Lost a pilot screw.

Got back from FL a few days ago, rode the VF every day for two weeks, big fun. Developed a problem though. Last couple of days of riding, the idle speed would fluctuate somewhat and the engine stalled a couple of times at a stoplight. Had a chance to take a look today and see if I could find the problem.......found it right away. The pilot screw has apparently vibrated out of #3 carb, it is GONE! Considering that, I am surprised that it still runs as good as it does. Anyone have a spare that they are willing to part with? I checked the fiches and the screws for the V30 Magna have the same part #s.

 

The bike can run with a missing Pilot screw?!?

 

Strangely enough, it runs great . It is difficult to see all the way into the pilot screw hole on # 3 as there is no direct line of sight to it. When I go out to the garage this morning, I will use a mirror and attempt to get a better look, maybe part of the screw is still in there.

 

Well......I said that part of the screw might be in there in jest........but......there IS something in there, can't really see what it is. Looks like I will be pulling the carbs :doh:

 

I have probably confused everyone with my dumass description of the problem. I am calling the screw a "pilot screw" when it is actually the synchroniztion screw for #3 carb, sorry about that. :doh: Anyway, pulled the carb assembly and it turns out that the screw has broken off flush with the flange, a piece of it is still in there, threads on the piece are stripped and it was loose in the flange. The threads in the flange still look OK, but I am going to have to find a replacement screw, it measures out to a 4X0.5. I thought I could use a slightly larger screw and run a die over it, but my tap & die set goes no smaller than 0.6. I'm going to try Fastenal Monday for a replacement screw.

 

Any pics? :smile:

 

Heres a pic of the piece of screw that was left in the flange.

 

Very odd. Sabotage by Florida gremlins?

 

LOL...you and your "gremlins".

Do you see them on the wing when travelling on airliners?

 

I think this guy in the window is the culprit...

 

Of coarse it can run without a pilot screw. It will run rich at idle though.
0-1/4 throttle controlled by pilot/mixture screw and pilot jet only.

BTW...It probably fell out because it was turned out too far anyway.
They do not just vibrate out. Maybe the spring was missing or the "o" ring.

 

Definitely the work of FL gremlins. The pilot screw didn't fall out, it looks as though it sheared off leaving part of the screw inside. Very odd. Not sure how this can happen.

 

Reread my post #5....I had a senior moment and misnamed the screw, it is actually the sync screw for # 3. I was unable to find a 4X0.5 screw, so since the threads in the flange were slightly damaged anyway, I ran a 4X0.7 tap through, installed a new screw, resynced the carbs and all is well. By the way.....when I bench synced the carbs this time, I used a .002 feeler strip to guage the butterfly openings. Seems to have worked very well, engine runs very smooth with only minor fiddling of the pilot screws, 2 1/4 turns out provided the best idle. I would like to measure the exhaust pipe temps, but my IR thermometer has taken a dump, I will be getting a new one and check the temps.

 

Shearing off carb sync screws is definitely in the job description.

 

What do you mean bench synced?

 

A bench synch is when you have the carbs off and you visually set (and measure) the gaps on the butterfly valves on VC carbs or the gaps on the older carbs and put them back on. This gets the carbs set close enough to where you should be able to start the bike and get a manometer on later.

 

The airflow through the venturis should be the same on all 4 carbs, getting all four butterfly valves in the same relative position to the carb throats gets things in the ballpark. As pointed out, balancing the airflow with a manometer after the carbs are installed provides the best result.

 

sounds good. Ill try it this weekend. Thanks!