How To - Motor Prep

Parts Needed, Tools Needed, Step-By-Step, Notes, To Paint or Not, What Do You Do First?, Head To The Machine Shop, Back From The Shop, Paint Prep, Final Prep

Topic:                           You decided to rebuild your motor. After disassembly and de-greasing, what should be done to get motor ready to assemble?

Expertise Required:      Intermediate

Estimated Time:            Depends on what you plan to do

Parts Neeed:               You will need the following parts:

      • Your brain

Tools Needed:             You will need the following tools:

  • Metric
  • Amellican

Step-By-Step:             Here's step-by-step instructions on how to get it done:

  • Step One - Remove the pump/ski from the bike - it will save you hours. Before you do, reach in and see if there's excessive play in the shaft (that would allow the impeller to contact the wear ring). It might be time to replace the nozzle bushing and seal.
  • Step Two - 


Saltwater use dictates that all raw aluminum surface need protection. Not so necessary on the impeller but very necessary for the pump and nozzle inner surfaces. Here's some of Wbbrian's work

To Paint or Not:              If you plan to paint your motor, you'll need to either remove the old paint, or scuff it up enough to get new paint to stick. Be aware that the stock paint (epoxy?) is very durable and it's a sumbitch to remove. The ultra heavy duty epoxy remover/stripper works OK, but you'll have to do 3 or 4 applications and use a wire brush, toothbrush and other things to try to dig all of the paint out.

You could also bead-blast the parts but you must be aware of the following:

a. Glass beads won't do anything but rough-up the stock paint

b. Aluminum oxide will cut it, but you need to use at least 90 psi. It also wears out quickly. Also, you need to put a bolt in every threaded hole prior to blasting. If you don't you'll spend DAYS trying to get the grit out of the holes. This is critical - especially on head-bolts and crankcase bolts.

c. Don't even think of glass bead-blasting the combustion chambers. It'll work great, but probably never get all of the particles out.

What Do You Do First?:    You need to do things in the proper order, or you may have to repeat a few steps. If you plan on cleaning-up the ports, you need to do that prior to boring the cylinders. All grinding, chamfering, re-shaping needs to happen first.

If you are not going to have the block decked, then take the time and LAP it. This will ensure that you have a nice, clean and flat surface for the head gasket to seal against. Same goes for the cylinder head - if it's not headed off to the machinist. Here's some lapping pics.

Continue to lap until the surfaces have a completely dull finish. Any low spots will be immediately visible. Here's one here.

After a while you'll end up with a good finish like this:

Head To Machine Shop:   Drop CLEAN PARTS off at the machine shop with clear and concise directions on what you want done. He/she will need to know how much clearance you need on the pistons, how much you want to mill off of the top of the deck, and how much to mill off of the cylinder heads. Have that info ready before you show up.

Most machine shops don't like dirty/greasy parts - nor do they like gritty ones (glass beads, porting dust, etc.)

While the parts are off at the machine shop, you can take care of more prep work - things like this:

a. Fasteners - it's especially important that they have clean threads (so you can get correct torque values). Also, you need to figure out how to get all of the corrosion and paint off of the heads/washers. Bead blasting works but so does a vibratory tumbler.

b. Brackets, lifting lug, intake, and magneto cover. If you are painting these, then you need to get them down to bare metal and ready for primer.

Back From The Shop:

Here are two 60 HP cylinder heads that have been milled - one more than the other.

You got your block and maybe cyl. head back from machine shop and they are probably covered with a light layer of oil. If your cylinders were bored they had better be covered with a layer of oil. Run a rag through each bore paying special attention to the edges of the ports. A good machinist will chamfer all of the edges after boring - but it's a good habit to check them for yourself. Use a small file to dress any edges that feel sharp and could hang a ring. Now it's time to give them a bath in degreaser and/or good soap.

I use the Old #99 (red soap) from Lowes for this step. It's a strong soap that cuts grease and rinses clean exceptionally well. Warm/hot water is the combo that works best. I think the heat helps the metal loosen it's grip on any particles and/or oil.

Note: Once you rinse your engine block you need to wipe the cylinders with oil immediately. They will rust before you can turn around and say shazam!

Paint Prep:                     Your engine and head need to be completely dry prior to painting. I like to give them 24 hours after the last rinse with water prior to painting. While waiting for things to dry out completely, it's a good time to mask off anything you don't want painted with primer and/or final color.

Primer - I use the Zinc-Chromate primer that's specified for aluminum engines in a marine environment. It's expensive but works great.

Final Color - you can use everything from top line automotive (high heat) base coats to rattle-can paints. One of the more interesting is the "hammer" type of finishes. Kind of a granite look.

Another interesting finish is wrinkle black:

Finally - the Yamaha Blue is an excellent choice of colors:

Once everything is painted, it's time for the final cleaning and prep.

Final Prep:                     You need to be thorough when prepping a block for assembly. Here are the things I do (in order).

a. Run a tap through all threaded holes. Pay special attention to the Head Bolt holes and the Crankcase Bolt holes. Never use a power drill for this step - even if you turned the clutch down low. You'll break one of the smaller taps off in a hole - ask me how I know.

b. Grab your countersink bits and make a pass across the top of all bolt holes - especially those on any machined surface. This helps put a chamfer on the tops of the holes - and minimizes the chances of any crack starting. It also helps the other holes (where the surface wasn't machined) remove any "ridge" that may have been created if the fastener was overtightened (pulled the threads up). Only takes a minute or two. Here's a pic of a hole that was missed at the Suzuki Factory.

c. Time to clean up the port tunnels. Take a cotton rag (old WHITE t-shirts work great) and a coat hanger. Shove the rag through all of the port passages and work back-and-forth. Continue this until rag comes through clean. Continue this for all of the ports on both cylinders.

d. Time to prepare the cylinder bores. Take a cotton rag and spray it with carburetor cleaner and run it through the upper bore. Continue to do this until it comes out clean. Amazing how much "grit" there was even after the cleaning right?

e. Once they are clean, apply a light coat of oil to the cylinder walls to prevent rusting. WD-40 will work good too - and spray a little through the port passages too.

Now you can get your parts laid out, get new seals put in the little aluminum housing and get ready to assemble your motor.

If you are gonna do a lot of motors, it's suggested to have 2 sets of tools - one set for disassembly and one for assembly. Or if you are like most of us . . . just clean all of your tools (especially sockets) really well prior to assembly.





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