Association Forum - Honda 8 mechanics (Rant)

Assn Members Area · Join

Home.

Association Forum

Ships Store

Cruising

Racing

Technical Tips

Photo Gallery - New

Boat Search - Updated

Manuals & Brochures

Swap Meet

Links

Officer Flag Line & Staff

Bylaws & Constitution

Members Area

Join the Association

Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.

Association Forum

Username:	Password:
Save Password
Forgot your Password?

All Forums

Catalina/Capri 25/250 Sailor's Forums

General Sailing Forum

Honda 8 mechanics (Rant)

New Topic

Topic Locked

Printer Friendly

Author

Topic

Page: of 2

Captain Bill
Navigator

Member Avatar

USA
148 Posts

Initially Posted - 11/20/2007 : 20:30:12

My 2001 Honda 8 hp has a unique problem. After running about 2 or 3 minutes it chokes itself out. The top plug is covered with soot. (It's a new plug). I cleaned it off, reinstall, and it cranks with one pull, runs 2-3 minutes and chokes itself out again. Remove plug, same sooty mess. Clean plug, one pull start, runs 2-3 minutes, chokes out again. Plug sooty again. (The bottom plug stays clean)

I called a Honda Dealer's mechanic. He said to try the adjustment screw on the top left side of the carburetor. I did. Turned clockwise and motor choked out very quickly. Turned it counter clokckwise and motor ran 2-3 minutes then chocked out. Plug sooty again.

He also said it could be a timing problem and the rubber belt could be slipped out of sink with the flywheel. It does seem to run rough above 50% throtle (in netural at the slip). Other than that it runs and idles very smooth. Insides seem clean and no evidence of any dust build up that he indicated might be present with the rubber belt slipping.

Fresh gas, no water problem, new plugs (corect type), fuel filter clean, fuel line and bulb seem to be working fine, screw on gas can opened.

The previous owner said he had about 20 hours on the motor, I've added about 5 hours. It looks new.

Please excuse the rant but I feel better already.

All suggestions welcomed,

Bill

1989 C25 TR WK, Sail No. 5914

Edited by - on

bigelowp
Master Marine Consultant

Members Avatar

USA
1761 Posts

Response Posted - 11/20/2007 : 20:50:48

Bill:

Not sure I can offer much of constructive advise -- but . . . I have driven Honda auto's for years and think they are second to none. As far as their other gas products I am not a believer! I have a 50 HP Honda outboard on my 17' skiff and it runs terribly unless the gas is pristine and all adjustments are perfect. My Honda lawnmower is a piece of S!*t and runs terribly all the time, so, I would not go with Honda small engines for demanding tasks, such as hanging over the transom of a sailboat that constantly pitches and only needs the engine in clutch situations. That (rant) being said, I would check your gas first to make sure it is fresh and clean. Overall my Honda engines have been hyper sensitive to the quality of gas. After that I would check the carb adjustment to make sure it is lean - Honda's seem to like that. And finally, look at Tohatsu or Yamaha!

All the best

Peter

Edited by - on

Nautiduck
Master Marine Consultant

Members Avatar

USA
3704 Posts

Response Posted - 11/20/2007 : 21:27:08

Gee, I have the opposite experience with small Honda motors. Both my 8hp and 9.9hp outboards have been rock solid, as is the lawnmower and the pressure washer. Sounds like time to take the OB into the shop.

Edited by - on

Leon Sisson
Master Marine Consultant

Members Avatar

USA
1892 Posts

Response Posted - 11/20/2007 : 21:35:32

Captain Bill,

If your 2001 Honda 8HP outboard is the same general design as previous Honda twin cylinders, it has the following characteristics: single carb feeds both cylinders, single camshaft, even a single ignition coil.

And you say the lower cylinder is working fine, but the upper one fouls its sparkplug. So, any suggestion to tinker with the carb or cam timing is barking up the wrong tree to put it politely.

On some twins of this general design (not necessarilly Hondas, it's a common small engine layout), the ignition timing signal comes from the crankshaft flywheel, and is exactly the same for both cylinders. I seem to recall the older Honda twins (B-series 7.5HP-10HP) triggered the spark from the camshaft, so whether both cylinders are fired from the same timing signal gets down to some hair splitting. The short answer is yeah, they pretty much are.

So what don't both cylinders share which could cause a fouled plug? Well, the plug. Try swapping plugs and see if the problem follows the sparkplug to the lower cylinder, or stays with the top cylinder. Also, check compression while you've got the plugs out.

