Gravity or siphon gas line

fatdaddy said:

I still think metal to metal is best, BUT, if you dont get both mounts flat, flat, flat, on the frame, yer gonna wind up with a corner or edge digging into the frame and it will break.
fatdaddy.

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It all starts where the back engine mount meets the seat tube.



This mount is what makes the engine one with the bike.
It is responsible for handling 100% of the drive force, and ~30% of the twist force the engine will be throwing at the bike frame.

The entire surface of the engines back mount block simply must meet 100% against the seat at a 90 and tight enough to hold the engine in place with no front mount.

The engine wants a ~65-75 degree seat post angle to fit in and operate as designed.

Just to be clear, if you have a different angle you can't make up for it by shoving filler in between the mount.

If that is the case make a new rear back block and back clasp or get it on right and make up for everything else like exhaust, intake, front mount with mods.


The front mount is only responsible for the remaining ~70% of the twisting force, but that is a big force.

Stock front and rear mount blocks are only 1 1/8" wide, plenty enough to transfer power in a horizontal line but not so hot at preventing the engines desire to twist and pull to the left.

I like a muffler clamp and plate pointing up the downtube best.
I won't go into the geometry of how to counter a twisting force inside of fixed structure, just that it is easy to test.

TIP:
If you are worried about you frame breaking at the seat post at the motor mount just cut ~3" off the bottom of your seat post and shove it down the seat post to where your rear mount attaches.

NOTE:
You don't have worry about any of this with a shift kit.
It gives the back of the engine a 2 point muffler clamp connection ~10" apart and a good muffler clamp front mount to fit your downtube.
In short, they become 'one with the bike' like nothing else.

Just tips from a guy that sells to the public and doesn't cut corners on quality or safety for cost.
It's right or it's not, and I won't sell not's, which reminds me of an old joke...

A piece of string goes into a bar and orders a beer.
The barkeep said "I'm sorry, we don't serve string here, you a piece of sting right?"
'No' said the string, 'I'm a frayed knot so give me the beer'.

I've used a seat post shoved down the tube to repair a broken seat tube, Ya shove in a snug peice of post then weld it up. It makes a very secure repair.
fatdaddy.

fatdaddy said:

I've used a seat post shoved down the tube to repair a broken seat tube, Ya shove in a snug peice of post then weld it up. It makes a very secure repair.

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My point was to not have to repair a broken frame.
Mount the engine right and you will never have to.
If that involves a piece of seat post tube shoved down to the mount point so be it.
Just make sure the back motor mount is one with frame and go from there.

KCvale said:

My point was to not have to repair a broken frame.
Mount the engine right and you will never have to.
If that involves a piece of seat post tube shoved down to the mount point so be it.
Just make sure the back motor mount is one with frame and go from there.

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Ditto..!

Front mount being correct is important, but the rear mount being "one with the seat post" is very critical and will be the straw that broke the camels back if not done right without rubber or things similar between engine and frame.

Some will say to wrap the mount area with tape or some other material to "protect the frame from vibration". I maintain that if the clamp fits right and is tight, it can't/won't move so therefore no vibration damage will occure.

Tom

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Voodo???? You mean the vibration from the motor magically disappears ?
Or: you have now turned the bike frame into a large tuning fork.
Where the vibration from sed motor is free to attack the frame at it's weakest point.
Say, fender stays or rear down tubes, rear welded on racks on some Huffy's and Schwinn's, ETC.......All prone to failure on gas bikes.
Oddly enough, you rarely if ever see those same type of failure on non gas bikes.
Aluminum is more prone to harmonic stress failures than steel.
But steel still falls prey to it.....

I agree with 2dore on the custom mounting method. As well as his point several posts beck concerning drilling the frame . BAD IDEA.
Exhaust clamps should also be avoided , ( IMHO ) as they are designed to crush the material they are applied to ( that is how they create a seal on exhaust tubing ) .Generally a bad idea on a bike frame.
IMHO , the best method to mount sed motor would be the method used by Hawk. Post and flange.
Not every one has the means to fab the mounts. I understand......
If one must clamp ( as I do on cruiser frames ) A good isolator that allows for a solid mount is best....
I know , I know , it goes against all that most of you seem to believe.
It's the engineer in me. Over engineering something is rarely a bad thing .
Under engineering leads to disaster.
I hope this clarifies my thinking and methods here.
As was stated earlier. Build the Damn thing however you like.
It is after all a reflection of you and your abilities. And is your machine.
Just try to be safe out there.....

boxcar said:

Voodo???? You mean the vibration from the motor magically disappears ?
Or: you have now turned the bike frame into a large tuning fork.
Where the vibration from sed motor is free to attack the frame at it's weakest point.
Say, fender stays or rear down tubes, rear welded on racks on some Huffy's and Schwinn's, ETC.......All prone to failure on gas bikes.
Oddly enough, you rarely if ever see those same type of failure on non gas bikes.
Aluminum is more prone to harmonic stress failures than steel.
But steel still falls prey to it.....

