dynojets for more power?

[zlam27]

ok, on my 400ex with a T-4, K&N, no lid or choke, i was runnin a 160 dynojet with the stock needle. i was told that i should use a dj needle if i was gonna use a dj main, so i bought a 158 keihn. i thought i might be runnin a little rich so i figured that would be just about right (also a dirtwheels article with the same mods -except the choke and 750ft higher- ran a 155). anyway, when i took it riding today, it just didnt seem to run quite as good as the dynojet did....

on topend (like 5th on the road) it didnt seem like it would wind out as far, acted like it was pullin but didnt have the power

the throttle response was a little worse, or else in the midrange it just didnt pick up as quick.

on decel, it seemed to pop and sputter a bit more (not real loud or anything, just enough to be noticeable)

overall it just seemed like it lost a slight amount of power/torque.
so what does everyone think i should do? do the DJ add a bit of power, or what is the point of buying them when you can get stock jets in different sizes?

anyone wanna sell a dynojet needle?

zach

[zlam27]

hey cal, if you read this... do you think screwing in that needle too far is givin me the problems listed??

[carlj75]

Your 160 dynojet is equivelant to a 150 stock jet according to this chart. http://www.ds650.net/mikunivsdynojet.htm Maybe you are running to rich with that 158 stock jet. Try the 150.

[cals400ex]

wait a second here. one little mistake carl. your comparing dynojet to mikuni. the thing is, we have keihin carbs. he is trying to compare keihin to dynojet. however, that i a nice little chart and i would love to see dynojet vs keihin. i have never dealt with dynojet but from what i have been told, dynojet #'s run one size bigger than keihin's. for example, a 150 dynojet is about a 152 keihin. a 152 dynojet is about a 155 keihin. as you can see, this math here is not exact. its just an estimate. if you really think the dynojet made the bike run better, you could try to run a 160 or a 162 keihin. i know that involves buying new jets and buying crap that you may not use sucks. since i am constantly rejetting my bike, i have every size keihin from a 150 to a 165. i found my bike to run best with a 160 keihin in. i have a complete x-6 pipe, uni filter, no lid, no choke. i am a few hundred feet above sea level and the temp outside is higher 80's. i still haven't got the bike totally tuned in since i received my pipe, but the 160 feels stronger than a 158 and a 162 so that is where i left it. if you think the bike is faster with the bigger jet in, i would use the bigger jet. one thing i would try to avoid is switching back and forth from keihin to dynojet. this will just get confusing. some claim the taper on the dynojet makes a litttle more power. is it true? i have no clue and i probally never will since i have every size jet that keihin makes for what i need. so i would either get a few more keihin jets or a few more dynojets. i have no clue if you need a dynojet needle for a dynojet mainjet. i do think the taper on the dynojet needle is different from stock. as for the jet needle, i noticed a decent loss in midrange on up when i had the jet needle skrewed all the way in. the bike ran fine without any misses or spudders but did not have all the power. i took the carb back off and did a little investigating. if you can picture this it may help: the mainjet is on the bottom of the carb. the mainjet skrews into the needle jet. skrewing the needle jet all the way in raises the needle jet and the mainjet. raising the mainjet may not let is suck fuel from the bottom of the bowl. i figured this had to be my problem. you should also realize that lowering the needle jet lowers the mainjet. you probally won't want the mainjet at the very bottom of the carb where it is more likely to pick up dust or dirt that happens to get in the carb. so what i found to work good was skrew the lock nut down on the needle jet to where you can count 3 to 4 threads on the needle jet. you with me?? for your deceleration problem, i assume you mean when you are giving the bike no throttle and just slowing down? this should not have anything to do with the mainjet. could a needle jet that is adjusted incorrectly affect this? i really don't know. i would bet it would have something to do with the pilot jet or fuel skrew since your at less than 1/4 throttle. it seems weird to me that it acted different by just changing the mainjets and not adjusting anything else. if you have any more questions just post them and i will try my best to help. good luck

[zlam27]

hey cal, i cant thank you enough for taking so much time to help me out. sounds like tonight im gonna take the carb back out and unscrew that needle a little bit.

as i was readin your post, i thought to myself... wouldnt screwing that needle jet in farther have almost the same effect as adjusting the clip on the jet needle. well that got me thinking about how the dynojet is so much shorter than the keihin and what kind of effects that had on everything. with the needle adjusted to the same spot, the dynojet is quite a bit shorter so im sure the dynojet needle compensates for that also. anyway, i wish there just werent so many variables in jetting - 99% of us get too confused with all the jets, screws, weather, etc.

another quick ? for anyone.... how do you get the spark plug out? i cant get a deep-well socket on it that will fit down the groove in the valve cover. any thoughts?

zach

[carlj75]

Oops, I just assumed that the chart would work for our carbs as well.
Zlam: do you have the tool kit that came with the bike? The spark plug wrench in it is the best thing I have found to use.

[cals400ex]

i also wondered if adjusting the needle jet holder up and down would affect the function of the needle itself. sorry, i think i was calling that piece that we are adjusting the wrong name. it is actually called the needle jet holder. i don't think the jet needle(the needle itself) rests on the needle jet holder but i don't know.



JOEX has attached this image:


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this is what the inside of the carb looks like.

[cals400ex]

sorry, the pic did not work. use the search button to type in "needle jet holder." i have a post that shows the the whole carb. as far as the plug goes, you will probally need a deep well socket or the factory plug wrench.