81 750XJ Starting Complications

Bike was running great. Put it in the back of the truck to transport. Push/Pull tests passed. First left turn=bike dump on it's right side. On main road so I turn around to parking lot I pulled out of. Lift the bike up, it has a new dent on the right side of the gas tank everything else looks fine though.

I let it sit for a few hours before attempting to start it. I go to start. Chug chug chug. I change the spark plugs as they were old anyhow and they were wet. She starts, but dies shortly after. I'm not sure if it's getting too much gas or not enough? New feature: gas is leaking out of 1st carb, dripping from the screw just above the float compartment. Tip over sensor? The red light is on even in the trying moments of running.

What did I do!

 

You dropped the bike. Welcome to the club
Now you have one or more stuck floats, which is what's allowing the fuel to overflow.
Two things to try.
1. Rap on the float bowls with a screwdriver handle to free up the floats.
2. Pull the carbs, drop th float bowls, and have a look.

After that chack your oil level and that th oil dosen't smell of gas. If it does, thn do an oil and filter change.

 

red light would be oil light it comes on when you hit the starter button to check bulb if on when running you are low on oil or your sensor is stuck/defective.

if you lay bike on side gas will leak from carbs and you will flood it out for a while

 

Will leak from carbs? From where, how much and for how long? Flood out for a while? Define 'a while'.

 

1. Past the open float needls and through the fuel circuits.
2. Until the gas tank is empty, or the bike is picked up so the floats can rise and shut the fuel flow off (unless they get stuck, which yours seem to be).
3. Until the excess fuel is blown out, or evaporates.

 

also will leak out the overflow port of the carb.
floats do not float well when they are on their side

 

His carbs don't have overflow ports.

 

I think there are overflow ports on the carbs, next to the screws that go into the boat part at the bottom.

Had someone take a look at it, they found there was water in the gas tank and he says that was an issue (though it did have trouble starting after letting it sit and before any rain came, but there has been plenty of rain here). He said there must be a leak in or around the gas cap. I emptied the tank and carbs, filled it with 91 and some heat, it started right up, but only for a moment and continued to sound like it was choking. The Warning Light starts blinking after a couple/few seconds and continues to blink also showing NO gas is in the tank (zero bars) but is quite full. The longer it sits, the longer it will run, but for no more than 30 seconds and if I even think! about pulling that throttle it only dies sooner.


Any ideas?

 

There are no overflow ports on the carbs he has (assuming the stock carbs are in place). None. ZERO. Any excess fuel gets dumped out of the needle jet and into the airbox and crankcase.
The fuel light is on because the sending unit is likely unplugged.

Thoughts?

Are you using the choke wnen starting and letting it warm up before using the throttle? As the engine warms you'll hear the idle rise, at which point you can slowly, and gradually reduce the choke (really an enrichment circuit) to fully off.


Water in the gas usually edns with water in the carbs, and that lads to corrosion. Drain the fuel you have in the tank into a gas can. Drain the flaot bowls. Mix one gallon of gas with one ounce of Seafoam. Dump that in the tank and prime the carbs. Start the engine on full choke and see if she'll stay running long enough to warm up. With a bit of luck the Seafoam will break up the crud.

 

What does one do with the gassy water or watery gas?

Also in this image:

http://thumbs4.picclick.com/d/l400/...aha-Xj650-Seca-Carbs-Carburetors-Carb-Set.jpg

What are the little ports/holes at the bottom, next to the drain plug? When I drained gas (and water) with the drain plugs fully removed, gas starting coming out from my 4th (battery side) carb.

I would also like to note that none of these problems occurred before I tipped the bike, not even the warning light.

I do use the choke, and only once used the throttle to see what would happen, otherwise treater her kindly.

 

Fire starter for the watery gas.
Those look like standard issue Hitatchi carbs, the hole in the center IS the drain hole, traditionally you loosen the drain screws and then the gas flows through the drain hole in the center. The drain screw does not need (and probably shouldn't) be fully removed unless you are replacing them with something like THIS.

Did you do as suggested and take the carb bowls off and check the functionality of float/ float needles?

 

They must have been replaced or came with those screws, because that's what was in there.
No I haven't taken the carbs off. I wanted to try the simpler and less time consuming step first. Does this still sound like the float/float needle issue? Why the Warning Light and No Fuel on my sensor? It was full before the tilt..is there a reset button on these warning lamps or something? I remember reading something about a tilt sensor in these bikes, but can't find that article..

