Honda 8 HP carb cleaning

[Pontoon24]

Hello,

I'm cleaning the carb on my 2000 Honda BZBC 8 HP Outboard. I noted that the adjustment screw was open 2 1/2 turns and want to verify if this is the right setting or if it was tampered with by a previous owner. Any online links to info on this rebuild would be great. Also, the float adjustment height would help.

Thanks for any help, Andy

 

[Flakeys]

Re: Honda 8 HP carb cleaning

I have a Honda Carb manual and the 2 1/2 turns is the listed setting for an 8 Hp engine. The idle speed shuld also be 1200 +/- 100 in neutral.

 

[Flakeys]

Re: Honda 8 HP carb cleaning

Missed the request for the float height. It is 9.85 - 10.15 mm Thats 0.388 - 0.40. A float gage will greatly help with that.

 

[Pontoon24]

Re: Honda 8 HP carb cleaning

Thank you very much for taking the time to answer.
What a great forum.

 

[Pontoon24]

Re: Honda 8 HP carb cleaning - Another Question.

Re: Honda 8 HP carb cleaning - Another Question.

So you know what I'm talking about, here is a link to my carburetors diagram.

http://www.boats.net/parts/search/H...2000001 TO BZBC-2099999/CARBURETOR/parts.html

My question, should part #20 in the diagram, listed as Jet have a hole that goes straight thru end to end or is it solid brass in the middle? (I'm not talking about the tiny holes that go side to side)

When cleaning, a wire put into the holes on either end stops just about midway so if it is solid brass it is only a 1/6th of an inch or less at the center of the jet. If it should be open then there would be a hole from inside the carb to the outside, (doesn't sound right to me)

Flakeys, if your out there, does your book tell you?

Thanks again, Andy

 

[isaksp00]

Re: Honda 8 HP carb cleaning - Another Question.

Re: Honda 8 HP carb cleaning - Another Question.

That diagram looks the same as on my 8HP BF8A from about 1994 or so. That is the low speed or idle jet, per my repair manual. On mine, the hole down the center, from the inner end of the jet, goes through the center of the tube to where the lateral holes go side-to-side, but does not go all the way through to the outer end of the tube. I had idling and startup problems that were solved when I removed that jet and cleared it. I happened to use a very thin copper wire strand, but have been told not to as it can scratch the jet and affect performance. I'm going to switch to plastic, like a floss threader (the kind the dentist gives you).

 

[Pontoon24]

Re: Honda 8 HP carb cleaning - Another Question.

Re: Honda 8 HP carb cleaning - Another Question.

Good, I didn't think that tube should be hollow all the way through and I appreciate you confirming it. It's been a tough issue this carb. Last night made the fourth time I opened it up to clean with different results each time. I've read and read and have ruled out all the other causes of loss of power at top end except for one other thing...

When re installing the carb I reattached the fuel line by simply slipping the rubber hose onto the fuel filter without a clamp. It seemed tight enough but I suspect at top end it was sucking air. Last night while putting it thru its paces it ran flawlessly with no bog at WOT and with the clamp on. This motor idles so smooth it sounds like a sewing machine.

I have still one more question and one other thing I may have overlooked, the float valve. Of course I took it out and cleaned the plunger and blew compressed air thru the passage all after letting it soak in carb cleaner overnight but one thing I did not do was to check if the hole the valve goes into was clean. How do you do this? Maybe something like a Q-tip. I'm aware how often a sticky valve here can cause problems and can imagine the walls of this hole coated with varnish in a motor left sitting. I'm thinking a wooden toothpick, possibly with one end broken off and the wood crushed to make it sort of like a small wooden paint brush. BUT, is there anything inside that hole that could be damaged, like a rubber bushing?

Thanks again for your help.

Andy

 

[isaksp00]

Re: Honda 8 HP carb cleaning

I'm not an expert and am not a mechanic, so take all this with a grain of salt.

I've seen advice here to turn the carb upside down and see if the float is about level, and to gently bend the tab if it isn't. That sets it for about the right level of fuel in the bowl. Then reassemble the bowl and blow through the (hopefully cleaned) carb fuel inlet, with the carb inverted. If the valve seat is OK, it should seal and no air should flow. Turn it over (upright) and blow, to see if the valve is now open. If all is OK, then you probably don't need to clean anything. I don't know how to clean that seat, other than the advice to use quality carb dip for the right amount of time. If it were actually damaged, obviously that wouldn't help.

