Post Mortem Exam :(

[ezimmerm]

My force 150 finally bit the dust.....last time I had it out it was much more difficult to start then it should be....this morning on the hose it wouldnt start at all. After checking spark, next test was compression which showed about 130ish on cylinder 1-4 and 10 on cylinder 5.

Circled in red it looks like a hole in the cylinder jacket on cylinder 5,
I'm guessing that this cylinder wasnt getting enough oil, any other thoughts? Is it worth a rebuild?

it had been running great since last summer and I never heard the overheat alarm go off (tested to make sure it works, it does).

:facepalm:

 

[Frank Acampora]

Re: Post Mortem Exam

From the photo it looks like she broke a ring. Cylinder appears OK though. A light honing and a stock 3.3125 piston should get you back on the water.

If that is all, it is definitely worth a rebuild.

Even if you need to disassemble, bore oversize on #5 and install an oversized piston, it is still worth rebuilding.

 

[ezimmerm]

Re: Post Mortem Exam

Thanks Frank. Do you have any recommendations on places to buy a rebuild kit from? I've done a lot of basic work but have never done a rebuild before. What does it usually cost?

It looks like theres a minor score mark on the cylinder, not sure if it would require an oversized piston or not. Hopyfully you can see it in the picture, very bottom of the cylinder.

 

[Frank Acampora]

Re: Post Mortem Exam

You don't need a rebuild kit. You need a piston and an intake manifold gasket. You can remove that piston through the reed opening and hone the cylinder with the engine assembled and on the leg. You may need to unbolt the lower shroud to get to it though.

For a number of reasons, I like Wiseco pistons.

That score mark really looks like it will hone out--but don't get too happy with the hone. It is possible to egg shape or taper the bore. But, only you can really tell. If it is so light that your finger can just feel it, it will hone out. If it is heavy enough that your nail will catch on it when dragged across, then it will require overboring.

If you don't need to bore it and do the work yourself, replacing the piston and honing the cylinder will cost less than 200 bucks and that includes buying a three stone hone. Head gasket should be reusable. If not, add another 50 bucks.

 

[ezimmerm]

Re: Post Mortem Exam

One last thing before I get to taking everything apart. By reed opening you mean through the reed opening behind the #3 carb?

To order everything looks like the following is needed
http://www.wiseco.com/ProductDetail.aspx?ItemID=W5216&ModelID=2983&ModelYear=1989&AppID=9265 (Bearing Kit)
http://www.wiseco.com/ProductDetail.aspx?ItemID=3129PS&ModelID=2983&ModelYear=1989&AppID=9400 (Piston)
Plus gaskets when taking out the reed's?

 

[ezimmerm]

Re: Post Mortem Exam

Frank was right (as usual) the rings on the piston are shot (and litterally fell apart when i pulled it out). This may be a dumb question but how do I make sure to get all the old piston ring material out of the engine before putting it back together? Any tricks/tips?

This is what the piston looked like, missing chunks.

Also on closer inspection the number 1 piston, it looks like the ring is warped. Oddly enough it has great (135lb) compression when i measured it.

 

[Sprky]

Re: Post Mortem Exam

You have gone this far, take it apart and do it right. I see lots of stuff in my shop where someone tried to bandaid a motor only to make things worse or miss another problem.

Broken rings are common, especially with a cyl that is out of tolerence. It's not a matter of if, but when, another cyl will do the same.

Chris

 

[ezimmerm]

Re: Post Mortem Exam

Sprky your right on, its going to have to be a rebore. The score marks I can catch a fingernail on. I guess this'll be a winter project....I'll be bugging you guys with more questions.

Speaking of which, can you bore just one cylinder to a bigger size and leave the rest the standard size?

Also if you do bore to a bigger size, is there going to be a problem with the standard head gasket?

 

[Sprky]

Re: Post Mortem Exam

There will be no issues boring only one hole. Have the machinest look at the other holes to determine if they are worn heavily at the ports.(This is what usually causes the ring breakage). If they are ok and you can afford it, go back with wiseco pistons. They have a ductile iron ring that you can almost tie in a knot,(very durable) and they have to have a little more clearance than cast pistons, therefore will take up a little of the slop.

Chris

 

[jason32038]

Re: Post Mortem Exam

Sprky there is an issue with boring...the issue is actually finding someone who wants to machine it. Ezim there will be no issue with the head gasket. I bored one cylinder .040 and had the other 2 lightly honed and there is no issue with the gasket. I also enlarged and chamferred both intake and the exhaust ports which I would highly reccomend if you disassemble the entire engine. After doing that the engine sounds beefier...havent hit the water yet though. If you decide to take apart the block make sure you put the rod ends back on the rod the moment you disassemble them. If you dont then you'll have a matching game on your hands..also make sure you number the pistons to install in the same hole they came out of..number them on the inside so you can remove the rings and clean the grooves without wiping your marks off.

 

[Sprky]

Re: Post Mortem Exam

Plenty of shops can bore blind holes.

Don't enlarge any of the ports. To realize a performance gain you have to remove quite a bit of material. You will also need to rejet........... for the average owner, it is best to leave it stock.

Chris