Hard Starting VF700

My 84 Interceptor has a starting problem. When starting cold with full choke the bike runs on all four cylinders for about 1 or 2 seconds then cuts back to 2 cylinders. Cylinders 1 and 3 fire while 2 and 4 don't. Depending how long it has been since it was last started it may struggle to run on cylinders 1 and 3 for up to a minute before I can nurse the revs up to get the front two cylinders to fire. Once they fire the bike starts running fine and will continue ok until the next cold start. Additionally the tach often flat lines only to pop back to life after an undetermined amount of time. My questions are: Are these related or are they two separate problems? Is the starting problem fuel or ignition related? Do I have a bad 2-4 coil or spark box? Thanks for any help you can give me.

 

sounds like it's your spark box that's why the tach flat lines. but.... new plugs and how do the wires look. have you tested the sparkplug wires to see what the spark looks like ??

 

I'll check the front wires and plugs. My factory manual says that a malfunctioning tach can be caused by a bad 1-3 spark box. Then why would the 2-4 cylinders not fire when cold? I've got 3 first gen Interceptors so I can swap a few parts from running bikes to find the problem.

 

thats like having more than one child........extra spare parts

 

try also changing out the coil packs...... but do that last. check and change that other parts fist. diff. check the plugs.

 

Start the bike for a minute or two. Then pull one of or both 2,4 plugs and see if they are wet. That will tell you the choke system is fine or not. If not then it's dirty carbs. Other wise what ever is connected to 2,4 cylinders. Plugs, coil, pulse generator,connectors and box.

 

I agree

Hey guys

I agree with GreyVF750F.Also try switching the coils.And mesure the pulse generator the manuel should say what the ohm should be.

Best regards

Gunnar

 

Thanks everybody for all the suggestions. I will start it on the 2 cylinders and then stop the bike and read the front 2 plugs before they start firing. I assume that I would be looking for a plugged choke circuit to the front carbs. If the plugs are dry then the circuit is plugged. If the plugs are wet but still not firing then it should be an ignition problem and I should start swapping out spark boxes, coils, etc. Have I got it right?

 

If the tach quits my money is on ignition not fuel!

 

Easy then you think

Hey

Take the plug 2 or 4 out put your finger in the hole start the bike if you get gasoline on your finger then it is the ignition.Then work from spark plugs and forward but end with the CDI units (spark units) because that is the only thing that cannot be mesured.

Good luck

Gunnar