I would think that the valve either seats and seals well, or has some sort of leak for whatever reason. If it has a leak, wouldn't the symptoms be that the fuel pump would keep filling the bowl, and gas would drip out of the carb overflow? If that doesn't happen while running, maybe that tells you it is OK. If it is sticky, maybe you would not have been able to blow air through the carb when rightside up?

 

[Pontoon24]

Honda 8 HP - New question

Honda 8 HP - New question

I've been messing with this motor for a while now. The problem no power top end. I thought I just needed to clean the carb but thats not it. One thing I have found is the motor is hydrophobic. Runs great on the stand and not in the water. I read about the effects of having the motor too low in the water, covering the exhaust ports. I remedied that and it helped but still no top end.

Now my question. - How bad would it be for the impeller if I do a short test on the motor with no water? I could start it up in the tub, get everything inside all wet and slippy then take away the tub and do a dry 30 second test. I'm thinking water may be going somewhere it shouldn't be going. I'll do a compression test also but I want to try a dry run.

How bad?

 

[pvanv]

Re: Honda 8 HP - New question

Re: Honda 8 HP - New question

You are probably still too lean, which sends you back to the carb. If you run the motor for even a couple of seconds out of the water, you will be in for water pump repairs, period, so don't do that.

 

[isaksp00]

Re: Honda 8 HP carb cleaning

Does it just idle well on the stand, or can you run it in the water on your stand and rev it up in gear, successfully? I can't imagine why it would rev up to high end performance on the stand, in water, yet not on the boat. Of course, I am a rank amateur, so that doesn't say much.

Could it be that the high speed fuel passages in the carb are not fully open? Maybe take the advice from a bunch of other threads and dip the carb in "full strength" carb dip (others have recommended brands in the past) and blast with air. On my older Honda 8, they are tiny, convoluted paths and I can't imagine any way to clean them, or even see them, mechanically. I can't recall the high speed nozzle - I think it is easy to remove and clean.

 

[Pontoon24]

Re: Honda 8 HP carb cleaning

I've cleaned the carb 4 times, high speed nozzel with fine wires, overnight in the carb cleaner, the works!

If I run it in a 5 gallon bucket of water it runs fine in neutral, revs nice, in gear it idles nice and if I go WOT it does not bog but jumps right up although after 2 or 3 seconds I turn it off because it blows all the water out of the bucket.

SO

I got a 55 gallon barrel and made a test tank. Low end is all still good but bogs WOT. It continues to run but slower and bogging and you can smell the gas and plugs removed are covered in black soot. Also when running in gear besides idle it is throwing water up high on the shaft.

If I shut it off for a minute, let all the water drain out then restart and quickly put it in gear and open it up it revs right up for a second or two but then bogs and will only run half throttle. Taking it out of gear until it again idles smooth and trying again it only bogs. I lowered the water in the tank to be below the exhaust ports, just enough water to be able to pump but the one common factor is that when water starts splashing up on the back of the motor, no top end.

I know that allowing water to cover the exhaust ports will mess with the way a motor runs so I'm wondering about exactly what is going on inside the motor when the exhaust ports can't breath right and I think that may lead me to the problem.

 

[Pontoon24]

Re: Honda 8 HP carb cleaning

PAYDIRT! OK, I did not fix it but I definitly isolated the problem. I put a plastic shroud around the motor in the tank with the exhaust ports above the plastic (and dry). I did this test with the engine cover off, although before when I did that it did not help.

View attachment 119460

Top end is back, revs and runs nice.

Now what in the heck is the problem? I can't keep water off the back of the motor in any real life boating use. So the problem I believe is internal, possible a engine gasket? Something related to those exhaust holes. I have no knowledge beyond the rudimentary fuel and electrical system so I'm going to need help from a genuine greaser on this one.

 

[Pontoon24]

Re: Honda 8 HP carb cleaning

OK, I tested again with the cover on, it bogged. As soon as I took the cover off, fine. Cover on bogs, off fine.

OK, I'm sitting down. Break it to me, how bad?

 

[Pontoon24]

Re: Honda 8 HP carb cleaning

Just a quick note to close out this thread.

After all the troubleshooting I did I was absolutely convinced the problem was an exhaust leak robbing the motor of oxygen when the cover was on but alas it was something far easier, the timing belt was off 1 notch. Took me all of 3 minutes to change and the engine ran fine at top end in a test on the water. However after about a mile and a half the rpm's slowed and it let out a puff of blue smoke. I idled it home thinking the belt had jumped back but no, so different problem? We'll see....

Update: motors fine. The problem was timing only.