new bike... questions?

Just rode home my 83 xj750 and while riding home my crankcase breather was spitting gas out? naturally I would think that oil and gas DONT MIX but does anyone here know what the deal is??? or what could have caused this?

 

If that's the bike in question (in picture) it's your aftermarket set-up. Those air filters require mucho adjustment to your carbs because the original set up was not designed for pods, as a result someone has gone overboard trying to tweak more fuel in to compensate (for the extra air flow). So you have overflow of fuel and it's in your oil now. I wouldn't ride until you get this fixed. Probably your float level is set too high. That's my guess anyway. Somebody chime in if my analysis is not right.

 

Ok this might be a stupid question... but this ismy first bike. So how would I go upon fixing this issue?

 

No stupid questions. Only stupid previous owners who screw things up by not asking questions before they start wrenching.

One thing make sure your fuel valve is set to "on" or "reserve" not "prime." These bikes have a vacuum activated fuel valve that can flood the carbs if it's set to prime all the time. It might be that simple but I doubt it.

You need to check your float levels. This is how high the fuel sits in the bowl on the bottom of the carb, if its too high then fuel can flow into the intake (instead of just atomizing through the carbs passages)and slip past the rings into your crankcase.

There are lots of useful links here that describe how to do this. If you want to just check and see if they are badly off (likely) then do this. Get the carbs as level as possible (jacking bike up on front while on center stand) and locate your drain nipples or hole on the bottom of the carbs-there is a drain screw right next to this. You will need a clear piece of fuel line at least 12 inches long to hook to this (if you don't have a nipple you will need something you can put in the hole to act as one-I used a vacuum adapter that fit right in). Once attached and held above the carb, use a well fitting screwdriver and loosen the drain screw. The fuel from the bowl will start to enter the hose (make sure you're on prime at this point). Position the hose so that it makes a gradual dip and comes up vertically right next to the outside carb body. It won't matter if you move the line up or down a little, but the fuel should come to rest just below where the bowl attaches to the upper part of the carb. If it's more than a few mm below (unlikely) or if it's above this point (uh-huh) then you're going to have to pull off you're carbs and adjust this level by bending a little metal tab on the float. I won't go into this here, there is an excellent write up on this, just search for float AND levels.

Just to let you know most here will tell you do not use pod filters on these bikes because they are notorious for making the carbs VERY difficult to tune. It can be done, but it requires effort and patience. You might want to consider going back to the stock airbox and selling your pods on Ebay. These bikes are plenty fast without increasing air flow.

Once you find out why the fuel is there and stop it, you will need to change your oil & filter & use motorcycle oil.

 

Thanks alot I will need to look into this more in depth... I didnt notice but I might have had the petcock on prime the whole ride so that could be my problem, I have a aftermarket petcock right after the original and use that as my primary fuel shut off. Also thank you for the "no stupid questions" comment I will be using this to my advantage :wink:

 

Looks like you only have headers attached is that right? If so that also effects the setting of your carbs. Reduced exhaust pressure changes the pressure gradient in the intake. I can't be certain how much because I've never run anything but a VW Bug with only headers attached (That was loud brother!), but it would be easier to tune with at least a straight pipe attached to those headers, and your engine will run cooler too.

 

Ya i got the bike today i am gonna fab some straights on there cause I was burning up and its too loud like wake up your neighbors loud...

 

A leaking fuel tap wont cause that problem UNLESS the float levels are too high or there is a problem with the needle and seat as well.

Read up on checking the float levels using the clear tube method.

After doing this, I would still recommend pulling carbs and seeing whats inside the bowls.

 

So I went down and checked my bike and I did have it on prime the whole way home (dumbass) but you say this is not the only problem and it must be something else?

 

Right must have high float level or bad seal on float valve, but if memory serves leaving it "primed" all the time can aggravate this issue.

Also with respect to your safety(i.e. life)-unless you know for SURE that the bike has had all the needed updates and maintenance which is pretty much impossible to know for SURE. You should follow the advice of the XJ Wizards around here and get a shop manual (Clymer) or two and do all the maintenance/replacements to be sure you're not going down the road at say 70 and your rear brake locks up or your front brake blows out etc.

 

Yes I believe I will take you up on your advice!

 

Just as an example on my 1981 XJ550 this was all done this year:

1) New rear brake (search "delamination")
2) New front brake lines (mine were stamped "1981" speced good for 4 yrs)
3) New front tire (old tire 5yrs old & was at 16psi - this cleared up a "wobble" and I discovered the front castle nut was torqued to 10ft-lbs should be 76)
4) Rewired fuse box
5) Checked and repacked front bearings
6) Rebuilt Master Cylinder & Caliper (bleed screw rubber cover was inside union bolt!@#$#@)

More was done but the above was the most critical. BigFitz is one of the guru's here and I will quote him "If you just put one of these old bikes on the road and ride without properly re-commissioning them, things are going to go wrong." Basically you don't have to replace or buy new parts for everything, but there are certain wear parts and critical areas you don't want to overlook. Keep searching through the XJbikes world of knowledge and you'll have a b..ching ride you can be proud of.

 

I will do that I have been working on cars for years but the difference is that if something breaks you just pull over... you dont always have that luxury on a bike!