I agree with 2dore on the custom mounting method. As well as his point several posts beck concerning drilling the frame . BAD IDEA.
Exhaust clamps should also be avoided , ( IMHO ) as they are designed to crush the material they are applied to ( that is how they create a seal on exhaust tubing ) .Generally a bad idea on a bike frame.
IMHO , the best method to mount sed motor would be the method used by Hawk. Post and flange.
Not every one has the means to fab the mounts. I understand......
If one must clamp ( as I do on cruiser frames ) A good isolator that allows for a solid mount is best....
I know , I know , it goes against all that most of you seem to believe.
It's the engineer in me. Over engineering something is rarely a bad thing .
Under engineering leads to disaster.
I hope this clarifies my thinking and methods here.
As was stated earlier. Build the Damn thing however you like.
It is after all a reflection of you and your abilities. And is your machine.
Just try to be safe out there.....

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Not to flame or come across in a bad way here at all, but I have to just kinda laugh when I see how you continue to disagree with all of us that have been building these bikes and working with them for several years as if you know more about all of this than any of the rest of us who have way more experience with them than you do.

We've proven over several years and thousands of miles of running these china girl engines what has worked out great for us and many or most like myself have never had one single frame failure of any kind even on high revving builds that can run for miles and miles at 40+ MPH.

Of course over engineer and build your however you want, but the repeated bashing of good solid proven advice and techniques that have been proven to work for many years of riding in some cases of our bikes is just getting a little old to be real honest with you, and by the way, the muffler clamps work great, yes they shouldn't be tightened to the point of crushing the frame, but many of us have used them for a long time just good and tight against the frame and use some loctite on the threads to prevent the nuts from backing off in time from vibrations.

Your honestly beating a dead horse here boxcar when you keep knocking the proven method of mounting these engine solid and secure to the bike frame with no other materials between the two.

Peace, map

2door said:

This is turning into an interesting conversation with some good points being addressed on both sides. No arguments, no hostilities, just good information for the new builder to see and read and digest.

I'm going to throw another idea out and I'm interested to see what Boxcar thinks about it.

The front engine mount pictured below is one I built for a Shwinnn Jaguar. The bike has two thousand miles on it and has never given me a moments problem.

You've all heard me preach about the evils of resilient mounts and this one, oddly enough, might by some defination fall into that catagory.

The main section is welded to the frame. It has a 3/4" pin, or boss that protrudes up through a urethane bushing, which in turn inserts into the engine mount saddle. The bushing has a durometer of 100, which is pretty darn firm. You can't dent it with a screwdriver blade. It's designed to be used in automotive suspension applications.

Resilient? Probably, by some standards. It's not metal but it's not rubber either. I cannot say with any degree of accuracy that it 'eliminates vibration' but it does isolate the engine from the frame with a material that probably has some absorbtion qualities.

The rear engine mount is pure kit style, saddle and clamp with the only change being I used Allen head capscrews as opposed to studs and nuts. Oh, and that shiny aluminum cap is just for looks. It serves no real purpose except to tighten things together, and look pretty.

Okay Box, what do you say?

Tom

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Oh yeah no hati g are hostility from me either and I apologize if I came a ross that way.

Dang Tom I didnt know you had made that mounting on the old Jag bike, I have planned to make a similar type mount myself, Im not sure that type set up wouldn't for back of engines as well as the front if it was designed right and the right materials used.

nice looking mount.

Now that's a nice mount, and there IS a big difference between a poorly engineered piece of rubber where it doesn't belong and a nice solid chunk of urethane on a welded mount, the urethane can't really move and the seatpost mount is nice and solid, as long as there's no tension or stress on that front mount it should work as well as solid to the frame... The easiest way to know it works is by riding it full wide open... if you don't feel any vibes at the grips or seat, it's working. If it feels like you got a pair of vibrators in your hands going down the street, well... it's not working.

Personally on mine I cut a slot on each side of my frame's down tube and slid in a piece of 1" wide 1/8" thick flat stock thru the frame then welded it into the frame so the front of the engine bolts directly to the frame. The rear mount uses 2 of the aluminum mount blocks instead of that flimsy steel strap that bends as you tighten the bolts down so it's a rock solid fit on both sides, the engine will Not move no matter how hard you try to push it side to side. As for vibration... There's none at the bars or seat at 9500+ rpm.

Nice mount.Well executed.... I like it allot. Sway bar bushing ?
One could expand on it by adding a second tab . It would be very like a gumball mount on some Harley's.
And to respond to you Map.
As you may have guess'd I'm an engineer. An automotive engineer ( retired ).
I have been designing and building everything from motorcycles to to boats , and just about everything in between. Excluding aircraft. For 35 years.
Owner : Resurrection Iron Works, We restore vintage vehicles . A great retirement...

