full fmf... v force 4 reeds... no spacer, mikuni stock carb, stock piston, stock intake boot with foam filter, 310 jet, its a beauty... until i changed to a uni filter right at the carby and now doesnt give me what it used to at the end of the revs...as if the last 1/4 of the power doesnt get enough fuel or something...tried from 310 to 350 jetting but the same... needle position is one richer than the middle groove... tried from the air mixure screw but still no luck... any help would be greatly appreciated...
intake change... jetting needed?
- Thread starter transmental
- Start date
In thinking about it the aerodynamics of having the filter direct on carb vs under the seat could also make it harder for the engine to get air because of the negative air pressure of air rushing by the filter, but I have never dealt with this issue, so don't take my word for it.
filters right on the carb works......for big carbs on drag engines @ wide open throttle only. IMO
for these little stock carbs, the turbulance the filter creates directly into the carb has caused more than a few jetting migranes.
the solution is putting some sort of distance between the carb and filter to allow the air time to straighten out and flow smoothly over the jets.
some on here have used 1-1/4" - 2" pvc as a velocity stack, 6" - 8" seems to be the magic #
there are DIY threads on here somewhere.
fittings and adapters for fitting different sizes together can be had here, best boots made IMO
http://www.siliconeintakes.com/intake-pipe-reducer/?osCsid=f312177062cec6c1edae64de8eb8d5fafor
for example, my 34mm carb to CFM airbox takes a 2.25mm to 2.5mm silicon intakes reducer
for these little stock carbs, the turbulance the filter creates directly into the carb has caused more than a few jetting migranes.
the solution is putting some sort of distance between the carb and filter to allow the air time to straighten out and flow smoothly over the jets.
some on here have used 1-1/4" - 2" pvc as a velocity stack, 6" - 8" seems to be the magic #
there are DIY threads on here somewhere.
fittings and adapters for fitting different sizes together can be had here, best boots made IMO
http://www.siliconeintakes.com/intake-pipe-reducer/?osCsid=f312177062cec6c1edae64de8eb8d5fafor
for example, my 34mm carb to CFM airbox takes a 2.25mm to 2.5mm silicon intakes reducer
mmm... never plug chopped... will try... also will move the filter back bout 7 inchs... leak test turned good... im guessing its just a 2 stroke behaving like a 2 stroke right... so will it normally ask for more fuel with the better airflow?
gonna move the filter back 7 inches? why not just use the stock system back when it worked fine for you?
sure will, any increase of flow, into or out of the engine, will require a jetting increase.
usually an airscrew adjustment, sometimes a needle clip move,
and always a main jet increase, confirmed by plugchops
i am close to considering putting the stock boot back on... tried everythng exept the spacer between carb and filter... if i can get a good tight seal with auto zone supplies will give it a try but really wanted that un filter right behind da carb... looked awesme...
90% of the time your leg is in the way. you want something to look awesome? polish a CFM airbox
got some work done today. all new oil seals in the bottom. some parts bolted on.
I always have, always will, run a foam filter directly bolted up to the carb throat, and I just do not do it for looks.
Yes you will experience some jetting problems, especially when the filter gets dirty or you over do the oil when you clean it.
I do it because I find I suits my style of riding.
Yes you will experience some jetting problems, especially when the filter gets dirty or you over do the oil when you clean it.
I do it because I find I suits my style of riding.
OR BUY A TRX 250R AIRBOX ON FLEEBAY FOR $3O WAYYY BETTER AIR FLOW AND ITS READY FOR A BIGGER CARB IF/WHEN YOU WANT TO UPGRADE
So i moved the filter back 6 inches with a radiator hose from autozone and its working like a champ... still wanted it right at the carb but wasnt able to succesfully jet it... this does take more than general knowledge to achieve but thanks to you guys i got that unifilter on there and trailed the Sunland Park NM desert... have a good week guys and ill keep posted.
