Took my airbox cover off

[trevor]

I thought I would experiment with the 750 and the issues I'm having with the bogging between 2800 and 3200 rpm and at the top of rpms when up around 7500 to redline I get some sputtering too. Anyway I took the cover off the filter box and went out for a ride. I was a little surprised that the bogging was almost not there at all but what really impressed my was how hard and clean it pulled all the way to redline. Any idea what gives? Is it ok to run my bike without the cover?
Thanks,
Trevor

[tkent02]

The cover makes it quieter, restricts the air flow a little bit. You must be a little rich, so a little more air works better?

[7981GS]

Is it ok to run my bike without the cover?
Thanks,
Trevor

The fresh air still has to go through the filter right?
My '81 1100EX has no cover and runs fine.

Eric

[trevor]

Yeah I'm really surprised what a difference there is. Not sure if I ever had it pull so hard to redline! That's fun!! I forgot to mention (not sure if it matters) I have a K&N filter in it and of course the V&H 4to1 stage one dyno. Thanks for the help guys, really appreciate it. Oh and it's ok to have the lid off then? And tkent I have been running a bit rich I believe.

[Billy Ricks]

The lid was probably not letting the K&N flow as well as it should. Jetting problems up top are usually rich conditions. If you still have the stumble down low that's needle position. A plug chop could help tell where you need to be on the needle.

[tkent02]

Spend some time tuning, get it perfect.
It will really wake it up.

[trevor]

Spend some time tuning, get it perfect.
It will really wake it up.

If what happened tonight is any indication, then it will be well worth it.
And Billy, I do think it is needle position too. Goody I get to take my carbs out.

[tkent02]

If what happened tonight is any indication, then it will be well worth it.
And Billy, I do think it is needle position too. Goody I get to take my carbs out.

The needles don't do much at wide open throttle, that's the main jet working. I bet someone put in too big main jets to compensate for the pipe/K&Ns, just took a guess at it, threw some jets in and called it good. You just made it a little less rich with the cover off. Find what size the bike came with, find out what size you have, go in between.

Pipe and K&Ns in the stock box shouldn't require a very big jet change. It's changing the intake that makes the bigger difference.

[trevor]

The needles don't do much at wide open throttle, that's the main jet working. I bet someone put in too big main jets to compensate for the pipe/K&Ns, just took a guess at it, threw some jets in and called it good. You just made it a little less rich with the cover off. Find what size the bike came with, find out what size you have, go in between.

Pipe and K&Ns in the stock box shouldn't require a very big jet change. It's changing the intake that makes the bigger difference.

Yeah Kent I was referring to the bogging at 2800-3200rpm. That's right isn't it?
Thanks,
Trevor

[tkent02]

With CV carbs the main jet will effect the lower circuits. CVs should be tuned from the top down, main jet first, then needles, then screws. It would be a shame to finally change main jets only to find out you had messed up something else and had to change back. You can take off an outboard float bowl, take a main jet out to see what size it is easily enough, maybe even swap all four without taking the carbs out. Most GSes you can if you are stubborn enough and have the right tiny tools.

I think it's likely someone just popped a bigger main jet in without really knowing what he was doing, if he had changed the needle position it wouldn't effect wide open at all. Since wide open was a little improved with the cover off I think he must have changed the main jets.

Find out what is in there first.

[Guest]

I have 115 main jets in my 750, that is what cleaned it up when I installed a pipe and a K&N filter. I also took into consideration the altitudes I ride at which would be between 3,500 ft and 9,000 ft. Once I get to around 6,000ft I usually have to bump up the idle a little.

[Frank Z.]

When i had my bike dynoed, the tuner removed the lid on 3rd run, as she was running a bit rich. Still have it off , and i have k&n filter as well (plus bored, cams, header). Not saying that this setup is ideal re optimum performance/tuning... tkent and others covered that pretty well in above posts.