Starting All Over

[R.Johnson]

Re: Starting All Over

A badly scuffed piston, and cylinder.

 

[tx1961whaler]

Re: Starting All Over

It would have to be 2 badly worn pistons and cylinders, or wouldn't the compression readings be different?

 

[R.Johnson]

Re: Starting All Over

We are dealing with what we think is a sound engine, but we really don't know for sure. Why not get to the bottom of this first. As for why they read so close, I have seen the damaged cylinder read higher than the good, more than once. If we want to play what if, do a running test on the ignition. Pressure, vacuam running test on the fuel system. We are just beating around the bush here. What is needed is a peak reading volt meter, low reading vacuam, and pressure guage, and don't forget the proper service manual,if available. If not! you can dance with this problem for a long time.

 

[JB]

Re: Starting All Over

I tend to favor devising tests to include/exclude specific systems rather than taking things apart or, worse, changing parts. Seems to me that if there was a scuffed piston or two that its behavior would be consistent, not come and go.

Do you agree that pulling the fuel line while it is misbehaving will include/exclude the "running rich" theory?

 

[R.Johnson]

Re: Starting All Over

The carbs' have been cleaned with new kits' installed. Hoses' have been replaced with a new fuel pump. One coil replaced. Sync, and linked according to manual. Timing set. Pulling the fuel line will give a slight burst before running out of fuel. I don't know how good of an indicator that might be. I would have had the head off, long before this. If pulling the head is a bad idea, then do a running test on the ignition, and fuel. I don't know what else to tell you.

 

[JB]

Re: Starting All Over

I have fixed a hundred "cleaned" carbs that were not clean and never found mechanical failure when PSI is within 5%. I guess we have had different experiences that we trust.

What I propose is a running test of the fuel system (without purchase of exotic test equipment or gasket). Based on possible results of that test I agree to a running test of the ignition, too. Both under load.

 

[tx1961whaler]

Re: Starting All Over

I found this to be interesting:

6. Took to shop because we were out of ideas. Mechanic found that the low speed needle valves packing was gone and needles had backed themselves out so much that it was actually flooding out the motor when trying to get WOT. Initially, this seemed to fix it, we got up to speed and on plane for a good 45 minutes and brought it back to shore. Next time out, motor bogged when trying to get to WOT. What happened?

I found it interesting that the motor apparently ran well for almost an hour after the needle valves were taken out and the air passages presumably cleaned. Maybe a red herring, but maybe not....

 

[R.Johnson]

Re: Starting All Over

JB: I have fixed more than one clean carb that had the float upside down. That will give a bog.

 

[JB]

Re: Starting All Over

Hahaha. That's one I haven't seen.

Actually, I guess carb cleaning (particularly without a Manual) is pretty close to neurosurgery, RJ. And if the original trouble was coming, unfiltered, from the fuel tank the trouble frequently returns.

But, back on topic. tx1961Whaler makes an important point. When the needles were R&Red the float needles and floats might have been cleared, only to stick again later.

 

[clanton]

Re: Starting All Over

My 2 cents. Compression when new was close to 160. When you clean the carb, there is a plastic seat/seal for the needle, carb cleaner and high air airpressure may ruin the seat/seal. New seat/seal comes in OEM kit. If the pistons have scuffed skirts crankcase pressure will not be high enough to transfer fuel from crankcase thru the ports to top of piston. I also agree with R Johnson.

 

[clanton]

Re: Starting All Over

The pn for needle seat/seal is 0314166 bearing needle valve. Pn 0316332 gasket nozzle, seals the passage for the fuel flow after it flows thru the main jet. If this gasket is bad some fuel will bypass the main jet and engine will run rich. Look at BRP web site for parts, gives a good breakdown of the carb.

 

[R.Johnson]

Re: Starting All Over

I wonder why we have not heard back from the owner? But then! we usually don't.

 

[tx1961whaler]

Re: Starting All Over

He probably got tired of us arguing, threw his old motor away, and bought a new one.

 

[jsalz]

Re: Starting All Over

Hi guys, sorry I have not responded. I took the family camping for the long weekend.
A couple of things:
I did have the cylinder head off. There was no visible scoring or gouges in the cylinder walls. They seemed very clean. I did notice a lot of carbon on the top of the piston (crown?)
As far as the inlet needles and seats go, they were both replaced when the carbs were redone. I'm positive I did not put the floats in upside down.
One thing I thought was strange is when I did the link and sync and brought the timing at wot back into spec, the motor actually bogged worse.
I will try pulling the fuel line while at wot to see if the rpms increase briefly. Will the carbon on the piston head make that much of a difference. Can I effectively decarbon the motor without getting thr rpms up to burn it off?

 

[jsalz]

Re: Starting All Over

Also, before someone asks, I torqued the head back down to the spec when I put it back on.
Is it possible for a new inlet needle and seat to stick? I guess it is possible but has anyone run into this?

 

[R.Johnson]

Re: Starting All Over

That's great you have no problems with the cylinders. I'm not sure what years they glued the sensor magnets around the flywheel hub, but I have seen them slip out of place. The reason I mention this, as you stated the engine seemed to bog when you brought the timing into spec. Grasp the sensor magnet, if it is a seperate piece on your flywhhel, and try to turn it.

 

[fire7882]

Re: Starting All Over

Maybe a dumb question but is there a fuel filter? Is it getting clogged? Is the fuel tank clean?

 

[jsalz]

Re: Starting All Over

That's great you have no problems with the cylinders. I'm not sure what years they glued the sensor magnets around the flywheel hub, but I have seen them slip out of place. The reason I mention this, as you stated the engine seemed to bog when you brought the timing into spec. Grasp the sensor magnet, if it is a seperate piece on your flywhhel, and try to turn it.

Thanks, I'll have a look at that tonight. Is it possible that it is under the flywheel. I'm not familiar with that part.

Maybe a dumb question but is there a fuel filter? Is it getting clogged? Is the fuel tank clean?

New fuel tank and the only filter is the screen on the fuel pump which is clean.

 

[R.Johnson]

Re: Starting All Over

Yes, it is under the flywheel. On some flywheels, the ignition sensor magnet was a seperate piece. It was a ring that held the magnet. It was epoxied in place around the hub of the flywheel. I'm grasping at straws' here, plus, I can't remenber in what years this was done. Hopefully, someone will come along, and help us out.

 

[JasonF]

Re: Starting All Over

Any updates yet??

Just a curious observer with the same motor..