION'. The former is what is going on if you have a 'before the spark' issue. Pinging, or detonation happens AFTER the spark..the flame front further compressing/heating the unburned portion of charge until it goes 'PING'.

And please don't confuse air/fuel ratio with premix ratio. While the latter does affect the former, it's not the same thing.

210# sounds nuts.

The person that needs to consulted here is EG. He's the one that did the work, and can answer your question for sure. Is it possible your head was NOT corrected for the overbore?

If you can give him a call, or contact him somehow, I'd sure appreciate hearing what he says. I have a cylinder in need of a replate..and the 225 'kit' sure beats a replate to std bore. I'd like to hear that everyone that's done it is really REALLY happy with it.

 

[Mac]

First of all CC I am very happy with the mod, it truely has Mo Power Everywhere. I am just worried because I was told that jetting changes would not be needed and that is not the case for me. I can lug a gear lower and the bike revs higher and can sometimes be scarey :scream:

I just talked to Eric and he confirmed that jetting changes shouldn't be necessary but maybe I wasn't jetted correctly before the mod but didn't have pinging due to less revs or some other reason??

Anyway Eric said that 210 psi was not unusual because the bike has higher compression when the powervalve is closed and the pressure would drop at higher revs. I could have sworn that I checked the pressure before the mod and it was around 180psi or so. Maybe that small increase was enough.

Eric suggested that I try a larger main which was on my list of things to do anyway and he also suggested that I retard the timing a little since I run at sea level. I am reluctant to do this because it will affect low rpm performance but it will give me more overrev (like I need more).

I think I will just verify once again that I have no airleaks then continue installing larger mainjets until I can hold WOT without pinging. I may also try the CCL needle since the CEL is at #4 and I may try #5.

Has anyone out there in cyberspace ran or tested the CCK needle or played with the timing? I am still interested in modified or stock cylinder pressures if anyone would be so kind to post.

 

[Brian]

My bike doesn't do this constantly, just an occasional 'ping.' Would this have anything to do with piston slap/rod knocking or needing a top end job?

 

[BRush]

Mac,

FWIW, I don’t have pinging problems on mine. I had the mo-better porting too, but Eric and I did have a conversation about my fuel preference (premium pump gas). I did not have to radically alter my jetting after the 225 kit. I’m running main jets in the 155 – 152 range depending on temps (160 in winter below 30 deg F) & altitudes between 400 to 1600 ft. One of these days I’ll have to buy a compression gauge and see where it’s at.

 

[canyncarvr]

Mac: I run retarded timing on my bike. I've tried several settings, like it a bit retarded. A 'bit' meaning about a mark width.

Yeah...I know which way the flywheel turns..and which way is retarded and advanced. Still...with the kdx timing retarded (from factory mark) the bottom end is considerably more tractable..reliable. I DID lose some topend pull (based on a drag race to a similarly equipped kdx that I HAD been even-steven with).

Oh..changed it back, and picked the topend back up, too.

Went back to where I'd had it (retarded).

Also..yeah..your compression pressure WILL increase with a bore job, because the RATIO goes up. EG says in his write up on the kit that the head is machined to take that into account.

I've seen pinging results more'n once. Man..you can take a piston apart piece by piece when you have detonation going on. Do whatever it takes to STOP it!!

DOES your head look any different than it did? Not to PING ;) on anybody, but if the head didn't get machined to match (got overlooked somehow), your combustion chamber pressures are going to be WAY up.

You did send in your head, right?

Piston slap/rod knock doesn't sound like detonation. Well...mine never did;)

 

[Mac]

Thanks for all the replies.

Brush, you have the RB carb mod so I'm not sure how to interpret your jetting compared to my stock 35mm but thanks for the reply

CC, it's odd that you say you lost top end pull when Eric said that retarded timing will help top end pull? Which way to retard timing, CCW?

I may try retarding 2deg just to see what the difference is. Did you use a special flywheel puller or will a generic puller work. I have a universal one but I dont want to damage the flywheel.

I did send the head with the cylinder and it looks like it was machined but you can see for yourself below.

 

[canyncarvr]

Yeah..I understand the conventional wisdom of 'retard=overrev' and all that. I also know what my rear-end tells me..and using another bike as a guage made it evident what was happening. Regardless of who says what, my bike is setup to suit me. If I don't understand all the particulars, I'm not going to argue the point. Well..maybe a little.....;)

I rotated the stator ring CCW for a retarded effect.

BTW..2º won't be any more than .040". You've done the math on that, I presume? I don't know the diameter of the stator ring. .040" comes from using a 5" diameter. It's probably less than that (hence less thousandths).

I used a 'generic' flywheel tool. Works like a champ with an air tool. Getting the thing off with HAND tools would be a bummer without a flywheel holding device.

Here's a tip. Make sure the flywheel is back on tight! I don't mean wrench it 10x spec..just do it right. The woodruff key will shear if you don't....and I guarantee that will happen a LONG way from your ride home! (no, that didn't happen to me...but I hve spent some time with a fingernail file making an SAE key fit in another kdx!)

Your head looks like it's machined to me. Maybe not enough?? Dang...over 200lbs. BRush....you really, Really, REALLY need that compression guage!!!! No, REALLY!!

One more thing. Get some allen head screws to replace the junk fillips ones on the stator ring. Good chance you'll need to replace 'em after the heads come off.

Might as well put in an electrex lighting coil while you're in there! That's a fredette tip for better spark. And it WORKS!!! Yeah...doesn't THAT sound right up there with retarding the spark making the bottom end better??? ha!! :)

Please do relay any new info on the pinging thing. I'd sure appreciate hearing what the upshot of the whole thing is.