Possible seizure?

Ok i will go through the steps that happened.
- i was riding my bike as normal with no issues.
- The bike began to make some strange noices and there was a sugnificant loss in power. Sounded like metal.
- I decided to head home and coast it back. I felt like only one piston was firing.
- All of a sudden the bike felt it wanted to stall so i decided to dip the clutch and give it some revs.
- The bike did then stall but when i let the clutch out the back tire emmediatly locked up nearly spitting me off.
- Now the bike refuses to bump start the back wheel just completely locks.
So not wanting to cause any more to damage i pulled over and tried to figure out what was up.

- The gear box goes up and down the gears whilst bike is off
- The clutch does disingage the engine so is able to free wheel.
-The starter does turn over the engine.

But as soon as a gear is engaged the back wheel locks completely.

Any help would be appreciated.

Welcome to KZR.
Providing some additional information will help folks offer useful suggestions. Most importantly, which year, make and model of vehicle are you asking about?
For example, if you have a KZ200, the fact that it is running on one cylinder is a good indication. If it is a KZ1300, you have a serious problem. If it is a Wankel powered Suzuki, you may be on drugs.
You say that the bike will not bump start, but that the starter turns the engine. Will the engine start?
The gearbox goes up and down with the engine off? If it is a KZ, it should not be able to go into any gears except first and neutral.
As soon as a gear is engaged, the rear wheel locks up. Of course, that is normal if the engine is off. If this happens when you are pulling on the clutch lever (clutch disengaged) then there may be a problem.
Honestly, based on my interpretation of what you describe, I'd guess that there is a problem with the clutch or perhaps the countershaft sprocket has come loose.

Thankyo
Sorry yes i forgot to say its a 1979 kz400.

I have not 1et the bike start just breifly preshed the starter to see if it turns. I did not want to cause any more damage.

Thats what i ment yes you can engage 1st and back to neutral.

Yes this is happening when the bike is on and attempting to bump start. But as soon as the clutch is let out the back wheel locks solid and skids. The bike was able to bump start previously.

Does the rear tire release with the clutch is pulled in and when was the last time you checked the oil?

RichHubb wrote: Thankyo
Sorry yes i forgot to say its a 1979 kz400.

I have not 1et the bike start just breifly preshed the starter to see if it turns. I did not want to cause any more damage.

Thats what i ment yes you can engage 1st and back to neutral.

Yes this is happening when the bike is on and attempting to bump start. But as soon as the clutch is let out the back wheel locks solid and skids. The bike was able to bump start previously.

Hmmm. The bike can freewheel/be pushed in neutral so it's unlikely the rear brakes have separated (brake shoe from backing plate).

The fact that it will not bump start now makes me wonder if your cam chain has broken, or possibly a camshaft has broken. If the cam chain doesn't spin the cams, the valves will not open and you may be trying to spin the engine against a cylinder where both valves are shut. A broken camshaft would do the same thing, and depending where it broke could cause the engine to run on one cylinder (I think).

But you said the starter will spin the engine. Are you sure the engine is actually turning over? Or is just the starter motor spinning? Does the starter sound the same as it did when you left to go on that ride?

Have you tried removing the spark plugs? If there are metal fragments in one/both cylinder(s) you may be able to see something. You can also try to check for spark to ensure the engine really is turning over.

Anyway, I'm thinking it's cam-related.

Question for the rest of the group: any thoughts on the primary chain? If that let go I guess the starter could engage and spin the sprocket but the engine would not turn over. Not sure how that fits into the bump-start issue, though.

A little update after some inspection in the garage.

- i have removed the plugs and there is no visual indications of metal fragments. Just normal looking plugs.
- With the plugs out i slowly turned it over with the kick start and i can see both pistons are moving up and down and the valves are opening and closing.
- The engine oil is very low.

My thoughts are filling the oil right up. Squirting a tiny amout down the pistons and attempting to start it and see how it behaves?

So i have filled up oil on the bike it was only at 1.5ltr and needs to 2.9ltr so very low.

The bike starts up perfectly and the clutch engages and disingages with no signs of the engine seizing.

The issue is that the when riding the bike the metalic nocking / tapping noice is there. There is also a significant loss in power. The noice also increases under acceleration.

When accelerating the power drops right off and i can compare it to feeling like the carbs are flooded.

Any thoughts

Sounds like spun and seized rod bearings to me.
If yes, sorry. Major engine overhaul.

If not already done, would just for grins check the chain for kinks and any need for adjustment or lubrication. And assure that the timing advancer isn't stuck in its closed idle position, and is otherwise functioning properly.

Good Fortune!

Is the bike stock or modified? If the airbox has been replaced by pods or the exhaust was modified then the bike could have been running lean which creates a lot of heat. And heat leads to stuck pistons.

Hello Nessisn,

Yes the bike is modified, it has no air box with cone filters and a free flowing exhaust.

I have check with the plugs off that the pistons are moving up and down.

Is it possible they are not rising all the way and this is making the noise?

Pics of the plugs? Run that way with no jetting changes can burn up the motor.
Steve