Damaged Carbs with over tightened pilot screws

[Vickersguy]

So I started out like all of us, at 2 1/2 turns out on the pilot jet screws after the carb rebuild.  First plug check was black and soot covered on all 4 plugs.  Went on the process of leaning out the pilot jet in steps.  Went to 2 turns and #2 cyl. was close to good, the rest unchanged, still sooty.  To cut to the chase, down to 1.1/4, 1 1/2, 1/3/4, and 2.  The sooting is almost gone but the new issue is that the bike is now almost impossible to start.  Have to get the choke just right or it cranks forever.  No power below 4000 rpm, #2 plug is wet and smells of gas.  Once it starts the idle seems OK.  It has barely acceptable power over 4000 rpm but not the power I hear folks describe.  I'm beginning to think that possibly the pilot screws were over tightened at some point.  Are the symptoms I'm dealing with consistent with this kind of damage ?  In my mind, I'm thinking that at hi vacuum, the fuel flow would be adequate but as the throttle valves open and the vacuum drops, the fuel flow would be starved, or maybe I have that backwards.  Anyway, I suspect #2 cylinder is not firing at idle because the right hand exhaust is significantly warmer feeling than the left exhaust.  I'm going to give the bike a run tomorrow and do another carb/plug check after the new adjustments.   If this isn't sorted out I will tear down the carbs and clean them AGAIN.  It would seem though that this won't fix the issue.  Those carbs are clean.  If it remains screwed up I suspect it is damaged pilot valve seats.  Anyone else chase this issue down ?  Is what I'm seeing consistent with damaged pilot jet seats ?

 

 

Edited September 4, 2023 by Vickersguy
spelling, clairity

[cimmer]

The pilot screws would be damaged before the seats would be. The screws are just brass and soft..  You can get replacement idle mixture screws but before I would replace them I think you need to clean the idle circuits in the carbs. One way to do it without removing the carbs is what is called "Shotgunning the Carbs". One of the guys on the Vmax forum has a write up on the procedure of what you need and how to do it. I was having the same issue you are having but not as bad. I just did my carbs on my 89VR and it starts now without choke and idles and rides so much better. I also just synced the carbs and will take it for a test ride tomorrow to see how it goes.

Check out this URL..  https://vmax.lvlhead.com/tips/shotgun.htm      

Good luck and let us know how it goes..

Rick F

 

Edited September 5, 2023 by cimmer

[Marcarl]

If the idle mixture screws are at fault there will be a crease in the tapered end. The taper should be smooth with no lines. Also, on the screw will be a small spring, a small washer and then a special size o-ring. Don't loose any of those. If you don't see or have an o-ring it could be stuck inside the carb, or the washer for that matter. You will need to fish them out or find new ones. Fishing can be fun and just because it doesn't come out easy, doesn't mean it's not there. Use a small LED penlight to look down the hole.

[cimmer]

Here is what you are looking for in part and this is a source for replacement parts if needed..

https://www.siriusconinc.com/products/detail/122566

Good luck.

Rick F.

 

[Vickersguy]

Well, this is where I ended up.  When I got the Venture, it would only run with the choke on.  That is a classic.  Dirty carbs !  Not an issue !  So I bought it.

Took it to my garage and did the carbs.  The instrument panel didn't work either, and I got that all repaired.  Greased the speedometer cable.  Got the class system on line.  Did new stainless brake lines, rebuilt the calipers and installed new pads.  Fixed the sensor issue in the rear master cylinder.  Did two valve adjustments when I found the bad data in the original owners manual.  New tires were purchased and installed, final drive lube changed along with the engine oil and new filter. ( Have to do the clutch and front brake master cylinders yet ). Something was not right.  There was no power and sometimes it seemed to drop a cylinder.  Hard to tell which one...  Changed out the plug wires, plugs and did a coil check.  They were fine.  I dipped into the TCI to be sure it was 100%.  Changed out a bad capacitor but got no improvement. But it ran rich, so I redid the carbs, reset the float levels Installed and balanced them AGAIN. Still ran rich.  Turned the pilot screws in by 1/8 turns to lean it out.  Then it started running slightly leaner, but also lost power. It also became almost impossible to start.   Finally, the #2 cylinder stopped working at all.  Spent several hours just staring at the thing.  What had I missed ?  You gotta have spark and I proved that was good.  Gotta have fuel and I got that 100%.  That leaves air.  I never checked the compression.  It never occurred to me, that just because the bike starts and runs, that it might be bad.  How could it be bad ???  I just put 40 miserable miles on it and it ran like garbage, but it ran !  Well, that is what the problem has been all along and I never spotted it.  I got 92, 98, and 102 PSI. ( Should have 170 ) Didn't even bother to check the fourth cylinder.  If I ever want to run this bike I have to do a valve job and might as well do the 2nd. gear issue at the same time.  I don't know.  It's a big job.  It will cost about $800.  I'm an older man and have other stuff to do.  I'm 70 next month and by the time I finish this I may lose another year of riding.  I just lost this year.  I was ready to go May 1st. this year.  I spent the entire summer's free time wrenching.   I am really sick of working on this bike and now I have a HUGE job to do.    She looks purdy but I think she wants to kill me.....

Edited September 10, 2023 by Vickersguy
missing whineing

[Marcarl]

Having low compression on these bikes is not an everyday occurrence, that is to say it's rather unusual.
Let us know that this is how you did it. Kind of difficult to do remote diagnosis.
So, 10w40 oil, warm engine, all 4 plugs removed, throttle wide open, then install compression tester and get a reading from all 4.
Then do it again but this time squirt some oil into each cylinder just before you install the tester.
Make sure to write down each reading as you get it.

[Vickersguy]

Thanks for reminding me to hold the throttle plate open.  Forgot !  New readings, 172, 174, 177, 180.  Good news.  Except now I have no clue why this bike runs so poorly.

[Marcarl]

Did you use the right plugs, did you check the gaps, did you check that they all fire regular like. Maybe a poor connection at the coils or plug ends. Maybe the resisters are corroded. If all that checks out it's back to the carbs.

[Vickersguy]

Have 9 coils total here, all check out good, swapped some out with no change in operation.  New wires of the correct type, new plug caps with 5K resistance, new plugs of the correct type, only fair spark, nothing great.  I'm agreeing with you.  Must be something about the carbs I missed. At least I can skip pulling the motor, for now....

[Vickersguy]

First thing first, I remounted the TCI on the air box.  I'm going to do some checks there on the way to the carbs,  Just to be sure, So back to the wispy red spark thread........