Morini S6-S Big Bore Build

DFlanagan · Oct 20, 2011

Hi all!
I have sold my first build and now I am starting on my next kick _ss build. I have purchased a Morini S6-S motor, had it bored out, and re-sleeved. Then sent to me. I am told that the motor will be producing 12+ hp with no port work! When I positioned the motor on the bike, I choose that the bike cranks do not have priority on the placement of the motor. The motor sets nice in the frame with the exhaust system in place. I choose to make three motor mounts out of 3/16" plate steel. To hold these motor mounts in place, I am using 1 and 1/8" U-bolts that will be welded to the metal frame. I have positoned the engine dead center on the frame.
Here's a couple pics of the build. As I move further in the build, I will post more pics.

flatblack · Oct 20, 2011

Motor envy...

Goat Herder · Oct 20, 2011

How about pictures of the bore?!! Inquiring minds wanna know! How much didja bore it out by? Was balancing the crank a prob? I might wanna try this,,,, be kinda cool to have a sleeper motor

Easy Rider · Oct 20, 2011

I heard Polini and Malossi makes a 70cc big bore cylinder.

Goat Herder · Oct 21, 2011

This is the stuff that keeps me awake at night

FarRider · Oct 21, 2011

Easy Rider said:
I heard Polini and Malossi makes a 70cc big bore cylinder.

70cc big bore cyl? I think im in love.
FR

FarRider · Oct 21, 2011

DFlanagan said:
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Hi all!
I have sold my first build and now I am starting on my next kick _ss build. I have purchased a Morini S6-S motor, had it bored out, and re-sleeved. Then sent to me. I am told that the motor will be producing 12+ hp with no port work! When I positioned the motor on the bike, I choose that the bike cranks do not have priority on the placement of the motor. The motor sets nice in the frame with the exhaust system in place. I choose to make three motor mounts out of 3/16" plate steel. To hold these motor mounts in place, I am using 1 and 1/8" U-bolts that will be welded to the metal frame. I have positoned the engine dead center on the frame.
Here's a couple pics of the build. As I move further in the build, I will post more pics.

What size is that frame? It must be a 23 incher!
Me likey...
please keep posting
FR

magrider · Oct 21, 2011

Is there another rear engine mount just under the carb? If so, I would attach a forth mount to the seat tube.

DaveC · Oct 21, 2011

The motor looks to be tilted back quite a bit, think there will be a problem with the clutch oil level?

DFlanagan · Oct 21, 2011

Goat Herder said:
How about pictures of the bore?!! Inquiring minds wanna know! How much didja bore it out by? Was balancing the crank a prob? I might wanna try this,,,, be kinda cool to have a sleeper motor

The company that I purchased my engine from is called
Rob's Racing Engines(COMPLETEENGINES). He took care of the boring and re-sleeving work. Rob did supply the piston. The piston is 44mm. Brings the cc's up to 63.43cc. He did not balance the crank.Rob builds pro circuit motors for dirt bikes and quads. He has taken many national championships with this setup that he has done for me. Another race team has even protested against him stating there's no way that Morini engine is that fast and under 70cc. Give him a call. He'll take care of you. I haven't mentioned my exhaust system yet....

If you got any more info about that carb. Let me know.

David Flanagan

DFlanagan · Oct 21, 2011

DaveC said:
The motor looks to be tilted back quite a bit, think there will be a problem with the clutch oil level?

You know that's a good question. I'm going to have to research this and see. Can't be having a burning clutch. I'll let you know what I find.

David Flanagan

DFlanagan · Oct 21, 2011

FarRider said:
What size is that frame? It must be a 23 incher!
Me likey...
please keep posting
FR

I measured the frame at 21". It took awhile to find a mountain bike frame big enough to have some room to play around in. It also had to be a metal frame.

David Flanagan

DFlanagan · Oct 21, 2011

magrider said:
Is there another rear engine mount just under the carb? If so, I would attach a forth mount to the seat tube.

The motor does have four mounts on it. I wasn't sure if it would be necessary to have four engine mounts that where welded to the frame? I thought three welded mounts would do the trick.

DFlanagan · Oct 21, 2011

Easy Rider said:
I heard Polini and Malossi makes a 70cc big bore cylinder.

This is not a big bore kit. Rob at Rob's Racing Engines has found a piston that works well in these motors.

magrider · Oct 21, 2011

All I'm saying is those Italian engineers have 4 mounts there for a reason. If it didn’t need it, it wouldn’t be there.

Goat Herder · Oct 22, 2011

DFlanagan said:
If you got any more info about that carb. Let me know.

David Flanagan

Thanks for the info! This bored jug kit sounds very exiting. Gonna look into it next week I wanna try one. As for the carb I think we are at similar elevations from sea level and I think you will like this arrangement a bunch? Posted here for the 21mm and 19mm . http://motorbicycling.com/f47/jet-sizes-s6s-carb-34044.html

magrider said:
All I'm saying is those Italian engineers have 4 mounts there for a reason. If it didn’t need it, it wouldn’t be there.

I have thought about this a few times. I think it is coincidental to different motorcycle manufacture arrangements dunno? My bike got's just one of those used the bottom one ,the jug bolt last the front bolt and has worked perfectly. Solid as rock no bolts have ever vibrated loose or anything.

DFlanagan · Oct 22, 2011

DaveC said:
The motor looks to be tilted back quite a bit, think there will be a problem with the clutch oil level?

Thanks for bringing that to my attention! I will have to re-position my motor. I will post some pics when its fixed. Let me know what you think.

DaveC · Oct 22, 2011

At least you have plenty of room to do that. Most bikes are really no good for a Morini mount due to the center exhaust port but that bike has lots of room.

cory151 · Oct 22, 2011

I run three welded mounts with zero issue on a S6-S although the thickest pieces of steel on the entire bike are the mounts.

DFlanagan · Oct 24, 2011

After talking to a Morini distributor and two motorcycle shops, they said that there would not be a problem with running the motor in the postion that I mounted it in. They did say however that if the clutch was hydraulic there would be a problem with where the clutch fluid would rest. With that said, I still remounted my motor. I moved it 2" down in the bottom front mount, 3" forward on the top mount, and .5" up on the back mount. Here's a pic. Not that it's important or anything but I did find out some info on how to mod the head on these at this altitude to get them to scream.

I also made some rear wheel backets to keep that back wheel on when I'm doing those powerwheelies that are so famous now.

For my exhaust system I went with a Pro Circuit exhaust pipe that is for a 04 LEM 50. This pipe is made for this motor. I am using a R304 Pro Circuit Silencer for the silencer. After re-mounting my motor, I had to have the exhaust pipe bent to go over the back tire instead of shooting right up my _ss! One of my buddies has some exhaust cloth wrap (black). He's going to hook that up for me so I don't burn my leg and to hide the finish that is now flaking off because of the bends!

Hopefully the motor mounts are welded tomorrow. Stay tuned..

Morini S6-S Big Bore Build

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