1986 R65 Misfiring

[Barry]

Looking back over the whole thread I at first thought you had eliminated ignition through parts substitution which was why I suggested it might be carb related.  But I missed the comment about being able to identify the misfire with a strobe lamp  

It was suggested that an inductive timing light be carried with me while test riding to allow both sides checked when the misfire starts occurring.  I have done this and can verify that the light strobes confirm a misfire on the right side of the cycle.  I cannot completely rule out that it might be occurring on the left as well but that has not been empirically observed.

That places it firmly with the ignition system as you are saying the strobe identified missing sparks.  What is puzzling is that the electronic tachometer doesn't register the misfire.

So it's an ignition problem; a marginal one where it just fails to generate a spark at the plug but still fires the tachometer.  Just a thought as a temporary test - you could try closing up the plug gaps a few thou to see if that helps by reducing the demands on the ignition system. If it does you still need to identify what is causing the poor spark but you will have learned something. It's not necessarily true that any ignition related problem should affect both sides because conditions in the cylinders and therefore threshold spark energy demands are not absolutely identical. If the the spark energy is gradually reducing for some reason it's perfectly possible that one cylinder will show it up before the other.  

[R80rider]

Thanks Barry,

As you no doubt noted, the coil wires were swapped last night prior to the ride in an effort to either get the problem to move from the right to the left side or rule out further investigation of the ignition system.  

The plugs and wires have been both changed and swapped.

It would seem that nothing is left but mechanical unless I am still missing something.  

Some have suggested carburetion but am unclear on what could/might change in the physics of a carburetor from say mile ~10 *fully warmed up* to mile 50?  

[Barry]

It's a puzzle. If I understand correctly you actually saw an ignition misfire when using the strobe lamp and that corresponded with the symptoms that the engine was displaying.  So did the ignition misfire or not ?   If it did then the puzzle is why one cylinder and not the other especially after changing the ignition components around. That's what I was trying to explore above by suggesting that each cylinder could have slightly different ignition requirements and a failing ignition system might therefore hit one cylinder first. Closing up the plug gaps costs nothing and is worth doing even if it only serves to dismiss ignition as the source of the problem.

It is hard to conjure how a carb could cause this problem in such a predictable way.

On the mechanical possibilities did valve clearances get mentioned and checked ?

[Bob_Roller]

By chance, when this misfire occurs, are there any high voltage cables overhead, or any other large electrical transmission equipment near by

My mother has a van, that if she takes a particular route that takes  her under some low hanging 400 KV transmission wires, all the lights and cautions on the instrument display illuminate and no throttle response if additional throttle is added .

It's a Honda and the dealership can't find anything wrong with the vehicle, there are no faults generated in the vehicles computer to do any troubleshooting .

[R80rider]

Thanks for all the input.

Yes, the misfires were verified with a timing light and did not move with the coil wire swap.  The valves have been set at least twice since this began happening.  

While it cannot conclusively be said that there were never any high voltage line, the misfire seems to be more based on time ridden/miles than location.  

Both spark plug wires have been replaced and now swapped.

Spark plugs were refreshed since this started happening.  

The gap of the plug on the affected side could be closed, please explain how this might help?  

Any other ideas, no matter how obscure are invited.

[mrclubike]

The gap of the plug on the affected side could be closed, please explain how this might help?  

You could be having an over all ignition system failure and it only shows up on the one side because it has more compression or leaner air /fuel  mixture requiring more demand on the ignition system
Closing up the gap will let that cylinder require less voltage to spark and the misfire may move to the other side ruling out any other problems with carb or compression.

After that I think you need to hot wire the the ignition system
Or you could  hard wire a volt meter into the ignition system in different location and watch the voltage
I have a feeling you have a electrical connection heating up and getting high resistance in it. When you stop and let the system cool down a bit it closes.
You can also feel the connectors  to see if one is getting hot  

I think the time it takes to act up is to long to be a carb issue and you have confirmed that you are loosing spark when the problem happens

[Barry]

This clutching at straws but it's just occurred to me that there is a small theoretical  difference between the two cylinders as far as the ignition system performance is concerned.  A dual output coil produces sparks of different polarity with the spark travelling from the centre electrode to the side electrode being more efficient than the other way around. That means  one spark plug is more efficient than the other at creating a spark and in very marginal conditions that might just count.

There is a way of testing for polarity but it's easier  to just swap the leads.  Did you try swapping the ignition leads over but only at the spark plug end leaving the coil connections alone.

