Another newbie idle issue - UPDATE - compression issue

[ceme24]

Hi All:

I am a newbie.  This forum is fabulous.  Thank you all for maintaining it and the constructive input provided here.

I bought a 1982 Vision in 2010.  It is my first motorcycle.  I really didn't know what I was getting in to, but have found that it's a really unique machine that's fun to ride.  I did, however, let it sit a while, and am now suffering the following symptoms I am struggling to rectify:
Starts fine.
At initial start idle is "OK" - not as smooth as I'd like but tolerable.
As it heats up the idle continually drops
After 5 minutes or so frequent stalls occur at idle - stop lights, in turns when de-powered (not fun), etc...
As it heats up it gets more "jumpy" at initial starts
In hot weather it will also over heat when stopped (perhaps running too lean)

It's to the point now where as a new rider I don't use it.  It's too difficult for me to manuever safely in traffic with the stalls and jumpy starts.

As stated it's a 1982.  It's a USA bike.  The YICS has been capped off and removed.  I am not sure if it has a carb modification kit on it (I think one was sold to fix some issues on the 1982's??).  I don't think so.  I have tried the mixture screws - nothing doing.  The carbs "look clean".

My next step is going to be to take them off and completely clean them (likely next week).

Any other ideas/thoughts? 

I have poked around on the search here and see several topics of the idle running up but not so much on the stalling.  Thank you!

[Re-Vision]

I had similar symptoms after Rick cleaned my carburetors, after synchronizing the carbs it ran really well.      BDC

[Rikugun]

It's to the point now where as a new rider I don't use it.  It's too difficult for me to manuever safely in traffic with the stalls and jumpy starts.

A very wise decision.  :) Think of your attention as a pie chart. As a new rider, a good deal of it is used up with the operation of the bike, controls, balance, obstacles, etc. You don't need an ill running bike further eating into the pie.  :D As an experienced rider, the operation is second nature and you might safely appropriate resources to an ill running bike and still be reasonably safe. Then it's just a PITA.  >:(  :)

[jefferson]

Lean will cause an increase in engine speed and rich will drag the speed down. You may be getting a rich mixture from leaking needles and seats or a float level that is too high. Since the bike sat I would lean towards needles and seats. In any case the carbs need a good cleaning and adjustment.

Jeff

[pinholenz]

Rikugun, sage words indeed, nursing a erratic bike in traffic is an accident waiting to happen! And not just for new riders.

[The Prophet of Doom]

Sage words indeed
It used to be all I could to get from A to B, now while I am riding I can text and talk on the cell, eat my lunch, smoke a dooby, have a couple of beers, scratch my arse and still get to point B safely.  I think a misbehaving vision would tip me over the edge

[Rikugun]

That's easily remedied. Just bring a passenger who is willing to scratch your arse for you. That will free up just enough attention resources to allow you to continue with safe operation even when the bike misbehaves.  ;)

[QBS]

roro must be the ultimate King of Multitasking.  All hail King roro.

[Ken Williams]

A potential problem other than the carburetors is inadequate fuel delivery to the carburetors.  A bad fuel pump, plugged fuel filter, plugged tank screen or vacuum building up in the tank could be the problem.  I once experienced symptoms similar to yours that were caused by a bad fuel pump.  I verified the problem by temporarily bypassing the pump.  A pump rebuild was the "permanent" fix. 

[QBS]

Simple check for bad fuel pump:  Does it run well with a full tank of gas and the petcock in Pri position and then begin to fail when the tank is about half gone?  If yes,  consider a rebuilding the fuel pump.  Or, with about of a third of a tank, pull the fuel line off of the petcoke output spigot, petcock in Pri position, start engine and observe fuel flow.  Flow should be pulse in nature and strong.  If otherwise, consider pump rebuild.

[Rick G]

I would start with syncing  the carbs . Jeff the needle seat O ring will cause the same symptoms. But then you know that!

[ceme24]

I Appreciate the feedback.  I hope to get to it this upcoming week.  I am pretty sure it's not the fuel pump.  Sounds like cleaning and syncing carbs I a great place to start

[ceme24]

well, I ended up doing a compression check before the carb cleaning.

Front is at 75 psi and failed a leak down test.  You can hear air coming out of the intake and exhaust.

Rear is at 120 psi.  We have not done a leak test on it.

I am thinking this could cause the idle issues as well?

Looking like this bike has more serious issues than I dared to think about...

[Jimustanguitar]

You can hear air coming out of the intake and exhaust.
Looking like this bike has more serious issues than I dared to think about...

Sounds like your valves aren't seating well. Part of this could be carbon and junk from combustion. I'd run some fuel additives to see if this improves over time.

[QBS]

Doing a valve adjustment might help.

[jefferson]

I second the valve adjustment as you mention your problem gets worse as it heats up. Sounds like the valves could be tight and as she warms up the valves are being held open the more she warms up.

Jeff

[Rikugun]

Normally I'd be the first to agree with the valve adjustment as it's often ignored. BTW, thank you for doing a compression check and saving us the grief of trying to diagnose a carb problem on an engine with a sick top end.  ;) Once you get the compression where it belongs, then we can worry about the sick carbs which it probably also has.  ;D

Jim's comment might be worth investigating. There have been cases on engines that have sat and the valves guides get gummed up holding the valves open. Adjusting the valves under those circumstances won't help much. Checking the clearance could still be usefull. A very large clearance may indicate a hung valve or maybe even a bent valve?

You might try fogging the engine with Sea Foam first. Or run a pony tank with just enough gas to start the bike. Keep adding Sea Foam until the engine stalls the let it sit at least overnight and restart it. The purpose of this is to clean carbon deposits from around the valve head and make massive clouds of white smoke for your neighbors to enjoy.  :o  ???  :D Maybe go through a couple of run cycles and then check and see if compression improved.