1986 VR Running on Three Cylinders

[twigg]

I appear to be having an issue with Number 2 Cylinder.

 

Gas mileage is not what I think it should be ... low thirties rather than at least high thirties, and I have long suspected that one or more cylinders isn't pulling it's weight.

 

On a recent ride home of about 90 miles, the rev counter started misbehaving. It would be steady at 4000 then drop to zero for short periods, jumping again to 4000 rpm.

 

That is entirely consistent with #2 Cyl. cutting out and in.

 

From a cold start, the exhaust to #2 remains cold. It will start running once it's revved a bit, but it's inconsistent.

 

So there clearly is an issue with that cylinder.

 

It could be any one or more of a number of things and I'm happy enough to pull it apart to find out what.

 

I plan to replace all the plugs, wires, plug caps as a matter of routine. I can easily diagnose a failed coil but I was wondering if I should be looking deeper than that.

 

As I understand it the only other parts in the system are the TCI and the Pick-Up Coils.

 

Does the failing Tach indicate anything that might pinpoint the problem? At the moment I am seriously considering the TCI upgrade too. I may well simply start by replacing the diodes in the original, but I can't help thinking that a long term fix is going to be the upgraded unit Dingy was selling.

 

Any thoughts?

[greg_in_london]

I'd check out the coil and the leads.

 

There was a problem on the early Ventures (someone else will know the engine numbers i expect) with the pick-ups, except the problem tended to be as the engine warmed up. the explanation that I heard was that the connections had been soldered too tight within the plastic casing, so as things expanded, there was tension on the connection and it could lose contact when the engine became warm. Yours is a problem from cold and then you said that it cuts in, which is the opposite of what I had (mine was made in Nov 1983).

 

Remember that the leads are removeable, so you can check if they just need to be screwed in further, even if they're a bit of a pain to reach.

[twigg]

I'd check out the coil and the leads.

 

There was a problem on the early Ventures (someone else will know the engine numbers i expect) with the pick-ups, except the problem tended to be as the engine warmed up. the explanation that I heard was that the connections had been soldered too tight within the plastic casing, so as things expanded, there was tension on the connection and it could lose contact when the engine became warm. Yours is a problem from cold and then you said that it cuts in, which is the opposite of what I had (mine was made in Nov 1983).

 

Remember that the leads are removeable, so you can check if they just need to be screwed in further, even if they're a bit of a pain to reach.

 

Thanks for the quick reply.

 

It's an '86, so I suspect not an early one. The coil can be diagnosed simply by swapping it to another cylinder and seeing if the problem moves. It's intermittent which is always a pain.

 

I just wondered really what might cause the tach to stop ... it actually only did that a couple of times and was accompanied by a loss of power when it cut, and a surge when it jumped.

 

So where precisely does the tach get the signal ..... and the tach does work from a cold start, even when #2 isn't warming the exhaust header.

[Yammer Dan]

As Greg said you can take those plug wire ends apart and clean them. Very small parts in there that can go flying to never be found again. Just be carefull when taking apart with larger flat blade screwdriver.

[Yammer Dan]

TCI might be due for trip to oven.

[twigg]

TCI might be due for trip to oven.

 

I agree, it might.

 

That probably should be done anyway ... ick!

 

I'll get a list of the needed diodes and warm up the soldering iron

 

As well as doing all the other stuff

[dingy]

If the tach is working when cold, it indicates that the #2 cylinder is firing at the TCI. Could be a coil problem still. Tach trigger is connected to wire in wiring harness between TCI and coil input leads.

For the idle condition not firing on #2 I would suspect low speed circuit in carb.

A dirty connection at the TCI will also cause the tach to be 'jumpy' or nonresponsive. 8 pin connector at TCI, Gray wire is the suspect here.

Gary

[twigg]

If the tach is working when cold, it indicates that the #2 cylinder is firing at the TCI. Could be a coil problem still. Tach trigger is connected to wire in wiring harness between TCI and coil input leads.

 

For the idle condition not firing on #2 I would suspect low speed circuit in carb.

 

A dirty connection at the TCI will also cause the tach to be 'jumpy' or nonresponsive. 8 pin connector at TCI, Gray wire is the suspect here.