[bubby-joe]

My 1980 r-65 gave me a problem last sunday the difference being my miss was both cylinders, I experienced a battery failure and as power from the battery became less and less available the miss got more and more pronouonced until the battery went right flat even the neutral light would not come on.  I charged the battery for 5 minutes and started and got home to have it fail again at the shed door 3000 yards and required a second charge to get in the door.  A new battery is on the way very pricey little bugger, anyone know if a YB-18L-A will fit in the frame CCA is better on this size than the no longer available in my area proper sized battery.

[Barry]

I think you will find that battery a very tight fit in the battery tray if it goes in at all.  The critical dimension is the depth because of the limited gap between the air box and the rear mudguard. The stock battery is approx. 80mm deep and the data I have on the YB-18L-A is it's 90mm deep.  It may just squeeze in but might require the tray to be modified.

[bubby-joe]

I think you will find that battery a very tight fit in the battery tray if it goes in at all.  The critical dimension is the depth because of the limited gap between the air box and the rear mudguard. The stock battery is approx. 80mm deep and the data I have on the YB-18L-A is it's 90mm deep.  It may just squeeze in but might require the tray to be modified.

I'll go to the landfill later today and look for an old one to try in the frame to check the size opens at 1:00pm local

[Bob_Roller]

The YB-18L-A battery is too large to fit in the battery tray of an R65 .

The dimensions of the YB battery are 11 inches in length, 7.1 inches wide and 6.4 inches high .

The battery that fits the R65, is 7.13 inches in length, 2.99 inches wide and 6.69 inches high .

[mrclubike]

My 1980 r-65 gave me a problem last Sunday the difference being my miss was both cylinders, I experienced a battery failure and as power from the battery became less and less available the miss got more and more pronounced until the battery went right flat even the neutral light would not come on.  I charged the battery for 5 minutes and started and got home to have it fail again at the shed door 3000 yards and required a second charge to get in the door.  A new battery is on the way very pricey little bugger, anyone know if a YB-18L-A will fit in the frame CCA is better on this size than the no longer available in my area proper sized battery.

I think you may want to check your charging system.
It sounds like your battery is taking a charge.
Symptoms of battery failure are generally slow or no cranking at all after you turn the key off and try to restart.

A battery can also short out causing heavy load on on the charging system  that will reduce system voltage to a point you can have a week spark.
But that doesn't sound like what you are having because if it was you would not be able to charge it up and restart  

[bubby-joe]

My 1980 r-65 gave me a problem last Sunday the difference being my miss was both cylinders, I experienced a battery failure and as power from the battery became less and less available the miss got more and more pronounced until the battery went right flat even the neutral light would not come on.  I charged the battery for 5 minutes and started and got home to have it fail again at the shed door 3000 yards and required a second charge to get in the door.  A new battery is on the way very pricey little bugger, anyone know if a YB-18L-A will fit in the frame CCA is better on this size than the no longer available in my area proper sized battery.

I think you may want to check your charging system.
It sounds like your battery is taking a charge.
Symptoms of battery failure are generally slow or no cranking at all after you turn the key off and try to restart.

A battery can also short out causing heavy load on on the charging system  that will reduce system voltage to a point you can have a week spark.
But that doesn't sound like what you are having because if it was you would not be able to charge it up and restart  

Load testing the battery after charging to full on my 2 amp charger the battery goes from 13.8/14.2 to under 3 volt in under a minute and under normal working conditions the charging system should be enough to run the ignition but with the headlight on the the battery gets so little the ignition gets nothing and misses bad and I shut it down put a light charge to get home 5000 yards and then another light charge to get it into the shed I really hate pushing it.  A proper sized battery gets here late today early tomorrow for the next 3 to 5 years.  And I was told the YUASA 51814 has been discontinued by local supplier.  Looking at the rear fender to make more room for a larger battery will mean modiiying the battery box floor and the rear fender to gain the 4.5 inch required for the YB-18L-A's depth and a more readilly available battery and better suited to also using my sidecar later.

[Barry]

Yuasa may not make the 51814 but others do including the OEM fitment Varta.  There is no real problem finding a battery - many here use one of the generic AGM batteries as listed in the top section of this board. They are a perfect fit and excellent value.

[mrclubike]

Replacing the battery is good but make sure you check the charging voltage after you install it.
Just because the charge light goes out doesn't always mean your charging the battery
You should have at least 13.5 volts after a minute or so at 3000rpm
if you install an AGM you will want to  turn it up to 14.2.

If your able to charge the existing battery up for just a short time and restart and drive the bike your battery is good. (well it is working but may have low capacity from being deep cycled)  

The new AGM batteries that fit the stock battery tray have more than enough capacity unless you do a lot of idling and stop and go traffic.