1998 evo flsts. Keihn carb with dynojet kit. 175 main, 45 slow, mix out 2 1/4, clip on needle on 4th clip down from top. Ev 27 cam, stock header pipe with VH slip ons. K&n air filter. Bike has no power in 5th gear. Runs strong in 4 th. When throttle is cracked from 1/2 throttle to Wot, nothing basically happens. Slowly builds speed but takes awhile. That is at 65mph.
Have checked timing, changed plugs, and put on Taylor plug wires. Also changed out intake gaskets and carb to intake seal.
I tried various jets up to 195 but no change.
Any ideas where to look next?

 

CV carb.. Make sure the slide diaphragm does not have any holes in it..

 

BINGO ! That happened to mine and I replaced it with a Mikuni HSR42. Throttle response is excellent and once tuned,has been problem free for 10 yrs now. My bike sneezed one day thru the carb and ripped a small tear in the diaphragm on the Keihn OEM carb. Bike ran erratic thru all 5 gears .

 

I will check diaphragm. Bike runs good and hard in all gears and rpm until I hit 5th. Am going to also check gearing. Snowing here, so further testing will have to wait for now.

 

you can buy a new slide/diaphragm or just replace the diaphragm for around 20 bucks.

 

Thanks bustert. I changed out the carb with a spare keihn that I had. It has the same set up as the carb that was on bike, except it had a 185 main jet. Bike ran pretty much exactly the same. Gutless in 5th when at wot against a slight head wind. Not bad when going with the wind. I have a couple other evos that I am comparing this bike with. One is bare bones stock with original air cleaner and carb. It has more power in 5th than this bike has. I did test the voes and switch doesn't close until I have 5.5 in. of vacuum. The manual calls for 3.5-4.5. Not sure if that would be the problem. Like I stated earlier the bike pulls really well all the way through 4th. 5th is the problem.

 

curious, what rpm are you trying to pull at and what is the drive ratio?

the voes will retard timing when tripped. it is mainly to help reduce heat load at wot. can you sneak up on the limiter?
will the response change when you tweak back the throttle?
lastly, what are your compression numbers?

 

Don't have a tach on this one, but i would think I'd be doing around 2800 rpm at 65 in 5th. Just going by what one of my other evo softail does that has a tach on it. 65 tooth rear pulley. Did compression test last fall, and the numbers were within spec according to manual. Have the numbers written down somewhere.
When at wot, and I back off to 7/8's, the bike wants to keep gaining speed.
I am going to recheck intake leaks tomorrow.

 

Does this bike have a cam in it? I'd run a compression check.. See what you got.. Does it have a 32 tooth front pulley? I take it you are not the original owner.

 

well at 2800 rpm, and in top gear, torque level will be low. if you back off and it starts to go, then there is a mix issue. if she sorta sputters, rich, takes off screaming, lean. there is on issue that can cause this on a slam and that is the accelerator pump. when the throttle is yanked open, manifold pressure goes atmospheric and flow stops, when this happens, fuel drops out. the pump squirts some fuel into the venturi to give the engine a boost since it has now gone lean. with the load, it might take awhile for the engine to recover and may even want to quit all together. remember, with atmospheric at the venturi there is little diff'l to pull the fuel up the jet and mixing well. which leads to maybe a clogged carb component.