 

Gary

 

Gary that was solid info that helps ... Thank You.

 

Did you sell all those after-market TCIs?

 

I will refurbish the one I have in any event, and even though it does seem to run well most of the time, but I am seriously considering the upgrade.

 

I would like to map the ignition towards fuel economy. The bike has plenty of power but in July I am running an LD Rally and I will need to cover up to 4500 miles in 100 hours.

 

That's a lot of gas and reducing the bill would be helpful.

[dingy]

I agree, it might.

 

That probably should be done anyway ... ick!

 

I'll get a list of the needed diodes and warm up the soldering iron

 

As well as doing all the other stuff

 

Diodes needed are 1N4001 up thrugh 1N4006.

 

1N4001 are rated at 50V reverse bias. which is plenty, higher numbers just increase rated reverse bias voltage. Won't help performance at all. You can get a pack of 25 from radio shack for about $5. They are random 1N4001 through 1N4006, does not hurt to mix them in this case. The marked cathode end is what is important that it is put in to match 8 diodes being replaced.

 

Very low wattage soldering iron, to much heat will lift traces right off citcuit board.

 

Gary

 

[dingy]

Gary that was solid info that helps ... Thank You.

 

Did you sell all those after-market TCIs?

 

I will refurbish the one I have in any event, and even though it does seem to run well most of the time, but I am seriously considering the upgrade.

 

I would like to map the ignition towards fuel economy. The bike has plenty of power but in July I am running an LD Rally and I will need to cover up to 4500 miles in 100 hours.

 

That's a lot of gas and reducing the bill would be helpful.

 

I will be seeing if there is enough interest between here and the VMax group to get another buy together in the next week or so.

I don't have any of the standard TCI's left from the last purchase. I do have one that has more functions built into it that will probably be my winter HP increase project though.

Gary

[twigg]

Diodes needed are 1N4001 up thrugh 1N4006.

 

1N4001 are rated at 50V reverse bias. which is plenty, higher numbers just increase rated reverse bias voltage. Won't help performance at all. You can get a pack of 25 from radio shack for about $5. They are random 1N4001 through 1N4006, does not hurt to mix them in this case. The marked cathode end is what is important that it is put in to match 8 diodes being replaced.

 

Very low wattage soldering iron, to much heat will lift traces right off citcuit board.

 

Gary

 

 

Thanks. I have a 10 or 15W iron. I have used it for working on the motherboards of XBox among other things, so it will be fine

 

Adding jumpers to the Computer Monitor on the VR was a breeze by comparison.

[oldandcrotchety]

One of my cylinders was giving me some trouble a while back. It would not fire much when it was cold and not much better when warmed up. I tried several things, but nothing helped. Then one day a friend of mine that rides a Honda told me to try something real quick and simple, just for grins. After all, I had nothing to lose, so I did. I opened the drain plug on the carburetor that fed that cylinder and when the bowl was dry I tapped the bowl lightly with a hammer and punch a few times and then closed up the drain. When I then started up the bike it ran as it should and hasn't given me any trouble since. May not be your problem, but it only takes a couple of minutes to try it.

[twigg]

One of my cylinders was giving me some trouble a while back. It would not fire much when it was cold and not much better when warmed up. I tried several things, but nothing helped. Then one day a friend of mine that rides a Honda told me to try something real quick and simple, just for grins. After all, I had nothing to lose, so I did. I opened the drain plug on the carburetor that fed that cylinder and when the bowl was dry I tapped the bowl lightly with a hammer and punch a few times and then closed up the drain. When I then started up the bike it ran as it should and hasn't given me any trouble since. May not be your problem, but it only takes a couple of minutes to try it.

 

When I got the thing I did some carb work. All the diaphragms were replaced as were two of the air cut-off valves.

 

They were cleaned and balanced.

 

What I did not do was remove the jet blocks and replace the necessary bits in there. That, and checking the float levels is all on the list of jobs to do.

[Yammer Dan]

Sea-Foam??

[twigg]

Sea-Foam??

 

Done that.

 

Generally Sea Foam is better as a once or twice a year treatment to keep things clean. It's not so good for cleaning out grime from clogged passages.

