Well, hello.

I've been lurking a bit on the forums, and have finally decided to actually register. I didn't think this would be necessary, due to the overflow of useful information from this site. However, I've stumbled into problems that I just can't figure out, and am tired of browsing post after post trying to find different problems and solutions, so I'm hoping I can get some help in some of my own threads.

I'm working on an '82 XJ750, or at least trying to. I am inexperienced when it comes to motorcycle mechanics, so please bare with me. While I don't know it all, I learn very quickly.

This is the first bike I've ever worked on, obviously, and would appreciate some more experienced help to walk me through what to do.


So, here's what I've done, with help from all of you:
-Checked clearances, all within spec.
-Attempted to sync carbs with a YICS tool.


I say attempted, because while I had the bike started yesterday, it will not start today. I have no idea why. It cranks and tries to start, but just won't catch. I've had it started several times in the past, and have done nothing between yesterday and today, besides remove the bolts to the YICS passage, and slid in my rod. (pun intended for your entertainment.)

Before starting any work on this bike, it would start and run fine. But once it got hot or warm, it would idle really high, around 3500RPM, and hang there. I've seen that this could be a vacuum leak, sync problem, etc, but.. I just don't know.

If I need to clear anything up, please don't hesitate to beat me into submission and explain better.





Thanks for any help in advance!

 

sounds like you need to clean the carbs out. thats where i started i just got my 750 a month ago. i have to check valves and do a sync still but my ran great after i cleaned the carbs

 

Then that's the first step after work tomorrow. Thanks for the speedy reply!


Also, what should I do after that? Continue to sync the carbs? I'm hoping to get it running right soon, so I can start riding! When weather permits, anyway.

 

no prob

bit of a tricky bike to start with, but hey you'll learn alot about bikes in general from doing it this way. i like to think of it as playing a new video game on the hardest difficulty

absolutely hillarious!!


now down to business, if it started before you worked on it, then you definitely did something to aggravate it. give me a min as im getting ready to eat and ill find the forum on syncing these puppys

if you have never worked on motorcycle carbs before you NEED to get a manual (haynes or clymer) make alot of space and work slowly, lots of little parts to be lost and kicked around the grage and or ingested again there is a thread around here (something about carb dissecting its named)

 

We think on similar frequencies.



EDIT: Between the time I started it yesterday, when it ran fine, and today, all I have done is remove the YICS passage's bolts. I haven't done anything else. So why the no-starty-starty?

 

did you check the plugs?

edit - three main components to start from when trying to get a motor running. FUEL. SPARK. COMPRESSION.

 

Fuel is going to the carbs, all 4 plugs generate a spark, and compression.. hmm. I'm not sure about compression, but the bike was fine yesterday.

 

compression should be good since it was just running. did you put your wires back onto the correct plugs? what color are your plugs btw? and did you put fuel in it recently? how old was the fuel when you got the bike? any idea?

in my shop when i get a customers bike i doont care if they tell me they just put fuel in 10 min ago, i drain it. and get my own.

http://www.mudinmyblood.net/forum/view. ... prkplgchrt

 

right hand coil goes to cylinders 2&3, left hand goes to 1&4. you should be able to see how wires for the outer cylinders (1&4) have different boots on them (usually just a small 90 degree boot) and the iner cylinders (2&3) have longs boots that are a 45 degree angle. this is all assuming the previous owner didnt change them

or use this crudley made diagram, the "0" is the coil, the number represent the wires coming out of the coils going to their corresponding cylinders.

4(0)1 | 2(0)3

 

I pulled the plugs earlier, to check for spark, and didn't really note the color. But trying to think back, since I'm too lazy to walk the 200 yards to the shop, I think they were a light brown, maybe a little darker than tan.

As for the plugs, they all have 90 degree angle boots on them. BUT, numbers 2 and 3 are shorter wires than 1 and 4.

I'll check to make sure that all the wires are running to the right plugs in the AM.

As for the fuel, it's fresh fuel. I had pulled the tank off and washed it out because I was thinking of painting it, but thought I'd rather get the bike running first before I worry about aesthetics.

