Engine flooding problem

[commodoretyler]

I'm at a total loss and so I'm hoping someone on here has some advice. I've been building an '89 FZR essentially from the ground up. I was given a frame for free and I got a motor from someone else. I've made really great progress with it and the only thing left to do is to get the motor to run consistently. So I would be forever grateful to someone who could steer me in the right direction.

Here's what's happening:

It turns over just fine, but only starts when I have the throttle all the way open. It will stay running as long as the throttle is more than 75% open, but obviously I can only hold that for a few seconds before I reach redline. As soon as I release the throttle it dies on me.

Then the engine floods. So I have to take the plugs out and dry them off and wait a bit for some evaporation, then it will start again but only in the above condition. If I try and start again without letting some of the fuel out, the carbs squirt fuel about 3 feet in the air. Sounds like a float issue, right?

I've cleaned the carbs out twice and all seem to be fairly free of buildup or blockage. I haven't done a leak test, but theoretically the bike should start and run anyway. Albeit, probably not well.

Anyone that has any suggestions on what to try next, I would appreciate it so much. I'm anxious to get this thing running before the riding season is up. What started as fun winter project has turned into a 6 month battle with physics. Thanks in advance.

[commodoretyler]

Ok so I figured out the flooding issue. I had the fuel hose connected to the carb vent hoses.

I admit that was a rookie mistake. But it still only starts with 100% throttle and after quite a few turns. Only starts on 2 cylinders, but after letting off the throttle then opening it back up the other 2 fire up. Maybe I just need to run it a bit. But if I'm just letting it idle, it still dies after about 30 secs of running.

Plugs are new. Wires get spark. Coils seem ok. Tried adjusting the idle, but no luck.

[lt61173]

You may want to look into the carb sync. It is in the wiki.

[thatkid]

You should first check the coils/plug caps are up to scratch.

Ignition off, disconnect both the Yellow and White connectors that feed the coils, inspect the connectors for any sign of corrosion.

The primary windings test point should be checked imho at the solder connections (top of the coils) connect an ohm meter to the Red/White wire and the Orange wire (coil for plugs #1 & #4) take the reading, then the Red/White wire and the Grey wire (coil #2 & #3) factory spec is 1.8 to 2.2 Ohms.

The secondary windings are tested between the ignition/spark plug wires, remove the spark plug caps. Connect an ohm meter between #1 & #4 plug wires, then #2 & #3 plug wires, factory spec is 9,600 to 14,400 Ohms.

Now check the spark plug caps, factory spec is 9.000 to 11,000 Omhs.

All readings should be checked when the coils/plug caps are cold I.E. 68 degrees F

Depending on how long the engine was stood (before you got it) the compressions could be low.

If it was a long period a squirt of oil into each cylinder (VIA the plug holes) will help the pistons/rings seal. You will also have some rusty valves/seats, until they bed in the engines breathing will change, so adjusting the carbs will be futile.

Have you checked the condition of the air filter/airbox?

The main & starter jets have the same thread, and can be easily mixed up.

Read this Everything you need to know about carburetors

[commodoretyler]

Thanks mawler. That was really helpful. the resistance seems to be ok. i get 2ohms at the top of the coils at the solder point. The plug caps read between 9.9 and 10.8. and the plug wires read 13.1k and 16k.

I've squirted some oil in the cylinders to try and get the piston rings to seat (if that was an issue to begin with). I think I might just need to run it a while and get some of the proverbial cobwebs out. Cylinder 4 seems to be the biggest problem one. After running for few seconds the exhaust header out of that cylinder is still cold. It seems like compression is there, but maybe not enough.

the carbs have all been synced prior to this issue, so i'm relatively confident its not that.

[yamaha_george]

Thanks mawler. That was really helpful. the resistance seems to be ok. i get 2ohms at the top of the coils at the solder point. The plug caps read between 9.9 and 10.8. and the plug wires read 13.1k and 16k.

I've squirted some oil in the cylinders to try and get the piston rings to seat (if that was an issue to begin with). I think I might just need to run it a while and get some of the proverbial cobwebs out. Cylinder 4 seems to be the biggest problem one. After running for few seconds the exhaust header out of that cylinder is still cold. It seems like compression is there, but maybe not enough.

the carbs have all been synced prior to this issue, so i'm relatively confident its not that.

The compression across the board should be within 10% of each other.

[thatkid]

which coil (plug leads) gave the 16k Ohms?

Remove the caps, snip 1/4 inch off the plug leads, see if that gives a reading within spec. 9,600 to 14,400 Ohms

Your carbs are not synced. They where synced to an engine that is not performing close to 100 percent (Your engine)

When tuning any engine. First ensure the ignition system is up to scratch. Then the compressions, If not fiddle away @ your hearts delight with the carbs. You will only waste your time and fuel.

You say you've cleaned the carbs twice. Clean #4 carb thoroughly, Totally dismantled and Every Jet removed including the pilots and mixture screw. If possible blast compressed air through all galleries/passages. Otherwise use Carb cleaner, after removing any rubber seals diaphragms (carb cleaner melts rubber)

When you get all Four cylinders performing as they should, sync the carbs.

[thatkid]

Memory fades with age.

I suspect you could have a faulty plug lead on #4. Was the high reading on the coil for #1 & #4? if so read This also swap #4 spark plug with a know good one, better still get new ones.

If the Secondary windings had a Low reading, that would indicate a short in the Secondary windings. Therefore both #1 & #4 cylinders would misfire.