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Bent Valves?

S

Skooter

Advanced Contributor
A bit of history...I was running my bf200 5000 RPMs when one motor abruptly turned off, almost like if I turned off key..Well, upon examination the timing idler pulley bearings gave out..my belt is good, but timing got out of whack...I have since replaced bearing pulleys and belt, aligned timing marks and crank, but now seems like no compression. I can turn crank with much less effort than the other "good" engine. Would bent valves do this? I know this is an interference unit, how can I examine the valves and decide which one, or both heads needs to be pulled. Would a compression test be suffice? What are your recommendations for this?
 
hello there... not a super boat mechanic but i can say i built many car engines and bikes... compression test will tell you where the problem lies as to a certain cylinder.. but a leak down tester your give you a better idea as to intake valve or exhaust valve being problems...

before you do any of that have you ensured that you are not 180 degrees out? sometimes it happens to the best of us not even realizing it... not sure about that motor but i do not like to go by the timing marks solely... cylinder one will be at TDC once before the intake valve opens to suck fresh air in and then once on combustion stroke... you obviously want the combustion stroke... but if this is the case and ur 180 out... you may be skating buy with no valve interference and but exhaust valves are open when they should be closed....


dont sweat yet and double check that first
 
Skooter,

Dang, man! That hurts! Sorry that bit you.

I agree with everything tzeliesko said. He obviously knows engines. So, if you have absolutely verified that you referenced cylinder #1 at TOP DEAD CENTER on COMPRESSION stroke to set the timing, then the leakdown test will confirm if it's valves for loss of compression.

Another "empirical" technique would be to put a boroscope (inspection camera) into the spark plug holes to look for signs of the piston 'kissing" the valve. This is usually not as conclusive as the leakdown test but could give you an idea of what kind of damage may be present before pulling the head.

Ouch!
 
Bent valve usually do not seat properly.------So remove valve covers and inspect for " overly loose " valve clearance.----------------Yes the 4 stroke outboards run really nice when they run, but the risk of expensive motor problems is always there.---------Many more 4 stroke owners will find this out as time adds up on these motors.
 
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