Another thing to check is valve lash. If the engine has 360* firing order (both pistons are at TDC together, one on compression the other on exhaust), check the clearance of each valve with the same valve of the other cylinder at full lift. (Check top intake lash with bottom intake valve's cam follower on the peak of its lobe, etc.)

Let us know what you find.

-- Leon S.

Edited by - on

Captain Bill
Navigator

Members Avatar

USA
148 Posts

Response Posted - 11/20/2007 : 21:36:28

Peter,

I've been battling this on and on since labor day (thus the rant)and finally realized last week what the problem is. I actually replaced the gas a few weeks ago after drying out the gas can and making sure there was no trash in it. I used premium gas. My old Honda was very sensitive to gas issues also.

Forgot to mention that the choke was in when it chokes itself out.

I hate to give up on this motor since it has been used so little. Especially like the one pull starts but what good is that if it only runs 2-3 minutes!

If no other suggestions I may try replacing the carburetor. If that doesn't work it may just drown itself in 6 ft. of mud.

And your last suggestion, I'm already looking into them. Good prices too.

Thanks for the input,

Bill

Edited by - on

Captain Bill
Navigator

Members Avatar

USA
148 Posts

Response Posted - 11/20/2007 : 22:06:05

Leon,

When I took the old plugs out the top plug was badly fouled & sooty and the bottom plug was relatively clean, a slight tan color, so it's probably not the plugs themselves.

I didn't think to check compression so I'll try to do that next time I'm at the marina. As to valve lash, that sounds way out of my mechanical abilities but is certaily a possible culprit.

Glad to know that the carb & timing don't seem to be the problem. I'll memtion the valve lash to the mechanic.

I was hoping I could get it running today. Took a day off from work but only resulted in frustration. I did manage to get one more coat of varnish on the rails. They look good to me.Tomorrow will be 76 degrees and 75 on Thanksgiving day then 50 degrees for the weekend. C'est la vie.

Thanks for your considered suggestions,

Bill

Edited by - on

Tom Potter
Master Marine Consultant

Members Avatar

USA
1913 Posts

Response Posted - 11/20/2007 : 22:13:55

One other thing to check is the top plug wire.

Edited by - on

bear
Admiral

Members Avatar

USA
909 Posts

Response Posted - 11/21/2007 : 06:48:06

Sounds to me like it could be sucking some oil in around the rings etc, do a compression check.....

Edited by - on

dlucier
Master Marine Consultant

Members Avatar

Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 11/21/2007 : 08:08:44

Does the Honda have a separate power pack (ignition coil) for each cylinder. If so, one might be weak and/or failing.

Oops, didn't see the replaced spark plug item...

Edited by - dlucier on 11/21/2007 08:44:51

Dave Bristle
Master Marine Consultant

Members Avatar

Djibouti
10005 Posts

Response Posted - 11/21/2007 : 08:37:58

Puzzling... If you had the same behavior (dirty top plug) with the old and new plugs, it's apparently not the plugs. There's only one coil and carb, so those seem to be exonerated... I'm suspicious of either a bad valve guide or rings letting oil in. Does it smoke like a 2-cycle, with an oil smell? A compression check will help lead you to an answer, although it won't give you the answer.

One more thing... Is the oil overfilled? That can cause problems... and if it wasn't overfilled before but mysteriously became overfilled, that's a sign that unburned gas is blowing by a piston into the sump, diluting the oil (also a sign of a ring problem). The diluted oil could in turn be affecting your upper cylinder this way. But I'm fishing here...

Edited by - on

Dave Bristle
Master Marine Consultant

Members Avatar

Djibouti
10005 Posts

Response Posted - 11/21/2007 : 08:42:07

I have one more wild-hare thought: A blocked cooling channel that causes overheating toward the top of the block. Your mechanic should have a laser temperature sensor that can check spot temperatures on the block.

Edited by - on

dlucier
Master Marine Consultant

Members Avatar

Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 11/21/2007 : 08:46:55

From somewhere on the interweb...

Carbon Fouled Plugs

Basically, soft, sooty carbon deposits, as shown below, have a dry, black appearance. If only one or two plugs in a set are fouled, it is a good practice to check for sticking valves, a cracked distributor cap, or bad secondary ignition wires. Fouling of the entire set might result from an incorrect heat range spark plug or an over-rich air/fuel mixture caused by a clogged air cleaner filter element, a sticking heat riser valve, or a faulty choke. Fuel injectors that malfunction can also lead to this condition.
Other causes include weak ignition system voltage or an inoperative pre-heating system (carburetor intake air) or poor cylinder compression.

