Motor Building Secrets

[Morgan]

So inspite of being knee-deep in work right now I thought I would jump on here and ask you guys a few questions. Who here would be interested in learning some more about building motors and learning new things about how to set deck height, clay checking, cam timing, etc.

 

We had a couple customers recently complain about our CNC head, but neither could tell me where the deck height was set, where the cam timing was set at, where the ignition timing was, NOTHING! Bugs me beyond belief. I walked one guy through all the small details that all add up when building a motor and guess what, motor went from 56 to 62 as a stockbore.

 

Motors are all about components used, and how they work together, the numbers will always reflect that.

[F-Red]

Please, be the Professor. How would you indulge that information?

[Loud450man]

sure all the info helps!

[Big D]

Here to learn :gr_cheers:

[El Mamito USMC]

im willing to donate my atv to be the test subject for this class.. let me know and ill drive it all the way from Las Cruces to Phoenix.. :wavey:

[TP Racing]

:metoo:

[Baileyguns]

Is a frogs ass water tight?? Does a bear shit in the woods?? Do we want to read good tech???

 

YES, YES and YES!!

[Burke]

This would be great info to have

[OTMTRX]

Is a frogs ass water tight?? Does a bear shit in the woods?? Do we want to read good tech???

 

YES, YES and YES!!

 

:stupid:

[StonedInNy]

All 3 you mentioned morgan would be great to know for us backyard mechanics. Thanks.

[alanbmx]

I am kinda slow I need pictures:metoo:

:secret2:

[bvet4dog]

beginner here. Has some tools and can borrow some technical tools. I'm down! heavy pics and tech write ups should do the trick for us.

 

If this is not a place for a beginner to learn.... i'll donate my bike and i'll wait to have it returned here with some love done to it

[want2bfast]

Lets get to posting...

[Zibilich]

awww yeaa im all eyes!

[ridinredjav]

and ears!

[chronicsmoke]

:smokin::popcorn:

[Guest Deven]

Morgan has been VERY busy lately. Im sure when he gets some free time he will chime in here and post up.

 

Lots to learn from someone who makes tons of power out of the Hondas and other machines.

[Zibilich]

Im sure hes in the works of getting something together for a copy/past ordeal.

[Morgan]

Finally had a little time to get some of this together for you guys. This motor is for one of my QuadCross Pro riders that we just finished up, so here goes...

 

Disclaimer: The deck height was already set on this motor before I remembered to have someone take pics as it went together, so I put a couple base gaskets back under the cylinder to simulate an incorrect deck height.

 

Setting the deck height: Install the base gasket with the alignment dowels on the cases, and install the piston onto the rod. Next, slide the cylinder on, rings are not needed at this point. I use a couple old wrist pins to tighten the cylinder down to ensure that the cylinder is nice and flat.

[Morgan]

Next, take out the timing plug on the clutch side cover (10mm allen head) and you will be looking for a punch mark on the crank gear. Rotate the crank with an 8mm allen to align the punch mark with the arrow on the side cover.

[Morgan]

Now that the motor is on TDC we will measure the piston on the intake and exhaust sides. When measuring the intake side, push down on the exhaust side, to account for piston rock. We shoot for .040 total and that includes the .027 OEM or Cometic style MLS head gasket. So, we want the piston to be roughly .013 in the hole. I don't see any reason to run it any closer than .040, you decrease Piston to Valve clearance, increase the chance of the piston hitting the head, which will break the rod, and rod stretch.

 

We use a set of digital calipers, Vernier or dial calipers, and a depth gauge will work fine as well.

[Morgan]

This illustrates an incorrect deck height at .041 on our calipers. We want .040 total so we know our current deck height is .041+.027 with our headgasket. With .068 we now know that .028 needs to come off the bottom of the cylinder for a correct deck height measurement. At this point remove the cylinder, and find a local machine shop that has means to cut the bottom of the cylinder. Do not try to cut the top of the cylinder, it will chip the Nikasil.

 

Chucked up in the lathe to cut and after cutting we smooth out any sharp edges with a piece of Scotchbrite.

[Morgan]

Re-install the cylinder in the same order as before, tighten down, and measure the deck height again. This time we come up with .013 on our calipers. We add the .027 for the headgasket and wind up right where we wanted at our .040.

 

The usual amount removed from the bottom of the cylinder is .010-.015 for most pistons depending on manufacturer, please remember I added base gaskets to get the illustrations.

[Morgan]

Now that our deck height is set we can move onto clay checking the motor. This step is very important, none of us want to see the valves throw a party in the combustion chamber. We clay check with an old headgasket to get a more accurate reading, and new headgaskets should not be torqued down numerous times.

 

We have our Demon Pro head all shimmed up and ready to install on the motor with running lash .006/.009. Shimming a new head on the bench is always recommended if possible to avoid dropping shims down into the cam chain galley. For this head we will be running/clay checking with the Web 208/921, 36 Del West flat face Ti and Ferrea 31 stainless exhaust.

[Morgan]

Place a small piece of modeling clay or Play Doh in the valve pockets of the piston. Overlap the clay over the edge of the valve relief to ensure that your piston will clear oversize valves if you are running them. Spray a small amount of WD-40 or oil on your finger and coat the top of the clay so that the valves leave their impression in the clay, but do not pick it up off the piston.