Pinging at WFO?

[fred2]

It seems that I have a pinging or rattling problem when I'm in 6th gear wide open. It's not a problem when the engine is under load but very noticable when I back off just a little after being WFO. I hope that states my problem clear enough. Here is my setup:

97 KDX 220

mods -
air box mod
RB Designs Carb Mod
RB Designs head mod
NGK BR8EG plug
Boyssen Reeds
FMF Fatty

I just cleaned the power valve hoping that might be the problem. Plus it really needed. yuk!

I couldn't find anything on this in the threads so I apologize if this has already been covered.

thanks,

 

[jamin326]

i've got a 99 kdx220 and it does something similar, pings or knocks at wot, my bike has airbox mod, rb carb, boysen reeds, fmf rev pipe, weisco piston, and i just took my top end apart and cleaned the kips, still does it... it's like it's doens't really have much of a top end, which i guess might be the case cause of the porting of the 220, i'm thinking of sending my clyinder and head to frp to have them done up, hey what are you running for jets?, i'm at i believe about sea level and i'm running a 40 pilot and 150 main with the airscrew about a turn and a half out

 

[Matt90GT]

Try running a colder plug to reduce pinging. The 9 series NGK.

You can also try running like a 24/75 mix of race/premium fuel. That should not throw the jetting off to much.

If the plug does not work, but the gas does, what have you done to increase the compression? Anything? If nothing, how hot is the motor getting? Try some water wetter and a new radiator cap.

Also do the basics like checking the intake gaskets, reed gaskets, reeds, intake boot, airbox boot, airbox boot seal, clean the air filter and the exhaust gaskets to make sure you have no leaks.

 

[fred2]

Crap, I knew someone was going to ask what the jet sizes were. They're the stock sizes for a 200. I know it's pretty sad that I don't know but I will find out.

I would love to send the head into FRP but not sure I want to drop the bucks for it just yet.

Matt,
I had RB Designs do the head mod. I'm not sure how much they took off but I don't think it was much. I have had a little trouble with over heating and the Water Wetter did help. I'll probably try the colder plug first and then maybe the race gas. ????

The sound actually scared me at first. The piston looked in pretty good shape so I wasn't as worried.

thanks,

 

[G. Gearloose]

Perhaps there is some air trapped in the head's coolant passage? Have you checked the vent screw?

 

[Mac]

I had a similar problem after porting and head mod. My cylinder pressure climbed from around 175psi (stock) to 210psi.

I tried to fix the problem with jetting but what a big mistake. Jetting richer helped a little but drastically killed performance.

I tried octane boosters like Hitrate which killed 75% of the pinging but it was still noticable under certain conditions.

Finally I decided to mix C12 with pump gas 50/50 and I haven't heard a ping since. After finding a good fuel mixture I rejetted and now the bike absolutly rips. :laugh:

One main difference I noticed with your problem is that you dont have pinging at WOT?? Your problen could be jetting (needle or pilot)

 

[dirt bike dave]

If the problem only occurs when you back out of the throttle after extended WFO in top gear here is my $0.02:

You are generating huge amounts of heat at WFO in top gear. But with the throttle open you are also getting lots of fuel and oil in there, too, which cool and lubricate. If you back off the throttle and do not pull in the clutch, the engine is still turning high rpm and generating heat due to thre friction, but you are no longer getting any fuel and oil.

Backing off the throttle w/out pulling int he clutch after extended WFO is a good way to damage the engine. Next time, pull in the clutch. Or hit the kill button while keeping the throttle open - this puts in lots of fuel and oil.

 

[canyncarvr]

What you describe and dbd explains is a situation ripe for lean seizure.

A couple of things that are problematical:

1. You have an rb modded carb and you don't know what jets are in it? Why do you think they are 'stock' for the 200? Did you change them back to stock after you got it back from ron?

2. You have a modified head and you don't know what jets you're running? ;)
There should be no modification of no head unless the machinist has some input from you (the rider) as to what you're after. The difference between a requirement for race gas and being able to run pump gas will be in the configuration of the head.

What did you tell ron you were going to do with it?

If you don't know what jets are in it, then it is unlikely it's jetted it properly (assuming your mechanic doesn't tune your bike for 'ya).

Before I went looking for problems, I'd get the jetting sorted out.

...imo...

 

[Jackpiner57]

The pinging or rattling that you describe is at high RPM's when you let off the throttle. That is not WOT. I think that the noise is normal.

 

[fred2]

Carver,

I told Ron exactly what my setup was so he put in the appropriate jets. And I haven't changed that setup. Ron said that I wouldn't have to run race gas with the head mod that he did. So I'm pretty sure that's not it.

I wouldn't be concerned about this but I've never noticed it before. DBD's suggestions sound right but again it's never been noticable. Do you guys think it might be the different plug I'm using? I'm using a NGK BR8EG. Can't remember who but someone here suggested it.

I feel pretty silly that I can't remember the jet sizes. :| But I really don't want to take it apart to check.

Thanks for the help fellas. Any other ideas are definitely welcome.

 

[canyncarvr]

I read somewheres:

Experience is something you don't get until just after you need it.

You could be learning that all over again. ;)

The fine-wire plug is not at all the issue.

While ron can get it 'in the ballpark', there is no way he's going to get it exactly right unless he goes riding with you and tunes the carb in the process.

Then, it will be good for that day! :(

How about talking to the one that did the work in the first place...that would be ron. You might take a look at the paperwork that was sent with your stuff. I'll bet'cha you'll find some jet numbers on there........

Here's the truth of the matter. Saying:

But I really don't want to take it apart to check.

Doesn't express much interest or concern over the matter.

If that suits you, it tickles me.

Lessee....where's that unsubscribe button....... :(

Cheers!

 

[fred2]

Carver,

I seem to be constantly learning something. Unfortunately it sometimes takes me a few times.

You're right that Ron set the jets at a "good starting point". Those were his exact words.

Don't lose faith in me. I'll figure it out and it really is important to me.

thanks,

gf

 

[dirt bike dave]

fred2,
In the woods, most riders rarely if ever see extended periods of WFO. So jetting that is perfect for the woods might not cope well with the heat generated by extended periods of high speed WFO. Same with sand riding - the engine works harder and generates more heat.

Some woodsriders will bump up their main jet a size or so if they are going to run desert or sand races to provide extra protection.

One way to think about it - pretend you have to push your bike across the terrain you are riding. It's A LOT harder to push a bike through sand than over hard park. It's also A LOT harder to push your bike twice as fast (simulating high speed).

Bottom line is if you are operating outside your normal conditions you may need to adjust your jetting or slow down to avoid engine damage.

 

[fred2]

Good point Dave. It's kinda hard to find any woods riding around here. ;) Thanks for the advice.