Poor top end power?

Experts, please help me out.

The bike runs pretty good, and pulls hard from 3500 - 6500, but there it really seems to taper off much past that. Seems odd to me, and I didn't notice this before I installed the baffle in my exhaust.

Three questions:

1. Is it normal to be a little flat in the high rpm range?

2. Could adding baffles/re-packing the exhaust contribute?

3. Anything I can do to fix it?

I'm fairly confident something isn't right at this point, just don't know what. I was having trouble keeping my ignition timing correct so I swapped the points/condensers for an electronic timing plate instead. Timing is dead on the marks.

I guess I'll start by pulling the carbs again. Maybe I've got junk stuck in the jets?

The bike definitely stops pulling hard after about 6500 rpms. Any suggestions? Would a lean condition do that?

hows ur valve adjustment

Valves were adjusted less than 500 miles ago. They were good then, haven't checked since.

LukeMacPU wrote: Experts, please help me out.

The bike runs pretty good, and pulls hard from 3500 - 6500, but there it really seems to taper off much past that. Seems odd to me, and I didn't notice this before I installed the baffle in my exhaust.


Could adding baffles/re-packing the exhaust contribute?

Yes.
It is obvious that if the bike was ok before you installed the baffle then the baffle is causing your problem .
Why now start playing with a totally unrelated areas of the bike and fu*k them up too ?.

Adding the baffle or over packing has created too much back pressure which will restrict engine breathing at higher revs.
The exhaust is restricted allowing gas pressure to build up in the system and choke the engine.

An engine is an air pump and needs a reasonably unrestricted intake and outlet to function.

The higher the revs a higher amount of gas is flowed.

Pull Baffle, Enjoy Exhaust Sound.

Sounds pretty simple. I guess I'll pull the baffle packing and see what that does.

Best case, my problem is solved. Worst case, I find out that's not it.

Don't know why I didn't think of that.

I'm with ZED1015 on this. It has been my experience that if my bike ran fine and then after working on it it doesn't then what I worked on caused the problem.
Either pull the baffle out or if you want it quieter then go down one size on the main jet.

Running a fuel filter? Check to see if it's clogged too.

At 6000 that bike should pull your head off.

Baffle on jet.

Do you know the jet sizes. What kind of exhaust? Roy

roy-b-boy-b wrote: At 6000 that bike should pull your head off.

Baffle on jet.

Do you know the jet sizes. What kind of exhaust? Roy

Don't know the jet sizes, I've not changed them, but could be anything in a bike that's been around since '75. I got a good look at the pilots when I had the carbs off, but not the primaries.

My exhaust is a 4-into-1 of unknown manufacturer. It has roughly a 1.5" straight-through baffle in a megaphone exhaust can. When I got it, there was no packing at all and the baffle, roughly 16" long, was loose inside. I was able to weld it back to the end cap and re-install. Just added packing recently.

It is quieter, but I didn't really expect much change in performance with the straight through design. I'll pull it out and see what I've got. If it gets better, I'll leave it out. If not, I'll pull the carbs off and get back to work starting with checking the primary jet size.

Thanks again for all the help. This site is great!

if it gets better when u remove the packing, u have confirmed the problem. next step would be to solve it. if thats the problem , and u prefer to have the packing in. then u may just have to rejet to get the top end back.