Help folks - 1986 will not run beyond an idle

[lonestarmedic]

Ok, I am ready to bury my bike with a backhoe!! It started running like the idle jets were plugged up. Erratic and low vacuum readings on the Morgan Carbtune. So sinc the carbs had never been off I decided to do a rebuild. Pulled carbs and used an ultrasonic cleaner on them. While cleaning I re-shimmed the valves. They were a little tight but not unusual for 30 years old. Replaced all carb gaskets. Replaced the cut off valves on the side of the carbs. Installed new rubber plugs in the jet block. Along with the usual O-rings. Main diaphragms are almost new. Replaced them a couple years ago. Started bike and it idled fantastic for not being synched. However it will not rev at all. Any throttle will cause a stall. And the carbtune registers no movement. It is all the way at the bottom!! Now, if I use the choke, it will rev up like the throttle was twisted open. I tried adjusting the idle mixture to no avail. Carbs are on square in the boots. Airbox is on tight. Something is drastically amiss here. All 4 cylinders have spark. Tomorrow I am going to check the compression, and install new spark plugs, and check for vacuum leaks. Bike ran great until a 5 month storage where I was unable to ride. Very frustrated at this point.

 

Lack of vacuum points towards either a massive leak or worn out motor. It has 80,000 miles.

Choke causing revving engine points to a lean condition. However idle mixture has no effect.

With no vacuum, I cannot adjust the synch even though I know it has to be way off due to removing screws and springs.

 

Any ideas will be considered.

 

JB

Floresville, Texas

[MiCarl]

95% of the time I see your symptoms at my shop it's low speed fuel delivery.

 

First though, do a compression check to make sure the engine is tight. Then throw in a new set of spark plugs to rule out something simple. You might check all plugs for spark before installing them.

 

At this point you should be sure you have compression and spark. The only thing left is fuel/air (assuming it hasn't been corrected now).

 

The next step is to make sure you've got good fuel delivery. Drain one carburetor at a time and cycle the key to make sure you get plenty of fuel from the drain when the pump runs. Do this for all four.

 

If everything is good so far the carburetors are all that is left. They need to be properly cleaned paying special attention to the low speed fuel and air circuits. AN ULTRASONIC CLEANER IS NOT A RELIABLE WAY TO DO THIS. You need remove everything from the carburetor including disassembling the jet blocks. Use spray carb cleaner and compressed air to make sure every jet and passage flows freely. Make sure when you spray carb cleaner into the pilot circuit the cleaner also comes out the little holes under the throttle plate. Blow dry with air and reassemble, making sure the slides and diaphragms move freely.

[lonestarmedic]

Thanks MiCarl,

The carbs were pulled apart including the jet blocks and the jets. Sprayed cleaner through before and after the ultrasonic bath. Installed new pilot jets because of small diameter. Floats were set and fuel flows freely from all 4 drains. I set up a level stand next to bike and ran fuel from bike pump to each carb to set the floats. All were at 16mm below the line on the float bowl.

 

All 4 cylinders have spark, but I have spare new plugs to install. I used a spark plug in each wire and grounded to motor. However I did not check each INSTALLED plug for spark.

 

I am going to do a compression check tonight. If that proves good, I intend to pull the carbs, split them in half and go back through the passages.

 

Intake boots were not removed from bike so I will use a propane bottle and hose to check around them ffor leaks before pulling apart.

 

I agree that it sound like a fuel delivery problem on the primary circuit. I am frustrated but almost bet I missed something someplace.

 

JB

[Great White]

Something is not right here.

If you actually have a zero vacuum reading, the engine would not be running...even the loosest, sloppiest, ring/piston/cylinder bore you can imagine will create vacuum behind a closed throttle plate if its running in any capacity at all.

 

 

Also, if someone used an ultrasonic cleaner to do your carb bodies and it didnt get absolutely every nook,cranny, passage and circuit clean they didnt use it properly, werent set up to do it properly and/or they just didnt care to do it properly. Wrong type of unit, wrong cleaner, not in long enough etc. Done properly, an ultrasonic brings components back to oem fresh specs.

