Carb adjustments after slip-on addition?

06450F

Member
Apr 17, 2006
22
0
Hey fella's maybe you can give me some insight on this before i go into my "trial and error" carb tuning session.

Ive added a Two Brothers M7 slip-on to my KX450F. The exhaust apparently is more "high flow" than the oem supplied muffler.

In riding the machine thus far it appears to have a little more punch in the mid to upper end compared to the oem pipe.

My concern and question centers around the drastic increase in decel pop with the new pipe.

Ive made adjustments to my pilot air mixture screw and it lessened the "snap" some.

I do understand a degree of decel snap or pop is common and to be expected, but the machine does it quite a lot and from all indications too much. The machine also feels as if the mid rang punch comes on ....leading me to believe the bike needs some adjustment down low.

How are you guys compensating for slip-on exhausts on your 450 4 strokes?

Just mixture screw?
Larger or smaller (i assume larger) pilot jet?

Needle adjustment??

Im leaning toward mixture screw and a larger pilot jet.

Any input is appreciated.
 

Rich Rohrich

Moderator / BioHazard
LIFETIME SPONSOR
Jul 27, 1999
22,838
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Chicago
Before you make any additional changes to the jetting make sure the pipe seals correctly at the headpipe/cylinderhead junction and the headpipe/muffler junction. If it leaks it can pull in cool air and cause serious backfiring even if the jetting is correct.
 

destructo

Member
Feb 24, 2006
100
0
Rich Rohrich said:
Before you make any additional changes to the jetting make sure the pipe seals correctly at the headpipe/cylinderhead junction and the headpipe/muffler junction. If it leaks it can pull in cool air and cause serious backfiring even if the jetting is correct.

Thats exactly what happened on my 05 yzf450 when I bolted up the gytr slip-on. After retitening and checking it over again it rarely every pops and it is noticably quieted. :ride:
 

06450F

Member
Apr 17, 2006
22
0
Thanks for the quick input guys.

I failed to even think about exhaust leaks until i posted the thread.

The Two Brothers Slip-on system has a strange oddity at the midpipe-header junction. There is no provision for a clamp or sealing device. The Two Brothers mid pipe slips fairly snug over the OEM header and thats it. There is no clamp or gasket, or even slots in the mip pipe last 1" or or more so that it could squeeze down if a clamp was applied.

My "guess" is if i were to buy a Two brothers header "it" the header would have th provison for the clamp.

But in any event i bought the slip on system new in the box. The directions are complete and show pictures and listing of all parts including stickers and noplace mention a clamp or clamping it to the header.

On a side note the OEM clamp will not work its much too large.


So.....
Do you suppose if i bought a smaller clamp from the auto parts store to fit the pipe it would clamp it, or squeeze it any tighter being there are no slots in the mid pipe or gasket material or such to even squeeze tight?

Maybe i should direct this question to "Two Brothers Racing". As it appears to be a poor design. Yet the muffler is nice and sounds great even with the spark screen .

Any input is appreciated.
 

Rich Rohrich

Moderator / BioHazard
LIFETIME SPONSOR
Jul 27, 1999
22,838
16,902
Chicago
Try Permatex ULTRA COPPER Hi-Temp RTV Silicone at the junction.

B0002KL67O.01-ADG953YR6NRBF._SS400_SCLZZZZZZZ_V1108728445_.jpg
 

06450F

Member
Apr 17, 2006
22
0
Yea, thats what i was thinking. Maybe i can make a bead on the inner pipe and let it "thick'n" up a bit then after its a bit goopy i can put it together, sort of like a gasket.

I will contact Two Brothers also and see what they suggest.
 
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