96 force 120 overhaul

[pnwboat]

When you buy a set of the Boyesen reeds for your motor, you get enough reeds to replace all of the original ones.

"Pulled top piston out and attempted to take some measurements and came up with 3.378 for the cylinder, not sure how accurate my measurements were. I inspected the cylinder pretty well and didn't find any noticeable scores When taking out the reeds I found two with corner chips and one broken. How many boysen reeds do I need to replace both reed blocks? I think the broken reeds might have been the cause of my idle issues. Right now I'm contemplating honing the top cylinder and installing new rings, replacing reeds, head gasket, and hoping for the best."

I would pretty much agree with your plan, if the cylinders look like the pistons.

 

[Jiggz]

It's a good plan. But even better is to go ahead and inspect the rest of the pistons and reeds. Unless you can verify there is no scratches or scoring on the rest of the cylinders. But even then I recommend to at least inspect the rest of the reeds.

 

[Chrisried]

I took out both sets of reeda. One set had a corner chip the other had a corner chip and one broken. I have inspected the other cylinders without removing the piston and I'm hesitant to pull the rest of the pistons because I'm not sure how the rings will seal back up. I am questioning the mechanics diagnosis. I'm not sure how he took the compression, end of last year I took compression and all cylinders were equal and now he is finding one cylinder to be lower but I'm not finding any damage and the boat has maybe an hour or two since. Any advice on honing cylinder in place? Thanks for the help

 

[pnwboat]

Yeah I would question the compression readings taken by the mechanic too. Maybe he didn't get the compression tester screwed tightly into the spark plug hole? The pistons and rings look like they're in good shape, pretty much normal.

As far as honing, I would do a very light honing to keep the cylinder diameter close to it's current size. Stuff some rags into the bottom of the cylinder to keep debris out of the crankcase. Kind of a pain because it's easy to get the rags tangled up with the hone but you get the idea.

I don't think that there is anything wrong with using the old rings as long as you get them oriented correctly, but that's just a personal preference. You might find it somewhat difficult to find just the rings. You have to take care to find the rings that are designed to work with the pistons in your motor. They look to be OEM style pistons. Some of the aftermarket pistons such as Wiesco require special rings that will not work on OEM pistons.

If it's possible, lightly bevel the edges of the intake and exhaust ports with a dremel to minimize the chances of catching a ring. Not uncommon for this to happen in 2-stoke motors.

One other thing to look at is the stainless steel baffle plate that sits under the exhaust cover. Inspect it very closely to make sure it doesn't have a crack in it that is allowing water to get into the cylinders.

 

[Chrisried]

. You might find it somewhat difficult to find just the rings. You have to take care to find the rings that are designed to work with the pistons in your motor. They look to be OEM style pistons.

One other thing to look at is the stainless steel baffle plate that sits under the exhaust cover. Inspect it very closely to make sure it doesn't have a crack in it that is allowing water to get into the cylinders.

I found the rings on another site that also has parts diagrams, hope they are correct.

As far as the exhaust plate can you generally reuse gaskets if no problem is found. I have not myself found any signs of water in any of the cylinders. I wonder if the mechanic is seeing carbon missing on the intake sides of the piston and is thinking it's from water when it's probably from power tune. I had pulled plugs the last time I had the boat out and cleaned plugs and i didnt notice any water or anything not normal. I'm really not sure where he came to the conclusion that there was water in the cylinders.

 

[Jiggz]

Mechanics are good and can be trusted with but only after verifying their claims. Lol

 

[Chrisried]

Mechanics are good and can be trusted with but only after verifying their claims. Lol

Very true.

 

[Chrisried]

Have the new reeds installed on the blocks. After looking at old reeds, it looks like without the broken reeds it would still have leaked a lot of air as there was a pretty big gap at the tops of the oem reeds. Head gasket and rings arrived today plan to install them tomorrow. As far as installing the new rings what is my best bet as far as honing the cylinder? I have been reading and there seems to be no clear consences. I saw on other two strokes people were using scotchbrite pads and oil. I really don't want to create any issues by doing it wrong. And I'm not really wanting to spend a lot or wait for a special hone that isn't available locally. Any suggestions?

 

[Jiggz]

When I replaced my piston with Wiseco, the only requirement was to at least de-glazed the cylinder. And I used a harbor freight honing kit that already came with the stones. I just used some oil and de-glazed.

 

[jerryjerry05]

Harbor Freight , Auto Zone and all the rest have fairly inexpensive hones.
​From the looks of the pistons there isn't much happening that I'd worry about.
The green scotchbrite, even the purple will do ok in a pinch.
Pics of the cylinders?

 

[Chrisried]

Put everything back together. Took boat out for test run. Idled much better and ran good. According to the directions from boyesen the carbs are supposed to be rejected. Is this generally necessary.

 

[jerryjerry05]

Rejected??
Re-jetted?? Not that I've heard?
​Maybe try this?? Run the motor at 45-4800 rpm's for a few minutes.
​Making sure the motors good and warm.
Then shut the key off while running.
Don't slow down or throttle back.
​Kill it while running.
Then inspect the plugs.
Look for any light brown or white deposits.
​YES? then you need to re-jet.

​But?? if they say you need it ask them why they need it and how to figure out the size you need.
Finding the new jets might be fun.

 

[Chrisried]

Sorry meant rejetted, phone thought it knew better. I read something in the installion instructions about rejetting, misplaced the instructions, and then found them. Rejetting isn't applicable because the idle mixture can be adjusted on carbs.

Had the boat out this weekend. Put 5 or so hours on and it is running well. After motor is warm I can start without putting it into high idle, which has always been an issue. Runs better than it has since I've owned it. Thinking I might need to change plug wires as I'm guessing they're original. Thanks for the help.

 

[Jiggz]

Just a little reminder, everytime you change a piston or ring and you actually honed or deglazed the cylinder, it is always recommended to do a break-in on the entire engine by running 25:1 fuel oil mixture. And this generally just involves running the engine on steady rpm at 1/2 throttle for the first hour, 3/4 throttle for the 2nd hour and then WOT for the next 4 hours. Thereafter break-in is complete and fuel oil mixture should be back to standard 50:1 ratio.

 

[Chrisried]

opps didn't break it in properly. What are the consequences of not breaking it in as advised?

 

[Jiggz]

Hopefully, nothing negative. Engine break-ins are mainly to seat the piston rings with the cylinder walls perfectly to a very stable match. Hence, the steady rpm at certain speeds and certain length of time. Since you already ran the engine longer than the required break in times and it is still running good, you can surmised it should be good to go.