Dellorto PHM 38 SD jetting KTM625

I think you are way way way too rich. 40mm Dells are used on the Husaberg 600's and up so with only a 38 on a 625 the venturi signal is going to be huge (which means that you will need realatively smaller jets as the beast is sucking hard)

Start going down on the main, 190 then 180 etc., my guess is about 170 will be the one, maybe even lower, a 160 perhaps.

Decrease the pilot jet incrementally also, around a 35 or 38 may work good.

Once in the ball park you may want to go to a leaner needle also as that controls 1/4 to 3/4 throttle.

The home brew screw sticking out is either the fuel screw or the idle screw. I think its the idle.

Dark0z said:

Ok, I have some main jets to change down to 170 with steps of 5. But with how many steps should I lower the Idle jet? 45/40/38/35 ? And should I also change my choke-jet (to 40?)?

And which Needle vale/seat should I use and which weight float?

Click to expand...

These are all the carb parts for your bike, I think, including original and optional jets. I can't predict exactly what your jetting should be. Obviously your bike runs so it is not too far out. Make one change at a time and retest. If you make multiple changes at the same time it could get very confusing.


1994 KTM 620 SX WP DIV OEM Parts

Part Number Quantity Unit Price
2: JET NEEDLE K51
4374800-001 Enter 0-99 $17.04
3: NEEDLE JET DR 266
4381069-001 Enter 0-99 $27.55
3: NEEDLE JET DR 268
4381070-001 Enter 0-99 $32.92
3: NEEDLE JET DR 270
4381071-001 Enter 0-99 $33.12
4: MAIN JET 135
4380414-001 Enter 0-99 $5.32
4: MAIN JET 170
4380424-001 Enter 0-99 $5.28
4: MAIN JET 180
4380427-001 Enter 0-99 $5.28
4: MAIN JET 190
4380431-001 Enter 0-99 $5.28
5: JET 38
4371950-001 Enter 0-99 $7.09
5: JET 45
4371953-001 Enter 0-99 $7.09
5: JET 52
4371956-001 Enter 0-99 $7.09
6: STARTING JET 45
4380450-001 Enter 0-99 $7.76
7: NEEDLE VALVE 300
4380477-001 Enter 0-99 $36.76
8: FLOAT 8,5 GRAMME
4380397-001 Enter 0-99 $29.99
10: RUBBER SLEEVE
4376950-001 Enter 0-99 $2.40
11: HEXAGON NUT M 5X16
4380444-001 Enter 0-99 $2.43
12: ADJUSTMENT SCREW M6X0,75
4380446-001 Enter 0-99 $13.08
13: CARBURATOR TOP PLATE
4375166-001 Enter 0-99 $9.01
15: RETAINING PLATE
4377623-001 Enter 0-99 $2.50
16: TAB WASHER DIN6799-RS 2,5
4371459-001 Enter 0-99 $1.58
18: ADJUSTMENT SCREW M6X0,75
4380445-001 Enter 0-99 $3.13
19: HEXAGON NUT M 6X0,75 DIN0439
4376943-001 Enter 0-99 $8.26
20: FLAT HEAD SCREW DIN963-M4,5X14
4371681-001 Enter 0-99 $0.72
21: COVER FOR STARTER HOUSING
4380453-001 Enter 0-99 $5.25
23: SPRING
4381081-001 Enter 0-99 $1.13
24: STARTING DEVICE
4380449-001 Enter 0-99 $4.73
25: WARM START BUTTON
4381083-001 Enter 0-99 $75.58
26: HEXAGON NUT M 9X0,75
4381084-001 Enter 0-99 $7.08
27: AH SCREW DIN0912-M 4X12
4371498-001 Enter 0-99 $0.50
30: COVER
4375171-001 Enter 0-99 $3.38
31: MAIN JET HOLDER
4380411-001 Enter 0-99 $7.51
33: WASHER 3,3 X 5,8 X 0,5
4380454-001 Enter 0-99 $1.20
34: SPRING AIR ADJUST.SCREW
4380402-001 Enter 0-99 $0.43
35: MIXTURE REGULAT.SCREW M7X0,75
4380403-001 Enter 0-99 $5.07
37: WASHER 5,1 X 8 X 0,8
4380455-001 Enter 0-99 $1.13
38: SPRING
4376916-001 Enter 0-99 $1.76
39: ADJUSTMENT SCREW M5
4380404-001 Enter 0-99 $3.95
40: FUEL FILTER
4371944-001 Enter 0-99 $5.48
41: HOSE CONNECTOR
4380400-001 Enter 0-99 $6.51
43: HH SCREW DIN0933-M 6X16
4371634-001 Enter 0-99 $0.59
46: STUD 2 X 47
4380396-001 Enter 0-99 $2.43
47: FLOAT CHAMBER WITH RUN OVER T.
4380399-001 Enter 0-99 $244.30
49: PLUG M12X1
4380401-001 Enter 0-99 $25.35
50: GASKET SET PHBE 36 HD
4380601-001 Enter 0-99 $28.75
60: PCV HOSE 3X6X270
4376854-001 Enter 0-99 $3.11
61: PVC-HOSE 3X5MM
4376949-001 Enter 0-99 $3.50
62: CABLE CLAMP BLACK
4384879-001 Enter 0-99 $0.41

