carb promlem but where ?

83 xj 750m maxim. everything is in spec, carbs cleaned and parts replaced no air leaks,. My problem is... Bike starts good on a warm morning with no enrichment, idles good, runs good, go down the road a ways come to a stop, light turns green give it gas and it dies. What the hell ! I need help please.

 

check sidestand safety switch remove sidestand relay to test.

how is the charging system working?

how long before the bike restarts?

 

Its running out of fuel, the petcock, gas cap would be first things to check. Maybe next time it happens open the drain scres to see if the carbs are full?

 

I'm sorry I should have mentioned that if I rev it a few times without being under a load then I can take off. If I just give it gas before I start letting the clutch out it will die. It will start right back up.

 

What do your spark plugs look like? Are you running rich?

 

how long do you have to be stopped for a light for it to stall?

I would look at battery and charging system
if the voltage drops when the motor slows under take off load.
snapping the throttle a few times may be giving you just enough of a charge/charging output to take off.

 

Spark plugs are a nice tanish color. I'll check charging system today

 

Just checked charging system... Just battery only, 12.73 v Turn key on, 11.90 v Crank engine, 10.70 v Rev engine to 3000 rpm, 14.50. The bowls are full of gas. When i come to a stop its pretty much right then is when it will die if i give it gas again. From the petcock i removed fuel line, and vac tube from #3 carb connected vac gun and squeezed the trigger gas came out the real nice. Ive double checked wet set floats spec on 3mm on all 4 carbs. anything else ? Thanks.

 

Does it shut off when it is fully warmed up? These can be a little cold natured and take a few minutes to reach good operating temperature.

 

Yes it does. It seems like its a little worse when the temps outside is hotter.

 

What do the plugs look like? Stock air filter?

 

Turn ignition on. Check battery voltage. 11.9 vdc? Now check voltage at coils. It should be nearly 11.9 vdc. If not, your carburetors have an electrical problem. It means you're dropping voltage. Coils are not getting enough current at idle. Check kill switch, ignition switch, connectors, etc. Corrosion at any of these places will can cause this kind of problem.

 

key on battery drops to 11.90 vdc. Coils... primary right side is 3.1 left side is 2.6 secondary without plug caps, 1 & 4 12.09 / 2 & 3 12,31. Caps on, 1 & 4 31.41 / 2 & 3 26.24

 

One thing i noticed #1 &4 plug caps dont have a resister in them and 2 & 3 do why is that ?

 

I think that since the coil fires both plugs together the resistor is only needed on one of the plug caps.

 

That makes sense. I'm still thinking something is not flowing smoothly in the carburetors.

 

Double-check the fuel levels.
Low fuel heights will cause the bike to starve for fuel when coming to a stop.

 

All of the plug caps should have resistors. Someone goofed, or put resistor plugs in and non-resistor caps when two of the caps failed, or....

 

My 82 750j is the same way. Fuel levels are spot on

 

I think it is typical that the shorter plug caps (1&4) can not be disassembled to clean the resistors, etc. However, they do have resistors as noted by your readings. Per the readings above, the 1 & 4 plug caps are reading more than the 2 & 3 and are adding almost 20K to the reading. I'm thinking the correct reading for the 83 maxim caps would be 5K each for a total of 10K +/-20%.

That's quite a bit out of spec with 2.75 max.

 

I know everyone is going to the spark...but just to ask about the fueling, did you synch the carbs? What did you replace?

I haven't know these bikes to start well without enrichment from cold (or maybe I just never try it). If your synch is way off you can still make the bike idle, but off idle performance will suffer.

 

Synch is spot on. I replaced everything in the carbs but the brass. I believe i did a stupid thing by not putting a inline fuel filter in the new fuel line and something got in there. Im just going to do a tear down again and clean. Thanks everyone.

 

Did you take voltage readings at the coils? It sounds like the current is too low at idle to get a consistent good spark. Voltage drops from corrosion at electrical connectors, kill switch, or ignition switch will cause the symptoms you are experiencing.