Which mounting points to use on motorcycle style engine?

[Aston jag]

i see your template reaches all the way over to the top mount. I wouldnt bother with that one and if you are, its easier to just get the lower mount in place, and build the top mount from the mount point on the engine up to the upper tubes below the seat.

your current location for the engine looks good. you have a small enough frame there that chain length shouldnt become an issue. again using a chain tensioner will solve a lot of problems when it comes to chain routing and keeping tension and keeping sprocket wear to a minimum.

if you want to move the engine forward some, you would be fine rotating the engine a few degrees to gain clearance. also, your intake a carb setup should be taken into consideration right about now. With the space in the frame you have, i would turn the intake around facing forward and mount the carb in the forward position. I am not sure what intake you have with your engine, but there are many different ones (from chinese quads) that position the carb in different places, before the starter, other side of the starter, or turned to the front like i recommended. You will want to mock it up though as some intakes will give you different carb angles, which is why you want to take that into consideration when making the mount.

also exhaust. i mean when building these kinds of things we always expect to have to make things "fit" by modifying, but trying to mount the exhaust before you finish the motor mount may let you position the mount to do less modification to make the exhaust fit, which will save you time and work


let me know if you need any more ideas. im full of them lol

Speaking of carbs, it seems to me the main concern is consideration of the float bowl, and how not being level would reduce the range of float functionality. I am glad you mentioned that. The intake manifold that came with the engine has the carb at about 16deg off horizontal, with the engine mounted parallel to the bottom frame rails. I don't understand why it would matter whether the carb faces forward or backward.

Regarding the exhaust, I don't know how similar this Loncin's connection is to other engines. It appears as though the engine end of the exhaust system will need a flange with the tubing extending something like 1-1/2" beyond the flange. The tubing beyond the flange has to fit into a sort of half-cylinder. Is that common among these sorts of engines? It looks odd to me and like it would tend to leak. But then, these engines are new to me, so I have plenty to learn.

 

[jdogg]

I am thinking about the placement of the engine, forward and aft, too. From what I have read on this forum some people have had trouble with keeping the front end on the ground with shifter bikes. What is yours like in that respect? If a problem, i wonder how much it helps to keep the engine forward.
Also, somebody pointed out to me how a failure of the rear chain on a jackshaft mounted brake system would cause a loss of brakes.

Mine isnt too bad with the gearing I have..........didnt seem too light in the front but my forks are thick......I think they weigh more than the whole frame!! :blink:

Yes the loss of brakes are possible with a jack shaft mounted brake....as little as I get to ride any of my minis I wasnt too concerned.......same thing with clutch mounted brake!

 

[ludicrous speed]

im sorta stuck in a similar place...
im trying to get my carb level,and my motor up,but it has a funky bump in the center of the bottom of motor.
i need at least another 4-5 degrees of tilt backwards to set carb right and have air cleaner.

heres my motor i dont know what it is besides chinese.
does it look somewhat like yours Aston?
it Was a dirt bike 250 cc that the frame and everything else broke on..
but i cant find any info on it and more importantly,how are you guys using the transmission?
my output shaft looks like this

 

[jdogg]

I hear daddy long legs add least 2HP..... just make sure you mount him counter clockwise on the output shaft and all should be good!! :laugh:

 

[Aston jag]

im sorta stuck in a similar place...
im trying to get my carb level,and my motor up,but it has a funky bump in the center of the bottom of motor.
i need at least another 4-5 degrees of tilt backwards to set carb right and have air cleaner.

heres my motor i dont know what it is besides chinese.
does it look somewhat like yours Aston?
it Was a dirt bike 250 cc that the frame and everything else broke on..
but i cant find any info on it and more importantly,how are you guys using the transmission?
my output shaft looks like this

Hey Ludicrous Speed, check out one of my pictures on my build thread:

http://www.oldminibikes.com/forum/projects-and-rides/133618-shifter-minibike-build.html

My engine, as you can see, is closer to horizontal. The sprocket floats on the splined output shaft.

 

[Aston jag]

I hear daddy long legs add least 2HP..... just make sure you mount him counter clockwise on the output shaft and all should be good!! :laugh:

Man, those California spiders are rough! Here on my side of the Cascade Mountains we don't even have poisonous snakes.

Is your rear wheel sprocket adaptor tight against the Astro wheel spokes, or did you use some standoffs to avoid that?

 

[jdogg]

Man, those California spiders are rough! Here on my side of the Cascade Mountains we don't even have poisonous snakes.

Is your rear wheel sprocket adaptor tight against the Astro wheel spokes, or did you use some standoffs to avoid that?

Hey Gary!! Yes I used some spacers.

 

[danbur55]

just remember the lock ring that bolts to the sprocket

Hey Ludicrous Speed, check out one of my pictures on my build thread:

http://www.oldminibikes.com/forum/projects-and-rides/133618-shifter-minibike-build.html

My engine, as you can see, is closer to horizontal. The sprocket floats on the splined output shaft.