Down under rebuild of 90HP Force

[hundee r1]

Re: Down under rebuild of 90HP Force

wow, some great tips there guys!! the exhaust port chamfer is one thing Id been wondering. Its something that is essential when porting the exhaust port on a Rotary motor for much the same reason. We talking a 1-2m radius edge? Might have to see if there is any vids on u tube or pix on the net.

Great tips in regards to the crank aswell, before even dropping mine in I have to install new sealing rings cos I broke them trying to take them of the crank whilst it was still in the case ( idiot, I know). Got 2 sets aswell incase I snap one as I slide it on.

New wrist pin kits and big end bearing pins will be used, existing big end cages tho. The main journals have been left alone, top crank bearing has been supplied in my kit and i will probs have it pressed on the crank even tho the existing seems ok.

In my kit I got some spaggetti seal, but my power head didnt have any in it, Im assuming its for my lower unit or maybe another Force model that does use it?

I also watched this vid in relation to the wrist pins:

Outboard Rebuilding - How to install a piston onto a connecting rod - YouTube

this made it quite clear yeh? I will have to punch out the standard pins from the assemblies first, and with 2 off the 3 pistons being ornament use only, I hammer and punch will suffice, taking care of the rod is my only concern.

many thanx!!

 

[Frank Acampora]

Re: Down under rebuild of 90HP Force

Taking the top bearing off the crankshaft requires a large press--10 ton or better-- and a special bearing puller tool. It looks like a large tapered plate split in the center and held together with two bolts. It slips under the outer race of the bearing, or if you are lucky, the inner race. Obviously the old bearing will no longer be usable.

The new bearing does not need to be and should not be pressed on. Heat the new bearing on top of a 100 watt incandescent bulb for about 10-15 minutes. Meanwhile toss the crank into a freezer. The difference in contraction of the crank and expansion of the bearing inner race will generate clearance.

Using gloves, QUICKLY slip the bearing over the crank. It should slide right to the bottom of the nose where it belongs.

 

[hundee r1]

Re: Down under rebuild of 90HP Force

wow, ok. So a normal bearing pulling tool wont get the old one off?

Im tempted to leave the bearing as is if thats the case

 

[jerryjerry05]

Re: Down under rebuild of 90HP Force

Your chance of taking the bearing off with that tool is slim.
If it's turning smooth just leave it.
The later year Forces didn't have a spaghetti seal in it.
The sillycone is all that's needed.
Just make sure the corners and the bearings are covered.

 

[Frank Acampora]

Re: Down under rebuild of 90HP Force

Chances are slim to none and slim just left the building. You will turn that puller into scrap metal trying to pull the top bearing--that is, if the jaws can even fit under the race.

 

[pnwboat]

Re: Down under rebuild of 90HP Force

As stated by Frank and Jerry, if the top bearing is OK don't mess with it. If you need to take it off, this is the type of bearing puller that you need.

Moped Crank Bearing Removal - YouTube

Do the new pistons have pressed in wrist pins, or are they floating wrist pins that are held in place with circlips?

 

[Frank Acampora]

Re: Down under rebuild of 90HP Force

NICE--I'm running out to Harbor Freight right now to get one.

 

[hundee r1]

Re: Down under rebuild of 90HP Force

As stated by Frank and Jerry, if the top bearing is OK don't mess with it. If you need to take it off, this is the type of bearing puller that you need.

Moped Crank Bearing Removal - YouTube

Do the new pistons have pressed in wrist pins, or are they floating wrist pins that are held in place with circlips?

Wow,thanx for your input. nice work with that puller, looks like the guy runs a shop tho? much easier to justify the $$$ on one.

A local re conditioner told me they use a big hammer and a punch on the inner race to remove the bearings on crankshafts.
To install the new one they use a couple inner races welded together that are slightly bigger than the bearing your installing and again , use the same hammer to knock the new bearing home.

I'm in 2 minds with mine, I can probs try the above methods or just leave it. Bearing seems ok, doesn't have any wobbles in it, but doesn't feel as smooth as the brand new one I actually have.


The new pistons are Vertex, yes, the wrist pins are held in with circlips.
I will have to disassemble the old of the rods tho. Again, Im thinking a drift and a big hammer? Not as if Il ever use the original pistons or pins again....Im sounding pretty dodgy right now hahahaha


I must say, the "instructions" that come with the Vertex pistons are a bit hard to understand. I will have a closer look , but finding the required ring gap on them inst the easiest thing!!

 

[pnwboat]

Re: Down under rebuild of 90HP Force

The puller shown in the video is actually a low cost Chinese import sold by a company here in the U.S. called Harbor Freight.

If you do replace the bearing, use some loctite on it to help prevent it from moving on the crankshaft as a precaution. This bearing is what hold the crankshaft in position and keeps it from moving up and down (or back and forth depending on which way the block is sitting).

I think you'll find that using a drift with a big hammer is not an easy way to remove the wrist pins. I've tried it and I've not been able to do it. You need at least a two ton press. I've done it using a manual arbor press like this. Had to take a pipe and extend the handle but it worked.


A hydraulic press would even be easier.

