Open Filters & Freeflowing Exhaust, But NO POWER!

Following on from my 'slipping clutch' post - I thought I'd start a fresh one to isolate any replies.

I've got K&N type filters (NO Airbox)
I've got a 4into1 Sebring exhaust
I've got good starting
I've got fair low speed running
I've got poor high speed running

I'm thinking its probably a jetting issue now I've got the filters on.
What are standard jets?
Anyone played with rejetting?
The bike was meant to be a cheap runner, so don't really want the expense of a full Dynojet kit, unless this is the only way to sort the problems.

Looks like I may be cleaning the carbs out this weekend at least!

 

the standard 650 setup, I believe, is 40 pilots and 110 mains. With pods and free-flowing exhaust, you will definitely have to rejet, otherwise you will run too lean and possibly damage the engine.

Here's a good post to help you select the right jets (or get close, anyhow).

 

Does anyone know the relevance of the numbering of the jets?
i.e. does 100 = 1mm
does 120 = 1.2mm
does 130 = 1.3mm etc

I currently have 40 pilots and 100 mains.

any info will be appreciated.

as per post in 'lounge' - i'm thinking of drilling out mains at least - anyone tried it?

 

your numbering sizes are right, keep in mind the drilled hole is going to be bigger than the drill that drilled it so a 1.2 drill will be more like a 1.3 hole
your going to have to put washers under the needle jet needle too
i'll take a very wild guess at a 1.2 drill and shim the needle 1 to 2 mm
if you back off the throttle quickly about a 1/8 turn and get a surge of power
your still lean, good luck

 

cheers polock!
been recommended a 128 by a u.k. carb specialist.
he also said may have to raise needle.
currently have carbs off bike to try and think about cleaning them....!
wasn't expecting the needle setup!
only ever worked on dirt bikes with 'C' clips on the carb needles for adjustment.
what you reckon about drilling?
not gonna be 100% precise, but worth a shot???

 

BUY brand NEW jets, 116 Mains, and 42 - 43 Pilots. You're supposed to have 41 pilots anyway, right guys?? European ??
Play around with the slider needle position later, after the idle and drivability is sorted out. Get the float level set right also.

If you really want to drill jets, you need to make sure you de-burr them internally, at the transition areas on both sides, where the funnel leads to the restriction. No additional restrictions !!

 

if you look at the chart Rick posted in your other thread, there's going to be gaps in the sizes you can drill but anything will be better than what you have now
then if it's not right after drilling you can make a educated guess and buy some the way you feel it needs to go or you might get lucky with the drills
if you've worked with carbs with needle clips, think at least one clip position
your going to have them off a few times to get it right so might as well check the floats on the bike and make adjustments as necessary

 

I have 128's and 42's with pods and 4to1 and have decent performance, though still a little lean at higher rpms (I have not raised needles). I'm going to build a pvc intake with one pod filter though to try to get closer to the stock set up. Mabey you should do the same... Search pvc intake

 

i'll have a look right after this.
due to the great British weather, I have been running with the filters wrapped in electrical tape, with just a 3/4" hole in the tape at the bottom - partly to keep them dry - partly to try and restrict the airflow a bit.
it has made a little difference. not major though!