Will I get my 100 ready in time for Taupo?

[Muciek]

What You think about this?



Here's link

[F5 Dave]

Mike has done it for me. He was DTIing it and boring then finishing it off in the lathe. Katie's crank came out spot on so I'm hoping this will be as good. No bush just bigger pin.

[F5 Dave]

Just got it back, apparently came in at .03 so that makes me happy considering the offset.

Now I just have to get my act together & sling it back into one piece.

Finishing the transfers is taking time.

[F5 Dave]

Well I should have done this days ago but with the will to live being drained out of me by work I've found it hard to get much done. So today with gusto I set in.
Start off by cutting a new centre gasket or rather 2 as I didn't like the first one. Then 2 base gaskets. Same reason. Pining for a std bike where you just order a stash of remade gaskets that fit straight up.


As I offer up the crank to the cleaned up cases I measure the divot cut into the Rhs seal run. Actually that will encroach one of the lip areas. Hmm, decide to fill the area with JB. When its dry I'll Polish it on the lathe. So another hold up.

I have left the barrel to get honed but there is more to do to try cup handle the transfers if only a little bit.


So will it be ready for Taumarunui?
I have a lap record to defend.

[Grumph]

Rather surprised you're using a center gasket Dave...My std practise for years has been to eliminate the gasket wherever possible.
Rub the cases on a flat abrasive board to true the surface and reshim the shafts accordingly. Three bond to taste...

Comes from doing too many Italian 4strokes which invariably develop a leak at the center case gasket.

[F5 Dave]

I actually run a super thick gasket for crank clearance.

[Drew]

I actually run a super thick gasket for crank clearance.

That seems like a very inaccurate practice, on a motor as highly strung as yours. Is there not a better way to do it?

Not giving you a hard time, it is structured as a sentence because I don't know the answer.

[F5 Dave]

They come std with a gasket & being a Honda it works well. I've just made
it twice as thick to give the relaxed clearance space on the rod (which widened the web slightly) to give more space to the mains. The case reed welded on means custom gasket.

[Drew]

On another subject, did you consider mounting the reed block at the front of your cases? Malcolm tells me that what looks like an engine mount on the front of an MB motor is in fact completely useless, could it be removed and have something similar to what you have as your inlet tract put there instead?

[speedpro]

I have a reasonable variety of alloy sheet from .2mm and on up thickness. I'm about to stack a pile together with thick bits each end, and cut MB100 base gasket shapes. I have been slowly going through the last stack I made.
You could easily cut an alloy sheet to the correct shape and assemble it all with Yamabond each side. I like the alloy base gaskets over the paper type as the thickness is stable.
It would work for the centre gasket as well. You could of course make it out of copper and leave it protruding on the outside like a cooling fin. It could also be left protruding on the inside in the gearbox to extract a bit of heat out of the oil which is bound to be getting a bit hotter than Mr Honda expected what with extra power and clutch abuse. A copper gasket along similar lines on the clutch cover could also be beneficial heat wise.

[F5 Dave]

Drew, I've seen that done on a sidecar, but it directs the flow through the crank which is no good. Plus my radiator, pipe & front wheel lives there.

[speedpro]

On another subject, did you consider mounting the reed block at the front of your cases? Malcolm tells me that what looks like an engine mount on the front of an MB motor is in fact completely useless, could it be removed and have something similar to what you have as your inlet tract put there instead?

The cylinder extends down from the gasket surface and effectively blocks any path to the area above the crankshaft but below the cylinder. There is also a bolt above and below that joins the crankcases that would inhibit placement. I've had a look at that and decided it wouldn't be worthwhile due to limitations.

[F5 Dave]

I use a .3 paper base gasket

[speedpro]

With this chatter about boring crank webs I've been thinking that instead of working to reduce the stroke why not increase the stroke, run 52+mm pistons and use a 24mm carb into a plenum.
With a stroke of 51mm(+1.5 over stock) and 52mm piston capacity is 108cc. If you have a rod with a 22mm pin and increase the stroke the full 2mm with an 1mm offset bored pin hole you get a stroke of 51.5mm and running the same 52mm piston end up with the engine at 109cc and 53mm piston makes 112cc and if you want to really push it go to 54mm piston for 117cc.
Rob has already proven that the 24mm carb is not actually a restriction.
You could have a velocity stack of the exact right length entering the reed block dead straight and the entry to the velocity stack would be the bottom of the plenum so anything that dropped out of suspension still went into the engine. Either that or have a small diameter hole in the base of the plenum that drained down into a similar hole in the cylinder or crankcases.
This would also have the benefit of not having to try and maintain some sort of acceptable mounting angle for the carb as it could be mounted at any angle feeding the plenum.
The plenum could also be an odd shape to fit around frame tubes without having too adverse an effect.

[F5 Dave]

The 'why not' might be the proximity of the rod to the cases. Already it almost rubs at BDC & needs a tickle. The metal isn't thick enough for a trench as we put on RZ cases. Some serious rework may resolve that.