Edited by - dlucier on 11/21/2007 08:47:09

DaveR
Master Marine Consultant

Members Avatar

USA
2015 Posts

Response Posted - 11/21/2007 : 09:14:23

I'd take the carb apart and blow COMPRESSED air through every orifice I could find and clean all jets. Of course clean the rest of the carb thoroughly. I understand there's only one carb but it feeds two cylinders and may have separate ports to to feed each.

Edited by - on

Sloop Smitten
Master Marine Consultant

Members Avatar

USA
1181 Posts

Response Posted - 11/21/2007 : 10:17:53

Bill,
For a plug to foul out in 2-3 minutes something has to be way out of whack. Since the single port carb feeds both cylinders and only one is having a problem I would concentrate on the cylinder itself. If a valve is stuck open, or sticking, you will not get the proper compression and the fuel mixture will burn cold leaving you with a sooty mess. It could be the soot has built up where the valve seats and is preventing it from closing. There is a product called Seafoam (sold at NAPA) that can be poured into the cylinder and mixed with your gas to clean up carbon deposits. The compression test will definitely reveal if a valve is sticking and at this point could eliminate a lot of the the frustration you are facing. It's not very difficult to pull off the valve cover on the rear of the engine and watch the valve train while you rotate the engine by hand. At some point each rocker arm should have some play in it when the valve is closed. It's just a few thousandths of an inch so if you have one that seems real loose you probably have a stuck valve. Good luck!

Edited by - on

ClamBeach
Master Marine Consultant

Members Avatar

3072 Posts

Response Posted - 11/21/2007 : 18:01:15

Here's some observations to toss in the mix.

I fouled a plug while salmon fishing on my Honda BF8 and discovered:

1) It will run on one cylinder and drive a C25 at about 3 kts if you open the throttle WFO.
2) It will idle running on one cylinder if it is in neutral. (a bit roughly though).
3) It will rev up nicely if you open the throttle while in neutral.
4) It will die at at less that full throttle if the engine is put in gear.

Check that compression...

Edited by - on

frankr
Captain

Members Avatar

256 Posts

Response Posted - 11/21/2007 : 18:28:07

Is the sooty cylinder plug firing at all? If you pull off the plug wire while it is running do the RPM's drop? Could be a scored cylinder wall/ crack ring or bad ignition.

Edited by - on

Captain Bill
Navigator

Members Avatar

USA
148 Posts

Response Posted - 11/21/2007 : 18:58:30

Great suggestions. Looks like a compression check is in order for sure.

I'll also check the wiring and the cooling system best I can.

Then I'll try taking off the valve cover and see if I have a loose vlave. Does anyone know the clearance for the valves?

Dave, I haven't noticed any smoke when starting and running it. The stuff covering the top plug is just plain black soot. Not oily at all. Guess that would eliminate a problem with the rings but not the valves?

It's sounding like a stuck valve, electrical or a heat problem.

I'll do my best to check those things first and then throw in a can of Sea Foam which I just used on my '74 MGB last month. (It is running better that ever!)

ClamBeach, you're absolutely right. I unintentionally pulled the cord yesterday and forgot to attach the top plug wire. It started and ran on one cylinder but a bit rough!

Thanks to all for your great suggestions. I'll keep you posted,

Bill

Edited by - on

Dave Bristle
Master Marine Consultant

Members Avatar

Djibouti
10005 Posts

Response Posted - 11/22/2007 : 11:04:00

You can do a very simple, rough compression check by:

1. Removing one plug, pulling the starter cord, and feeling the resistance...
2. Replace that plug, remove the other, and do the same.

If the two feel different,...

(Note: The newer model Hondas have some sort of automatic compression relief when pulling the starter, so I don't know how much this method will indicate.)

Edited by - Dave Bristle on 11/22/2007 11:07:30

Sloop Smitten
Master Marine Consultant

Members Avatar

USA
1181 Posts

Response Posted - 11/22/2007 : 11:58:20

Bill,
If the engine will run on one cylinder, put the compression tester on one and run the engine for 5 seconds using the other. Then reverse the procedure for the other cylinder. Your not looking for an accurate measurement as much as a discrepancy between the two cylinders. If the questionable cylinder is low you can concentrate your efforts there.
By the way, my 99 model uses .005" for the intake valves and .008" for the exhaust valves. Make sure you are looking at thousandths of an inch, not millimeters (mm). Yours should be close to this however Honda varied year to year as they tried to meet EPA requirements.

Take out the spark plug and check the position of the piston. Rotate the engine until the piston is at its top position. There is a notch in the flywheel that lines up with the notch in the small pedestal that resides between the camsprocket and the flywheel when the cylinder is at top dead center. At that point either both valves should be closed (fully up)or the exhaust valve will be open (fully down). Do it with the good cylinder first to get a feel what you are looking for. The two valves in the center are the intake valves and the two on the top and bottom are the exhaust valves.

