P-38 on a 520 EXC?

[robin_des_bois]

I have a wr400 and I am going to turn orange. Is the p-38 modification for carbs worthwhile for the 520. And what about the needle ocebn (or something like that!). Holes on air box have been discussed (from search) but it does not appear to have a cencensus about that.

What are the standard well known modification on that bike to get more power, keeping the stock exhaust. Is the standard air filter good or it should be replaced by a k&n?

[Chris_in_the_Mojave]

The stock filter is a Twin Air and seems fine.

As far a other mods, I had P-38 and aftermarket exhaust on my YZ400, the 520 runs great stock. I've thought about a P-38, air box mods and a T-4 exhaust but it is so quiet and so strong stock... I've just left it stock. I've just been changing the oil and keeping everything stock.

Only "problems" I've had are trying to make it TURN! ? I'm still working that

[motodude]

Chris- If you haven't tried already, the 16 mm offset triples are the way to go with the RFS. I'm working on a 17 mm offset steering stem for my 400 RFS, only got to try it for 15 minutes. My valve adjuster nut came loose and went to the bottom of the engine, so I'll post my opinion when I get my bike back from the shop.

01 400 EXC

01 TT-R125L

02 TT-R90

[Jo_VdB]

Originally posted by robin des bois:

Is the p-38 modification for carbs worthwhile for the 520.

What are the standard well known modification on that bike to get more power, keeping the stock exhaust. Is the standard air filter good ?

Hi,

a P38 will not give you an advantage. Best thing do to is to keep the diaphragm (accelerator pump) clean.

Standard air filter is OK

If you keep "everything" stock and the bike is a EXC 520 , use this carburetor setting

OBDVR (position 4)

idle jet : 50 (instead of 48)

main jet : 180 (instead of 175)

Fuel screw 1,75 turns out

(a friend of mine -former works mechanic for several companies- is going to test the OCEMN-needle. This is a "yamaha"needle. A guy named James Dean says this is THE needle to use)

Jo

[ November 26, 2001: Message edited by: Jo VdB ]

[robin_des_bois]

Is the OBDVR the standard needle that comes with the 520 EXC? You confirmed what I think about the p-38 and the filter.

I've seen a lot of enthusiam about the OCEMN but there is still not a large amount of guy who use it so I wait until getting more info and... tget the bike!!

[Old_Stroker]

If you want to see a major power increase to the 520, use the following....

EMN needle, clip #4

This is a Sudco needle,not a Yamaha needle..Yamaha needle is a EKN

160 Main jet

Fuel screw 1-11/4 turns out

Want more power yet!!

P-38 with the spray timed at 1 second (stock is 3 sec.)

EMN needle, clip #5

162 Main jet

Fuel screw 1-11/4 turns out

Make sure when you get your P-38 it's for a KTM and not a YZ. It seems as if some Yz's are getting shipped by mistake and they have a different spray time.

A side benefit of the P-38 is that you'll get about another 20 miles to a tank of gas. ?

[Jo_VdB]

Originally posted by robin des bois:

Is the OBDVR the standard needle that comes with the 520 EXC? You confirmed what I think about the p-38 and the filter.

In Europe you get 2 standard needles with an EXC . The OBDVR and the OBDTM.

Forget the P-38 modification.

Jo

[Strick]

The P-38 on my 400 was as good a bolt on power product as the Delta II reed cage on my 300. The P-38 makes the bike rip!

If you have followed the BK mod at all, this would be the KTM answer to what BK accomplished on the YZ's.

Hey Jo, have you tried one for yourself?

[Old_Stroker]

Jo

Why do you want to forget the P-38 modification?

The factory KTM's and the factory YZ's use them. Look in this forum under YZ 426's for the BK mod. That stands for Bryan Kinney modification. He's Tim Ferry's factory mechanic. The BK mod. works the same as the P-38.

Did you try the P-38 and not like it? If not, as you can see from my earlier post, you have to adjust the spray from the excelerator pump to 1 second and then richen up the needle 1 clip and the main jet 1 size. If you used the P-38 did you do this? What needle were you using?

Rather then say, don't use it,it would be helpful if you gave the reasons why.

What reason are you giving for not wanting better gas mileage??

[ November 26, 2001: Message edited by: Old Stroker ]

[Taffy]

i just had a laugh, ha-ha-ha-ha-ha!!!

just been to the DR site and a bloke had been running his bike without the APJ connected. he was distraught. OH MY GOD!!!!

fitted it back on and it ran even worse haw-haw-haw-haw!!!

go buy that P-38 and remember spend-spend-SPEND!!!!

ha-ha-ha-ha-ha-ha-ha!!!!! ?

Taffy

[Strick]

I apologize for my ignorance, but what's an APJ?

[RetSenior]

[ March 28, 2002: Message edited by: RetSenior ]

[Taffy]

accelerator pump jet is the official name of that finely tuned piece of delicate junk on your prestine orange machines.

Taffy ?

[Strick]

Taffy; I am fairly new to thumpertalk. What bike does your signature relate to? Would you mind deciphering the Carb line in your signature. I can only make out about half of it.

'Taff timed cams', lid off, PB header, euro 'zorst, 14 x 48T, 10oz sirloin, magura juice clutch,

Carb; 150MJ, 160MAJ,EMM-clip 4, 38PJ, 55PA(J)Screw, PS 1.5 and no APJ!!!

Also can you elaborate on why no APJ. I have never heard of this before.

Thanks

[ November 27, 2001: Message edited by: Strick ]

[Jo_VdB]

@ Strick , Old Stroker and ...

No, I did not use the P 38 modification, because

a guy I know (former works-mechanic for Husaberg, Husqvarna with very good connections with KTM and the KTM works teams here in Europe) does test the P38 for the makers of it. He has to give his comments so they can improve the design. Untill now, they haven't found the right design. It might give you a little advantage, but not always.

Jo

[Eurorider]

Hi Jo

We are working with Glenn on this one, and we are not finished with the testing of the P38.

The results to date have not been as expected but we do not discount the P38 as a well engineered and worthwhile piece of kit. Hell there are plenty out there working just fine on other bikes.

I would not draw any conclusions or change any customers mind in fitting a P38 based on the testing we are doing in Belgium.

[Old_Stroker]

Eurorider

Is Glenn the guy Jo say's has connections with KTM and the KTM works team in Europe? What kind of bike is Glenn testing for you? If it's a KTM, is it a 400 or 520 and can you give us some prelininary info on his jetting with the P-38 and the adjustments he's made to the accelerator pump linkage? Squirt time and etc.

Thanks Bob

[Jo_VdB]

Originally posted by Eurorider:

[QB]Hi Jo

The results to date have not been as expected but

Well this is what I'm trying to say !

Hell there are plenty out there working just fine on other bikes.

My English is not that good, but this I said also ? ¨Untill now, they haven't found the right design. It might give you a little advantage, but not always.

I would not draw any conclusions or change any customers mind in fitting a P38 based on the testing we are doing in Belgium.

Well, I think this is up to the readers of this forum. I'm just expressing my .02 cents on Robin Hoods question. So, keep testing on the 520 RFS, and I'll buy one when the tests are finished and the results are as expected.

Jo