I know that this isnt a Yamaha bike, but you guys (and gals) are always very helpful, and I would really like to get this sorted out so that my wife can start riding this bike.

Well, I have changed all of the fluids (except brake) on the 81 kz305 I just bought my wife, but have ran into a problem.

Here is some back story: The bike was "running fine" before it was parked around this time last year. The bike has not been started since then, and had barely been touched.

I brought it home, removed the old fuel from the (lined) gas tank, removed and cleaned the carbs with compressed air (pulled the bowl off and removed the jets to blow them out), changed the oil and filter and added the amount of 10-40 that it calls for on the side, added a new battery, topped it off with premium fuel, and tried to start it.

It didnt want to start at first, but I kept at it and finally got it to start after bumping it once or twice.

I rode it about 200 yards up and down my apartment lot and it died, and there was quite a bit of blueish white smoke coming out of the exhaust pipes (mostly right side, but some left).

I pulled both plugs and checked for spark. Both spark, but I dont have any way to check gap. The left plug was dry and had been blackened, but not with any buildup and no smell of oil or gasoline. Right side was soaked and smelled strongly of gasoline. Oil (or perhaps uncombusted gas mixed with the soot inside the pipes) was dripping out of the right hand exhaust fitting where it joins the header pipe.

What does this sound like to you? I am worried that it might be a bad piston ring letting oil by on the right side but am hoping that I am wrong. Could this be happening just because it is running super rich on the right side?

Sorry for the novel, and I appreciate any help you all can provide.

Thanks!

I, from my limited experience, would say its either piston rings or valve seals. Since seals are a bit easier, I'd start there...but while you have the head off, you might as well look for scoring on the piston walls. You have to replace the head gasket anyways.

I'd check the gap on the one plug, a gap tool is like 98 cents at autozone or whatever. Was the blackened plug all black, or was there any grey area at the tip?

I know that this isnt a Yamaha bike, but you guys (and gals) are always very helpful, and I would really like to get this sorted out so that my wife can start riding this bike.

Well, I have changed all of the fluids (except brake) on the 81 kz305 I just bought my wife, but have ran into a problem.

Here is some back story: The bike was "running fine" before it was parked around this time last year. The bike has not been started since then, and had barely been touched.

I brought it home, removed the old fuel from the (lined) gas tank, removed and cleaned the carbs with compressed air (pulled the bowl off and removed the jets to blow them out), changed the oil and filter and added the amount of 10-40 that it calls for on the side, added a new battery, topped it off with premium fuel, and tried to start it.

It didnt want to start at first, but I kept at it and finally got it to start after bumping it once or twice.

I rode it about 200 yards up and down my apartment lot and it died, and there was quite a bit of blueish white smoke coming out of the exhaust pipes (mostly right side, but some left).

I pulled both plugs and checked for spark. Both spark, but I dont have any way to check gap. The left plug was dry and had been blackened, but not with any buildup and no smell of oil or gasoline. Right side was soaked and smelled strongly of gasoline. Oil (or perhaps uncombusted gas mixed with the soot inside the pipes) was dripping out of the right hand exhaust fitting where it joins the header pipe.

What does this sound like to you? I am worried that it might be a bad piston ring letting oil by on the right side but am hoping that I am wrong. Could this be happening just because it is running super rich on the right side?

Sorry for the novel, and I appreciate any help you all can provide.

Thanks!

I could pull the plug again and check, but it was black. not super dark, and no deposits, but it wasnt ashy grey either.

i wonder if I can pull the head without pulling the engine.... there is quite a bit of wiggle room between the frame and engine.

I, from my limited experience, would say its either piston rings or valve seals. Since seals are a bit easier, I'd start there...but while you have the head off, you might as well look for scoring on the piston walls. You have to replace the head gasket anyways.

I'd check the gap on the one plug, a gap tool is like 98 cents at autozone or whatever. Was the blackened plug all black, or was there any grey area at the tip?

need to use it, rings will be stuck and to unstick you keep the engine going.

carbs will have deposits in them and are a bugger to shift

make sure the battery is charged and serrvice the complete engine including timing

need to use it, rings will be stuck and to unstick you keep the engine going.

carbs will have deposits in them and are a bugger to shift

make sure the battery is charged and serrvice the complete engine including timing

Alright, that makes sense. I saw all of that smoke and shut it down because I was afraid I was going to damage something.

