BF100 stalling with cover on

I have a BF100 that idles perf

I have a BF100 that idles perfect with the cover off but stalls within 30 sec after the cover is installed. I have searched this forum and found some ideas. I have visually checked the exhaust pipe for leaks and found none. I have checked all the breather lines for leaks and found none. I have replaced the seal at the bottom of the exhaust tube and the gasket to the head. I filled the exhaust tube cavity with water while running and found no bubbles to indicate leaks.

Is there something I am missing? Does anyone have any ideas?

"So that you do not think you

"So that you do not think you are being ignored...your problem is pretty challenging.

I assume you have pulled the power head and replaced the oil pan gasket and the exhaust pipe gasket when you replaced the exhaust pipe seal.

How about pulling the crankcase vent hose that vents out the bottom of the case on the port side. There are actually of couple of hoses that vent there. Pull the hoses and be sure that no critters have made a next in them. Mud dobbers like these areas.

There is also a check valve in the crankcase breather body. The valve may be corroded shut and forcing the venting from inside the hood area instead of through the bottom of the motor casing. There are three hoses that go to the breather body. It is approximately 2 inches in diameter and about an inch thick (from my foggy recollection)located starboard of the intake to the carburator, under the flywheel/pullstart). Be sure those hoses are all clear also.

One last and pretty simple thing...check to be sure that the air intake vents are clear. I can not remember for sure if the vents on this model are in the rear area of the hood (like the recessed area in the back where you grab it to lift it off). If the vents are not there, there are some small line of holes under the front of the metal motor casing by the carrying handle.

This should give you a few other things to check. Meanwhile, someone else may get a brainstorm.

Good luck!"

"Thanks, Mike

Yes, I pulled

"Thanks, Mike

Yes, I pulled the power head and while it was off, I replaced all the seals and gaskets and reseated the valves. I have also removed the crankcase breather body and checked the check valve and o-ring. All the breather lines were cleaned and vacuum checked for leaks.

The gasket between the intake manifold plate and head was replaced since it appeared to be a potential location for an exhaust leak.

Also all the breather holes in the hood and the case vents are all clear. with all this work, the problem has not improved.

Since the engine starts to slow down the instant the cover is locked down, I still feel it is an exhaust leak. I am going to check again with water in the exhaust housing area with my son to look at it in case I am missing any bubbles in hard to see areas.

Other than that, I am about out of obvious ideas. If I can't find anything I may fabricate a fresh air duct to outside air."

"I had a similar problem with

"I had a similar problem with an 8hp honda, turned out the exhaust tube was cracked causing exhaust gases to back up under the hood and starve the oxygen.
It was a bit of a labour intensive job to remove it and replace the cracked one but it fixed the problem."

"Two small bolts to remove tha

"Two small bolts to remove that finger hold at top rear of cover and you can see the air intake holes.

There are three and room to drill two more.

If anyone has to replace that exhaust tube, it's a lot easier to just pull the cylinder head than the power head.

If you get a new exhaust pipe from boats.net (on "oil pump" page; #18 has replaced #17), it will be the newer style with a 'water-jacket'."

Update

I have rechecked the

Update

I have rechecked the crankcase breather body for cracks or leaks and all checks out OK. I have replaced all breather hoses with no change.

I have removed the power head to recheck the exhaust tube. I pressure tested the exhaust pipe and found no leaks. I am reluctant to spend $75 for a new exhaust when I can't find a leak.

I did find the seal where the shift rod enters the housing below pivot tube is cracked which would allow exhaust to enter the pivot tube leading to the area near the carburetor intake. I have ordered a new seal and will install it when it arrives. I will post the results when I get it back together.

Update: Success

I replaced

Update: Success

I replaced the shift rod seal at the top of the extension housing and the problem finally went away. Aparently the previous owner removed the lower unit without removing the shift rod clevis and damaged the seal.

I have not seen this solution posted on this forum. Maybe the experts here can add this to their list of fixes for future reference.

"Yes, it should help someone i

"Yes, it should help someone in the future...maybe even me! Thanks for sharing the solution Mike.
GoodOnYa!"

Nice find!

Nice find!