66 2-stroke, Schwinn Meridian Trike, looking for an alternative engine! Ideas please!

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turbobuick1

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Nov 6, 2012
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I put together 66cc powered Schwinn Meridian tricycle for a friend, but am fighting a major vibration issue. At first I thought it was just a poorly balanced (internally) engine, as it was a brand new, never run China girl. I switched engines with one of my other, well-ridden motorized bikes, and the results were unchanged. The vibration is felt VERY strongly in the seatpost, really at any speed above 10mph.

I changed my motor mounts from solid to rubber engine mounts (I know how controversial those can be) and it made a slight improvement, but still not a solution to a bad vibration. I've also filled the aluminum seatpost insert with sand and used a rubber expansion plug to hold it in, with minimal improvement.

I'm beginning to think it's just the nature of the frame of the bicycle. As opposed to some other trikes, the Schwinn is not a one piece steel frame welded with the rear axle assembly. The front portion of the bike is essentially a normal, all aluminum frame, but with 1/4" thick rear aluminum dropouts, and some reinforcement where the seatpost meets the crank.

The rear axle housing is all steel, and is fastened to the bike only at the rear dropouts with 4 bolts. I feel like this is the root of the vibration problem.

I've invested some time into this project, and it's disappointing that it is almost unrideable at anything above 10mph, as ther vibration makes your rear end go numb within 5 seconds.

And so, I'm considering another powerplant. An electric motor would definitely be a perfect solution, but the cost of batteries keeps this out of the picture.

I've also just begun looking into Harbor Freight's predator engines, four-strokes (do these have less vibes than a China girl?), Honda engines (also pretty expensive, but I know the quality is there), and so on.

Let me know what you guys think, in terms of:

1) possible solutions for the vibration

2) alternative engine suggestions

3) links to other gas-powered Schwinn Meridians, or very similiar projects.

Thanks guys!

As you can see in the pics, I've fabricated the jackshaft chain drive, engine mounting plate, fuel tank, and what I call "the cage".
 

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chainmaker

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Jan 19, 2010
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Re: 66 2-stroke, Schwinn Meridian Trike, looking for an alternative engine! Ideas ple

The HFs work pretty well, and the price is great. Should be able to work it out pretty easy.
 

turbobuick1

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Re: 66 2-stroke, Schwinn Meridian Trike, looking for an alternative engine! Ideas ple

The HFs work pretty well, and the price is great. Should be able to work it out pretty easy.
Are they are smoother running engine? I'm looking at the 79cc and 212cc horizontal shaft engines on their website, and both have good reviews, but the 79cc seems to have a lot vibration according to some of the reviews for it.
 

Stormsorter

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Jun 10, 2010
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Re: 66 2-stroke, Schwinn Meridian Trike, looking for an alternative engine! Ideas ple

The vibes on my 79cc are nothing like my 2 stroke was and only exist in the idle to 3000 rpm range after that its nice and smooth. The 2 stroke would rattle so bad my mirror was useless at mid to full throttle but it never bothered me like you mentioned.

I'm on 20x3in tires and had to have a 11.56:1 gear ratio for 28mph top speed. I have to treat it like 2 stroke kit and pedal up to 5 to 10 mph on takeoff or it will jerk and vibe me and the trike to death literally. But thats with a super cheap 6 shoe clutch. A nice disk clutch like the Cheetah may take care of that even with a low gear ratio like mine.

Since yours is a 26in 25mph=15:1 and 18.5:1 for 20mph. You might even be ok for a standing start on the cheap clutch with those ratios. Or is that the 24in version you got that would be 13.5:1 for 25 and 17:1 for 20

.trk
 

turbobuick1

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Re: 66 2-stroke, Schwinn Meridian Trike, looking for an alternative engine! Ideas ple

The vibes on my 79cc are nothing like my 2 stroke was and only exist in the idle to 3000 rpm range after that its nice and smooth. The 2 stroke would rattle so bad my mirror was useless at mid to full throttle but it never bothered me like you mentioned.

I'm on 20x3in tires and had to have a 11.56:1 gear ratio for 28mph top speed. I have to treat it like 2 stroke kit and pedal up to 5 to 10 mph on takeoff or it will jerk and vibe me and the trike to death literally. But thats with a super cheap 6 shoe clutch. A nice disk clutch like the Cheetah may take care of that even with a low gear ratio like mine.

