Yamaha XJ 600 1985 - trouble starting it, high idle etc

YamahaXJ600 · Wed Jul 06, 2016 2:42 am

Hi, Im new here and I did some searching in the forums but couldnt really find my problem. I bought a Yamaha XJ 600 1985 model so that I could start practicing. I bought it really cheap so my hopes was not that high.

The thing is that the bike is hard to turn on. When I have charged the battery full, it started without at problem. But only with the choke on and fuel on "PRI". I left it alone for a few days and it was the same problem again with the ignition. I went and bought a new battery and it started without problem. Then after it got warm the idle went from 1000 rpm to 3000 rpm and stayed there. Also when I turned the throttle just a little and let it go, the rpm went really high (6000 rpm) and went down after 1-2 seconds. It was not easy to practice when the rpm goes that high at the begining.

I havent touched the bike for 2 days and now it wont start again. What could the problem be? Im gonna check the fuses today so that they are not wet but besides that I dont know what to do. I have zero mechanical skills so be gentle =)

Sorry for the bad english. Im swede! =P

Thanks in advance

Maxnettoz · Wed Jul 06, 2016 4:55 pm

Perhaps start with a carburetor overhaul. It seems daunting at first but you will soon get the hang of it. There are plenty of videos on Youtube you can watch get a good understanding of what they are about. Grab a good service manual. I find the "How to" page on this site are an excellent guide no matter what carby you are working on.

Slartibartfast · Wed Jul 06, 2016 11:27 pm

My bike almost always needs choke to start, even if it's only for a few seconds.

You could also look at your vacuum line to the fuel tap and an overhaul of that.

You'll be surprised at how easy they can be to work on, grab a Haynes manual and this website - take your time and most of its not that difficult!

And your English seems pretty good to me

YamahaXJ600 · Thu Jul 07, 2016 2:28 am

Thanks for taking your time to answer. Glad to hear that it is easy. It sounds like a good start with the overhauls. Is it easy to remove the carbs by myself?

The fuses looked like this:

https://postimg.org/image/6bf6cz01z/

Any ideas?

Maxnettoz · Thu Jul 07, 2016 5:07 am

Looking at the plugs from left to right I'll call them 1 to 4 Number 4 is not discoloured at all suggesting to me no fuel no bang. 1 seems okay perhaps a little lean. 2 is probably firing well & 3 perhaps too rich. I gather all were in the same condition as number 4 at first start (new). My opinion is the carby's are definately contributing to the poor running. Could be bad float heights, stuck needles, perished seals, incorrect mixture settings or combination of all. I'd start there with a good clean and overhaul.

If anyone else has a more accurate thought on the plug condition please put it up there so I can be better informed as well. :thumbsup:

YamahaXJ600 · Thu Jul 07, 2016 1:27 pm

Thx for the posts. I've taken ur advices and disconnected the carbs for cleaning. What do I need to think about when I clean? Anything that I can destroy? Does gasoline work for cleaning the parts? (Yes I am making this easy for me instead of searching the net =P )

https://postimg.org/image/dvcwgfd5t/

YamahaXJ600 · Fri Jul 08, 2016 3:04 pm

Its really fun to dissemble the carb but really hard. Lots of screw are stuck. I need some help

https://postimg.org/image/4nuthlq4h/
What are these screws? I cant get them out without destroying them,

https://postimg.org/image/nv51nnmy9/
Does the membrane dry out when they are out in the air?

Slartibartfast · Sat Jul 09, 2016 1:07 am

I would definitely agree that one of your cylinders was getting little/no fuel

With the carbs set up I would also suggest checking your valve clearances, it's another one of those slightly daunting-looking jobs that's actually fairly straightforward.

Radare is an absolute wizard with these carbs, there is an excellent write up on here with tons of photos, I just can't work out how to hyperlink to it on an ipad

YamahaXJ600 · Sat Jul 09, 2016 6:12 pm

Im done with the cleaning now. Seemed that there was alot of dirt in the carbs. Ive adjusted the pilot air screw 2,5 turn from seated and the idle screw. Is there anything else I should adjust? Can I blow up the bike or the engine with wrong adjustments? Thx for quick answer! =)

YamahaXJ600 · Sun Jul 10, 2016 6:08 am

Okey I have a problem now, i think.

To fill the carbs I put the petcock on PRI. The problem is that its coming gas out of the left tube that is attached to the carb.

Anyone knows what the issues is? Im a bit affraid of starting the engine now lol

Edit: Nvm. It got fixed with some taping on the carbs. I'm finally done now. The engine starts right away without prime or choke on. The only problem that remains is the high idle even though I have turned the idle screw all the way out. I used the carb cleaner on the intake rubber thingys and the tubes on top of those. The intake rubbers seemed to be fine but the rpm changed when I sprayed on the 4 tubes on top of the intake rubber. I rearranged and put them in harder. Now only 2 of them take in air so i'm gonna buy a new one tomorrow and hope that it's the last of my problem =)