Honda BF20D vacuum leak

[JonnyBGood]

Hi there guys

Recently I've used this forum for advice and now it's my turn to tell my story and ask some questions.

I recently got a new to me Honda BF20D. BAMJ-1507745. Not sure of the year. It was hard to start and after the previous owner ordered a new Stater enrichment valve and chinese regulator rectifier and connected the RR incorrectly, leading to smoke escaping the smoke container. He swiftly put it up for sale, finally done with it.

In I walk. Troubleshooting begins.

Enhine starts with FE circuit open but stalls as soon as it's closed.

Took the carb off and realised then were no gaskets either side of the isolator and the silencer gasket was in poor condition.Cleaned the carb. And ordered replacement gaskets. In the meantime made my own gaskets and put it back together. Now it actually started and idled but ran roughly, popping back through the exhaust and then dying after a minute or so and then would not restart. Idle screw did nothing from 2 1/8 turns out to almost out the hole.

Checked spark plugs they would fouled. Cleaned them up. And tried again same thing multiple times. Then read through this forum and then actually cleaned the carb properly this time. Got ahold of the Honda Marine Carburettor manual. Idle screw o ring found in poor condition. Blew through all the circuits and cleaned the jets in the ultrasonic cleaner. Interestingly I've only got a main jet size of 115... Can't find a 120 to buy in Norway at the moment.

Carburettor rebuilt with new o ring set. New gaskets installed. Idle screw still does nothing.

Adjusted float level.

Engine idles but engine RPM is hunting. Idle screw still does nothing. Squirted wd40 around the carb and then realised I had a vacuum leak around the isolator, found a crack in the isolator through a bolt hole. Isolator on order.

New isolator installed no vacuum leak there anymore potentially never was there...

Engine runs well. Starts with no issues, idles with no issues. But hesitates on acceleration and slow to deccelerate. Fast acceleration stalls the engine.

Using the tube on wd40 method I realised I might have a vaccum leak on the throttle shaft both sides. Took the shaft apart found a bit of play on the bush and reassembled with hylomar.

Runs maybe slightly better... But still hestitates and is slow to deccelerate. Hunting RPM has gone. Did not try fast acceleration.

I have read from jgmo that the accerator pumps do not work particularly well on these carbs. Or maybe I'm getting my wires crossed (read far to many of these posts) so I'm not too worried about the hestiation. But the slow deccel and the pick up in rpm when I spray the throttle shaft has me thinking am I focusing my efforts in the wrong place? Has anyone ever found a vaccum leak there? Are we worried about a vacuum leak there?

Kind of thinking it's about time for a new carb as I can't find part numbers to rebuild the trottle shaft assembly.

Any thoughts and advice will be appreciated.

And can I just say thank you to all those who contribute on here.

 

[jgmo]

Hi JonnyBGood,

It looks as if your outboard might be a 2008 model. But I'm not 100% positive about that.

They're all the same from 2003 on anyway so not something to stress over.

Yes, it was me that said the accelerator pumps on these are near worthless except for when they are brand spanking new.

After a few weeks/months they are completely worn out. And, even if the piston and cylinder lasted forever, the fuel inlet check ball that's staked in the bottom of the chamber comes loose from vibration and renders the POS useless anyway. Basically a waste of time worrying about them or rebuilding them.

I wouldn't expect the idle mixture screw to make a huge difference past 2 1/8 turns out.
What I would look for instead is how it effects idle as you turn it inward. It should stall the engine as it closes.

Sounds to me there may be more cleaning needed.

Ironically, while the accelerator pump isn't worth a
ding-dang-doozle....
.....the accelerator pump circuit delivery tube and orifice is critical.

You need verify that the accelerator pump spray nozzle orifice is COMPLETELY clear!

With the throttle plate propped wide open, the nozzle should shoot a stream of carb spray out the back of the carb throat 8 feet.

This is NOT listed in the carburation manual. I learned this the hard way and it IS very important. If that tube won't shoot spray out the back 8 feet, the carb just won't work right.

Back and forth flushing of that nozzle is often necessary.

You may need to backflush all the delivery orifices at the top of the throat MANY times.

Spray into the primary jet tube and make certain fluid sprays from the primary orifices in the carb throat. Backflush them and ensure liquid flow FROM the primary jet tube.

Backflushing the orifices helps clear the slow air jet and main air jet too.

Flushing should be done using your fingers as plugs to block the slow jet feed hole and idle mixture screw hole to help increase velocity and effectiveness of the fluid.

When fluid exits a location when spraying into a passage, move your fingers to block that flow and spray again. You literally need to "jump around" with your fingers to block exits and increase the velocity of the cleaner inside the carb.

A very dirty carb requires a lot of back and forth flushing to dislodge deposits.

It's a tedious job that the sonic cleaner just won't do all that well sometimes.

As far as play at the throttle shaft, it's a judgement I can't make as I have never found one that I thought was bad.

The replacement carb isn't too expensive and I wouldn't criticize anyone for making that call. You gotta do what you have to in order to get her running right.

Other things I would do are check/adjust valves...

Verify timing and that the belt is in good condition and is tight....

Empty all liquid from the fuel chamber that's mounted on the oil dipstick tube.

These are truly GREAT outboards.

Good luck.