Battery is brand new.

Carbs are coming back off tomorrow to be broken down all the way and cleaned in the carb cleaning bucket/strainer I got this evening.

as for the other servicing, i am probably going to have to have a shop do it since I dont have a timing light... perhaps I should go get one.

so here is an update...

I replaced the plugs today and then disassembled the carbs, using a carb cleaner bucket and dipping basket I re-cleaned all the parts. They were pretty much spotless, the pictures below are from before i used any cleaners on them... no deposits of any kind that I could see.

It only will run with the choke on, and will not rev above 6k.

Right side is blowing blue white smoke once the engine starts to warm up, and really wants to die off when this starts happening. the last picture in the series is the oily liquid that is dripping (or misting when the engine is running) out of a pinhole in the right side exhaust.

could the right side just be running super rich?

so, I am assuming that my next three steps are as follows

1. Make sure carbs are properly adjusted

2. Remove engine and cylinder heads. check to see if oil is leaking in from the top end.

3. While heads are removed, check cylinder walls to see if there appears to be damage to cylinders from bad pistons/rings...

am I missing something? Thanks for the help thus far.

Right side is blowing blue white smoke once the engine starts to warm up, and really wants to die off when this starts happening. the last picture in the series is the oily liquid that is dripping (or misting when the engine is running) out of a pinhole in the right side exhaust.

This can be the seals on the exhaust valves, as the exhaust gasses become hotter they start to burn off some of the oil leaking into the exhaust port, but may not burn it all hence the oil in muffler. however I dont thik it is the only problem as this shouldnt make the engine die off, so could be coupled with any one of the other possibilities. On the other hand leaking seal on inlet valves usually cause lots of smoke right from go, becoming less as engine is run so could it be rings and exhaust seals?

Edit.. I've been thinking about the dying off and changed my mind there, I think the hot gasses and flames are igniting the oil and the resulting smoke is getting into the cylinder because the exhaust valve is open which is in turn affecting combustion

I expect that from cold start there is no mis-firing as at this point the leaking oil is not ignited

I expect that from cold start there is no mis-firing as at this point the leaking oil is not ignited

exactly... started up just fine this time, but began running rough as it warmed up. specs say redline is at 9.5k on this bike and it wont rev past 6k cold, or past 4k warm. is also idling around 800 and adjusting idle screw has no affect.

So if you do decide to change the seals on the valves, You will no doubt find the exhaust valves very dirty and carbonised from all this burned oil so you will need to remove and clean them. Also gently lap in any valves ypu work on!

So if you do decide to change the seals on the valves, You will no doubt find the exhaust valves very dirty and carbonised from all this burned oil so you will need to remove and clean them. Also gently lap in any valves ypu work on!

dont really have a choice but to replace the valve seals it sounds like...

new to do list:

1) learn how to lap valves

2) get head gasket / valve seals

3) find time to remove engine

4) get a factory service manual.

will i need a valve spring compressor? any special tools i should get?

dont really have a choice but to replace the valve seals it sounds like...

new to do list:

1) learn how to lap valves

2) get head gasket / valve seals

3) find time to remove engine

4) get a factory service manual.

will i need a valve spring compressor? any special tools i should get?

Yes you will need a valve spring compressor, gather all your bits and pieces first, valve seals, lapping paste, sucker thingy for lapping valves, valve spring compressor, etc, not done any of this kind of stuff since i was a kid, so ask others for tips. You might find info on internet, or workshop manuals etc

Just found this on another forum, Never heard of it but I must say I like the idea, Dont know how it fits with your bike though.

You know you can change the stem seals without taking the head off dont you.

A bit fiddly but it can be done using a bit of polly rope fed down the spark plug hole with both camshafts and plugs removed and the piston still rising feed some polly rope down the plug hole and then gently turn over the engine until it locks up. remove the valve spring by pushing down the valve cap and remove collletts. Hey presto remove old stem seals and replace............very fiddly but a lot cheaper than a new head gasket.

Just found this on another forum, Never heard of it but I must say I like the idea, Dont know how it fits with your bike though.

You know you can change the stem seals without taking the head off dont you.

