Maxim 750 leaks gasoline

Thanks to you guys I have rebuilt my carbs and took it for a test drive and it runs like a champ. Scary quick compared to my Ventures.

I do not have an owners manual so I'm not sure what the words on the petcock do. I do not see a off position. Up it says RES which I assume is reserve. The right says PRI which I assume means primary and I assume again that this is the position you run it in while riding. The bottom says ON and I don't know what that is for. The gas runs most freely when you point the lever at PRI.

None of the positions completely cut off the flow of gasoline. Is that normal? Does not seem normal to me.

After my test ride I parked the bike and an hour or so went back to the garage and I smelled gasoline. There was a big spot under the bike where gasoline had been leaking. The petcock was in the ON position as it seems to let less gasoline flow in this position but it does flow in all three position.

I pulled the air cleaner and the air box was full of gasoline. Could that be from the leaking petcock? Or did I do something wrong when I rebuilt the carbs.

I have looked at aftermarket petcocks and they do not two tubes for the two hoses on the XJ750. If it is the petcock will they work and if so what do you do with the extra hose on the Maxim. I don't know if Chacal has the petcock but I will check once figure out if I need one or not.

Thanks once again,
Harry 8O

 

You need to rebuild your petcock. PM Chacal, the kit is easy to install.
Normal position is ON- there is a vacuum valve to shut off the fuel when the bike is not running.
PRI- bypasses the valve and fuel flows all the time. Don't leave in this position unless you want fuel all over the floor and in your engine.
RES- reserve of course, turn here when you run out of gas and go fill up.
You most likely have gas in your oil now, change it .

 

PRI is to prime the carbs after a long storage or any time you have the carbs totally empty (for maintenance purposes for instance).

It is not a goos idea to run the bike on PRI, and specially if you don't know for sure that your carb floats valves work properly. Apparently, yours don't.

You said you had gas in your airbox, you may have some in your crankcase also. Remove the refill cap, and smell you rengine oïl. If it smells like raw gasoline, change your oïl and filter.

You will have to take care of those floats soon.

 

Thank you both. I was reading the past forums before I posted this post. One post said you can not always rebuild the petcocks. That is why I was looking around for aftermarket petcocks. But they do not have the vacuum nozzle. So how do you know if you can rebuild it or if you are just throwing money down the drain? :?

 

If you buy a new manual petcock, you won't need the vacuum hose anymore. If you go that route, just remove the vacuum hose and put a rubber cap on the carb vacuum port.

You will not know for sure if your petcock is rebuildable unless you try it!

Most of them are rebuildable but some aren't because they were not well machined at first.

 

Thank you. I will try to rebuild it first. I have an extra OEM used petcock but it seems to leak more than this one. I took the oil filler cap off and smelled the oil. It did not seem to smell like gas. I think all the gas came from sitting with the petcock leaking. It leaks so bad that just putting the gas tank on the bike and hooking up the lines the gas leaks all over the engine and floor. The vacuum hose seems to be a little too large. Slips on and off real easy. I doubt if it is tight enough to hold a vacuum. Would a Yamaha dealer have the proper size whatever that is. Every other part I try to get from Yamaha they tell me is discontinued.

I will change the oil as a precaution after I get the petcock squared away. I don't have a manual so I will need to look up the spec's on the oil anyway.

I have PM's Chacal to order the parts.

Thanks

 

http://www.4shared.com/dir/1570443/a2eb ... r=DVtAfjvr

 

The one time I had gas leaking around it was because of a stuck float in one of the carbs.
You may want to check these also.

 

Thanks for the link. That is Great! It could be a stuck float I guess but I just put in 4 new float valves and 4 new float needles. I'm sure the petcock needs rebuilding and if that doesn't stop the leak I will check the floats.

Thanks

 

You have it backwards.

It IS a float issue; a petcock that isn't working correctly only ENABLES the leaking problem, it's not the cause.

If the float valves were working properly, you could leave the petcock in PRI and there wouldn't be any leaking.

After you put in the new float valves and needles, did you accurately wet-set the float levels using fuel and clear tubing? That process is described in detail here: http://www.xj4ever.com/setting%20fuel%20levels.pdf

How to tell if your petcock can't be rebuilt is covered in the "how-to" on rebuilding them: http://xjbikes.com/Forums/viewtopic/t=25058.html

But again, the petcock only controls fuel flow TO the carbs. The float valves are supposed to shut off said fuel flow when the bowls are full.

 

One other thing

That problem would prevent fuel from flowing if the petcock was working properly. Vacuum is only present when the engine is running, and the vacuum pull opens a small valve in the RUN circuit of the petcock. I would replace the vacuum line, but it's not causing your current issue. Like Fitz said....float valves.

OK two other things. Did you put an inline fuel filter on? There might be tiny flakes of rust finding their way into one or more float bowls. The flakes can prevent the float needles from seating. Have a good look when you pull the bowls back off.

 

Adrian1 thanks for the link but I can't get the link to open. All I seem to be able to open is ilivid.com. I'm not sure it ilivid highjacked the link or what but that seems to be the only thing I can download.

bigfitz52 yes I did use the clear tube. The tube was very stiff so it was hard to get it up next to the body but it appeared in tolerance to me. but by moving my position just a tiny bit it appeared to change the position of the gas in the tube a little.

