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lining up the counterweights on BF15A

M

maremsk1

New member
Hello all,

Im rebuilding a BF15A and want to verify something before going further. The crankshaft has a gear on it which mates with 2 weighted gears on either side. There are punchmarks on all the gears so that everything can be lined up correctly. However, there are 2 ways to line them up. One will set both pistons at TDC, and 180 degrees out of phase will set the pistons at BDC. (Both will have all the punchmarks lined up). The manual just says to make sure the marks are lined up, but thats it. Im guessing TDC, but don't want to guess on something like this.
 
I'm with you in thinking it would be TDC. But, I don't know for sure either. This is one that we may need to wait on hondadude to answer. I just wrote to let you know we see the post and to say welcome to the forum. Well, that and I'm curious.

I was unaware of this engine until I saw your post. Looking at the parts breakdown of the crankshaft, it shows both rod journals in the same plane. So this is a 0 degree engine? Meaning both pistons rise and fall together, firing at the same time? In the parts depiction below, it shows the rod journals in what looks like the TDC position and the counterweight gear timing "dots" lined up. But, that is some pretty sketchy info to go by.

http://www.boats.net/parts/search/Honda/Outboard Engine/1997/BF15AM SA /CRANKSHAFT/parts.html

Hopefully you'll get the "scoop" from the Honda forum's main "scoopster" soon.
 
One cylinder is on the compression stroke while the other is on the exhaust stroke.Only one cylinder produces power at a time.----The other fires on the exhaust stroke.--Most small 4 strokes are aranged that way.
 
You got me on this one. I did look at the operating principal of the two shaft balancer in section 15 of the manual.

It looks like at top dead center, the weights on the balancers are located opposite (180deg) from the pistons. When the piston is at the bottom, the weights are both oriented toward the pistons.

Let us know if that works out, when you set it at TDC.

Mike
 
Is there one mark on the crankshaft and 1 mark on each gear ?-----Then I would say that you line up marks one one gear and the crank.--Then rotate to line up marks on crank and other gear.
 
It looks like there are 2 marks on the crank. 180 degrees apart. They are very faint tho, so I hope Im looking at this right. The balancers have 1 mark each (very well defined).

And yes, both pistons move up and down together but are on different parts in the cycle according to the valve / cam arrangement.

I guess we are all in agreement then on TDC then?
 
Once you go with TDC, then check the relationship of the weights to the pistons. Referring back to Section 15 of the manual. There are good pictures of their orientations. If the pistons are at top dead center, then the weights should be as 180 deg from the pistons. Also, when the pistons are at the bottom of their movement, the weights should be to the top of their movement (towards the pistons).

Since no one is saying for sure, make sure that it makes sense to you. It can only go one of two ways. You do not want to have to take it apart again to correct it.

Mike
 
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