Hi All,

My 06 Sporty 883 was running pretty well with stock air cleaner, stock jetting except for .20 shim under the needle and pilot needle adjusted, but around 20k mi I started getting enough blow by oil to get oil all over the side of my bike and on my jeans. So I've fitted a breather kit which re-routes blow by down a tube to a filter and modified the air cleaner element to block the holes that used to be for the blow by to get into the air cleaner. Now the bike runs nicer at idle and part throttle, but is leaner across the whole range - enough leaner to surge at 1/4 to 1/2 throttle opening. There are no vacuum leaks and the filter is a new, good filter.

Now I don't mind rejetting - I'm going to shim the needle up another .020 and see how that goes but for the life of me I cant figure out why not having the breathers routed into the carb is leaning the mixture off, unless the oil vapor makes things richer....

Anyone experienced this? any thoughts?

Thanks!
Joe

 

Have you changed your jetting? Maybe go up to a 45 pilot jet and 170 main jet?

Can't help on the breathers, I have an old SE air filter, and it mounts to the head breather bolts. I don't seem to get any blowby however.

John

 

Now 100% of the air has to pass thru the filter causing slightly more restriction than you had before when some air could "free flow" into the intake thru the crankcase vent.
That extra restriction should be causing it to run slightly richer rather than leaner I would think unless as you pointed out the oil laden crankcase air was burning as it were fuel causing it to run "rich".
Try your extra shim but also be prepared to remove the one you have in there if it runs worse with the extra one.

 

I think the surging is far enough up the throttle and rev range that its a needle / main jet prob. Thing is I think the '06 already has a 180 main in it standard.... but i'll give the 45 pilot a try anyway after the needle if that doesn't sort it out. Thanks for the input.

 

Yeah I would have thought if anything it would be richer too... it feels really lean tho. But I've been wrong before.....

 

I think you might have hit the nail on the head.... Im gonna try pulling the filter later and see how that changes things.... If thats the case I better start looking for a better breathing filter.

 

Update - It was the filter. For anyone making the same change; the stock filter is too restrictive to run without the extra air from the head vents. If you install a breather kit, you'll need a free-er flowing filter. Im trying the K&N unit that fits in the regular housing. I looked up the specs and it does flow a good deal more air than stock. Not sure if its going to be enough extra air to need a bit of a rejet tho.

Thanks Hotlap for pointing me in the right direction.