Question for the experts.....

[daselbee]

Re: Question for the experts.....

OK here is a video. The engine is running at 1250. I do a spark/cylinder drop test first. You see no response from #2.
Then upon re-start, I drop it in gear from 1250 it drops to 650 and eventually stalls.
If I increase the idle to 750 in gear at idle, then neutral is way up at 1800, and that is too hard on the gearcase.
I don't want to do it again, for fear of damaging the dog.

 

[daselbee]

Re: Question for the experts.....

Phill, I remember reading your posts.

I have run it with the carb linkage removed, throttle springs holding all three closed. Been there....
No real help.
I will try Seafoam on #2 to see if I can decarb it.

If I remember right, yours has the slotted cam mechanism, right? This one is a different from yours, a bit.
Your link and sync is trickier. Don't you have the timerbase arm/rod that is adjustable? Mine is fixed length.

I am tempted to pull the head and measure the bores to check for out of round at the bottom and try to see any scuffing low down on the cylinder walls. Can't see the piston skirts.....
That will be the last resort.

 

[Bosunsmate]

Re: Question for the experts.....

That number two is really ill.
Have you tried, as EMD said, to see if the plug gets wet if you ground the HT wire elsewhere?

 

[Bosunsmate]

Re: Question for the experts.....

Another interesting thing about that video is it sounds to me to run better when two is disconnected. Almost sounds to be firing out of time but you,ve checked timing on it.....

 

[phillnjack2]

Re: Question for the experts.....

it sounds bad full stop.
something is definitely not right about that very loud ticking banging sound.
this could be something loose under the flywheel, ive seen it on the 2 cylinder models a fair bit.
I would definitely be looking into that number 2 cylinder for sure,
but that loud ticking is definitely not right, I had that when my timing was way out of synce, almost
sounds like small ends rattling around, mine was like that for a while.

are you sure the plugs are all ok ? is there any chance of ignition leads leaking spark, check in the dark to see
if any fireworks are happening.

.

 

[daselbee]

Re: Question for the experts.....

it sounds bad full stop.
something is definitely not right about that very loud ticking banging sound.

Not sure I understand what you mean here. When I pull #1 off, I hear a high pitched ticking that is not there when the wire is on. I just assumed it was arcing back at the coil post to ground, causing the tick. I will check in the dark for fireworks.

You dealers out there (or those with access).....Fazt....are there any service bulletins on these carbs? 1981 70. I looked at the parts list (carbs) for a 1982 70 and I see they went to completely different jet sizes. Wonder what was up with that?

I have 2 1981 engines here, one is a parts engine, and the carb sets are identical regarding casting numbers and jet sizes.
That leads me to believe that I have the right jets in there.

 

[tomhath]

Re: Question for the experts.....

In your very first post you say the compression is 135, 120, 135. That is probably your major problem. Cylinder #2 being 15# lower than the others is a big red flag.

Have a knowledgeable shop perform a leak-down test on the cylinders and I'll bet that you will find your idle problem.

Yea, really sounds like the place to focus is why that cylinder is low.

 

[daselbee]

Re: Question for the experts.....

Pulling the head today.
I wish I could see the piston skirts, but I will not be able to.
I will measure the cyls and see if they are out of spec.

 

[daselbee]

Re: Question for the experts.....

OK, head is off.
I see smooth cyl walls on #1 and #3, cannot detect and remaining crosshatch.
I see light scoring on #2, which can account for the lower compression on that one.
There is not problem at all with the head gasket.

But, I have another problem I am sure. When piston is on the downstroke, and I stop turning the flywheel, I can press on the tops of #1 and #2 and hear and feel significant movement/play. I bet #1 moves at least .010. #2 is not as bad.
There is absolutely no movement in #3.

Additionally, I have removed it from the tank to pull the head, and all heck's worth of unburned fuel is dripping out the prop. It is alot of fuel. At first guess, I would assume that was fuel from #2 not contributing.

I will see what the owner wants to do about it. It is now at a point that a total rebuild is called for.
Get the compression up, new pistons, pins and bearings (hope it's only the little end of the rod), etc.

 

[daselbee]

Re: Question for the experts.....

Additionally, there is enough play in the two pistons to account for that ticking that was mentioned earlier.

 

[daselbee]

Re: Question for the experts.....

OK...check that about the piston movement I mentioned in post #29. Not the case. This noise and movement is being caused by pushing on the piston top OFFCENTER causing the skirt to move and bump the side of the cylinder. I will try to post a vidoe and maybe the sound will be loud enough.

All three do this, #3 not near as much.

 

[Bosunsmate]

Re: Question for the experts.....

Doesnt really say why 2 was a dead cylinder though does it?
Ive never done a test like that on a piston in its bore when its fully down stroked

 

[Faztbullet]

Re: Question for the experts.....

Just quote customer $$ to bore and rebuild it and call it finished...