2 Engines, 1 Bike....Ludicrous Acceleration

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lowracer

lowracer

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Oct 17, 2008
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Charleston, SC
I gotta give props to 5-7 Heaven for pioneering the 2 engine MB. I've had the urge to build one but didnt have two engines for one bike until another fellow MB& 'er on here was nice enough to sell me his barely used engine (Thanks Cannonball2). I just got it hooked up & am awaiting some new bearings for the clutch driver to come via eBay (I messed them up playing with friction drive).
One of these big bore high compression Pocket bike engines is more than plenty for a bicycle & just the thought of putting two of these little monsters on a hardtail no suspension bike was bordering on the insane...but what the heck.
Here's what it looks like so far. Gotta re-install the clutch driver & expansion chamber.
-Lowracer-
 

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cannonball2

cannonball2

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Oct 28, 2010
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Colonial Coast USA.
LR you are really over the top now! That thing has got to sound awsome. You know me, always analyzing. Arent you going to have 2 different ratios? Gonna have seperate throttle controls to sync the engines? I think you love challenges, me too!
 
lowracer

lowracer

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Oct 17, 2008
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OK,
I got the bearings in one of the Staton drivers to cooperate enough (using a hammer & screwdriver) for a good test drive today. Only thing I can say is, "SCARY FAST"!
When you pull both throttles (2 seperate brake levers, one on each side) the thing shoots forward with violent intensity & reckless abandon. I did play with it some by pulling one then the other to feel & hear the differences. I felt like a kid in a candy store. 5-7 was right about the concert of engine noises you get with dualing engines. I passed a few people in my neighborhood & the looks I got were quite different than the usual 'one engine on a bicycle' look. They kinda had that constipated face trying to figure out where all that 2 stroke rage was eminating from...lol
I think its a cool contraption, but is it practical? is it legal? is it fun? (No, No, Yes)
I'll receive the new bearings probably Mon or Tues & will replace them, then ride it around a little more. Here are a few more pics of the finished product.
-Lowracer-
 

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dmb

Active Member
Dec 4, 2010
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lakewood ca
i think i heard that the front wheel has to turn a little faster than the rear so you are pulled through turns... on the 2wd rokon trailbike or was it the other way? you might want to look into that if you have problems. have fun
 
moonerdizzle

moonerdizzle

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Jun 28, 2009
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Cheese head capitol
dmb said:
i think i heard that the front wheel has to turn a little faster than the rear so you are pulled through turns... on the 2wd rokon trailbike or was it the other way? you might want to look into that if you have problems. have fun
Click to expand...
On a Rokon the front wheel freewheels when you turn the handle bars past a certain degree. But yes. The front wheel would have to turn faster in turns.
 
lowracer

lowracer

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Oct 17, 2008
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Cannonball2,
Yeah its the v-belt system I have been fine tuning for awhile now. Instead of flip flopping back & forth from front to rear engine, figured I might as well do both at the same time? The throttles are independent of eachother. The exhausts make different sounds so I can kinda tell which one is pulling more. The ratios are also different. Front is a 1.5" pulley on 650c wheel & rear is a 1.5" pulley on a 700c wheel.
-Lowracer-
 
5

5-7HEAVEN

Well-Known Member
Aug 2, 2008
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dmb said:
i think i heard that the front wheel has to turn a little faster than the rear so you are pulled through turns... on the 2wd rokon trailbike or was it the other way? you might want to look into that if you have problems. have fun
Click to expand...
The front wheel does not have to turn a little faster thru turns. I mean, how much time does a street bike spend, pulling thru turns?

Don't forget that rear-engine MB's front wheels do not turn faster than their rear tires.

I can almost guarantee that this will not be an issue. Ask me how I know, lol.

The cool thing about running different ratios and twin engines is that it sounds like a gear shift, when you switch from single engine/lower gear to other engine/higher gear.
 
2door

2door

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Sep 15, 2008
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Littleton, Colorado
That thing just has to sound wonderful. Reminds me of the early go cart days. Twins running flat out, that harmony of noise, in stereo. Too cool. I'd like to see a vid too. Thanks for sharing.
Tom
 
lowracer

lowracer

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Oct 17, 2008
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Charleston, SC
I got home from work today & took this bike out for another ride through the neighborhood.
Some of the conclusions I'm coming up with:
1) Hearing two engines singing at the same time is cool & reminicent of my old 2 cylinder, 2 stroke (Yamaha RD400F Daytona Special)
2) its too fast for a bicycle anywhere from a dead stop to ludicrous speed.
3) its too noisy for a MB (sounds more like 2 dirtbikes racing eachother down the road)
4) its Bad to the Bone.
One high compression big bore pocket bike engine is capable of pulling 11,000 rpm's under load, can hit 50+ mph & accelerates quickly without the need for a shift kit. Two of them is overkill...
-Lowracer-
 
5

5-7HEAVEN

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Aug 2, 2008
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In the beginning, we all go flat out. After things settle down, I found that sweet spot where just enough throttle on both engines gave me just enough power to push the twin-engined beast briskly up the hill, or through that headwind. Both engines sharing the load puts less stress on them throughout the power range.

I used mild-mannered Mitsubishi TLE43cc engines. They behaved at all speeds.dance1
 
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lowracer

lowracer

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Oct 17, 2008
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5-7,
True that about going flat out...(for testing purposes only, of course)
I noticed I am getting a very small amount of sidewall wear from the close tolerance I have between front v-belt & tire. The belt is rubbing the tire enough to cause alarm. I did some research & can run a 3L instead of the A belt & can increase my clearance. I'll need to run a slightly larger pulley though to keep similar gear ratios since the 3L sits further inside the pulley enough to make a huge difference in gearing. Grainger has a good pdf on their website that I'll link here.
http://www.grainger.com/tps/power_t...e.pdf?cm_sp=TPS-_-VBelt Reference Guide-_-Top
-Lowracer-
 
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