Reving High With Low(er) Power

[Nighty]

I am reading bens jetting faq at the moment.

GREAT STUFF!

 

Since a few weeks my banshee lost a few mph.

I didnt care much at first since top speed is not what i ride alot.

 

but while doing a drag with my cousin i felt/noticed a powerloss

in the high revs.

After trying a bit i found out that it will rev higher but it just wont deliver power.

Since i also installed a timing plate set at 4 degrees advanced,

I want to rule out first that this can be caused by to much timing advantage.

 

The spark plugs look fine but i will try with fresh plugs to make sure.

Any chance this is caused by the timing? or will this definatly be a lean jetting issue. (which is likely since temp has dropped 20 deg Celcius)

 

Bike runs great in all the other rev ranges. no bogging no hesitation just giving up in the high revs.

Also compression was great 3 weeks ago 125 psi both sides.

 

Thanks for any comment!

[boonman]

I am betting that the jetting is lean. Revving "zingy" and not having alot of ass means that it is lean. Lean is mean, but sometimes better safe than sorry....

[BenBB]

I agree with boonman, sounds like you could go up a size on the mains. Did it get colder lately? If so that's a good indication that it's lean now...

[Aussie Quad Racer]

changing the ignition timing can affect jetting.

[Nighty]

Oke thanks all so far,

 

Yes it has become colder, i'll try the choke trick tomorow.

 

Ausie do you happen to know,

how i can check that timing is not the issue?

 

Or will this be a mather of testing.

Going back to 0 deg advantage and test?

[Aussie Quad Racer]

the more advance you give the engine, it will have more time to burn before tdc so therefore the more advance the leaner the engine gets.

 

For plus 4degress you may have to go up on size on the main

[Banchetta]

Sounds to me that your lean...The "lean is mean" expression is bullshit....I had more hp on the dyno w/ a chocalate brown plugs, then w/ tan plugs....Go up on the mains a couple of sizes and do a wot test in 6th gear for 5-10 seconds, shut it down, coast to a stop and check the plugs...

[Nighty]

will do!

i have new plugs,

currently running 280 mains.

 

i'll up the mains to 320 since i dont have any other jets at hand.

screw in new plugs and do the wot test.

 

Can i hack open the old plugs to see my overal jetting?

 

thanks.

[BansheeBrian]

After a WOT in 6th.You bet!!

If you have a 13 tooth on the front it will almost feel like your lean because you rev out in a hurry.

[Nighty]

Its a 15 tooth.

With a 14 tooth. its noticed even more.

 

Havent done the mains yet.. my axle bearrings are toast..

 

Work in Progress

[National Banshee]

That sounds like older FMF pipes.

[Nighty]

Axle bearings fixed,

Air filter cleaned,

Frame painted,

uped the mains to 340.. since i didnt had any other on hand.

replaced brake pads.

 

Have to place the fenders tomorow and do the wot.

I hope it doesnt bog.

 

if it does.. time for a k&n filter.

 

National banshee.

I'm running t5's

[Nighty]

Tried the banshee today,

 

It ran like crap.

Idle is good mid range good

throttle pinned is bad. in the low rpms it bogs, after helping the engine up to speed with some nice clutch work, or slowly adding throttle from start

it will hold up in the high revs.

 

Went back home and took an old airbox cap drilled holes in the cap and placed it on the banshee.

 

Tried again,

Runs absolutly fabulous, no more bogging at wot the speed loss at top is gone.

but if i'm cruising around 1/4th throttle low rev in lets say: 2nd gear.

and just SLAM the throttle wide open the engine will start to rev.. bog 3 times right before the powerband and then just flies away.

 

I searched the jetting faq for this problem but WOT at low rev is not discussed in it.

 

Any idea's what should be done?

Ill try my air screws tomorow.

 

Thanks for the info so far its much better already! if i can get the bog spot out i'll be flying again.

[shortys racing]

Tried the banshee today,

 

It ran like crap.

Idle is good mid range good

throttle pinned is bad.  in the low rpms it bogs, after helping the engine up to speed with some nice clutch work, or slowly adding throttle from start

it will hold up in the high revs.

 

Went back home  and took an old airbox cap  drilled holes in the cap and placed it on the banshee.

 

Tried again,

Runs absolutly fabulous, no more bogging at wot  the speed loss at top is gone.

but if i'm cruising around 1/4th throttle low rev in lets say: 2nd gear.

and just SLAM the throttle wide open the engine will start to rev.. bog 3 times right before the powerband and then just flies away.

 

I searched the jetting faq for this problem but  WOT at low rev is not discussed in it.

 

Any idea's what should be done?

Ill try my air screws tomorow.

 

Thanks for the info so far its much better already! if i can get the bog spot out i'll be flying again.

should up the compression a bit... 125 is stock, 150 is more like where a banshee likes it.

[BenBB]

You're on the right track Nighty, keep at it:

 

You started at 280 mains and it was lean, went to 340's and it was way rich, drilled holes in the airbox lid to lean it out and it helped (if I'm reading it right), try 330 mains and see how it runs...