Engine going weak when riding

I have an issue that I has me stumped. My bike will crank up and run but when I try to rev past 5,000 rpms (in any gear)it boggs down. What the hell is going on? Please help me, I just want to ride. It's a kz440 LTD btw.

Check to make sure your timing advancer is not frozen.

I'm sure I sound like an idiot but what is that and how can I check it?

You don't sound like an idiot at all. Under the point cover on the right side you will find the timing advance unit attached to the right side of the crankshaft. There should be 2 screws holding this cover on. The easiest way to check this is with a timing light. With the engine running and the light hooked up, when you rev the engine you will see the timing mark on the advancer move as the engine gains rpms. If you don't have a light, try to find a buddy to borrow one from or possibly check with autozone (they have a program where they will loan you tools with a deposit). I hesitate to tell you to tear the points plate off and remove the advancer to verify it's condition since that is going to require you to reset the points and timing. Better to verify it first in case it is not stuck and it turns out to be something else.

in addition to that also check the fuel filter to make sure its clean and not starving for fuel

BSKZ650 wrote:

in addition to that also check the fuel filter to make sure its clean and not starving for fuel

I must admit, I am still a little perplexed about the timing thing. I am going to check my manual and see if I can borrow a timing light but maybe there are some other things I could check in the meantime (besides the fuel filter, I'll check that too)?

Rather than bum a timing light, I would go ahead and buy one, get a inductive pick up, they are not that expensive, and you will use it several time during the life of the bike or bikes

The Gringo wrote:

You don't sound like an idiot at all. Under the point cover on the right side you will find the timing advance unit attached to the right side of the crankshaft. There should be 2 screws holding this cover on. The easiest way to check this is with a timing light. With the engine running and the light hooked up, when you rev the engine you will see the timing mark on the advancer move as the engine gains rpms. If you don't have a light, try to find a buddy to borrow one from or possibly check with autozone (they have a program where they will loan you tools with a deposit). I hesitate to tell you to tear the points plate off and remove the advancer to verify it's condition since that is going to require you to reset the points and timing. Better to verify it first in case it is not stuck and it turns out to be something else.

FYI, the '81 440 has electronic ignition--no points.

What type of air filters are installed on this bike?

I know that bogging sound well. Fought it all last Spring. In my case it turned out to be a torn diaphram in the carb. Once it was replaced it was fine.

The problems never showed up unless I was revving above 4500-5000 rpm's. Wired George could explain better, but I believe that's when the diaphram is supposed to lift the needle and open up the needle jet allowing more fuel to flow in the 1/2-full throttle range.

No lift - no fuel - depressing bogging sound.

Good luck!

I replaced the slightly torn carb diaphraghms with some clean ones that I got off an ebay set of carbs. That helped but it is still bogging down. Since I replaced the diaphraghms it is more responsive and goes up to a higher rpm before bogging and the bogging isn't as intense but still there.

A side note, when you replace the carb diaphraghm are you supposed to lube the sides of the slides?

Post edited by: EasyRider1, at: 2008/02/04 14:08

I don't think so. My kz750's carb's slides were actually stuck together with corrosion. I checked with Wiredgeorge over on his website he said to clean them up with emory cloth (I think). Just tried to search the archive over there to check but the post was gone.

My guess is that the tolerances are so tight that anything that could increase the friction between the slide and the body should be avoided.