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BF50 leakdown test how do restrain crank for rotating

N

normo

New member
"New member. Third attempt to

"New member. Third attempt to post this message. Hope the others are in the forum recycle bin.

A DIYer, me, would appreciate detailed advice on how to safely restrain the crank for a leakdown test on a BF50.. Have only done this test on a 2 stroke which has much lower compression than the BF50. For that test I was not able to find the precise position (TDC) where the crank wouldn't turn unless restrained when 100 psi was applied to the combustion chamber via the leakdown tester. What I ended up doing to restrain the crank was dumber than dumb which is the reason for this post.

I know how to use the tester and interpret the results. Just need advice on safely restraining the crank when it is very very very close to TDC.

thanks"
 
"I don't work on this engi

"I don't work on this engine so I might be way off here but I'm bored and thought I'd throw a couple of ideas your way. Honda sells the holding fixture for the flywheels and, of course, that is something no self respecting DIYer has or wants.

I routinely work on the 20 horse Hondas and I use a chain wrench wrapped around the pull start bell to hold them.

The problem with that little technique is that you need to be careful about the chains inherint tendency to gouge and deform things. Works for me but might not work for you.

A good strap wrench around the flywheel circumference would be a better choice but most of the ones that are readily available are too short so you would need to extend it somehow.

One other thing that comes to mind is to remove the pull start bell and then thread the bolts back into the flywheel and use a good sized prybar wedged between the bolts. The danger here being that you could bend a bolt or two.

If you want a "hands and helper free" device then the Honda tool and or some creative fabrication will be required.

Now I'll just sit back and wait to see one of the guys here on the forum blow all my ideas out of the water and tell you a really easy trick way to do it. Then, you AND I will learn something.

Good luck."
 
JUST-IN-TME: This looks like

JUST-IN-TME: This looks like the safest approach for me. I would appreciate your input on how to interpret the results when doing the test at the lower pressure. I'm hoping to buy an engine that is capable of another 600 hours or so before major powerhead work is required.

jimmy-dixon: thanks for your suggestions as well. I going to keep checking for ways to hold the crank. I got a real chuckle from your witty comment about " . . that is something no respecting DIYer has or wants. "
 
"If the piston is at TDC, ther

"If the piston is at TDC, there should be no problem holding it there. Put a socket on the flywheel nut and hold it with a breaker bar."
 
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