A bit fiddly but it can be done using a bit of polly rope fed down the spark plug hole with both camshafts and plugs removed and the piston still rising feed some polly rope down the plug hole and then gently turn over the engine until it locks up. remove the valve spring by pushing down the valve cap and remove collletts. Hey presto remove old stem seals and replace............very fiddly but a lot cheaper than a new head gasket.

interesting.... i think that i would rather just replace the seals the old fashioned way... this bike has a two part head like my xs500. I am wondering if I will actually have to replace the head gasket afterall, or if I can just do the repairs I need to do by removing the top portion of the cylinder head (valve cover maybe?)

interesting.... i think that i would rather just replace the seals the old fashioned way... this bike has a two part head like my xs500. I am wondering if I will actually have to replace the head gasket afterall, or if I can just do the repairs I need to do by removing the top portion of the cylinder head (valve cover maybe?)

It will depend on your valve compressor. If you have a C-Clamp type compressor, the whole head has to come off (one end on the valve and one on the spring cap) and so the gasket has to be replaced. On the XS400, the head cover is only sealed with liquid gasket and there is no paper gasket to replace. You will need to see if the cover on yours has a gasket or not.

I have seen valve compressors that can attach solely to the valve cap and allow you to remove the collets without separating the head from the rest of the topend.. I havn't used one of these though, but if you give it a try let us know how it works!

It will depend on your valve compressor. If you have a C-Clamp type compressor, the whole head has to come off (one end on the valve and one on the spring cap) and so the gasket has to be replaced. On the XS400, the head cover is only sealed with liquid gasket and there is no paper gasket to replace. You will need to see if the cover on yours has a gasket or not.

I have seen valve compressors that can attach solely to the valve cap and allow you to remove the collets without separating the head from the rest of the topend.. I havn't used one of these though, but if you give it a try let us know how it works!

but if i need to clean and lap the valves, wont I have to remove the whole head anyway so that I can remove the valves themselves?

oh, and the cover has no gasket from the parts breakdowns that I can see.

but if i need to clean and lap the valves, wont I have to remove the whole head anyway so that I can remove the valves themselves?

oh, and the cover has no gasket from the parts breakdowns that I can see.

Yes, you're best off taking the head off to clean the valves and lap them in.

I have used a different method for changing Valve guide seals before

Basically you unscrew the spark plugs and remove the cams or followers. All Valves are then seated.

Then you simply screw an adapter into the sparkplug hole and connect an airline gently to bring the piston right down then connect at full pressure You can then remove the collets etc and change the seals without removing the head.

Personally I prefer doing a full rebuild, since this is faster and will give you a better engine

It's risky not taking the head off... If you drop a valve in the cylinder you'll have to take it off anyway.

The pressure method is much more reliable than the afore mentioned rope method... How do you stop the piston from moving down? If by locking it they mean force it to tdc... then this will put pressure on the head which could cause it to warp

HTH

Olli

Like the air pressure idea Olli, good if youve got access to compressed air, maybe even able to do that with a cheap car tyre inflater

Like the air pressure idea Olli, good if youve got access to compressed air, maybe even able to do that with a cheap car tyre inflater

I also posted this on another site, and I have been hearing a lot of chatter that it could be something as simple as the carburetors not being balanced properly....

I dont understand how that could be the case, given the color of smoke that it is putting off.... it would be nice to have it just be a carb issue, but I suppose that I have to check compression first to make sure.

I also posted this on another site, and I have been hearing a lot of chatter that it could be something as simple as the carburetors not being balanced properly....

I dont understand how that could be the case, given the color of smoke that it is putting off.... it would be nice to have it just be a carb issue, but I suppose that I have to check compression first to make sure.

No me neither, smoke comes from burned oil, balancing would just be rough running, and anyway it could still have good compression even with Knackered seals, Its just that if you remove the valves for a thorough clean, you will need to give them a quick lapping in because you disturbed them.

No me neither, smoke comes from burned oil, balancing would just be rough running, and anyway it could still have good compression even with Knackered seals, Its just that if you remove the valves for a thorough clean, you will need to give them a quick lapping in because you disturbed them.

So, after nearly a year of work, I thought I would give you all an update on the issues I was facing.

Turns out that the timing was so far advanced that it blew a hole in the right side piston.

I ended up doing a full rebuild on the engine, all the way down to splitting the case and starting from the ground up.

Most of my time was spent waiting on parts, but I have to say it was an awesome learning experience. I just hope that nothing like this happens with my xs, because the parts are so much harder to find.

Anyway, it's running like a champ now...

Thats all. Now I just have to get my wife on it.