 

[hundee r1]

Re: Down under rebuild of 90HP Force

Ah , Ok, will go to my mates shop on saturday morning and use his press.

Ive re read the postings in regards to boring, and Im concerned. I understand that it should be accurate etc. But Im still confused in regards to what figure to aim for.

the standrad bore is 3.375, the 20thou over bore would put it at 3.395 (comfirmed on the piston box). Now looking thru the factroy manual, the standard piston to bore clearance is .005, but in the Vertex box its say .003 MAX clearance.

Rang the machining place and they are going to the nominal 3.395 which will give me factory .005 clearance. Should I be ringing them and telling them to give me the clearance specified on the piston specs? The specs are very vague and seem quite generic, not to mention on the box it is clearly stated as 3.375 bore!!

Having said all that, I havnt got the tools required to measure the actual pistons accuratly enough, maybe they are sized so when the bore is 3.395 I do have 0.003 thou clearance.
The machine shop does have the actual pistons with them tho

 

[Frank Acampora]

Re: Down under rebuild of 90HP Force

Quit driving yourself crazy and overthinking the rebuild. Bore it to 3.395 and install the .020 oversized pistons. It will run well.

Pistons are cam ground with a major and minor diameter to account for uneven heating under running conditions. Perhaps the difference in clearance is because the factory and the piston manufacturer measured clearance at two different places. Who knows? Does .002 really matter? ---NOT!

 

[hundee r1]

Re: Down under rebuild of 90HP Force

Quit driving yourself crazy and overthinking the rebuild. Bore it to 3.395 and install the .020 oversized pistons. It will run well.

Pistons are cam ground with a major and minor diameter to account for uneven heating under running conditions. Perhaps the difference in clearance is because the factory and the piston manufacturer measured clearance at two different places. Who knows? Does .002 really matter? ---NOT!

yeh fair enough mate. Just thought I was being thourgh thats all. Dont really want a rattle motor nor do I want nipped up pistons and a failed rebuild

here is the paper slip that comes inside the piston box:



after reading this thread aswell:

Vertex piston/cylinder clearance?

the clearance maybe the same as the factroy if the table above is a radial measurement instead of overall.

thanx for your patience

 

[hundee r1]

Re: Down under rebuild of 90HP Force

Opps

 

[hundee r1]

Re: Down under rebuild of 90HP Force

Your folk are probs over hearing about this, but anyway:

Got my block back, spent a while taking the sharp edges off the ports. I also had the machine shop press off the upper crank bearing for me, I installed the new one using a hammer and suitable die.

Ive assembled all the pistons, pnwboat was indeed correct, using a punch didn't work removing the factory wrist pins, used a press at a mates shop = easy.
Checked the ring gaps,all in spec straight out of the box. Did notice that the lower ring had "top" written on it, but the top ring didn't. But the ring has a big taper on one face and this matches to the tapper machined into the piston ring groove, so this taper goes up.

Installing the wrist pin circlips into the new pistons caused me a lot of grief, but by the last one I worked out that using a 6mm Open ended spanner to send the clip home would've saved alot of tears and lost skin.

Installed my new crank sealing rings on and sat the crank in the block just to see how fiddly it is, took a bit but I worked out how to line up all the bearings on the locating pins.(thanks Jerry)

I also swapped out the upper ( easy) and lower ( pain in the arse due to corrosion) crankshaft seals that came with my kit.

Its all clean, and waiting for me to come home from work. I have a mechanic friend coming over tonite to over see the assembly of the case.

Wish me luck, and once again, thanx for all your tips. I just re read this thread and there is quite a few!!

 

[pnwboat]

Re: Down under rebuild of 90HP Force

Sounds like you are making good progress. Good luck!

 

[hundee r1]

Re: Down under rebuild of 90HP Force

Force case is together!!
Was pretty fiddly getting all the needle rollers in the big ends in, placing the crank, lining up all the bearing dowels and crank seals, but we got there. By the 3rd piston it was easy hahaha.
Torqued the case up and left it at that for the night.
Head still has to go on , along with all the side plates and ancillaries, but so far , so good !!

Couldn't have done it without your help and guidance guys!!

thanx a heap

 

[jerryjerry05]

Re: Down under rebuild of 90HP Force

Now take the top nut and put it on and turn the motor over.
Should move free with NO binding(plugs out).
If it drags at all then something's not right.
Like I talked about in another post.I bought new bearings for the connecting rod at the crank.
Put it together and it was too tight????
I looked and I checked and looked again and found the bearings were oversized/wrong and had to replace them.

 

[hundee r1]

Re: Down under rebuild of 90HP Force

Yep, did all that, all worked as it should

 

[hundee r1]

Re: Down under rebuild of 90HP Force

Guys, about to put the powerhead back on the motor, noticed this hole in the side of the case, I cant see in my left over bits anything that will bolt into here, its just under the exhaust cover plates:

 

[jerryjerry05]

Re: Down under rebuild of 90HP Force

That was for a pressure relief valve. WAS!!! Nothing there now.
They found that the old setup was clogging in salt water and it really wasn't necessary.
Get it running!!