650ex jetting

[tayyo789]

i recently built a hybrid using a 400ex frame and an xr650r engine and i am using a mikuni tm40 carb. i ride mostly dunes here in oregon, so elevation is around sea level. im just looking for a good starting spot with my jetting that i could work from. i hope you guys can help me, and if not maybe point me in the right direction

[2muchquad]

dude,seriously,get yourself a keihin fcr carb.Verry few people can jet a mikuni non round slide carb.not to mention the fcr carbs are easier to jet and have more performance,thats why they were on the mx bikes.You can get them cheap if you look around.

[tayyo789]

actually, i have had both an fcr and an edelbrock quicksilver 2. the edelbrock was nothing but a pain, and the fcr was far too large dimensionally to fit in the space that i have for a carb. arlen at led built my exhaust to fit around the edelbrock, and the boot that i fabricated requires the same dimensions as the edelbrock as far as the parts that connect to my boots go. the fcr only fit if i turned it at about a 60 degree angle from vertical. and i have done quite a bit of research on the performance of the mikuni in comparison to the fcr and the results seemed positive as long as the jetting is correct. i dont mind spending the man hours to get it perfect, i just want as much help for a starting point as i can get. oh, and i also ran a lectron for a while, but the throttle cable came out the top of the carb, which caused some issues with my gas tank, so that brand is out too, although it ran great.

[2muchquad]

try a 220 main and a 17.5 pilot,whats your current settings?that tm series carb uses the same hex style main jets as the tmx series carbs that came on the late 90s yz125s and 250s correct?

[tayyo789]

it doesnt seem to have that type of main jet in it. if it helps at all i have also seen it labeled as an hs40 as well

[2muchquad]

is that one of those cv style(constant velocity)carbs that they use on street bikes and utility quads?what size main is in it now,round style or hex?

[tayyo789]

the mains are round, and it came with a 140 out of the box. the folks on thumper talk that are running this carb on their xr650r's are giving me some ideas, but im just looking for as many opinions as i can get. im not entirely sure on what these carbs come on, but i know that some harleys have them, because i have to go to my local harley dealer to buy jets

[tayyo789]

heres a link to the exploded manual:

http://www.mikuni.com/pdf/hs40_manual.pdf

[boosted3g]

You seriously need a 45mm carb on that thing. TM45s are cheap also since they are just glorified Harley carb. It will really wake up the top end, its probably super snappy with that carb but is lacking top end.

[tayyo789]

the lectron that i was running was a 46 and it was so big that i couldnt even pull the top half of third gear. i dont use much of my top end anyways. i like short technical hills, thats why i went with a torque monster of an engine

[2muchquad]

go with a 400ex carb..seriously,if you want a low to mid range monster,the 400ex will do it,i guarantee it,you may not have killer topend but it will still pull strong up top.The ac pump will work good with that motor,plus they are cheap,nothing ventured nothing gain,you'll like it though,it'll feed that thirsty beast of yours..no doubt.bigger isnt always better;) throttle response will be off the charts,wheelies at will

[tayyo789]

with all the carbs i have used in my life, i have a good feeling about this one. im really fond of the accelerator pump adjustments. this is the carb for me. i honestly do not want another one. maybe its that im getting tired of going from one to another, but all im asking for is jetting suggestions, not what kind of carb i should have bought. ive done my research, and this one is right for me.

[2muchquad]

its hard for someone to give suggestions whithout a accurate description of what its doing.Its it flat up top or bog off idle what?for as far as we know it may run fine with it as is who knows,obviously you dont think its performing up to your standards or you wouldnt be trying to troubleshoot your current jetting.We need to know what rang does it run poorly at?

[tayyo789]

i just bought it last week, and it arrived yesterday. i cant get it started and before i ruin my already feeble leg by kicking it for 3 days, i would like a good starting point. mikuni did not provide me with jets, because it was an ebay carb. i cant even get it to kick over as it is, and once it starts, i can fine tune just fine myself, i dont need help with that. i just need to start it, thats all. as my original post stated, a starting point.

[SilverBomb]

I run a TM45 on my DS650 and run a 145 main at 4500-5000ft here in Utah. I run a direct mount K&N though. If I run a full intake I go up to 155. I ran pretty good with a 155-157.5 in Glamis with the direct mount K&N, which is at sea level. So let me know what kind of intake you're running and I'll have a better idea of what to tell you. So in a nutshell if you run a direct mount K&N I would start out at 155, if you run and intake boot/air box I would run around 165 at sea level. Try that out and see how it runs. Good luck man.:D

[tayyo789]

i have a full intake with an air box. the lectron 46 i had was actually off of my dads ds650. if you ever get tired of the tm i strongly recommend a lectron. people say theyre hard to tune but i think theyre one of the easiest. no pump though:ermm:
but thanks for the suggestions. im backed up right now getting all of our utility bikes ready for bow season this weekend, and getting back to corvallis for school, so it will be a while before i can get back and get my bike ready for our next trip to the dunes. were shooting for glamis at christmas, and 5 bikes to rebuild. i have my work cut out for me lol