1986 Venture - need help!!

[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

 

[one2dmax]

Are you testing with the airbox off or on?

 

[dannymax]

if I use the choke, it will rev up like the throttle was twisted open.

Do any of the Carbtune rods come up when you do this...or still no readings?

I'll run them on the test stand if you'd like to send them up.

 

[jfeagins]

Chances are great, on that old of a Venture, that it's CDI box is going to throw some chit at you, perhaps off & on, as well. My friend finally had to go aftermarket with his 87 Ventures' CDI to correct his. His bike would give all sorts of fits and run as if the carbs were badly in need of cleaning and/or syncing, yet we'd done all that - more than once.

Is it possible you fubarred the reinstall of the 4 carb linkages as you reassembled the rack?

 

[lonestarmedic]

Dannymax, I started this project after emailing you a while back. I decided to do my own for the experience. Wow what an experience! Going to go back over them and check my work. If that fails I will bow out and send them to you.

No, no bounce on carbtune with throttle. Will check using choke and report back.

Had to have missed something someplace. Have been working on these V4 creatures for about 15 years.

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[lonestarmedic]

One2demax - I have the airbox installed with filter in and lid on. Did not bolt lid down. Ventures are like Vmaxs they run like crap without an airbox.

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[lonestarmedic]

Jfeagins - Anything is possible on an old bike. And the CDI is in the back of my mind. Had the box out and inspected it before starting on the carburetors. Clean, tight and looked pretty good inside. Did not see any ruptured or swollen caps.

The linkage and cables look right. I am going to compare to a carb bank on my bench. It is 100% factory. And I intend to print out pictures I took during dis-assembly to verify that.

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[lonestarmedic]

And as a note, the vaccum sensor hooked to the number 2 carb does cause a slight increase in RPM when hooked up.

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[Dragmaxster]

Are you sure you put the small springs back in the right place after rebuilding the carbs?

 

[lonestarmedic]

Dragmaxter- going to check that too. I have a sample carb bank to look at plus a lot of pictures I took for the purpose.

 

[Traumahawk]

Did you bench sync the carbs (so they would be close) before putting the carbs back on?

 

[lonestarmedic]

Traumahawk I did NOT. Beyond an eyeball. I am going to pull carbs in a bit and check all the suggestions. And then use some fine wire or a piece of paper to do just that.

 

[davesax36]

I forgot a whole slide spring last week and got similar results. You don't have an "extra" one on the bench do you?

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[jfeagins]

I forgot a whole slide spring last week and got similar results. You don't have an "extra" one on the bench do you?

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Little f'ers can be a PITA at times, especially if your fingers are as big as mine while trying to reassemble...can't count how many times I had one jump back out of the rack and onto momma's kitchen counter top. lol

 

[lonestarmedic]

Yep they can become airborne for 50 yards.

 

[Traumahawk]

Traumahawk I did NOT. Beyond an eyeball. I am going to pull carbs in a bit and check all the suggestions. And then use some fine wire or a piece of paper to do just that.

Good...I heard of other instances where carbs werent bench syncd, and they do WILD things the first time that they are run.

 

[lonestarmedic]

Ok, step one done. Compression check. Had to make a checker. Put a hose between the rubber end of my push in checker and gauge. Pain in ass to hold in and crank. Results are: 1) 185, 2) 190, 3) 190 4) 185.
Even discounting minor loss for Rube Goldberg contraption this bike should run!!

 

[lonestarmedic]

Pulled carbs, split banks and removed jet blocks and all jets. Blew carb cleaner through all passages. Then compressed air at 100 psi. Repeated 4 times. Inspected all jets under magnifying glass. All open and sizes verified. Put 125 in main. The 170 under the diaphragm. And the 80 in the top. All gaskets good and setting correct. Rubber plugs in bottom of block new and tight. Idle jet is brand new and soaked in carb cleaner. It is a 37.5 as original. Put back together keeping floats and needles matched. Installed mixture screws at 2 turns open. Bolted back together on level surface using lower flange as reference. Then checked springs and linkage for proper install and smooth operation.

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[lonestarmedic]

Next step was using drill bits to bench synch. Got a couple 1/32 bits and measured. Only .003 difference. Went #2 to #1. Left bit in #2 and went to I believe #3. Whichever is hard link to left side. Finally went to #3 to #4. So, should be close.

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[lonestarmedic]

Pulled intake runners off and inspected. Insides great and outsides good. #3 had a couple hairline cracks but not inside. Smeared a bit of black RTV into cracks. Then checked head surfaces. No evidence of leaks. O-rings pliable and good. Checked with straightedge and they are above surface. Set in grooves and used RTV applied with toothpick to dress the outboard edge. Thin line half the diameter of oring. Confident they are sealed. Installed using straight edge to check level. By now it is midnight so install is tomorrow. Anything hyou folks think I need to double check just post it.

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