A rider ...

[pd]

A question on carburaters :

 What is the original carb suppose to be ?

The carb that I have is a Tillotson MT9B . It is configured a bit different than what is shown in the parts manual , but I think I can make it work if it's not too far out of venturi range .
Does anyone know what the model #s on the Tillotson carbs indicates ?

[pd]

I rec'd my order of wood bleach ( Oxalic Acid ) and thought it best to test it before I subjected my fuel tank for rust removal .

I mixed a rather mild solution for the test . Here are some before and after pics :

Before :



After :



The parts looked almost this good after just a couple of hours bath , but I left them in over night to see if the deep reaches would be 'taken care of ' . The pulley was totally rusted .

I pulled the parts and rinsed them in a bath of hot water , then let them dry . The Oxalic acid seems to eat rust and leave a protective coating . I wiped some of that coating off the rear brake plate . Also note that the acid does not effect painted parts ( a big plus ) .

My tank is now filled to the brim with Oxalic Acid .

[pd]

I've read on this forum about both the pulley ( note the loosening instructions ) and the small wired anti vibration nut :

[LARRYBROWN]

  Hi there   ,  spongy stuff in the intake port drain is felt , to keep the outside air from entering the crankase ,  ( other end of hole exits between the two ribs that support crankcase .   the funny shaped port is supposed to prevent flooded fuel from filling op crankcase ) .   port timing can be altered , but there always will be consequences ,  earlier servicycle engines had more restrictive port timimg and benefitted the direct drive models by providing more low end torque at push start speeds ,  increased port opening time worked better for transmission models,    I have used coils from old style point system briggs engines , ( flathead twins ) and modified by square fileing the center hole to fit Phelon bikes  resist the temtation to spin and let the spary try to jump a big gap , this practice is detrimental to coil integrety ,  I have not experimented on wico replacements , ( yet ) though I have the winder and materials ,     fingers starting to hurt ,   bye,   Larry.

[pd]

"Hi there   ,  spongy stuff in the intake port drain is felt , to keep the outside air from entering the crankase ,  ( other end of hole exits between the two ribs that support crankcase .   the funny shaped port is supposed to prevent flooded fuel from filling op crankcase ) ."

Makes sense . Thanks .

I need to replace the crankshaft main ( left ) bearing . I can't seem to find a suitable replacement . Suggestions , Please .

[pd]

Is this the OEM piston configuration?

This is the only piston skirt I've seen that uses the slots instead of holes for transfer 'timing' or are the slots meant to aid in skirt lubrication ?



Those rings are new . You can see that they are not fully seated , yet . I haven't run the motor with them installed . Just a few revolutions by hand .

[admin]

Those slots may help aid lubrication, but I think they where put in to keep the piston from seizing when it got hot.  Wayne's replacement, as well as the ones that used to be available from Bob Kerr, had no slots.

Rick

[Ricks]

A question on carburaters :

 What is the original carb suppose to be ?

The carb that I have is a Tillotson MT9B . It is configured a bit different than what is shown in the parts manual , but I think I can make it work if it's not too far out of venturi range .
Does anyone know what the model #s on the Tillotson carbs indicates ?

The original was either an MT1D or MT22A.

Here is a little secret.  Dennis Carpenter Cushman sells a MT replacement carb.  This carb needs 2 simple modifications to work for us.  First, move the throttle linkage to the correct position.  This is as simple as loosening a screw and reindexing the arm.  Second, drill 2 more holes in the main nozzle.  The stock MT1D has 4 holes, the replacements, only 2.  Look in the simplex parts manual and it is easy to see.

The air cleaner bolt holes on the replacement carb are larger than stock, so either make something, or Wayne sells the correct ones and then the aircleaner bolts on like stock.

[Ricks]

Thank you for the 'invite' Larry . I may just do that .


The rotary valve is an interesting design also . I wonder if anyone has tried opening the crankshaft 'intake' hole to broaden or possibly quicken the draw time for fuel intake ?

Speaking of intake , what is the purpose of the hole at the bottom of the intake tunnel ? It angles downward to a hole inside the base mount 'towers' . It is plugged at the bottom with something fairly soft .

And what purpose does the screw just under the carb mount have ?