 

This (below) is starting with the simple things:

Trust and believe, the majority of advice given here by many members is very solid advice, your other symptoms may be something totally different - get your fingers into too many pies and you can't shake hands with anyone . . .
What I mean to say is - be methodical and verify one issue at a time.

I know nothing about a tilt sensor - I also don't know much about a 750 . . .

 

Thank you

 

There isn't one.

The foat bowl drain holes are standard, and used for wet-setting the float levels, and draining the float bowls of fuel before servicing or storage.

Homework time.

IN THE CHURCH OF CLEAN

THE SECRET LIFE OF CARBURETORS

Inside your Carbs


You probably don't need to do a full rebuild of the carbs, but you do need to understand how they work.

More reading for later.
The Information Overload Hour

 

Okay. Took the carburetors apart and cleaned them. Tested the bike with the carbs in, without hooking up to the airbox/filter and it sounded great. I attached the boots from air to carbs and this is what it sounds like:



Everything inside the carbs looked pretty clean, maybe a little clog, but nothing major. When starting it, if I give it some gas, I'm sure I could keep it going. Someone tells me I need to go ride it around and 'burn' through everything, and 'blast' anything through. I'm reluctant to do so. It sounds great when the air was disconnected..

 

It does not sound great.

Are all four header pipes hot? It sounds to me like you're not running on all four.

After a thorough cleaning you don't need to "burn" anything out.

I am revising my original advice. You need to break the rack and to a full refresh of the carbs.

 

Ok ...you need to check wiring from sending unit ...your sending unit inside of tank maybe hung up. Next agree with k-moe 100% bike does not sound right sounds like it is not hitting on all 4 cylinders. Take carbs to Church. I ran my 82 750 Seca last night ...runs sooo good. My carbs are very religious as they have been to the full mass at church.

 

Sounds like you're not running on all cylinders.

A little clog something major. You have wrk to do. Dropping the bike has woken up the sleeping issues.......dirt, water in the gas, sluggish floats, etc....

The bowls have two holes.....on is the hole with the drain screw IN it.....aimed to the side of the bowl. Turn that screw out, and you open the passage for the other hole (in the nipple sticking straight out the back) which is the drain itself.

You're mis-understanding how the bowl drain works.

You're getting fuel flowing back through carb four when you open the drains because: when you open the drains--
Fuel drains out of the bowls
The floats get lower
The fuel valve opens
Fuel is running into the carbs
Your 4th float is either too low, or sticking open

That also gives pause for another issue-- do you have your petcock on PRI? Turn it to run, and the fuel flow should stop. If it doesn't, you also have a petcock in need of servicing.

It won't be the sending unit...... That ONLY tells you how much fuel is in the tank. It is a completely different thing and is separate from the petcock. It is NOT a sending unit like on a car

 

Sorry Hogfiddles but I disagree in the Seca it DOES have a sending unit with a float , this is what gives bars on the ATARI . One problem he posted was his fuel qty quit displaying after bike went down. This was what I was referring to.

 

1981 xj750RH


Sndr Ut Assembly, F/Mtr

5G2-85752-01-00

it doesnt pump gas just fuel level indicator look for pinched wire or connector came off.
you can use a multimeter to check for variable resistance to check it

 

Here's my take...
Fuel level sensor, check the wiring like the others said. you mentioned "it has a new dent on the right side of the gas tank" could that be impeding the float movement? Still check the connectors, these guys are pretty sharp!

Running issues, if I bought a used XJ, even if it was running I would still clean the carbs. Maybe not break the rack but a dissemble, clean and inspect, wet set floats and sync. Like Hoggfiddles said "Dropping the bike has woken up the sleeping issues" yes yes yes your carbs need to com off.

And Please! before you try to start it again, change your oil. There is no way it's not contaminated with fuel by now.

 

i"m not sure what you're disagreeing with.......I never said it doesn't have a float.

You're talking about why the display might not show correctly. Which is what the sending unit does....ONLY

I"m talking about the fuel flow that is still occurring. Which has NOTHING to do with the sending unit. That is bowl floats and/or petcock issues.

As far as no bars on the display-----it maybe as simple as someone unplugged the pigtail from the harness when removing the tank and simply forgot to hook it up, or the clip came apart with the jolt--but yeah, check the wiring for that----

 

I think there's some confusion about terminology.
A sending unit has to do with measurement; sending an electrical signal to a gauge.
I think what some people may be thinking of is an in-tank fuel pump, many of which also have an integrated fuel-level sending unit.

 

Which is exactly why I said..