 

I would have to say that if this happened as you were riding home then the gas in oil was a pre-existing condition, and the P.O. had to know about it. The only time that raw gas can flow past the carbs, valves, pistons is if the bike has sat a while with a combination of faulty petcock and float issues.
When the bike is being ridden then the gas that is flowing is being used to create combustion and should not have enough volume to get down into the bottom end.
So if this is the case then like the other guys have mentioned, "what else needs fixing" that you can't see by looking at the bike or riding it around?
It'd be a shame to have your "New to you" bike grenade on you for the sake of the P.O. telling you everything works fine.
Keep us informed and ask as many questions as you need to. I'd rather see this thread go three pages long with questions and answers than end on one page with you saying "My bike is broke"!
Good luck!

 

I will take you up on that... So I may have a problem with the charging system the electrical system on the bike needs work and some serious organizing, I have taped off wires all kinds of random wires so thats my task for this weekend. My question is what connects the stator to the battery? Does anyone have a schematic that I could reference? this may not even help because it has all been redone over the years. So I may have to trace the crazy wire maze, but I figured I'd give it a shot. Also what oil do most guys on here run? And last but not least my rear brake pedal feels really spongy and doesn't give much stopping power... What to do. What would anyone recommend checking on this bike, any specific areas that need special attention?

 

One last thing I forgot to metion... I have no speedo, I really need one because I commute through Camp pendleton every day to work and the MP's dont like speeders so is it a easy hook up or what all do I need? anyone have any for sale I just want a small analog pod nothing fancy.

 

I have a speedo/tach that I could sell you. It's off an XJ550 so you will need to check and see if it's compatible. I think it is but don't qoute me on that. It's fully functional but has cosmetic issues (cracked glass and some cracking on plastic chrome). Could post a pic if you're interested.

Yes replace your rear brake. Like now.

Look at the thread "Rewire" under XJChat. I posted a wire schematic there for a 750. You could use a wire "toner" if you have access to one. It sends a tone down the wire that you read with a wand. But you could also unhook your battery and use a 9volt battery (little cell) with wires attached and a volt meter to trace any wire.

Go back and look at the list of things I posted in this thread that was done on my XJ. You might need to do all of those things as well.

I run motorcycle specific 20w50. I don't ever have the bike out in cold (<40F) weather.

 

GEEZ.

IN ORDER OF IMPORTANCE:

Rear brake, before you wreck: http://xjbikes.com/Forums/viewtopic/t=15874.html Seriously.

Then: If you're spitting gas out the breather, you have a serious "gas in the crankcase problem." DO NOT EVEN RUN THE MOTOR, let alone ride the bike, with gas in the oil or you'll quickly destroy the motor.

Gas in the crankcase requires two things:

An "unending" supply of fuel, which could be a petcock problem OR you left it on "PRI" and we already covered that (although the "secondary shutoff" doesn't bode well for the petcock to be operating as it should)

AND (and more importantly)

FLOAT VALVES (in the carbs, and there are 4 of them) that aren't doing what they should, which is to shut off fuel when the bowls are full.

This can be caused by dirt in the float valves/seats, deteriorated parts, or misadjusted float levels.

You need to address this problem before you ride the bike any more or you're gonna blow it up.

While you're in the carbs, you can see what jetting the PO left you with, if he's tried to re-jet for the pods or left it stock, etc.

THEN

Once the REAR BRAKE has been fixed, and you're working on the carbs, you'll need to check the valve clearances; if out of spec, the carbs won't sync right for you.

While you're about it, have a look at the front brake lines. As pointed out previously, they had a recommended service life of four years. As "conservative" as that may have been, you're WAAYYY past any designed-in margin of safety. The date codes are embossed in them--- when were they made?

THEN worry about how fast you're going; after you can run the motor without hurting it and stop the bike.

Sorry, I know how excited you are to have this bike. But the honest truth in this situation is that the guy who sold it to you had "given up" on some issue or another (or had realized that there's more to putting a bike this old into real SERVICE than making it look cool) so he sold it to you, who (no offense) simply didn't know any better.

If you really want to ride and USE this bike, you've got a bit of work to do. I'm not trying to scare you; I just want you to understand what it is you've taken on. You've got someone else's "dead end" project, for whatever reason. We'll do our best to help you, but you're going to have to start with some really basic stuff that was obviously overlooked. And #1 is that rear brake; then gas in the crankcase.

Hold off on the speedo for now.

 

Well said Bigfitz. Like always you speak the truth.

 

well the gas coming out of the breather hasn't happened since I left it on prime for a 30 mile ride so that's hopefully the problem. Also I will look into the rear brake this weekend. I cant ride because I pulled pretty much every wire out and am basically making a new wiring harness. The last time I rode it was yesterday, I ran out of gas but after I fueled up it was sputtering really bad at low RPM' s with a full tank. I called the local shop and he said most likely water in the gas and to use this stuff called ISO HEET. This thing is giving me a run for my money. sadly this is my daily rider... as in my main source of transportation. So I need to get this all taken care of ASAP. I appreciate all the help. I used a schematic for the new setup that I found on the site really basic stuff I just want to make sure it will all work.

schematic link below...

http://cycles.evanfell.com/wp-content/u ... n_Fell.png

 

You missed out point about gas coming out the breather. For gas to have been coming out the breather, IT'S IN YOUR CRANKCASE. YOU ARE RIDING ON GAS-DILUTED OIL. You need to immediately change the oil, then keep an eye on the situation until it's fixed for real.

Just because gas stopped coming out the breather doesn't mean the problem's "fixed" it just means it isn't dumping as bad. But we already know there was gas in the crankcase, that's how it got to the breather.

QUIT RUNNING THE MOTOR until you change the oil or you are going to blow it up-- for real.

 

Yes I will be changing my oil ttoday or tomorrow but definatly before I run the engine again. I really need a reply on that wiring diagram any one have any input...?