Carb tuning suggestions welcomed!

[fmcandrew]

Hey guys, just got my bike back on the road and it's running OK, but not great. I installed a holeshot exhaust and I have a Morley kit. With Sean's advice I hve the following settings:

160 mains
Stock needle (1 very thin shim)
Stock springs
Air correctors
Morley lid
Slides are NOT drilled
A/F 3 turns out
Carbs are spotless & synched

It needs choke to start. Idles fine. When I blip the throttle the RPMs drop about 500, then revs with no issues. At steady throttle I feel a slight surging (1/8 throttle)...roll it slow and I feel the slight surging, roll it hard and it accelerates just fine. At 4500RPM (the setting for my VBoost), I get a huge drop off, then it recovers and accelerates.

I think I'm running lean on the needle because when I left for work this morning it was about 60 degrees...when I got close to work it had warmed up and it was running better...

I do have stage 7 needles and I've noticed just about everyone using them...can I jet this thing with the stockers or am I wasting my time?!?!?

Your input is greatly appreciated!

 

[Vmaxnl]

Change the pilot #170 for #150 great result

 

[sdt354]

I'd put the stage 7 needles in Frank, 4th clip from the flat end for starters. I assume that's a 160 Mikuni jet?

 

[fmcandrew]

Steve - Yeah...it's a 160 Mikuni. If I put the stage 7 needles in do I need to jet down on the main? I think most are running 150s or 147.5 with the stage 7...

 

[fmcandrew]

Change the pilot #170 for #150 great result

Are you refering to the PAJ2?

 

[Vmaxnl]

Yes behind the the throttle slide/diaphragm

 

[fmcandrew]

Are you running stock needles with a full exhaust & Morley lid? just curious as I've seen very few members suggest changing the PAJ2...

 

[[email protected]]

It's been about 5 years since I had stock needles with Seans setup. Here is what my notes say:

I started with 160 mains. It was a little lean in spots then I changed to 162.5 main, stock needles w/2 shims, dj springs, undrilled slides. Ran great. Was going to see if I could drop drown to 1 shim only but never did before I sold the exhaust and carbs and went a different direction.

It can be made to run with the stock needles. Stg7 needles offer more adjustability though.

 

[sdt354]

Steve - Yeah...it's a 160 Mikuni. If I put the stage 7 needles in do I need to jet down on the main? I think most are running 150s or 147.5 with the stage 7...

i think 160 is fine for your elevation Frank. regardless of needles.

 

[thor_eyerdhal]

160 with stock needle is not at all like 160 with S7 needle ...!

 

[veebooster]

With stage 7 needles you will need smaller mains. Stock needles I ran a shim and 170 mains, 177.5 PAJ2. Ran pretty good 35-40 mpg.
Stage 7 needles I'm at 155 mains, 3rd notch on needles, 170 PAJ2. I think I might be able to go to 152.5 mains. 750 ft elevation.

Dale

 

[fmcandrew]

It's been about 5 years since I had stock needles with Seans setup. Here is what my notes say:

I started with 160 mains. It was a little lean in spots then I changed to 162.5 main, stock needles w/2 shims, dj springs, undrilled slides. Ran great. Was going to see if I could drop drown to 1 shim only but never did before I sold the exhaust and carbs and went a different direction.

It can be made to run with the stock needles. Stg7 needles offer more adjustability though.

Yeah, I swaped back to stock springs from the shorter springs, but I think it ran better with the shorter springs...I think I'll throw in the stage 7 needles I have... Not sure if I want to pull the rack to jet down the main 2 sizes...running a bit fat wont kill it...

 

[thor_eyerdhal]

No, but it will be lazy in the mid range and overall loss of power...

 

[fmcandrew]

Well...I was somewhat incorrect with my initial settings (chaulk that up to old age)...I actually had a 165 MK main and not a 160 as initially posted. I know this because I decided to rejet the mains yesterday and install the stage 7 needles. I put in 155 MK mains and set the clip 4th down from top (blunt). Bike fired up nice and seemed to have much better throttle response - will test ride when I get a chance...

 

[veebooster]

You'll be close with that set up.

 

[fmcandrew]

I'm really baffled by the main jet size...I know many are running MK 150 mains with air & exhaust mods...but that makes very little sense given that the stock main is 152.5 (I believe). I mean lets face it...if you add a blower or turbos to a car you have to increase the fuel...more air - more fuel - more power. If folks are now running smaller than stock mains with mods it can only mean that the stock mains were couple sizes to rich to begin with...or am I missing something here?

Thx

Frank

 

[thor_eyerdhal]

Yes...
Stock needle but with S7 needle... This is like a bigger jet with stock needle

 

[fmcandrew]

Well...rode the bike to work today and it now pulls like a freight train above 4k...so that's great. But, still have stumbling issue while cruisng at 2.5 to 3k or 1/8 throttle. I'm on the 4th clip (from blunt) of the stage 7 needles...would raising that to the 3rd position clean that up? My A/F screws are 3 turns out as well...getting close...I can feel it (litteraly)...

 

[Rusty McNeil]

I'm really baffled by the main jet size...I know many are running MK 150 mains with air & exhaust mods...but that makes very little sense given that the stock main is 152.5 (I believe). I mean lets face it...if you add a blower or turbos to a car you have to increase the fuel...more air - more fuel - more power. If folks are now running smaller than stock mains with mods it can only mean that the stock mains were couple sizes to rich to begin with...or am I missing something here?

Thx

Frank

Yes, stock setup is generally believed to be too rich. Afttestkey exhaust and leaner on mains seems to help a lot versus the "sage" old advice of bigger richer

 

[fmcandrew]

Thanks Rusty...I knew that had to be the case...an engine is an engine regardless the fuel delivery system...