 

Also, besides the hanging at high RPM while hot, I've noticed that when I rev to around 5k RPM or more, it takes a little longer than it should (IMO) to idle back down. Suggestions?

Average time back to idle is 8-12 seconds.

 

sorry i edited my post above to show you the coils in a crude manner, and what did you "wash" the tank out with?

 

are you sure you didnt mess with those carbs at all? turn any screws?

 

After not being able to start it, I did mess with the (?)mixture screws. (On top of the carbs, sort of)


I turned them all the way to the right (tight), then moved them back left 2.5 turns each. This is all while following off-site instructions for carb sync.

Please don't tell me I killed it

Also, I poured it out, allowed it to try, then used a general purpose cleaner and splashed around in it. I then poured this out and allowed to dry again. Was this a no-no? Nothing got down into any lines or anything. Everything was removed from the tank.

 

no its not dead, 2 - 2.5 turns out (from all the way seated) is the general rule of thumb to start at when you first put carbs back on a bike after usually taking them apart and cleaning them or rebuilding them. Try putting them at 2 turns and see if it starts. Yamaha says that these screws are not to be adjusted and shouldn't ever need adjusted, but they werent thinking right on that one. BUT, the carbs will most deff need to be synced now that you messed with those screws, but you should be able to get it started at least.

now when you said you checked clearances, what did you check? valve clearance? its just that there are ALOT of instances the word clearance comes up on motorcycles, so it was a little vague but no biggy. here is the best thread for doing valve clearence check.

http://xjbikes.com/Forums/viewtopic/t=1 ... rence.html

what all purpose cleaner? like an antibacterial counter top stuff? with bleach?

 

Yes, valve clearances. Sorry for bad terms.

Also, just a bit of soap, really. A little bit of purple power, to some dawn dish soap, and a 3/4 tank full of water. Sloshed around until most liquid had splashed out, then poured/rinsed the rest out. Left tank inverted so hole was absolute bottom so all liquid would drain. Then re-assembled.

 

no prob, but on the tank wash out thats not the best way to do that. they make certain chemicals for that type of stuff. some are a 1 step process, some are a 2-3 step. just depends on your preference. and you might of made it worse doing that because now you will probably have flash rust and or little specs of rust. Make sure you get a filter on that fuel line ASAP. ask around at your local motorcycle shop for one, they are little cone shaped things with a stone filter in them, usually gold or silver in colr. if you ever wash a tank with water (or any other chemical that doenst belong in a tank or that causes rust) you want to rinse it with gasoline. did you rinse with gas or with water?

and this shouldn't have anything do do with your bike not starting UNLESS you had a significant amount of water left in that tank to mix with the gas you put in there, and always use fresh gas after you drain a tank no matter what. but if there was soap in there.....idk if soap burns to well lol

EDIT - actually now that i think about it if you did try to start the bike AFTER you cleaned that tank that way, you may have clogged jets. just to clerify does the bike start right now? or even pop off? and was it doing the high rev thing before or after you started tinkerin with it?

 

It was high rev'ing before.

And I can get it to run if I spray starting fluid. But not unless I do use the starting fluid.


I have a new filter on it, as recommended in another thread elsewhere. And before filling, I shined a light to look for rust in the tank and didn't see any. I am fairly certain that there isn't rust, but I'll drain and check again.

 

It was high rev'ing before.

And I can get it to run if I spray starting fluid. But not unless I do use the starting fluid.


I have a new filter on it, as recommended in another thread elsewhere. And before filling, I shined a light to look for rust in the tank and didn't see any. I am fairly certain that there isn't rust, but I'll drain and check again.

 

ok stop trying to start it with starting fluid. ether, i am assuming you are using is very flammable as you know but also burns extremely hot and with a very fierce, and violent explosion. (just sprap some on the ground and toss a match, then you will see whats going on in your motor when you do that) you will run the risk of blowing a valve if you keep doing that. carb and choke cleaner is the way to go when trying to start a motorcycle with a "helper" chemical.

and it sound like to me that you have clogged gets, definitely would start with a carb clean and/or overhaul depending on how all the guts are looking. again i cant remember the name of that thread about XJ carb cleaning, one of the wizards would know off the top of their heads.


ahh now i remember, the thread was called "the church of clean" but i cant seem to find it when i do a search (not surprising)

 

Well, it's good to know before I actually do blow a valve. I'll start using carb & choke.

