TOPIC:

Time for a summary;
Symptoms;
Bike makes a rattling/knocking noise at any RPM past idle. Starting is a bit difficult but idling is just fine. The bike won't go past 4000 rpms when under load. Shifting to the next gear gives it some ability to further accelerate but again, not past 4000 rpms, and when the clutch lever is pulled -- e.g. to stop for a traffic light -- the engine slows down and dies.
This kind of shitty running must be caused by either ; Bad compression, no good fuel supply or a bad spark. (assumptions)

-I refurbished the head, relapped the valves, reset clearences, replaced head- and exhaust gasket, checked the cam chain tension and timing. All seem o.k.
-I cleaned the carbs, replaced the vacuum diaphragms and checked if the fuel supply from the petcock was in proper working order. All seem o.k.

Last straw I have is a problem in the electric system. The Timing advancer is moving smoothly and the pickup-coil touches the eccentric piece precisely at the F-mark. The battery is pretty flakey though.
A quick test of the ignition coil measured 2.6 /2.7 ohms at the primary coil. A measurement accross the spark plug read 0.6 / 0.7 Mega-ohms.
Lastly; Last time after I had ran the engine (with choke on, statically) the spark plugs appeared somewhat moist. Again a symptom of a mediocre spark?

Could it be that my issues are simply electric problems? After all; A rattling inside exhaust tube can not affect performance this way, can it?

Does your bike have a counter balancer? On the 750 twins they did. You might check into this. What year and model is it?
Steve

Jep it has a counterbalancer that is -- i believe-- driven by a chain. It's a 1981 kz440 LTD A2 model. Don't see how an offset counterbalancer causes this kind of issues though.

I seriously hope that isn't the case because besides all the hassle of fixing it i will have to withstand all the bullshit and ridicule of my flatmate who is fixing a triumph 21 3TA -- A non balanced parallel twin -- that has vibrated itself to death and is now being brought back from the depths of destruction, claiming british '50 engineering is the pinnacle of human civilisation.

Well then, get yourself a Z1 or KZ 1000 and let him smell your fumes. It was the Jap bikes the doomed the Brit bikes. I see Triumph Has a triple out as well as a twin. I had a Norton Commando and a Trident in the 80's. Wish I had them now. I still rode my Z1 as a daily driver and sold the Brit bikes to a friend.
Steve

Janklaassen wrote: Could it be that my issues are simply electric problems? After all; A rattling inside exhaust tube can not affect performance this way, can it?

I'd say not, but the loose inside #4 pipe made it sound (and feel) like the engine would come apart if pushed too hard. If I remember correctly, I was reluctant to take the engine past 4000rpms because the vibration became intense at that engine speed, after starting at around 3500. Below that though, the vibration went away.

Pull the top end off so you can check the rod bearing's.
I bet the big end on that rod is nice and blue.
IMO it's spun a rod bearing. You've check every thing but that and haven't found the problem
so nothing else left.

I was thinking broken piston skirt.

swest wrote: I was thinking broken piston skirt.

Heck, a Harley friend had a brand new Nightster with a loose bolt hidden inside his brand-new Stage-3 Screaming Eagle motor. It ran for a short time...then left him stranded. Warranty covered it, but he missed the best weather for riding that year.

I had a Huge biker ask me, "I don't want to know why you ride a Kawasaki but why you don't ride a Harley." Not wanting to hurt his feelings I told him I don't like the image. The truth is, I like to ride not wrench.
Steve

I just tell em I don't like over priced slow chit then call them out for a race and
have them back pedal because they can't stand to get beatin front of their buddy's by a POS JAP. bike.

I've always been a loner. When I come up to hogs on the road, they sneer at me as I ride by. That V/H 4/1 growls at them as I pass. They want no part of it. We've bee on top of mountain trails, desert dirt roads, twisty high speed turns and one end of the state to the other. Going for a "putt" isn't the word for us, It's called an adventure.
Steve

Forget it, Piston ring(s) are blown.
I remember seeing a little oil seeping through the clutch cover mating surface but thought it must have come from the chain spinning fast whilst running. This was before I installed a new head gasket. Today I tried to run the bike with a borrowed ignition coil to see if it would make a difference. Somehow decided to take off the oil cap off to see if any noise was coming from in there. Might as well have put a cork in the exhausts because an insane amount of gas was coming outa there. This is gonna be a winter job I suppose. Find a nice little work bench somewhere and take the top completely apart.