This is a discussion on 05 yfz 450 Athena Big Bore Jetting within the Yamaha YFZ450/450R (2004-Present) forums, part of the Performance /Technical category; Looking for some jetting help here.
Elevation is 500 feet. Athena 480 big bore. Yosh full exhaust. Venterd air box lid. Vortec cdi. Stock carb ...
Elevation is 500 feet. Athena 480 big bore. Yosh full exhaust. Venterd air box lid. Vortec cdi. Stock carb with ziptie.
Low end and idle are great. Mid to top end is terrible. Hesitates badly.
Spark plug looks a little white. Adjusting the mixture screw has little to no affect.
Carb setting right now are 170 main, 45 pilot, needle that came with jet kit (slightly smaller taper than was in it originally) set at clip positon 6, mixture screw out 1 and 1/2.
Head pipe gets bright red very quickly. Acts like maybe it is running lean.
Bump the main to a 180, bump the pilot to a 48, pull the needle and if it is not a nvcq needle then go get one and set it to the 3rd clip. Set the screw to 2 to start and then adjust it once the bike is warmed up to get the smoothest idle. I assume that you are using keihin jets, if not, then let us know or switch over.
Bump the main to a 180, bump the pilot to a 48, pull the needle and if it is not a nvcq needle then go get one and set it to the 3rd clip. Set the screw to 2 to start and then adjust it once the bike is warmed up to get the smoothest idle. I assume that you are using keihin jets, if not, then let us know or switch over.
Tried this setup and it still misses like crazy in the mid to upper range. Bumped up to a 195 and 200 main and still no different. The spark plug with the 185 main and the setup you recomended looks good.
Cant find any air leaks around the carb. Is it possible the spark is crapping out in the higher rpm range?
It will be stamped on it and it will have 7 slots for adjustment.
When was the last time the valves were adjusted? How long has the BB been on it? How were you checking for intake/exhaust leaks? Has the carb ever sat for long periods of time with fuel in it?
It will be stamped on it and it will have 7 slots for adjustment.
When was the last time the valves were adjusted? How long has the BB been on it? How were you checking for intake/exhaust leaks? Has the carb ever sat for long periods of time with fuel in it?
Not sure when the valves were adjusted. Just bought it about a month ago. So not sure how long the BB has been on it either. According to my step brother who I bought it off of at the dealership, It was started every day to bring it in and out.
I checked for leaks by spraying starting fluid around the intake side of the carb while it was running to see if there was any change in the idle.
The needle I have has 7 slots but it is not satmped. It came with the dyno jet kit.
OK, so grab a copy of the shop manual from here, YFZ450 Garage and adjust the valves so they are with in spec
You will probably have to go get shims, and if you are always going to do your own maintenance, grab the hot cams kit and while you are at it, grab a 170, 175, 180 main jets, a 45 and a 48 pilot, and make sure they are Kiehin jets, and a NCVQ needle and set it up like I said before and when you are changing the jets, spray out the bottom of the carb with carb cleaner and compressed air, making sure you don't get any on the slide. This will ensure the carb is cleaned out.
OK, so grab a copy of the shop manual from here, YFZ450 Garage and adjust the valves so they are with in spec
You will probably have to go get shims, and if you are always going to do your own maintenance, grab the hot cams kit and while you are at it, grab a 170, 175, 180 main jets, a 45 and a 48 pilot, and make sure they are Kiehin jets, and a NCVQ needle and set it up like I said before and when you are changing the jets, spray out the bottom of the carb with carb cleaner and compressed air, making sure you don't get any on the slide. This will ensure the carb is cleaned out.
I ordered the Kiehin jets, and NCVQ needle. I will adjust the valves try the recomended setup again, and let you knwo. Might take a day or two.
Went to check the valves with the piston at top dead center and none of the feeler gauges would fit in. Is this typical. Is it possible that the shims are to large? It was like this for both the exhaust and intake side.
If you can't get the feeler gauges in, then you are to tight and they need to be adjusted. Follow the procedure in the book to the letter and they will step you all the way through it. Get those valves adjusted and lets see how that thing runs!
If you can't get the feeler gauges in, then you are to tight and they need to be adjusted. Follow the procedure in the book to the letter and they will step you all the way through it. Get those valves adjusted and lets see how that thing runs!
Adjusted the valves and it runs perfect now. Thanks so much.
05 yfz 450 Athena Big Bore Jetting
Linear Mode