Dark0z said:

I just installed a 195 main jet. But when I give full throtle it holds in/hesitate. So I think it's now to lean on the main jet, because with the 200 I can rev to the end.

or could the mixturescrew affect this?

Click to expand...

The mixture screw only affects idle and below. Read this:


ROLL-OFF:

The Roll-Off technique is the quickest and is almost as accurate as the Roll-On method. First, one gets the engine warm on the way to a safe roadway. If there is room, use fourth gear as this allows more time to assess the result.

Now, get the engine rpm high enough that it is on the cam and in its power band. This may need to be as high as 4000 rpm with some cam choices. Apply full throttle. Let the engine accelerate for a couple of seconds until it has settled in and is pulling hard. Quickly roll the throttle off to about the 7/8ths position. When you do this, the mixture richens slightly for a second or so.
If the engine gains power as you roll the throttle off, then the main jet is too small and you need to fit a larger one.
If the engine staggers slightly or has a hard hesitation, then the main jet is too large and you need to fit a smaller one.



http://www.mikuni.com/fs-tuning_guide.html

Dark0z said:

I just installed a 195 main jet. But when I give full throtle it holds in/hesitate. So I think it's now to lean on the main jet, because with the 200 I can rev to the end.

Click to expand...

Your 200 main jet may be a little plugged up causing it to be a little smaller than a 200. A welders torch tip cleaner works good on jets.

Float height?

Have you the right floatheight?
Regards
Jampe

Re: Float height?

Dark0z said:

jampe said:

Have you the right floatheight?
Regards
Jampe

Click to expand...

Don't know... Will check it tommorow. What effect does it make when it is out of line?

Btw, above the holder for my mainjet there is some sort of cover. Something like this: \___/ is that normal? I don't see it on the parts diagram :/ http://www.motoguzzisti.com/files/dello ... ts-sec.pdf the mine is above part 78

Click to expand...

Yes the shield around the main jet is normal.

If the float level is too high it can cause a rich condition. If its way too high it will leak out one or more of the overflow tubes.

Re: Float height?

Hello
I had problems when i came up to 4-6 gear and had open throttle, it almost died or hesitated.
And in very tricky tracks an lot of bumps it died sometimes
It was to little fuel in the carb, my flotheight was to low.
Regards
Jampe

Dark0z said:

jampe said:

Have you the right floatheight?
Regards
Jampe

Click to expand...

Don't know... Will check it tommorow. What effect does it make when it is out of line?

Btw, above the holder for my mainjet there is some sort of cover. Something like this: \___/ is that normal? I don't see it on the parts diagram :/ http://www.motoguzzisti.com/files/dello ... ts-sec.pdf the mine is above part 78

Click to expand...

Hi!

I have a year 2000 Fe400e with the stock PHM 38 carb, and i was wondering if there is a way to tune my bike a bit. I've tried to serch, but it seems that there is no jetting kits for my Berg? So any hints how i could improve the performace?

I allready have the newer headers and Remus silencer.

Thanks!

*Tsounas*

Hej.
I have in my 400 -00 and 400 -99 following jetting, Dellorto PHM 38.
(Same as in the 501 -99 but with Dellorto PHM 40)
MJ 210
Atomizer 272DR
Needle K51
PJ 35 (perhaps 33, not 100% sure)
SJ 45
Mixture screw 2 turns out.

Tried smaller MJ from 175-200 but went back to 210, little rich but runs and start lovely.
Original exhaust.
Regards
Jampe

Another little question. On the right of this picture there's some own manufactured screw http://img180.imageshack.us/img180/3945/img2846e.jpg what does that do? I can push it in and out for a few mm's. Should it be in or out?

Click to expand...

if you can move it in and out it is probably leaking air and thus a vacuum leak. needs a good tight threaded fitting. you can tap it and fit a screw with a pointed tip.

Hi DarkOz

I have a ported head on my 400, and allways seems that I've needed larger mains, don't know if thats your case.

I have also one 600 with PHM 40, and never needed such large jets as you need ???

Also if you are one turn out on the PS, I don't think you will need a larger PJ.

:cheers:
ZAGA