Since yours is a 26in 25mph=15:1 and 18.5:1 for 20mph. You might even be ok for a standing start on the cheap clutch with those ratios. Or is that the 24in version you got that would be 13.5:1 for 25 and 17:1 for 20

.trk

This is exactly what I was hoping to hear. I really appreciate your input, Im going to buy a 79cc engine tomorrow, redesign my motor mount a bit, and gve it a shot, and see if the vibration is less. Im sure I can find one, but where did you get your chain sprocket for it? I understand it's a 5/8 keyed shaft coming off the engine?
 

Stormsorter

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Jun 10, 2010
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Jasper County Illinois
Re: 66 2-stroke, Schwinn Meridian Trike, looking for an alternative engine! Ideas ple

You will need a clutch or CVT for the 4 stroke and yes it's a 5/8 shaft on 79cc. Sadly CVT on a 5/8 shaft is about $300. You can grab a cheap clutch for $30 but you will need to find a black 3000rpm spring for it since the stock 2000 is to close to idle on these engines. For a nice clutch like the Cheetah you'll need something like this http://www.ebay.com/itm/5-8-X-3-4-X...ore-Reducer-Sleeve-Bushing-Key-/370873714885?. Sadly that wont work on the cheaper 3/4 shaft CVT's.

What is tooth count on each gear you have now? Always better to know what gear ratio and chain size your going for before buying a clutch. The 2stroke had a built in 4.2:1 ratio so you will probly need a bigger sprocket on the engine side of your jackshaft.
 

turbobuick1

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Nov 6, 2012
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Re: 66 2-stroke, Schwinn Meridian Trike, looking for an alternative engine! Ideas ple

You will need a clutch or CVT for the 4 stroke and yes it's a 5/8 shaft on 79cc. Sadly CVT on a 5/8 shaft is about $300. You can grab a cheap clutch for $30 but you will need to find a black 3000rpm spring for it since the stock 2000 is to close to idle on these engines. For a nice clutch like the Cheetah you'll need something like this http://www.ebay.com/itm/5-8-X-3-4-X...ore-Reducer-Sleeve-Bushing-Key-/370873714885?. Sadly that wont work on the cheaper 3/4 shaft CVT's.

What is tooth count on each gear you have now? Always better to know what gear ratio and chain size your going for before buying a clutch. The 2stroke had a built in 4.2:1 ratio so you will probly need a bigger sprocket on the engine side of your jackshaft.
From the engine, the chain goes to a 17 tooth sprocket on the left side of the jackshaft. On the right side, is a 11 tooth sprocket, and from the there the second chain goes to a 36 tooth on the axle. This is a 26" wheel trike btw. You wouldnt happen to have a picture of your bike would you?

I think a CVT is not an option because of the price. Do you have a basic shoe clutch right now?
 

Stormsorter

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Jun 10, 2010
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Jasper County Illinois
Re: 66 2-stroke, Schwinn Meridian Trike, looking for an alternative engine! Ideas ple

You would need to switch to a 40t on the left and a 9 on the right to get to 14.55:1 giving you a top speed of 26mph without the governor. Keeping your 11t would put it at 11.90:1 for 32mph. A 10t would be 13.09:1 for 29mph. An 8t would put you at 16.36:1 around 23mph. This is all with an 11t on the clutch, the smallest I have found for #35.

Your best chance of getting one that size to fit is going to #35 chain on the left side. A #35 40t sprocket has a diameter of almost 5in.

If your jackshaft is 5/8 just grab the clutch and 9t from AGK. That clutch is pre modded for these engines, wish I had gone that way. I had to take mine apart, cut 10 rings off the spring, shave 2mm off each shoe and wrestle it back to together. The back together part was the biggest pain and I don't think it changed the engagement rpm near as much as it was suppose to. But it did just barely stop the shoes from tapping the bell at idle.

Mines a working work in progress you can find it here http://motorbicycling.com/showthread.php?t=49174
 

1204really

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Feb 9, 2021
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Change the engine altogether...i am almost done with my trike build..i put a 5 horsepower 160 c c Honda engine in and mounted it upright in the back basket I built and it hauls but...going to register at dmv,, got the headlight put a small generator underneath to power the tail lights and brakes also...worth all it took to get it the way I wanted....soooooo happy
 
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MickeyThompson

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I've had both the 2 stroke and 4 stroke and I'd have to say the vibration is coming from the firing of the piston and since it fires twice as fast as the 4 stroke produces your unwanted vibration, I didn't like it, given the opportunity I decided 4 stroke for the trike with all the available room on the back end.
Have you thought about the seat? I had a small Schwinn seat for the 2 stroke and the grandpa seat for the 4 stroke, the grandpa he's more spring and is way more comfy.
 

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