 

I've used em to clean everything from jet engine fuel nozzles to fine jewelry. At work and at home. But the one for jewlery wont nessesarily do the proper job on the jet nozzles and vice versa. Its like any other tool: right tool for the right job and all chemicals/ultrasonics are not created equal.....

Edited July 16, 2015 by Great White

[lonestarmedic]

I agree something is not right. The cleaner is a 2.5 liter industrial unit. Heated to 150 degrees F. One carb at a time and at least an hour. Looked new coming out. There is vacuum, just not enough to move carbtune rods. Starting to think it is just so far out of synch that it will not register. However I am going to go basic tonight and come back at it. Acts like the idle jets are plugged solid.

[Great White]

Seeing as your symptoms seem to contradict each other (idle screws no effect, idles but wont take throttle, needs choke, for throttle etc), i'd lean towards something was reassembled wrong in your carb assemblies. Thats Where i would look first....

[garyS-NJ]

I'm having the same problem and see in my timing inspection port that my timing isn't advancing.. But my bike backfires out carbs when I give it throttle. If your bike just dies with throttle or needs choke then I'd say fuel.. did you try giving fuel straight to the carb set with a funnel?? take the pump and filter out of the equation..

[lonestarmedic]

garyS - not a bad idea even though filter is new and pump output looked good when checked. I get a great flow out of all 4 drains.

[lonestarmedic]

Compression on all 4 between 185 and 190. So it is not a lack of pressure.

[93 venture]

have you made sure your air box is back on tight and air filter installed?

[Marcarl]

I'd go with getting the wrong jets in the wrong places when you redid the carbs,,, can give you all kinds of issues.

[cimmer]

Just another thought here, what did you use in the ultrasonic cleaner as a fluid? I read not to use carb cleaner as there are o-rings around the throttle shafts and the cleaner would destroy there if left to soak in it for any length of time. Might be worth checking into.

Also the first indication you had before the rebuild with the Morgan Carbtune was getting low and erratic reading, be sure that you have the restrictors that are in the hoses near the carbs and not near the Morgan tune. Yes I did this and had the same issues that caused you to rebuild the carbs. I noticed I could squeeze the hose and they would became readable and then realized my mistake. Switched them around and then got the correct readings on the Carbtune. Just something to think about. I also will do what is called "Shooting the Shotgun" on the carbs and that helps a lot also. http://vmax.lvlhead.com/tips/shotgun.htm

Good luck and I hope you get it resolved.

Rick F.

[garyS-NJ]

Keep us posted because I'm pulling my tci today and gonna try to refurb it.

[lonestarmedic]

Restricters are at the carb end. Used Krud-Cutter and water for first bath. Then white vinegar and water. Finally just water. All heated to about 150. Carb cleaner was sprayed into orifices. Then compressed air. Should not have destroyed anything.

 

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[lonestarmedic]

And I did the Peashooter and the Shotgun on the bike before going this route.

 

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[BlueSky]

It may be as simple as some water is remaining in the carb orifices/cavities. I remember waaaay back in 1968, I rebuilt my 65 Chevelle carb at the Ft. Bliss craft shop. After disassembling it I soaked in a bucket of acid I think. The shop has a 5 gallon bucket of something they used for carb cleaner that smoked when the lid was off. Then I washed the cleaner off with water and thought I had it dried before putting it back on the car. The car wasn't running well. I kept driving it and stopping to adjust the idle screws multiple times before it got all the water (or cleaner) out and started running correctly. Afterwards it ran better than before. It was running fine before. I cleaned it and installed a new accelerator pump just because.

[lonestarmedic]

Ok, I did something right!!!! IT RUNS AND TAKES THROTTLE

 

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[lonestarmedic]

Now I have no idea exactly what fixed it. I started at the intake runners and had everything apart up through the airbox. Idle is a bit erratic as of yet. But the carbs were bone dry and cleaned so I suspect all needs to wear in. My Morgan Carbtune is not working correctly. My bench check will have to do for now. Two rods not moving. Going to pull apart and check brass bushings and slide rods. But, free revving is about perfect. And it sounds correct.

 

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