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Honda BF50A timing belt

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Bike wrench

New member
I need some help - checking the cam timing.
The unit is the 2007 Honda BF50A 50hp

I use the community pontoon boat once per year for about 8 days. Last year, the BF50A fired up like a Honda and ran well. This year it started out with a notchy cranking, then spins like the plugs are pulled out. Upon further inspection, a bunch of wasps built a mud nest around the timing belt pulley on the crank. I think the belt has slipped a few notches, explaining the loss of compression. I got all the mud out, and checked the belt, it looks OK.

What I need to know is how do you check the timing belt position/cam timing? I see the T mark on the cam pulley, and matching T mark cast into the head. I also see the T mark on the outer edge of the flywheel.

Can anyone please give me a good description of the correct method of checking/adjusting the timing belt?

Also, is this an "interference" engine (like most Honda bikes)? Will the pistons hit the valves if the timing is off far enough?

Thanks to all for any help. This is supposed to be my #$@&*% vacation! I just want to pull the tube around the lake for the kids. ARRRRGH.
 
The flywheel timing mark should align with the port side base of the lifting ring.

The cam timing marks should also be aligned.

At the same time the #1 piston should be at the top (top dead center)

If the timing is only off a couple of notches, the valves will probably be ok. If the motor has been running, the damage would have already been done.

One warning...rotate the flywheel counter clockwise only. If you go the other way, it could hurt the impeller.

There is a fairly lengthy was to properly reset the timing belt...too long for this forum.

Here is a way to take a shortcut if timing is not off too much. You will need a helper who has pretty strong fingers. You will also need a long narrow screwdriver (to put carefully in the top spark plug hole to check for top dead center.

Remove the spark plugs.

Rotate the flywheel to align with its timing mark.

As you align the flywheel, check to see if the cam timing marks are getting close.

As the cam marks come close to the #1 mark, make sure the piston is coming up.

Once the flywheel marks are aligned, and if you are close to the #1 cam mark, and if the #1 (top) piston is close to the top....check to see how many notches off you are on the cam.

Again...you can proceed if only off a couple of notches. If more than a couple, you might damage the valves if you force anything. The valve clearances should be totally loose, to eliminate any damage.

But...let us proceed like you are very close.

Have the helper with the strong fingers, very carefully, lift the work the timing belt up off the cam. With two hands, your helper should be able to hold the belt out long enough for you to move the cam to the timing mark. You may then have to help your friend get at least a few notches connected on the cam. When you rotate the flywheel, the rest should fall into place if you use care and go slowly.

Rotate the flywheel (counter clockwise) around again but this time align the cam timing mark first, then check the flywheel timing mark. If the flywheel mark is 180 degrees out, you will need to rotate the flywheel more for one rotation of the cam.

If at anytime, you feel a pretty good restriction, it may valves, so do not force the rotation.

If cam and flywheel marks line up and the #1 cylinder is at the top...you should be good to go.

This is not the official way to reset the timing belt, but sometimes you have to do what you have to do.

Mike
 
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Mike,

Thank you for the lengthy and detailed directions. I called the local Honda Marine dealer, Avin's Marine in Florence, SC before I read your response. Mr. Avin, who did not know me from Mr. Spock, gave me a similar, but less detailed, set of directions right off the top of his head. Kudos.

The cam had shifted a bit less than 90 degrees from the proper timing. I loosened up the tensioner, and worked the cam backwards, one tooth at a time, by gathering the slack in the belt and moving it like an inchworm over the cam pulley. I did not encounter any serious resistance during the process, but I felt that having the valves moving late by nearly 1/2 of a crank revolution, the piston probably hit the late-closing exhaust valves before the intake stroke.

I re-tensioned the belt, put everything back together, and cranked the engine. It would pop but not run. I drained the carb bowls, used a little starter fluid, and after several minutes, got the engine to idle and rev with the throttle and no load. Idle was a bit lumpy

Out on the water, it will not produce any power. Anything above 1/2 throttle, and it stumbles and dies. The pontoon boat has a 9hp Nissan trolling motor also, and the BF50A is about equal in developing thrust.

I docked the boat, pulled the cover, and pulled the plugs. Number 1 was looking bad and the other 2 were fine. I do not have a compression tester, but I think I have at least 1 dead cylinder due to bent valves. Bummer.

Gotta give the bad news to the cottage manager (5 family-owner group - including my parents). I already called him when the engine would not start, and I discovered the mud wasp nest. At least I can arrange for the dealer to check it out and maybe pull the head off the engine to save them a few bucks. A problem with that idea is - what if the wasps return while the engine is open? I don't want to think about it.

Thankfully the neighbor, a former part of the owner group, let me use his pontoon boat for a cruise. We have drafted our Sea Doo GS for tube pulling duty and are going to try it with skis tomorrow.

Thank you for the time and effort answering my question Mike. You are an asset to your community and I am lucky to have stumbled onto a forum with a guy like you who knows their stuff and shares it freely when asked. I can not return the favor, but I can acknowledge your acumen and character to any of the readers. Best of luck in all your endeavors.

Ted
Follow these links to see what I do back in Ohio-
www.buckeyecam.com
www.atsi-tester.com
 
Here, here to your toast to Mike! He's saved a boatload of people here a boatload (pun intended) of time, money and heartache with his generous and accurate observations. I know of only one other forum that can provide anywhere near what happens here with advise and assistance but that is a professional auto technician's site with litterally hundreds of thousands of techs onboard and I pay quarterly for the priveledge. So, I think hondadude makes up, singlehandedly, a huge part of the cadre of this site and I thank him.
Ok Mike, now get back to work!

Try this to keep the "critters" out of your engine compartment. Soak a spool of thread in diesel fuel and then zip tie (ty-wrap) it to an out of the way spot where it won't chafe against any wireing or critical component. I've found over the years of storing vehicles in the country that pests don't seem to like diesel fumes all that much. When I put up a car or truck for a period of time, I leave a shop rag damp with diesel in the engine compartment and I get no "habitation infestation". Good luck with your outboard.
 
jgmo,

The diesel stink pot is a great idea! Thanks a bunch. I have a million applications for that one, living in rural SE Ohio. Motorcycle air boxes seem to attract mice like a ball of cheese.

I use a handfull of moth balls in traffic signal cabinets for a similar effect, but that does not work in hot engine bays or anywhere that is likely to get wet beyond damp.

Keep up the good work gentlemen!

Ted
 
Guys,

Thanks for the kudos. Always glad to help. Bike Wrench...sorry things did not work out the way we hoped. As they say...close only counts in horseshoes and hand grenades.

Just pass the favor forward in some way.

Jimmy always has some words of wisedom...he must be 110 years old!

Mike
 
Ditto on Jimmy's comment on Hondadude's huge contribution to this forum. Ditto on Hondadude's comments about Jimmy's many words of wisdom and/or wisedom.

Jimmy - well I learn something new every day on this forum, and the diesel soaked thread is another one. Thanks.
 
Well guys, I guess it comes down to if my little trick works on Ohio wasps or not. It may turn out that I just provided some well intentioned WISDUMB.

And no, I'm not anywhere near that old! I just look and feel like it;~)))
 
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