what carb kit please?-with modified pipes/K&N filters? BS38s

philby

hi guys! I'm back in Oz after 6 months of dicking with my carbs in the philippines and no results! so its time to reach out and solve the problem as people will send me parts here down under!

Im running K&N filters and have cut my pipes short and added my own 'staintune' type 3" endcaps. check my posts about how i modded them- theres thumbnails there in the posts (muffler section?).
the carbs are stock bs38's. the diaphrams look ok and have no splits/holes. theres no vacumn leaks now and theyre pretty clean outside and in. just cant get them to run any good.

what size jets should i be using?
should i adjust the needles on the slides?
-(take them up or down a couple of pegs?)
ive fitted a pair of new needle and seats, but should they be a certain size?
and what else can i do?

John, I'm sure you would have some answers for me, particularly in regards to your needle sets, but can you ship to NSW australia? and do you have sets for bs38's?

it seems one cylinder is firing fine yet one seems to run cold (especially at low revs). im getting bad backfiring when deaccelerating or idling yet she hammers out on the highway...

any help greatly appreciated!

jayel

there is no set jetting for what you are looking for, your best bet would be to buy a stock carb kit with the adjustable needles (canadian set) then you will need to adjust up or down on the pilots and mains according to what your plugs tell you, since it makes no sense to buy a full range of jets buy two extra sets of the smallest (mikesxs or 650central), get a set of acetylene tip cleaning drills (very small sizes) and start drilling one set of jets out one size at a time, (keep track of what size you are at) then when you go to far you can drill the second set to correct size....... moving the needle clip up and down will allow mid-range adjustment but you need to get the pilots and mains good first..... one cylinder running cold, weak coil, bad plug wire, bad cap or condenser to find carb kits mikesxs or 650central or ebay (sirius consolidated) may have the kits (warning sirius kits may contain incorrect componets) hopefully with your homemade exhaust and pod filters you won't have changed things so much that you have to get into changing nozzle jets and different needles..........bad backfiring when deaccelerating ---you're lean on that side or losing spark, again, weak coil, bad plug wire, bad cap or condenser, check carb intake boots and throttle shaft seals also, sucking air at either place will lean that side......... and don't forget that little O-ring under the nozzle jet

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

What year carb set? You must base your re-jetiing on what was stock for your year carbs. Usual scenario is one or 2 up on the mains, lower (lean) the needle one step if larger mains cause midrange break-up, go up one on pilots if lowering needle causes off idle flat spot.

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