When I was younger I raced both MX and GP cycles as well as sports cars.
I am well versed in 2 strokes 4 strokes big blocks, small blocks etc.
A motorized bike is kind of a no brain'r .... Please, take no offence!!!!! None intended.
I'm not looking to flame any one or get flamed. If I was i'd go to Pirate off road....
I'm also not looking to massage my ego... My wife does plenty of that.
But I have noticed a trend here.
Warnings from the masses to "not run fenders or to avoid certain bike frames " because of what are obvious stress failures caused by vibration.
The majority of these bikes , I have to assume ,( because it seems to be the preferred mounting method ) are solid mounted builds.
It's in my nature to solve problems not ignore them....
I live in Oregon . It rains here , allot , I like fenders.
And while I am not a huge fan of the " Panama Jack style bike " some here are.
I'm pretty sure you get the idea why I am making the argument that I am now, and don't need to repeat it yet again.
Consider it a good alternative to the poor guy who can't hold on to his handle bars and has tried everything else , save a new crank.... Not a bad idea, in this case.
This has been , and i'm sure will be a very interesting conversation.

boxcar said:

Nice mount.Well executed.... I like it allot. Sway bar bushing ?
One could expand on it by adding a second tab . It would be very like a gumball mount on some Harley's.
And to respond to you Map.
As you may have guess'd I'm an engineer. An automotive engineer ( retired ).
I have been designing and building everything from motorcycles to to boats , and just about everything in between. Excluding aircraft. For 35 years.
Owner : Resurrection Iron Works, We restore vintage vehicles . A great retirement...

When I was younger I raced both MX and GP cycles as well as sports cars.
I am well versed in 2 strokes 4 strokes big blocks, small blocks etc.
A motorized bike is kind of a no brain'r .... Please, take no offence!!!!! None intended.
I'm not looking to flame any one or get flamed. If I was i'd go to Pirate off road....
I'm also not looking to massage my ego... My wife does plenty of that.
But I have noticed a trend here.
Warnings from the masses to "not run fenders or to avoid certain bike frames " because of what are obvious stress failures caused by vibration.
The majority of these bikes , I have to assume ,( because it seems to be the preferred mounting method ) are solid mounted builds.
It's in my nature to solve problems not ignore them....
I live in Oregon . It rains here , allot , I like fenders.
And while I am not a huge fan of the " Panama Jack style bike " some here are.
I'm pretty sure you get the idea why I am making the argument that I am now, and don't need to repeat it yet again.
Consider it a good alternative to the poor guy who can't hold on to his handle bars and has tried everything else , save a new crank.... Not a bad idea, in this case.
This has been , and i'm sure will be a very interesting conversation.

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i understand completely being I like to solve problems as well, but many of us give the blanket warning on mounting and fenders for the exact reason Tom described in his post, not many people who get into this hobby have a way to do some of it right so that its safe and reliable so we try t9 keep it simple, I even keep my builds simple so I can relate what I do better to the beginners here that can only do simple builds for lack of tools and experience.

I take a step back here and apoligize for coming at you a little strong in earlier post, we have dealt with so many people in the past on here that try to steer newbies in the wrong direction so some of us get a little up in the air after a few post that are contrary to what we try to advise for the reaso s already covered.

Thank you for your input and I know theres no doubt many of us here can learn from your personal experience in what you've done in life and hopefully some of the ideas you'll possibly share with us on here.

Shan

Really good stuff fellows!
Fly

Look up Whizzer gas tank on ebay. Much sturdier.

Yes the Wizzer tank is a good alternative as well.
A bit large at 1.2 gal (JMHO) but has a far better mounting system.
Unfortunately it wont fit on as many different frames as the CG kit tank due to the tunnel
dimensions.
I'm going to start a build on a Dorado Sherpa next.

Will be using a Honda Mini Trail 50 tank.



Should be a fun build. It will be a hunting bike for my Future sun in law...

KCvale said:

My point was to not have to repair a broken frame.
Mount the engine right and you will never have to.
If that involves a piece of seat post tube shoved down to the mount point so be it.
Just make sure the back motor mount is one with frame and go from there.

Click to expand...

And a great idea it is KC, But most wont think to do it or think it unessesary untill its too late. I think its a good idea and I still haven't done it to my own bike. Seat post tubes DO break, but in over 10 years of building I've only seen one. Two if ya wanna count the bike that got hit by a car. I'm just sayin, It also makes for a pretty good solid repair if needed. I've seen a lot more front downtubes break, And I still dont have a good way to repair those. welding works but weakens the area AROUND the weld and sure to break again. I usually junk the frame and start over.
fatdaddy.

waynestore67 said:

Look up Whizzer gas tank on ebay. Much sturdier.

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Ya, but a bugger to mount if you have a rounded top bar.
This is a Wizzer tank on a 29" Macargi sporting an HF 86cc 4-stroke.
Note the long spacers and M-clamp grip part I had to use to attach it.



Doable, just awkward.