83 versus 89--weak spark

[frankd]

I bought my 83 in 4/83 and rode it until a couple of years ago. I gave it to my brother when I found a low mileage 89, but I still maintain it for him. As long as I can remember, if the battery was a little weak, you'd have a heck of a time starting it because the spark was weak when cranking. If the plugs were getting old that made it a lot worse. Mark doesn't ride it as much as I did, so he has this problem a lot worse than I did.

 

The battery on my 89 is going bad and it doesn't have the same problem. The last time I rode it (before it snowed) it'd been sitting about 3 weeks and when I cranked it, it hardly went arouind BUT it fired right up. The spark seems to be a lot hotter on the 89.

 

Do others with 83's notice the same problem?? How about other years?? We all thought the only difference between the 83 and the later TCI units was how the vacuum advance was connected. Maybe there was another difference.

 

Frank

[dingy]

The electronic circuitry will have to be different in the 83's from the 84 -89 models.

 

This will be necessary due to the way the 83's interpret the signal from the vacuum sensor.

 

It could be that the 83 has diodes that are on the verge of completely failing. There are 8 diodes that fail due to a form of corrosion. Once any of these diodes fails, the TCI will fail to provide spark to the cylinder that that particular diode was controlling.

 

Another cause could be the plug wires have higher than normal resistance.

 

Gary

[skydoc_17]

Hey Frank,

I think that Dingy has touched on the two main problem areas with the high voltage system on the 83'VR. Now, the TCI problem is a tough one to cure because of the limited options you have as far as a replacement TCI goes, BUT the replacement of the spark plug wires and keeping fresh plugs in these 1200 motors is something that can easily be addressed, and for a moderate amount of money, will give you the best chance of having your 83'VR start dependably until the TCI finally fails. I keep a back up TCI available for my MKII 87'VR and if I had the MKI 83'VR, I might even have two! I can't even begin to tell you how many "problem VR's" I have worked on that have totally changed to a dependable first start bike, when the TCI was swapped out. When a VR with "spark/start" problems comes in for repair, If it has 20 plus year old ignition wires still on it, that is usually the first thing I change. I consider spark plug wires and spark plugs "perishable items" and in more than 50% of the time, the replacement of these two items yields a drastic improvement in the performance of the high voltage system. Now don't get me wrong, a set of plug wires is not going to correct an ailing TCI, but with that variable removed, it makes troubleshooting the TCI a heck of a lot easier.

Earl

[bongobobny]

Yah! That is my thought as well, bad wires!! They are probably the original 27 year old wires! Also, plugs should almost be changed on a yearly basis on these scoots for proper performance.

 

If only one cylinder was firing poorly I would begin to suspect the coil itself. but I more so would change the wires and plugs first...

[Marcarl]

Or it could be the resistor in the spark plug cap.

[mbrood]

AS I understand it, the Venture has always had a nortoriously weak spark... even new. Since the TCI or CDI simply close and then momentarily open a ground path for the primary side of the coil, a newer coil or a new substitution could likely cure a lot of problems. As said, the quality and cleanliness of the plug wire, plug cap and plug are paramount but easily replaceable. There's bound to be lots of 3 Ohm primary coils out there... just haven't seen any trials on our bikes.

[Condor]

I used to have the same problem with my '83. Fresh plugs, especially after running Sea Foam thru it, and a DEKA AGM battery took care of it. Generally a weak batt will not spin it fast enough to fire. It's old.....

[frankd]

Well, I do have a new set of plug wires in the parts cabinet and they ones on the bike ARE original. I've kept an eye on the plug connectors and the last time I checked they were still good (they measure about 5K ohms--just measure from through the connector to ground). I will replace the wires and connectors when Mark brings the bike up next spring. Also his battery is trash and that undoubtadly was making things rougher even though we were jumping it off a car.

 

It's not an issue of 1 bad cylinder. When it starts it fires up on all 4 cylinders right from the beggining. I plan on pulling both the 83 and the 89 TCIs and replacing the diodes. I'll be able to get to mine soon and his when he brings it next spring.

 

This problem with the 83 was refreshed in my mind yesterday....Mark couldn't get it started to run the Stabyl into the carbs. The carbs are in good shape and I didn't want to see them infected with green slime so I drove down (190 miles), got it started and drove back home. That was a lot easier than cleaning the carbs come springtime.

 

Frank

[timgray]

are you sure you are not running resistor plugs in there? Resistor plugs with resistor caps = weak spark.

 

I found out that I cant get Non resistor plugs around here, so I simply removed the resistors in my caps and replaced them with chunks of copper I cut from a 10AWG solid wire and filed to fit perfect.

[snow4brains]

Although I cant speak to your Venture, there is one common problem with hard starting due to batterys. A battery that has 1 bad cell and 5 healthy cells can sound like it's cranking the motor over at a good speed because the battery still has most of it's cranking power. But, the voltage (during cranking) can drop low enough the ignition system my barely work, but once the motor does start, everything seems just fine.

 

Float chargers are wonderful things.