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Fixing timing, cannot turn crankshaft past 180 degrees...

S

Samav

Contributing Member
Motor is BF30A

Hello all! Very frustrated novice DIY mechanic here. Let me run you through a series of events that have plagued my very existence and have all led to the pinnacle of my frustration. Perhaps these events will also shed light on why I am having this problem in the first place.

- No clue about mechanics, want to learn, decide to buy a boat, figure what better way to learn than throw myself in at the deep end (Horrible idea, I know.)

- Boat runs solid for a while, then motor starts having a few problems

- First problem: Timing belt is slightly torn

- Replace it, and after much difficulty (and also posting on this forum), everything is running smooth again

- Several months later, motor seems to be overheating

- Take off water jacket cover and find thermostat to be corroded and broken

- Replace thermostat, gasket, water jacket cover gasket, etc.

- Start motor...

- Notice clicking sound coming from crankshaft. Pretty loud, can hear it distinctly when I turn over engine, gets faster as I increase engine RPMs.

- Notice that timing belt is slack, see that the tensioner slipped.

- Take motor apart, fix tensioner, go through tensioning procedure, think I got timing PERFECT.

- Motor hard to start, finally start it and it seems to be firing all over the place.

- Check spark plugs, realize one has barely any gap. Weird because I checked them yesterday and they looked fine

- Put in new spark plugs, try to start motor, still hard to start.

- Decide I screwed up timing. Take motor apart the next day, take timing belt off, want to rotate crankshaft by itself, free from the camshaft, just to ensure timing is perfectly aligned.

- And now.. The crankshaft will not turn more than 180 degrees, clockwise or counterclockwise. It stops about a quarter turn past the TDC mark going clockwise and counterclockwise. I am rotating it by using the flywheel as leverage..just throwing that out there.

- I think it's worth noting that the crankshaft was rotating perfectly fine while the timing belt was still connected to the camshaft, but the second I took the timing belt off and tried to rotate the crankshaft by itself, it seized up.

So what do you guys think? Did I bend a piston? Something wrong with the gears? Obviously I did something stupid.



TL;DR: Rookie mechanic makes rookie mistakes.
 
You cannot turn the crankshaft alone, the camshaft must turn with it or the pistons will hit the valves. Reset the timing and carry out compression check to make sure you havn't bent any valves, if you have no compression on one or more cylinders then you will have to remove the cylinder head and get bent valves replaced.
 
You cannot turn the crankshaft without turning the cam with it. The cam, when stationary like that, will be continuously holding a valve or two open and the piston associated with the open valve will make contact.

If you want to rotate the crank with the timing belt off, you MUST back off all the rocker arms so that none of the valves can be held open.

The closed plug gap is definitely a concern. That is usually an indication that there is something on top of the piston that shouldn't be there and is contacting the plug ground strap. Either that or the plug is too long for that engine or the top of the piston is damaged and deformed enough to contact the plug tip.

I would use my little $20 flexible camera that plugs into my smart phone and put it in the spark plug hole to try to see what's going on in that cylinder.

Good luck.
 
Ah.. I kinda figured that was the case, but thanks for clarifying. I will definitely be checking compression and I have a flexible camera I will use to check inside the plug hole. Any ideas as to what would be causing the clicking noice from the crankshaft though?
 
Well, if something in the cylinder with the closed plug gap is actually hitting the end of the plug, it could also be "ticking" up against the top of the combustion chamber too.

Things I've seen do that in my career are:


A broken off piece of valve head.
A broken off piece of valve seat insert.
A piece of cracked off ring "land".
A nut someone dropped in through the intake.
The greater part of a piston crown that melted and twisted up due to a lean burn condition.

Sorry for the gory sounding scenarios but it happens.
I would focus on that cylinder for sure. If you have the little mirror that comes with those cameras, put it on and try look at the valves and seats if you don't see anything out of order with the piston top.

Good luck.
 
Hey guys, so I just reset the timing, and the motor is running well and idling perfectly. I also ran a compression test and got 119 PSI from each cylinder. Is that good compression for such a motor? My BF30A is over 20 years old. Also, does this mean I am in the clear, as far as bent valves goes? Or should I run a leak down test to be sure?
 
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