Edited by - on

Arlyn Stewart
Master Marine Consultant

Members Avatar

USA
2980 Posts

Response Posted - 11/22/2007 : 19:11:41

Why do you think it is choking itself out? Two strokes can usually be detected for running rich and choking themselves out or running lean and dying... because a lean engine increases rpms before it dies and a rich one just loses rpms and dies. 4 strokes don't act the same way and are much harder to tell which.

By keeping an open mind that it may not be a rich issue, that opens the door to looking at a host of other reasons for the motor dying... many of them far simpler than the choking assumption. Are you sure that cleaning the soot off and it restarting is not fooling you. Will it restart if you let it just sit an equivalent period that it took to remove plug and clean the plug?

I'd confirm before proceeding.

Edited by - on

Captain Bill
Navigator

Members Avatar

USA
148 Posts

Response Posted - 11/22/2007 : 20:43:10

Joe & Dave, thanks for the info. I've never done a compression check before. Your suggestions are really appreciated.

Arlyn, I cranked it up on first pull after it has sat for two days. Surprised me because when I left it it had choked itself out.

If it will start after waiting several minutes what are you suggesting?

Edited by - on

Arlyn Stewart
Master Marine Consultant

Members Avatar

USA
2980 Posts

Response Posted - 11/23/2007 : 11:02:12

I'm suggesting it could be dying for either cause rich or lean but it is not an issue with one of the cylinders.

If rich, it could be the float needle is stuck open. If lean, then it becomes starved for inadequate fuel supply.

Based on the lack of calling the plug wet when pulled, I'm leaning that it is starving for fuel. The most likely cause of this would be poor replacement of fuel into the carb bowl. The engine runs fine until it exhaust the bowl supply.

Two very prominent causes of this are

1. The fuel supply is retarded by the tank vent being closed, a clogged pickup in tank or an air leak in the fuel line.

2. Some water in the fuel. Water in the float bowl is common and can block fuel flow past the needle valve and mixture jets. The solution is usually a simple float bowl draining and I think there is a screw on the motor to do that. I've experienced this several times on the older Honda 8 Classic with symptoms exactly as you describe... runs fine for a few minutes and dies...restarts in a few to do same again. Draining the float bowl cures the problem.

A 3rd cause is varnished fuel passages or a sticking float needle, both would require a carb cleaning. The first two should be ruled out first.

Edited by - Arlyn Stewart on 11/23/2007 11:09:11

dlucier
Master Marine Consultant

Members Avatar

Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 11/23/2007 : 11:12:31

Arlyn,

If you suspect it to be a fuel problem, why would it only affect one plug/cylinder?

Edited by - on

ClamBeach
Master Marine Consultant

Members Avatar

3072 Posts

Response Posted - 11/23/2007 : 16:46:37

"why would it only affect one plug/cylinder?"

Methinks the sooty plug may be a red herring... it may be due to another issue unrelated to the engine dying after running a couple minutes. That's why I pointed out that these engines will run on 1 cylinder.

Edited by - on

Arlyn Stewart
Master Marine Consultant

Members Avatar

USA
2980 Posts

Response Posted - 11/23/2007 : 17:16:33

Hey Don,

My experience tells me these motors will start and run without serious difficulty on one cylinder, though seriously short of power and smoothness. The motor quits so it is either running too rich or to lean... or there is an outside chance that the spark goes bad with warming up.

Normally if a float is stuck open, the motor won't run well at all so the short period of running fine doesn't fit but that would fit with a stuck choke.

As he said a knew plug looked sooty, it could be a choke stuck closed.. and once the engine heats up the mixture goes too rich to run. That motor has an auto choke.

I'm not discounting that the upper cylinder has more blow by than the lower as when he did maintenance and replaced the plugs, he found it fouled more than the bottom but my old Honda 8 would develop a fouled plug with too low of rpm operation and that could simply be some manifold imbalance.

Based on a new plug looking sooty... a sticky choke would be where I looked first... barring that I doubt if the problem is a stuck open float and I'd then look to the possibility of it going lean.

Edited by - on

Arlyn Stewart
Master Marine Consultant

Members Avatar

USA
2980 Posts

Response Posted - 12/17/2007 : 17:52:24

Captain Bill.... have you found the problem yet?

Edited by - on

Page: of 2

Topic

New Topic

Topic Locked

Printer Friendly

Jump To:

Association Forum

Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.