1983 XJ750 Maxim Build (Updates and Questions)

White smoke is NOT oil, its steam/water vapor, probably from water collected in the exhaust system somewhere. After a period of time it should dissipate.

Blue or bluish-gray smoke is oil, and it smells "oily".

Can you confirm what you are seeing/smelling?

 

Sounds like the old 'chain tunnel gasket' issue

There's no water jacket on the '83 xj750, so it's not going to be an anti-freeze issue

 

I was thinking it was oil burning because the level dropped from a bubble at the top of the sight glass to the very bottom of the sight glass. But I think this was from the new filter filling with oil. I started it again today and I did not see any smoke. I believe the smoke was coming from the newly wrapped headers.

I took a video of the idle. It will start climbing on its own with the choke off.

<iframe width="560" height="315" src="" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>

 

Were you on the center stand or on the side stand when you saw it was at the bottom of the glass? The filter doesn't take THAT much oil to fill up...

 

It was on the center stand both times. I left the petcock "on" overnight and now I smell gas in the oil.

 

Leaky float valves in one or more of the carbs..........

 

AND a leaky fuelvalve.....

 

I replaced the petcock with a non vacuum petcock from XJ4ever. I believe just leaving it on overnight was the issue there. I also rebuilt the gas cap.

I pulled the carbs off the bike to check out the float valves. I am going to go over everything else on the carbs to make sure I didn't make any mistakes when re-assembling them. If I can't figure out the carbs I may send them over to you Dave for a blessing haha.

 

In which case, the petcock wasn just leaking......it was allowing full-on fuel flow lol

Give me a shout when you need......

Dave

 

the idle goes up because when the idle is low it's missing bad, as the rpm's go up the miss gets not as bad, it was still missing when you shut it down.
but with the petcock leak, maybe it was just flooded. it acts the same after a ride ?

 

I am not sure I fully understand what you are saying. You think that the RPMs rise because the engine is misfiring? Yes it acts the same after a ride.

 

you have 2 cylinders firing 100%, 1 firing 75%, 1 not firing at all.
the idle is set so it runs like this, but that 75% starts going to 85-90% and now the rpm's start to go up, up enough that the one that never fired before starts kicking in.
the rpm's go up some more, to the point that the 85-90% cylinder is hitting 100%.
more rpm's, now the one that wasn't firing at all is hitting 80% and your up to run away speed

 

Thank you for the clarification. If I understand correctly the idle screws are the reason this is happening?

 

Maybe....

its ONE reason this CAN happen.
Bad float levels can cause that.
Bad sync can cause that
Clogged passages can cause that
Bad TCI can cause that
vacuum leak can cause that
A flat tire can cause that

 

i hate when that happens

 

Here's a wall of text for my day working on the bike.

I did pull the carbs today to check them out. Everything looked good. I broke the rack again and put silicone lube on the throttle shaft seals. (I did miss this step on the initial cleaning) I polished the diaphragm piston and bore. The did pass the clunk test before polishing but i just wanted to be safe. I checked the diaphragm for pin holes. I did not find any holes. I pulled the bowls and inspected the float/needle/seat. The screen on on the seat was a bit dirty because I was running without a in line fuel filter.

After that I gave them a quick clean before reassembly. I used a piece of plate glass to align the intake side of the carbs. I did the bench sync according to a post I found from hogfiddles:

"For bench sync, I open til the middle hole on #3 is totally uncovered. (that way they are all open far enough that a different butterfly won't hold anything open or close too soon). Now ai adjust the remaining three to match. Doesn't matter what order. Once all match, I back the idle screw out til butterfly 3 covers half of the middle hole. Fine adjust the remaking three to match. Order doesn't matter. I snap them open a shut a few times, then check. Adjust if needed. install. Start up and do running sync."

I put the idle screws at 3 turns out from soft bottom.

I checked it set the floats and everything was good.

Also re-checked the valve clearances. I had two just out of tolerance and I swapped in new shims. Everything was in spec after that.

After putting it back together I had the same idle issue persisting.

I ran it around the block to warm up and set the idle. It still had the hanging idle.

I connected my multimeter to the battery when it was running. The volts hang around 12.3 at idle. When I bring up the rpms the volts drop down to around 9.0 With the bike off the battery sits at 12.7v

 

Your stator isn't charging, or something isn't hooked up, or your regulator is shot ( my bet)... you're running off your battery

 

Just checked the stator and it is toasted. The connector was melted together and I found debris in the alternator cover. Resistance between the three white wires was .9, 1.3, and I could not get a third reading.

On the rotor I got a reading of .253 The rings on the rotor looked worn.

Will replacing the stator improve the rotor resistance or will I need to replace both?

 

The resistance on the rotor seems quite low, are you sure of that reading? Did you measure at the lead-in wire connector or directly on the copper rings?

Alternator Rotors and Field Coils:

gp2) OEM new and aftermarket re-wound Alternator ROTORS perfectly replace the originals. Rewound rotors are sold on a "core charge" basis and you must return to us a usable, same-model rotor core in order to receive your core charge refund. Re-wound rotors will output at least the same current as an original.

Checking alternator rotors or field coil: the resistance across the two lead wires (usually brown and green) at the connector should be as follows. Note that worn or damaged alternator brushes can affect these readings, as can "dirty" copper commutator rings on the rotor face (where the brushes contact the rotor):

4.0 ohms +/- 10% for all XJ650, all XJ700, all XJ750, XJ900RK, and XJ1100 models.



Sounds like the stator and the rotor brushes (at least) need replacing, and a new set of the plastic connector shells and terminals at the least.

 

I checked resistance at the lead in wires