Fuel tank vent question

[Bob_Roller]

R80 Rider,

Are you sure it's a fuel tank venting problem, and not an electrical issue causing your stalling problem ??

[R80rider]

Hi Bob,

Not positive, but I can report that I loosened the fuel cap and rode the cycle 80+ miles on a hot day over the weekend and did not experience any problems.  Today, however, I took the cycle to work which is 18 miles up the freeway and it ran fine, but at lunch I took it for another 10 mile ride and it started stalling again (the gas cap was fully racheted), when I pulled over during the last stall, I loosened the cap and could hear a sucking sound when it hit a certain point.

I rode the cycle home with the cap basically just sitting in the well, and had no problems.

Am I chasing a ghost with the venting because the electrical is so intermittant?

*sigh*

[Bob_Roller]

I question it, because you installed a fuel cap from another bike that doesn't have a problem.

Are you sure it's a sucking sound, and not pressure being relieved ??

A fuel related problem should have the same effect of runnng to reserve, one cylinder will start running rough, than as the other cylinder runs out, the engine will quit.

So if your bike is just quitting, it's not a fuel delivery problem.

I would check the ignition coil for cracking, condition of ignition leads, and check the ignition control module under the tank to see if there is any di-electric grease between the module and the finned heatsink.

Another possibility is a loose electrical connection, I chased a similar problem on my '81 R65, the engine would just quit, never really positively identified the problem.

I had to go through the electrical system and check for security and condition of all of the connectors, quite frustrating to say the least !!!

[R80rider]

It may have just been pressure being released.  Per suggestions on here I serviced the ECM with fresh di-electric and even swapped between cycles.  with no change in symptoms.

The problem did not begin until just after I had the charging system rotor arm changed at Irv's BMW in Orange and then it wasn't until 200+ miles later (I was on a weekend trip).

The cycle is an 86 but only has 32K so this is frustrating.  I suppose since the Monolever R80s use a single coil, this is the next place to check and then onto the beancan and with the Hall sensor.  

Agreed?

[Bob_Roller]

My suggestion would be to remove the front cover on the engine, and check the wiring connections to see if by chance that something was not installed correctly, or if by chance some electrical connection was dislodged during the repair on the charging system.

It may be just coincidence that the bike developed this issue after having work done to it, but I have seen  a lot of problems that were 'collateral damage' due to maintenance being performed on some other non-related problem.

[R80rider]

Thanks Bob!  I will proceed with your suggestion and report back with my findings.

Bill

[Bob_Roller]

Before you remove the front cover on the engine, remove the positive battery lead from the battery, there are "hot' connections in there, that have power to them all the time, regardless if the key is on or not.

[R80rider]

I am glad you mentioned that.  I will do this after work tomorrow and have a report posted when I complete the inspection.

Thanks again!

[nhmaf]

>>>"Per suggestions on here I serviced the ECM with fresh di-electric and even swapped between cycles"

I hope that you meant to say "heat sink or thermal paste".  Dielectric grease is not the proper stuff to use
between the ignition module and its metal heatsink.   The heatsink paste (look like white zinc oxide) is
designed specifically for improving thermal conduction.   Dielectric grease is not the same stuff and doesn't
conduct heat nearly as well and is meant to prevent corrosion/oxidation.  

[R80rider]

Yes, yes, it was heatsink paste.  Thanks for the clarification!!

Bill

[Ed Miller]

Before you remove the front cover on the engine, remove the positive battery lead from the battery, there are "hot' connections in there, that have power to them all the time, regardless if the key is on or not.

I think it's safer to disconnect from  the negative terminal, as it's easy to touch your tool to the frame and cause a short circuit if you do the positive one first.  

[not-so-fast-ed]

Saw it done once..... Not a pretty sight!!!