No Start, spark, fuel smile, back fire

[Shiftthru]

85 Yamaha Ventue, 49998k miles, just bought.  New battery, fully charged, new starter.   Started up,ideled 15 minutes, took down the road.   Died and hasn't started since.  Changed plugs, backfires actually, but nevers starts.  Is this a CDI issue or a Stator issue or something simple?.....

[Marcarl]

Guess we will need more info, all diagnostic.

Battery voltage at present.

Condition of air filter, or is there one there.

Check the spark on all four of the plugs.

Which plugs were installed.

Does it backfire through the carbs or exhaust.

Does it spin over normally, or does it hesitate.

Do you hear the fuel pump clicking when you first turn on the ignition after a 5 minute sit.

Will it run if you spray some carb cleaner or brake clean into the carbs.

How old is the gas in the tank.

 

[saddlebum]

It is not uncommon for something like this to take place in these bikes if they have sat for a while. Sometimes they take a little help to get started and once you do try keeping the RPMS up for a while until the bike warms up. once it warms up ride up and down the street for a bit in 1st gear and keep the RPMS well up.  Or if the gas is old drain the carbs into a glass container, this way you can check for water in the fuel. If possible after letting the bike sit undisturbed over night, drain the fuel tank as well with shut off set at the reserve setting. Drain the 1st bit into a glass container so you can again check for water. In any case if the fuel is old replace it and the fuel filter.

If this does not work,  Start with the simple things. Make sure it has spark. If you have a compression gauge check compression while you have the plugs out. If compression is bad on any cylinder do a cylinder leak down test to pin point where the cylinder is losing compression. It may also be a good idea to check your valve settings. Too tight may prevent a valve from fully seating fully as the engine heats up and an overly excessive gap could indicate a sticky or damaged valve, such as a bent valve stem or debris between valve and seat.

Make sure the fuel cock is open. Check the fuses if it still has the old glass ones its possible the fuse holders have corroded and weakened with age sometimes the fingers even get so weak they just break away. Take the top off the air cleaner and trickle a bit of gas in each barrel to see if it will then fire up. If not or if there was no spark, Go over your electrical connections, specially the ones going to the ignition module regulator and stater. Check for any green or white powdery looking coating on or bridging the terminals and clean with a good electrical cleaner (ACF50 is my preference as it does a great job of cleaning and protecting ). If it does, look into your fuel system make sure fuel is getting to the carbs you can open the fuel bowl drains and turn the key on. You should hear a clicking noise indicating the fuel pump is running and eventually fuel should run out of the fuel bowls. Try shooting some good carb cleaner through every orifice. At this point though avoid removing the diaphragms to access more orifices for now since you wont know their condition and for now is better to not disturb them, You can remove them later when all else has failed. With the top off look down into the carb and check the sliders  make sure they move freely. 

If the the bike has been sitting for some time it is possible that crap has built up in the carb and plugged orifices and/or jets If initial attempts to flush carb with cleaner appear to fail you can now remove the diaphragms since if this step fails to work your next step will likely be to remove the carbs anyway and try flushing  the remaining orifices reinstall the diaphragms and sliders and try again  (make sure the hole at the needle end is in the six oclock position. 

If after all this and everthing checks out Ok other than the only time the engine will run is when you trickle fuel down the carb than I would be inclined to considering removing and O/H the carb

Edited December 12, 2021 by saddlebum

[Shiftthru]

Update:   We checked the spark yesterday, but only on cylinder 1 and it was good.  I did change the battery for a little better one today and got it to crank.  Ran it for a little bit and noticed it wasn't running quite right.  Got to checking and there's no fire on the front two cyclinders.  We checked the ohms on the pick ups coils and they tested fine.  So I believe it's the CDI unit as everything else appears connected and in working order.    

So that being said is there anything else I should check or is it time to replace the CDI?

Thanks

[Marcarl]

Check the high tension wire ends, unscrew the ends and cut back the wire to expose a new cut. Also check the resistors in the wire ends, take them apart carefully (small parts involved) and clean them.

[luvmy40]

I chased this rabbit on my '83. In the end, I replaced 3 coils, the plug wires and caps and went to the Ignitech CDI.

My advice would be to get the Ignitech module, new plug wire and NGK cap/boots, and Ohm out the coils by them selves. If it only misses under load, the coils may Ohm out OK but but arc out through broke down insulation. Fire her up in the dark and mist some water on the coils(easier said than done, I know) and look for fireworks.

Regardless of whether you replace the CDI or not, relocate it to the top of the air box for ease of access and better cooling and water protection.

Edited December 12, 2021 by luvmy40

[Shiftthru]

Currently there's no spark at any point on the front two cylinders.  Back two fire and back will run and drive with those two.

[saddlebum]

15 hours ago, Shiftthru said:

Update:   We checked the spark yesterday, but only on cylinder 1 and it was good.  I did change the battery for a little better one today and got it to crank.  Ran it for a little bit and noticed it wasn't running quite right.  Got to checking and there's no fire on the front two cyclinders.  We checked the ohms on the pick ups coils and they tested fine.  So I believe it's the CDI unit as everything else appears connected and in working order.    

So that being said is there anything else I should check or is it time to replace the CDI?

Thanks

Check the connectors at the ignition module (CDI). I almost replaced mine for the same same symptoms. No spark on one cylinder. As I was removing it I noticed the build up of green and white crap in the connector and on the terminals. I cleaned all the terminals with slivers of fine emery cloth and electrical terminal cleaner followed with a second cleaning of ACF 50 then gave it a good saturation of ACF 50, then reinserted all the connectors. that was three years ago and the bike has run like a dream ever since.

Edited December 13, 2021 by saddlebum

[Shiftthru]

Update:  Well checked and cleaned connections on CDI unit and still no spark on front two cyclinders.  I went ahead an ordered the Ignitech CDI and should arrive next Wednesday. Until then I'll do a little more cleaning and see who in my area can recover a seat.  Thanks for all the advice so far!

[Shiftthru]

Update:  Installed the new CDI from Ignatech today.  Fired right up!  No choke, no throttle, just pushed the start button and instant purr.  

 

[Shiftthru]

Now just have to get some mufflers/exhaust.   Currently doesn't have the slip ons

[Marcarl]

Good news, thnx for the info, it might help somebody else.