bike is stubborn to start... please help!

Hey fellas, I'm at a loss on this one. I have an 81 xj550..she alsways has been stubborn to start but would run well until I suddenly stopped riding it about a year and a half ago. Dug her out of storage...replaced the oil, plugs, battery, gas,and popped the carbs off to see how they looked inside...they were clean but Iremoved and soaked the jets anyway and put them back on. I simply cannot get the darn thing to run...I have gotten it to fire up twice...after alot of starter fluid and persistence...gave it several good revs and it seemed to run strong...but after I killed the engine I can't seem to get it fired up again. I get spark and she will sputter, but it she just won't fire up... any suggestions on where to focus my attention would be helpful. Thanks!

 

It takes three things to run an internal combustion engine...compression, ignition, and fuel. To me it sounds like you have the first two, but let's back up a bit...have you checked and adjusted the valves? Any issues with "hard to start"...start with are the valves in spec?

 

That is my project tonight....are those accessible and can they be adjusted while on the bike? The reason I ask is because the air box was removed before I got the bike and I am assuming the jets were replaced...so factory specs might not be ideal . If I can adjust while cranking it over I might be able to find the sweet spot. Does this make sense.

 

That is my project tonight....are those accessible and can they be adjusted while on the bike? The reason I ask is because the air box was removed before I got the bike and I am assuming the jets were replaced...so factory specs might not be ideal . If I can adjust while cranking it over I might be able to find the sweet spot. Does this make sense.

 

That is my project tonight....are those accessible and can they be adjusted while on the bike? The reason I ask is because the air box was removed before I got the bike and I am assuming the jets were replaced...so factory specs might not be ideal . If I can adjust while cranking it over I might be able to find the sweet spot. Does this make sense.

 

Damn. Sorry about the reposts......

 

Big Fitz did a terrific write up on this subject...pictures and very detailed instructions (he's so detailed, it's actually a lot easier to do than it seems from the write up, in other words, don't over think it):
http://xjbikes.com/Forums/viewtopic/t=1 ... alves.html
Cut and paste that (I'm not real computer savvy) There is also an "Air Head Valves part duex..that you can find in the FAQ section.

 

Sorry, just noticed I hadn't answered your question..Yes, they are accessible, and done ON the bike.
They are not done while cranking the engine
They are done with a metric feeler gauge (If you don't have a metric, get one...don't rely on using Imperial and doing the conversion). a 19mm open end wrench and a manual.

 

^ +1 Setting the valves to factory specs is entirely ideal if you love your engine, regardless of what you've done to the carbs and intake. Valve lash is set to allow the valves to close completely, which seals the combustion chamber, and also allows the valves to transfer heat to the head via the valve seats. If they aren't set to factory specs the engine will not run optimally (if at all), and you'll eventually cause quite a bit of expensive damage.

 

<whispering> It actually take four... You forgot about oxygen.

 

STOP.

Nothing can be accomplished by trying to adjust things while "cranking the engine."

The 550s are equipped with Mikuni carbs, which combined with their smaller displacement makes them even MORE sensitive to things like pod filters and tight valves.

-STEP ONE: check and adjust the valve clearances.

My apologies if I OVER-explained it; I wanted to supplement the sorry-arse manual and give everyone a chance to see what it looks like before they "tear the motor apart" (boy how many times have we heard that one?)

You're not going to find any "sweet spot" adjusting while cranking the motor. What you will do is kill the battery and saturate a set of plugs, rendering them useless.

Wanna fix it?

-VALVES. Get 'em in spec. FIRST.

-PROPER carb service; including the basic recommended re-jetting for pods

-Float levels

-Bench sync

-Running vac sync with YICS blocked

THEN you try to get it fine-tuned to run right on the pods. But everything else has to come first or you will fight with it until you do it right.

Then we'll talk BRAKES.

