Xj 600 51 j weird engine sound

Hi to everybody,

First I want to apologize to open a new thread without presenting myself in a dedicated post, it's just that I don't know where to do it.

So, I'm from Portugal and I found an old xj 600 51j in a garage, running from time to time, acording to the last owner. Cosmetically, she wasn't in the best conditions and I thought that I could make something.

As I was passing my motorcycle driving licence, I decided to bring it home and do the work myself.

I runned with the bike a hundreds of klm withouth problems and weird noises. Made some cosmetic work too, until she spoke only in 2 cylinders.
I removed the carbs (filled with dirt), cleaned the tank. Cutted the rear end frame, and some other work, front fork seals, brake calipers, electrical wiring, new speedometer, etc... I just didn't remove the motor (and inside nothing opened) and wheels from the frame.

All with the help of foruns (xjbike), youtube, and the manuals.

Yesterday, after assembling, I wanted to turn on the bike and the resulting was what the video show:



So far, I tested only compression (results are standard) and starter motor, that runs without that weird and constant sound.

So, any hint about that sound or steps that I should take.

I appreciate the help and eventually sorry for my english.

Regards

 

My first thought is a gasket that's flopping around like the reed in a clarinet. Probably on the intake side.
Did you remove the intake boots from the heads at any point?

 

If you have a mechanic's stethoscope probe around the engine--intakes, clutch area, etc and see if you can isolate the noise. If you do not have a stethoscope a long screwdriver will work if you hold it against your ear while probing Stethoscope is a lot better and easier and very cheap. Here is a simple one I got from Harbor Freight. You can probably find one similar to this one.

https://www.harborfreight.com/mecha...3297&msclkid=3dd069fba1861fe8b355348e3a866076

 

A length of rubber hose works too.

 

Never tried that, but I can see how it would work, especially if a short metal rod was inserted in the probing end. I’ll have to keep that one in the back of my mind.

 

No rod needed. It's a diaphragmless stethescope.

 

Yes, I did remove the intake boots from the head and put new gaskets on. I tightened the screws by feeling with no special torque, as I didn’t find the specs on the manual...but I would say 10 N/m. Nonetheless, before going to bed, I checked and there was one or two that seems to be loose.

Thanks for the stethoscope idea, I will try today and see.

Another thing that scratched me was the exhaust gaskets. Those are not like copper gasket (bronze color), there are metallic and with a blue and white coumpound. The screws were not tightened enough even if the collectors didn’t move at all.

Thanks

 

Hello to everybody,

So, thank to you xjbikers, I think I may have found the source of the weir sound.

After work, I removed the carbs and inspect some things like float and fuel heights, leaks, or some loose screw. The carbs seemed to me good, so there were mounted one more time. I just opened up 1/2 turn the mixture screws. Then,
I tightened the collectores, put the tank on, and start the bike.

The sound continued the same and the bike will shut off if not giving some gas. Also a smell of something burning appeared, but I tought it might be coming from the exhaust wraps.

After inspecting further and inspecting the engine, carbs, tank, forks, whells, etc... I remembered what k-moe and tamaka 45 said about the rubber hose and stethescope. I got up to search the hose and, while walking, I remembered another thing, from k-moe, the intake boots and the clarinete lol. I did stop and look at the intake boot that was next to me, the right one. As I was looking, a smell of gas appered suddenly and a wet strip on the side of the boot also.
It was gas and as I reved up the throttle I could see literally gas spit out from the boot. Also I could see the gasket flopping around. No other boot spit out gasoline but had the gaskets flopping.

The intake boot seemed to me to be reconstructed as some signs of paint or glue was on it.

So, now I will removed the carbs another time, take out the boots and put another one to see.
Some questions remain, like why the other gaskets were flopping but no sound was coming from. I checked for signs of gas but found none.

I have another set of intake boots, are they interchangeable ?

Thanks very much for the help.

 

And what torque should I tight the intake screws?

 

I've just read another thread from user xj650rebuild and the sound of the engine is like mine.
It appears that it was a vacuum leak on an intake boot.

Do the intake boot and reuse of same gasket solved the issue?

Well I will see

 

The intake boots can crakc with age. The old fix (before new ones were available) was to clean and degrease them thorouglly (inclusing the cracks, and spread on a layer of black oil-resistant RTV gasket maker (working it into the cracks), then smoothing it over with a wet finger.

The gaskets don't always seal as well as they should. I recommend using a spray-on gasket dressing on both sides of each gasket. Let it cure per the directions prior to installation.

The bolts for the intake boots should be tightened to 9.76 Nm. I recomned using a medium-strenght thread locking compound (locktite) on the bolt threads to keep them at torque, and to stave-off corrosion.

 

Is Permatex brand a good solution?
Will the gasket-makers do the job without the actual gasket?

Thank you