Come on, Wizards, I summon thee..

 

here is this write up, looks to cover everything

http://xjbikes.com/Forums/viewtopic/t=2908.html

 

Is there even fuel getting to the carbs?Petcock working right turned on?

Just somthing to check first clear up the simple tings before you have to smack yerself in the forehead and say DOH!!

 

read ^^^^

 

Symptoms point to clogged pilot circuits/jets, so a carb cleaning is in order. Also your high idle is likely a vacuum leak, check intake boots, and rubber caps on vacuum nozzles. It could also be a bad synch. Does it idle fine when cold and return quickly to that point?

When your adjusting your mixture (pilot) screws you want to bottom them gently and screw them CCW or out to the 2.5-3.0 turns out as your starting point.

Best to clean your tank with phosphoric acid after removing the gum and varnish with a caustic cleaner, then coat with an upper cylinder lube, like marvel mystery oil, and fill with gas.

 

My bad missed that one Foolber
Im new to this reading thing 8O

 

all good, just pointing it out. i like your sig btw, need to use that on my girlfriend sometime....

like i said above (and as murk pointed out) my guess is he clogged the jets after "cleaning" the tank, more just jostled deposits around in the tank but to live is to learn

 

Agreed with all of the above, a thorough "church of clean/whole nine" style carb cleaning (all this sort of info can be found in either the "XJ4EVER supporting vendor" area or the "FAQ" areas) is in order on any new to you bike IMO whether it ran great or not, if only to help understand what they're doing with your fuel & air and to be 100% that any running issues are not carb related.

And in line filters are pretty essential (I think I read you fitted one, good) as Yamaha's tap strainer & carb "beanies" aren't ideal from either an efficiency or ease of service point of view.

Go slow with the carbs & do 1 at a time if you're not confident/organised enough to pull all apart at once (it's not that bad if you keep all your parts in a seed tray or similar).

Also, I think it's pointed out in the articles but worth saying again DO NOT SOAK THE CARBS IN CARB CLEANER UNLESS THEY'RE ENTIRELY STRIPPED OF ALL PARTS AND DON'T ALLOW ANY RUBBER COMPONENTS TO BE IN CONTACT WITH THE STUFF

Sorry shouted by accident there but it's important anyway so won't edit it haha

Welcome to the forums by the way, any questions that searching doesn't answer feel free to ask

 

I have checked all the rubber seals and boots to the carbs, from the carbs, etc. No leaks detected. Gonna follow the guide and tear into cleaning the carbs. Wish me luck.



Thanks for the welcome, and the help. I appreciate the community.

 

You don't need luck, you got the walk-thru guides and the members on here But best of luck anyway, be careful to use properly fitting screwdrivers, read the guides before you start & refer to them as needed & be thorough with the enrichment jets and you'll be golden.

 

Thanks dude.


As for the guide, I'm just gonna print it out. No way I wanna tear the carbs apart from memory, and have to run back to the house to get a little detail. Sounds risky when I'm dealing with small parts.


Thanks for all the kind words of advice. You guys know how to make a guy feel welcome.

 

Very sensible idea, I'm fortunate enough to be able to rebuild chunks of bike in my living room on the sofa, brew in hand & computer by my side & any way you can manage to have the guides for immediate reference is highly recommended.

You can tell what kind of place the XJ forums are when you see I only joined 22 days ago & got addicted that quickly! The people here really prove that the world still has hope for the human race... I'm gonna stop spouting on about how good it is here now & let you get on with more pressing matters

 

Best of luck on the carb clean. Mind the bench sync. Getting to the butterfly valve adjuster screws after they're mounted up again is a bit of a pain. Totally agree that removing problems with the carbs is good first step forward.