 

Well....here's the update.....I have attached a photo of the valve I attempted to adjust. They are located on the top, engine side of the carb. I pulled the carbs off and backed them out a little. I could not access them while the carbs were in place. It turns out that while fiddling around with the carbs I noticed the vacume line had a hairline crack on the backside that I could not see. I replaced the line and the bike fired immediately!!! The problem is, it was redline idling....I mean roaring! So I killed it immediately and backed the idle screw out, thenffired it back up. I repeated this until the idle screw was almost falling out, with seemingly no change. Then I pulled the carbs back off and returned my previously stated valves ( shown in the picture) back to two and a half revolutions from set. Now the bike idlles dangerously high...and after a few seconds kicks up to an even higher rpm. What did I do!?!?! Was this even the right valve to adjust? Good news is she fires right up, bad new is I tinkered her into a frenzy... obviously I need to sync it...buy what could be causing the surge after a few seconds? Thanks again everyone!

 

Just another reason to keep it stock.

 

yanni, I can't see any picture...

From what you explained, I think you were playing with mixture screws, this has nothing to do with valve clearance.

I strongly suggest that you have a look at the link patmac6075 put in his post. It is really well done.

 

I hear ya....unfortunately I inherited a lot of this crap..and I'm just trying to get on the road again. I'm not sure if I attached the photo before.I think it was too big..hopefully this time...

 

Dude. Seriously.

You're messing with the carbs. VALVE CLEARANCES are mechanical.

READ: http://xjbikes.com/Forums/viewtopic/t=14827.html Read it. Carefully. Don't just look at the pictures. YOU GOTTA DO THIS. Study it.

Then read: http://xjbikes.com/Forums/viewtopic/t=29209.html which will help.

Screwing with the carbs is just going to make things worse, and possibly damage the motor.

STOP. READ the advice given. READ the articles we've posted links to. And leave the carbs alone until you know what you're adjusting, and you currently do not.

 

.....I will take a look at that link...thank you very much... hopefully I can clean up this mess I got myself into.

 

You surely can, Adjusting the valves looks more complicated than it actually is. Read carefully, be methodic, go slowly, take pictures and ask questions if you're not sure.

 

So i assumed this was a carb issue the whole time, i think i got confused by some of the responses to the thread, so when i heard valve , i wrongly assumed it was carb related, and messed with the mixture. So, now that i have gone through the valve clearance info, it makes sense why there is so much confusion. Whew, now that that is cleared up, does anyone have a good link to sync and set carbs?, now that i need to redo that.

 

You're not supposed to just read the instructions about adjusting valves, you're supposed to actually adjust them too, lol!

A link to sync or set the carbs would be useless for the moment.

 

lol, i read ya loud and clear, one thing at a time. I just was hoping to get the carb link in this thread so i have it together with the other ones. eventually i will need to undo the damage i put my carbs through and dont want to go searching through the forum.

 

You need to do more with the carbs than try to adjust them back to where they were. That's not going to happen.

You need to pull them off and service them. You can start with a basic "service" and depending on what you discover in that process will determine whether you need to go deeper. Do not submerge still-assembled carbs in any sort of cleaner or you will cause more problems.

You need to accurately wet-set the float levels. http://www.xj4ever.com/setting%20fuel%20levels.pdf Mikunis are very picky about their fuel levels.

Then, once the valve clearances are in spec, you'll be able to begin to adjust the carbs properly.

But there is no "turn this screw this many turns" quick fix for your issue. Get a service manual (you're going to need it) and go through the procedures I outlined, IN ORDER, don't skip any, and you'll get your bike running nicely.

Shortcuts will not solve it for you and will only lead to further frustration.

 

Sounds good. I do have a manual...but it pales in comparison to help I get here both in knowledge and clarity. I appreciate all the help guys. Thanks.

 

Yanni,
Please take the advice given by the others as a seriously as they are giving it. These bikes are very particular in the order of restoring the engine to proper running order. Do one thing and not the other, or try to short cut, or skip something and the bike will aggravate you until you feel like your going to explode. Do everything right and in order, with meticulous perfection and accuracy, especially wet setting the floats, and these bikes run like brand new and reward the owner for the tlc. It is your choice, but in the end, if you don't explode and get rid of the bike, she will win and make you do it her way...

Hope this helps..