 

I was lazy when I had the carbs apart and now it's time to do the job properly.

 

As an aside .... Do the needles require any shimming when you change from the standard air filter to a K&N?

[jasonm.]

I will be seeing if there is enough interest between here and the VMax group to get another buy together in the next week or so.

 

I don't have any of the standard TCI's left from the last purchase. I do have one that has more functions built into it that will probably be my winter HP increase project though.

 

Gary

New TCI's---Could you wait till the spring...when I have some $$$ ...?....NO , needles do NOT need any shimming w/ OEM shape K&N filter. But you may need to slightly adjust the low speed screws out another 1/4 turn...MAYBE. Drive it 1st.

Lastly, I will upset some here. But Seafoam is simply a very mild cleaner. It has no ability to desolve what we call , varnish. I have tested it on, open carbs, that were caked w/varnish. Did nothing. It's just a thicker WD40. That is weak when compared to Chevron Techron, Berryman's and other true cleaners/solvents. As you know WD40 is similar to Kerosene and will make your engine run hotter...if too much is used. People have melted spark plugs when using too much. Hotter engine exhaust can clean EGR valves on cars. Other than that, I find no use for it.

Edited December 29, 2011 by jasonm.

[twigg]

New TCI's---Could you wait till the spring...when I have some $$$ ...?....NO , needles do NOT need any shimming w/ OEM shape K&N filter. But you may need to slightly adjust the low speed screws out another 1/4 turn...MAYBE. Drive it 1st.

 

Thanks

[mother]

i found a bad spark plug on my 86, installed a new one and cylinder firing again. then changed the other 3.

 

cheers, Scott

[eaglerun]

I had a problem similar to yours with my 83 a few months ago. Turned out to be a bad solder connection on what I have heard called the tip over switch. You can get to it through the headlight. With the bike idling I was moving the wires behind the headlight and I moved the right one and it speeded up and idled smooth. There is two for sale on ebay now if you want to see what it looks like. Hope this helps as mine was a easy and no cost fix.

[jasonm.]

i found a bad spark plug on my 86, installed a new one and cylinder firing again. then changed the other 3.

 

cheers, Scott

I also forgot to mention...I also recently have had bad spark plugs from NGK. At last count, 6 in the past 3 years(2 resistor, 4 non-resistor) . I switched to Denso iridium. If you don't believe ne. Maybe you could buy NGK iridium DPR8EIX-9. Which may be made better than their standard plugs.

[twigg]

I have a bad plug cap on cylinder #2. It is showing "open". I temporarily replaced it with a spare from my Triple, and it ran just fine. Still a Rev Counter issue though.

 

So ....

 

I dragged out the CDI and opened it up which wasn't as easy as it should have been.

 

The whole inside has been covered in some "brown" goo. Probably waterproofing for the board. I completely failed to desolder the headers, so I cut the box.

 

The diodes are in perfect condition, they show no sign of deterioration at all, so I left them alone. The danger of lifting a trace or other damage is worth it if those diodes need replacing, but not worth the risk if they don't. There are no swollen capacitors either ... everything looked clean so I put it back together and reflowed the solder in the header pins.

 

Some silicone around the cut and all should be well at least for now.

 

What I need to do is make sure that the connectors are clean before it goes back on the bike. It's going in the left fairing pocket. It's dry in there and the audio equipment is coming out. That way it's easy to get at and ready for the Ignitek that I plan on buying.

 

New wires, caps and plugs and that's an area of the bike I can feel happy with.

[dingy]

I have a bad plug cap on cylinder #2. It is showing "open". I temporarily replaced it with a spare from my Triple, and it ran just fine. Still a Rev Counter issue though.

 

 

If the motor is firing on #2 cylinder, the tach issue is not in the TCI (CDI is different technology).

I don't know an easy way to check the signal the tach is getting without an occiliscope. But if coil is firing, it would then fall to a wiring issue to the tach head.

If tach is fluctuating, try a seperate RPM reading source. There are low cost meters that wrap a sensor wire around a spark plug wire & give a digital readout. This may give an indication of an RPM fluctuation that would then be an indication that #2 is loosing the firing signal from the TCI.

Gary