1990 Force 120HP #2 Cyl zero compression and upon opening piston shows damage

[racerone]

???----It is a cast iron sleeve !!---If you look at the intake and exhaust ports you can clearly see that it is a sleeve.------The sleeve is not removable !----A ball hone will give you a " nice looking " finish and it follows all imperfections .-----A hone with 3 new stones will show imperfections and will true up a cylinder to some degree.

 

[gica]

Thanks for that, good to know so being cast iron I don't need the aluminum oxide hone? I can get the Silicon Carbide right?
Ok I got the flex 240 grit 3.5 size Silicon Carbide. I will get a 4 inch stone hone from Harbor freight but they only have the Aluminum Oxide.

 

[gica]

Ok so everything is out
Only 2 things that were a pain thebflywheel and the cover that allows acces to the bolts that face down.
It was frozen into place and I had to heat it up. So for the first time doing this one I thing I did good. Only broke 2 bolts.
Odf thing was when Intook the adapter plate apart there was oil there and it was black. Got to look în the book to see what that is. There is a plug there so I am sure oil goes through it.
Even with all the frozen in place parts this is a piece of cake compared to the Yamaha 1200ltd jetski. There is no room to do anything in that one. Really complicated stuff with 3 carbs that are way on there. Bad design for sure.

 

[gica]

Does anybody know what this part is. It came off when I removed the engine.

 

[jerryjerry05]

Called a stand pipe, used to keep excess water out of the motor housing.

The mid section/rear/bottom has 2 holes that when just setting in the water and not moving they keep the water at the right level.
#25 in #47 #47 you can't see the holes (2) because the cover is turned wrong.
Just glue them back in place unless they're melted then just toss em.

 

[The Force power]

A 3.5 ball hone aluminum oxide should be enough right? This is an aluminum cylinder right? Or did you use the regular type? And the grit, did you use one size? I never used the flex always used stone în the past. And do you do dry honing or honing oil, 10-30 oil,Water etc

Make sure you file the edges (slightly) on the exhaust ports, the rings apparently can get caught on them

 

[The Force power]

???----It is a cast iron sleeve !!---

Sorry , I should of said; can't be removed

 

[gica]

I did the honing the damaged are disappeared on number 2 it took 10 minutes with tye 240 stone hobe. I have not done the flex ball yet. By the way the #1 piston when I took it out a1/2 inch piece of the top ring was broken off and fell out. Do I really need new pistons for all, can I buy used standard? Found 4 for a 100.
I am trying to measure the ring gap and am looking at tye specs. I want to make sure I am reading it right. Top ring .010/.020

 

[gica]

Ok so after honing I measured tye end gap on all 4 cylinders and 1,3 and 4 have .016 throughout while the one I had to hone deeper is .035. So .019 difference in gap
#2 measures 3.3820 now.
Otherones at 3.375 now

 

[racerone]

There is no way you can run a standard piston in #2 cylinder.----Needs to be bored and an O/S piston / rings fitted.

 

[gica]

I already honed it to get rid of the issue. The top ones are also honed. So I cannot use standard with oversized rings .010 on 1,3 and 4 and .020 on 2?

 

[gica]

So if I take it to a machine shop, what pistions and rings should I get. I mind aswell bore them all then. But I need to buy the stuff before hand right?
Mind aswell surface the head and block.
I'd like to be able to get away with tye least expensive scenario if possible.

 

[racerone]

Measure the #2 piston near the piston rings.----Will likely be around 3.365"------A standard piston in #2 will not last long !!!----Just will not run properly.----Find a good used block on E-bay ????

 

[gica]

3.365? 3.375 is standard right? I measured and it is 3.3820 all the others are 3.375. What is the point of oversized up to .040 if they woun't last? If this one won't last the other ones should not be far behind.

 

[racerone]

Well---3.375 " is the BORE size and a new PISTON might measure 3.365" near the ring lands.-----I think I am going to step aside here.----This is going nowhere.

 

[racerone]

Well----In post #1 you state that you " have the tools and the know how " -----I believe you need to study some more ---Sorry.

 

[gica]

Well----In post #1 you state that you " have the tools and the know how " -----I believe you need to study some more

Well----In post #1 you state that you " have the tools and the know how " -----I believe you need to study some more ---Sorry.

I think I misunderstood the request to measure the piston, I misread thinking I need to measure the bore. My mistake. I do have the know how to do the job mechanically but I still need the knowledge to what to use and do it right. I have looked for engine cores and have not found any here in SoCal.

You said the standard pistons measure 3.65 at the rings so an oversized one should do better. There has to be a piston size to fit in the 3.3820 bore? I was under the impression that if standard is 3.375 you can get ovwrsized up to .040 You are right I have read a lot but I obviously need to read some more to get this damn figures right. I am not doubting your expertise I just need to work with what I have. Getting a new block is not in the cards right this second and I want to get this boat on the water.

 

[racerone]

New piston might be 3.365 /3.367 " at the rings.-----3.372"at the skirt.-----Aluminum pistons expand at around 0.000012"/ inch / degree F ------New pistons are tapered and sized with clearance when cold.------When engines run clearances change.

 

[gica]

I read a bit about the 1990 120HP engines so there were 2 different ones. The A 120s had the 3.312 bore size
The B and C modelshad the 3.375 bore size. Both my engines measured below 3.375 before the honing. Right arounf 3.370 So am wondering which model I have?
If it's A then the cyls have been rebored and are outof specs. If it is the 3.375 nobody touched them so based on what I read I have up to.030 according to factory
recommendation and .040 to the book to install oversized pistons.
This info was obtained from an older post here on Iboat forum many years ago. The guy's bores were way above max. So he could not do anything. I don't know what mine is. Have to find out, have no clue where it's listed.

 

[Nordin]

From the model number of your engine you should be able to identify if it is a 3,312 in or 3,375 in.