Noob jetting question

[crazybrit]

I'm a total dirt newbie (98 KDX220 is my first dirt bike ever) though have about 15 years street/dual sport riding experience.

I'm finding it difficult to manage the throttle response of the bike on tight trails. Part of this may be that I need to start off on jeep trails and easier trails -- which I will.

The other is that I think the jetting may be wrong but I'm not sure how much this is a factor? Others have told me I should have started off on a 4-stroke :-)

I just replaced the B8ES plug with an BR8ES. I cleaned a fair bit of what looked to be solid carbon buildup off the old plug electrode with a wire brush. After one ride (bike seemed to run well but I have zero 2stroke experience) the new plug seems to be oil black over the insulator and electrode (I realize I need to check the base for correct jetting) and also there is a lot of oil buildup inside the spark arrestor.

I'm assuming first thing is to pull carb, check float, verify what jets I have presently installed and compare them to the suggested default?

Only modification from stock is the snorkel has been removed and several 1 1/2" holes drilled into the airbox cover.

How does this airbox mod change the 100% stock jetting recommendation for a stock 220R of 42 pilot jet, R1173L jet needle 2nd from the top clip position, 142/145 main jet and fine tune the pilot circuit using the air screw ?

So far all my riding has been at around 2500-3000' ~60 degrees.
Running 40:1 using AMSOIL Interceptor Synthetic.

Thanks

Tony

 

[John Harris]

Tony, you are well read on here and perhaps elsewhere on your jetting problems. I ride a 200, but I suggest that everything would appear to be ok on your carb, but the jetting. With the stock pipe and your elevation, I would suggest a 38 pilot and a 140 or 142 main, with the needle second clip from the top. Being new and riding trails, you are riding primarily on the primary circuit and the hit comes when you get on the main and clean things out and then your bike begins to run like it should. With the stock pipe, your elevation and hot weather, even a 38 may be too rich. Not many 2 stroke engines that I have ever heard of seize at low speed! Jetting will do more for your bike than anything else for the money, next is springs in the forks. Cheers John

 

[crazybrit]

Hi John. I'll use what you recommended as a starting point. I'll get some cheap Champion [R]N3C plugs for plug chops and a few new jets from Sudco.

I have noticed that the forks seem excessively damped (gets skittish on rough stuff) but havn't yet noticed them being too softly spung (I weigh 190). I don't want to put a lot of money into the bike right now so looking for cheap fixes -- guess I'll be removing shims from the stack and changing fork oil rather than getting Gold Valves.

Whats the best bang for a cheap buck for the fork springs for my weight? XR400 or RaceTech? Anyone who's upgraded to KX have some used springs they'd like to sell?

Also would I notice any throttle response benefits from a cheap set of 607 reeds or are my problems mostly of the jetting/clueless variety?

thanks

 

[krazyinski]

Jetting is time consuming, so I would advise take it to the trails and take your tools and jets and spend a few hours dialing it in. the old tune around the yard rarely works. I have not worked on two strokes for 20 years it took a while to get in the groove. your end result should be a smooth power band from bottom to top. If your feeling a hit then more than likely your running rich to lean.

 

[John Harris]

Tony, for goodness sake, if you have the forks off to change the shim stack, etc. be sure and change the springs. there are lots of threads on here about fork springs. Many of us prefer the XR springs (longer so more spring and less spacer) and real Honda springs are hot wound and the aftermarket ones are not. There are some that swear on lots of "research" that hot wound is better than cold wound, but I know that the Honda XR springs in my forks made a ton of difference. Again read the threads, and if you use XR springs you have to make a spacer for each fork tube. Easy to do, but there is discussion again on how long to make the spacer (how much preload you want on the springs.) There are two weights of XR springs for different years, and I use the lighter ones. Your weight is on the border line for choosing so choose depending on how agressive you ride! You will also be happy with the aftermarket stiffer replacement springs at the correct stiffness. Cheers John