hi all, Have an '88 sav which I have upgraded with one of Lancers vm36 carb kits I have a ryca RR-1 header into a sportster dyna silencer ( the one with the tab about halfway down the silencer ) tickover ( idle ) set at 1100 rpm air screw about 2turns out - main jet 175 pilot jet 20 and the needle clip is on the 2nd one down  I cant seem to lean the engine down the exhaust is still smoking and backfiring more than I would like when changing down ( from 3rd to 2nd to !st ) - not as bad as it has been but maybe one backfire and a couple or three pops, I dont want to keep messing as maybe its curable with something other than what I'm doing ( main jets and fiddling with the air screw ),any one got any advice, oh yeah at the moment when in mainly third occasionally second at constant speed it feels like its surging a little, any help welcome and if I've left anything out please say,cheers

I installed one of Lancer's kits.  I used an Oxygen sensor and meter to adjust my carb.  I live at an elevation of 500' - 800' msl, and I have a cam, Wiseco and self made exhaust similar to the DYNA.

Lancer's carb ran well right out of the box - however I did tweak it a bit using the O2 sensor.  I ended up with a 195 main jet, needle on the second notch from the bottom, and a # 20 pilot.

My bike runs really well.  It will pop and bang on deceleration if you completely close the throttle - you need to hold the throttle just a bit off idle if you want to make it run quiet.  It doesn't smoke out the exhaust or do anything weird........it runs very well.

Dave  

When you close the throttle completely when shifting or decelerating, you are closing off all the fuel flow to the engine except the idle circuit.  The high engine vacuum pulls a lot of air past the slide - but there is little fuel to mix with it and the fuel/air mixture is so lean that the spark plug cannot ignite the mix in the cylinder.  When you hold the throttle open a little bit you are lowering the vacuum and opening up the needle jet to allow a bit of air flow.  It will not hurt a thing to hold the throttle open a hair....

The Pilot Circuit only functions at idle a a bit higher - most of the partial throttle mixture is controlled by the needle.  Here is a good video on how to adjust your Idle Screw.  The stock carb has a idle fuel screw, the VM has an Idle air screw...so turning the screw in makes the mixture richer...turning it out allows more air flow and makes the mixture leaner.
https://www.youtube.com/watch?v=zm5mB3R8Ucw

Dave

Steddy58 wrote on 08/18/14 at 06:03:42:


No big deal....you have to jet the carb for what you got.....and the engine will tell you what it wants.  The only thing that would scare us, is if you were running a drag pipe or megaphone without any kind of baffles.

I used a big foam filter and a bit of the original rubber boot to extend the filter back between the frame rails.

Dave

OK tweaked and fiddled with and is now running to my satisfaction very few backfires or pops everything is rosy in the garden again thanks to all for the help, here is a pic of the machine you have been keeping running. moving the battery further back next so no doubt a few questions will be raised