Smoking 550 MZ after repair

[Guest]

Hi all!

I finally get back my little katana It is strong now, running good This is the good news. Bad news is, it is smoking!!!

Valve stem seals are changed, piston rings changed, piston wall bored up, carbs cleaned, new gaskets. It is performed by a motorcycle mechanic, who is a professional(???).

At starting---- no smoke!
from 0-80-90 km/h ----- no smoke!
from 90 ---- lot of smoke!!!
after I stopped it is smelled like hell, and smoked lot of white smoke! And I could see fresh oil film inside the exhaust pipes. But not all the time! After that I go another round, and it doesn't smoke at stop. Ok, I go just with 70-80 km/h second time.

Maybe just the new rings have to find their new home, after 1000 km of brake in, i can tell if the rings are the problem.

What can be? My petcock is awful, and my exhaust pipes are more open than i want. What could be the problem? I spent lot of money to this surgery, please help me!!

[kawfeedave]

The way you're assigning road speeds to the smoke problem is confusing. What RPMs are you pulling at those speeds in top gear? Can you get smoke out of the engine by cruising at those RPMs in lower gears?

[SqDancerLynn1]

Was it re bored with new pistons ?? Other wise it may take 1K miles to seat the rings

[gabos666]

New rings, with old pistons. Pistons was perfect, just the rings failed under the 30 year of abuse, and scratched the piston head's wall surface. It is rebored, and got a bushing, this way I can use the old pistons.

I dind't go over 5000 rpm. Today i rode to work with the small katana, and there was no big smoke. Maybe just the rings have to broke in.

I decided to not panic about that. I ride some 1000 km's. Time will tell. Under this time, I can check the main problem points, like BikeCliff sad. I was so negative last day, today I hope time will help to my katana.

I love to hear your oppinion, sure it can help.

[Rover]

What does your professional mechanic say?

[gabos666]

He sad if the smoke didn't turn off after 1000 kms, the head is broken somewhere.... so fingers crossed not....

[MisterCinders]

I am still getting my head around how you can bore cylinders and then use old pistons with a bushing. Not saying it doesn't work or that I know any better (I don't), it just confuses me.

[SqDancerLynn1]

Me too !!!! maybe he is talking about honing them ? Maybe the cylinders are too worn ??

[gabos666]

I was told, the cylinders was so worn, there was 1mm space between the pistons and the cylinder wall. I don't know the exact name this process, so i write bushing. I was told the cylinder's surface was reworked to be smooth again, and got a tube/bush, this way the machine shop could use the old pistons to remach the original spacing. I don't know any further information. I will try to investigate my mechanic about this topic.

[Sci85]

It might be when they take the piston and they "expand" the size by punching a bunch of little raised notches in it. A machine does it and its hard to describe but it's a cheap way to bring the clearance back in spec.

White smoke of any kind is coolant being burned and indicates water entering the combustion chamber due to leaking head gasket, cracked head or warped head.

I think I would use a different mechanic...

[john82q]

I would say the OP means the the cylinders had sleeves fitted, a common enough method.

sci85 it would be a great party trick to be burning coolant in a air cooled engine... oil buns with a lite blue to white smoke...

gabos666 if it smoked the first time you ran the engine I would worry too much, youe wont have to wait 1000k , 100 will be enough to know if some things wrong.

[gabos666]

Thank you guys!

Yes, I don't sure about my mechanic.... he is a good guy, if he got the time and will to do the job. I just think he doesn't want to s*ck with a 30 year old bike. I wait 8 months to get it back!!! This time is more than enough to investigate the head problem....I think. I am diasppointed, but not about the bike! There are less smoke now, but didn't disappeard completely. I think if things will go wrong, I will handle the problem myself. There are plenty of mechanics around, but none of them are reliable, and they didn't accept the job, to restore the baby katana to it's original glory. I will ride it, and time will tell... I will keep you infromed here, and in the project section.

I think I begin to search a good head, and an untouched cylinder wall, there is a cheaper way to buy new pistons and rings than the original Suzuki? There is a reliable aftermarket source for engine parts?


Thanks you

[Nessism]

There are too many unknowns here. A sleeve was pressed into the existing sleeve? Never heard of that one before.

I seriously doubt there is anything wrong with the head other than maybe worn valve guides. Heads don't "break" causing oil leaks. Your mechanic sounds like he's just talking it up because he did a bad job.

If the smoke doesn't stop soon I'd pull the engine down myself and start inspecting everything. That's the only way you will know what's going on.

[gabos666]

OK, new infos there. I can ride some more, not just to work, but about 200 kms long.

There are none, or very small amount of smoke in lower speeds, and at starting. In higher speeds, I suspect an overheating situation. After some highwas cruise, there are lot of smoke, smell, and hard shifting. Ohh, and low idling speed, like it is want to stop. I think the problem is these ugly exhaust silencers:


I think, there were no rejet. And there is a leak in one of the exhaust joint. I must dismantle the carbs, and rebuild them with appropiate jets, O rings etc., etc. Also I have to stop the exhaust leak. Very hard to set my petcock from one stop to another. It is almost stuck. So I think a new one needed,too. I hope the smoke will disappear than.

The head is bulletproof as you sad guys, and yes, there are numerous variables. I try to eliminate some of them, and we will see, ho left in the end, as the smoke generator

Any tipp or help, highly welcome.

[Sci85]

OMG John82q...what the hell was I thinking? Man that's funny. I think that was the day after Racing where I broke 2 ribs. I blame my stupidity on the drugs lol.

Now, who wants to buy used GS water pump for cheap