I have thought about opening the hole through the crankshaft, like porting a intake port, for more flow.

The angled hole was to help with flooding, or so I have been told.

As for the screw, I have no idea. Does not seem to do anything.  I thought maybe the hole was used as a locator in the machining process, then just filled with a screw because it was easy.  That's my story and I'm sticking to it until someone tells me better!!  LOL!!

[Ricks]

It's been about 2 weeks since I posted pics of my stator .

No one has commented on the ignition coil . I have to wonder if it looks like one of Wayne's 'new' replacements .

Sorry I have been off line for a while with the storm.  Wayne's replacement coil is a single output coil. I am currently running one in my 53.  I have had a NOS wico twin coil in there, and there is zero, nada, zilch difference in the way it runs.  Even simplex admitted it didn't do anything to help the engine run better, as evidenced by the fact that the last cylinders they made were single spark plug.

If anyone has knowledge of a coil that puts out more spark, please speak up.  Also, does anyone know where we can get our flywheels recharged? This would probably help get a stronger spark.

[pd]

I heard the island got hit fairly hard . Hope you and yours are fine .

I always figured the dual spark plug was an attempt at a cleaner or more complete burn . We know the oils of 50 years ago weren't as refined or developed as some of the oils available today . And , I'm not sure how the gasoline differs from then to now .

Larry Brown thought a flywheel with rare earth magnets might increase the coil output . I'd like to see the results of that experiment .


"As for the screw, I have no idea. Does not seem to do anything.  I thought maybe the hole was used as a locator in the machining process, then just filled with a screw because it was easy.  That's my story and I'm sticking to it until someone tells me better!!  LOL!!
"

I bet it was for fitting a nitrous setup . You know , for the racing circuit .

[pd]

What are the measurements for the main crankshaft bearing ? The bearing that is in my motor is a Hoover 205 . I'm told that it crosses to a 6205 , but , the 6205 seems to be about a mm to big on the outside measure .

Please and Thank You .

[Ricks]

What are the measurements for the main crankshaft bearing ? The bearing that is in my motor is a Hoover 205 . I'm told that it crosses to a 6205 , but , the 6205 seems to be about a mm to big on the outside measure .

Please and Thank You .

Pete, what is the width of your bearing? I think they used 2 widths over the years.  The earlier M engines used a 20.6mm wide bearing where as the later M used a 15mm bearing.  The problem I had is, I could not find the wider bearing in a single row bearing, like the original.  In a double row bearing, it is available and the part # is 5205.  I have never tried one as Wayne had a wide single row bearing for me.  I just called him, but he was not in to ask if he had anymore, or a part number, or if he had tried a double row bearing.  I will post an update after I speak with him.

As for outside diameter, they are 52mm, Inside diameter is 25mm.

A 6205 bearing would be correct if your original bearing is 15mm wide.


If you think your bearing is too large, it is like because you are trying to install it into a cold engine case.  NEVER, EVER POUND THE BEARINGS IN OR OUT OF THE CASE WITHOUT FIRST PREHEATING IT!  This can cause the case to split. The engine case must be preheated in an oven.  400 degrees for 15 minutes works.  The first time I did it, it stunk up the house, and I have been using the gas grill outdoors instead.  I just light half the grill and put the case on the other side, away from the flame.
The bearings will come out with some easy taps of a mallet when at proper temperature.  To reinstall bearings, I do the same, but I also stick the bearings in the freezer for a few minutes, and they slip right in with a slight tap with a block of wood.

[Ricks]

Update:  I spoke with Wayne, he has the wide single row bearings available.  He didn't know the part # cross reference.  I asked about the double row bearing and he didn't see why they would be a problem, said it would just be overkill.  We can get them for about $10 from http://www.thebigbearingstore.com/.

[pd]

Rick , from what I'm seeing the 5205 is 20.6mm wide because of the double row bearings . The 6205 is 15mm wide . Both have the same inside and outside measurements .

I haven't removed the original bearing , yet . But , it seems pretty obvious that the 6205 is too big just by looking . Note in the 2nd pic how the small dark line just under the new bearing disappears as it gets farther away from the point of alignment at the upper edge .





The 6205 is going to shrink that much ?