Lets assume my float needles are not closing that would mean the gas in the tube would be lower than 4mm from the edge of the bowl? (3mm +/- 1mm) Correct? Thank you for the link to the petcock rebuild guide. It is jar better than the info I had found.

K-moe I will replace the hose and I will check the floats again. I did put a new inline filter on before I started.

One more thing. Does anyone have any suggestions on putting the carb boots back on? That was the hardest part of all.

Thanks

 

I do think it is your floats. They need to be pretty much perfect so it is a good idea to use a flexible hose.
I used a little silicone to put the boots back on. Much easier but you will still have to man handle them a bit.

 

Thanks OldBikerDude. Everyone hear seems to agree it is my floats. I am going to take them off and adjust them again. Strange because it ran real good when I test drove it. I am going to put an on/off valve in line with the petcock and let the new owner decide who he wants to tackle that issue. I agree with everyone here that the number one problem is the floats and the number two problem is the petcock.

Thanks

 

I wouldn't do that. Once you get the floats set right you shouldn't have a problem.
Didn't know you were fixing it up to sell.
I would think that a new owner would want it right and not rigged. Just my 2 cents.

 

Your absolutely right OldBikerDude. I have made it perfectly clear to him I am no mechanic and I have know idea what I am doing and since I don't know what I'm doing when I get it running he needs to take it to a real shop and have it gone over and he will need to pay a real mechanic to get the bike right.

I have a list of things that I have made that he will need to address at a later date. Like a new fuse box, the rear brake light no coming on when you pull the hand brake lever, turn signals not flashing at low RPM's, and things like that. The on/off switch is just another band aid until a real mechanic can fix it.
So I am being honest and up front with him so that he has no surprises. I have no idea what the bike is worth but I may have to take a few hundred off so he can have it worked on if I don't get the floats right.

Thanks,

 

Do let him know, if you want to be upfront with him, that he will have to fix it himself because a shop isn't going to be able to do it.
The mechanics in the shops today do not know how to work on these 30 year old bikes.

 

Thanks OldBikerDude. I will let him know that. He says he has a friend that is a mechanic. I will ask him to ask his friend if he thinks he can work on one of these old bikes. Thanks for pointing that out. I would not have thought of that.

 

Not sure why link is not working for you. From memory, you could view them for free but pay a small fee to download?

Anyway, have a look around this site then.

http://www.scribd.com/doc/45173840/Yamaha-XJ650

 

The list of things "wrong" is so minimal they're almost non-issues.

Upgrading/rebuilding the fuse box is a simple DIY job;

The brake light issue is probably just the switch (either unplugged or failed, it simply snaps in/out, no tools required except maybe a toothpick.)

The turn signals not flashing at low RPM indicates a weak battery.

I hope you're not selling it simply because of these minor issues. Make sure the new owner understands that it will need things like a valve adjustment before the carb sync; etc. and OBD is right, finding a shop that knows what they're doing with XJs is rare.

 

Thanks adrian1. I had to register but I did get the manuals late last night. If I did not register it would download ilivid.com which is some ad they have on that page. Thanks for your help.

bigfitz52 no I am not selling it for those reasons. It is actually my sons bike we bought him so he could ride with me. He never got into the riding bit. I have two Royal Star Ventures that I ride so I don't need it. My daughters fiancee's brother and mom want to buy the bike so that is why I am trying to get it running. I actually like the bike very much but at 60 I need a little more comfort.

 

Ok I can't seem to get my computer running until a part comes in so I took the carb off again. Boy it sure was easier to get the carb boots off the second time. I hope they will be easier going back on with the help of some silicone grease.

Tomorrow I will start checking the floats again and adjusting them. Tonight I will read the shop manual covering that section again and before I start checking the floats again tomorrow I will read the section here on adjusting the carbs again.

My biggest problem and it may well be the reason for my dismal failure the first time is that the clear hose is not flexible enough to bend up beside the carb itself. It I try to bend it to much it starts pulling off the nipple. I will use more hose tomorrow. I will loop it around so I can put the hose up next to the fuel bowl. I assume it does not matter how big the loop is.

I know it has to be level from side to side and that is not that difficult to do. But how do you make sure it is level from front to back. The carb hat is not very big so there is not much surface area to put a level on.

 

UPDATE

I have reread the shop manual and the link here on XJBIKES. I think the XJBIKES instructions for checking and setting the proper flat angle is much better than the shop manual.

I see I misunderstood something about the clear tube method of adjusting the floats so that the proper amount of gasoline is maintained in the bowls. Now that I have a clearer understanding of how to check the fuel height I will be attempting to adjust the carbs again but this time the right way.

I will also be changing the oil and oil filter as a few people have suggested.

Thanks for everyone's help,

 

:cry: Ok found another problem. Leaking gas coming from I think the tubes that go between each carb. I guess disassemble and reassemble twice did it or maybe it was leaking before and I missed it.

The o-rings seem to be flat o-rings or either that have flattened over the last 30 years. I have an o-ring assortment that says works with gasoline (it is safe to use in gasoline). They are the right size but they are not flat. They are what you think of when you think of o-rings. Is this what everyone uses to replace the flat o-rings? Seems like they would work to me. I could not find anything about replacing them in the carb rebuilt instructions.

Thanks,

 

Contact xj4ever. Picture your expression when you see petrol dribbling out of carbs rebuilt with the wrong o rings...

 

Thanks Adrian1.