I Want To Reach And Maintain 40MPH..I Am So Close!

5

5-7HEAVEN

Guest
Using "The Dragon Lady", a dual-engined girlie cruiser to commute 12-mile roundtrip to work. Mostly flat ground with two medium hills I can easily handle.

Bike and fully loaded rider weigh 300 lbs.Aerodynamics is challenged by full front basket and rider with raincoat always on. Raincoat needs to be worn.

Twin 2.2hp Mitsubishi engines on friction drive. Front has 1.375" roller; engine screams at 10,500rpm @ 38mph. Stock exhaust, flame arrestor removed.

Rear engine has 1.5" roller; engine buzzing at 9600rpm with ADA S1 expansion pipe.

Redline/peak hp rpm is probably 8900rpm.

Extreme rpm at WOT(wide-open-throttle) at intervals only on a 2-mile stretch of highway. Riding in commuter traffic. Claiming the curb lane.

I can keep up with traffic. I just want to be able to maintain 40mph for a safety margin.

When not buzzing at insane rpms, engines and I are cheerfully humming along between 20-25mph. That's at 6900rpm-front engine and 6300rpm-rear engine.

Engines have never protested but I'm pushing my luck. I need to change something so I don't kill them or wear them out prematurely.

The simplest and zero-cost solution is to switch the rollers front to rear. Rear engine location is the quietest and the screaming engine can suck on the expansion pipe as a pacifier.:giggle:

Next option is to buy a second expansion pipe for the screaming front engine. However, exhaust must be rerouted; if not the fumes blow constantly in my face.

Another choice is to buy another 1.5" roller to drop engine rpm. Cost of roller and, drum and spacer w/shipping is $120. Local machinist charges $80 to loosen the drum.

Staton charges me $14.39 for a pair of bearings w/shipping. I bought TEN on ebay for $30, including shipping.

How about carburetors, tuning or air filters?

Maybe offset timing keys to shift power to higher rpms.

I realize the powerband would shift and I'd lose HP and TQ at the low end ...

but I have TWO engines so power loss is not an issue.

An EXPENSIVE and labor-intensive option is buying a 4.25hp GP 460 engine..or two. Clutch issues can be solved with 3000 rpm springs. However, I'm doing research on them to see if they're dependable and reliable.

Any ideas, fellas?

I am SO close to 40 mph. That's as fast as I wish to go.
 
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Does Mitsu. have a power pack with new carbs and Velocity stack like Tanaka does.
I have read that It can give you 5 MPH boost.

Maybe you can see if any go carters are using the Mitsu TLE 43 and find some hot rod carbs!!! or buy some NITRO !!!!
 
Well, I've been using 87octane gas. I'll try 91octane.

No nitro for me, not even race gas at $15/gallon or whatever it is.

Notwithstanding the two engines, I'm trying to keep it simple.

The ADA pipe should push the bike to 40mph.

I'll go check the go kart forums. Been lurking at gopednations for research.
 
5-7,

you are kind of in a either or situation.

from the research i did 2.2HP is about the max fully usable on friction due to extra power requiring added down force on spindle to hook up to the point of causing tire deflextion that just eats up the extra power again, thus no gain.

i have about 3000 mls. on my 460, clutch springs are a MUST. these are the engines that most all the gopeds come with stock. many of the guys over at gopednation have many times more miles on them than i do, and there are quite a few that are running them daily with 15:1 cylinders, custom reed cages and chambers.

early units were known to have poor cylinder plating, this is being reported less and less all the time now. the pull start is weak and i fit goes CAN take out the flywheel and coil. there are conversion parts available to fix this as well.

if you look around the 460 is THE bang for buck engine out there at this time. you've been here since before i came on forum and may have followed my build history using this engine. you are not going to have ANY problem with the 460 itself that will equal trying to find a reliable way to harness the power on tap.

a single 460 with either GEBE or chain will give you a maintainable 40mph WITH reserve speed above that.

PM me if you want to go into this at more length and detail.

steve
 
GP 460 +Mitsu?.Power reqd. vs. speed curve goes up steeply at 40mph.For each mile increase, close to 8% more power is required.To go from 38 to 43 mph takes about 40%. more power!.You could try a streamlined bike helmet,the kind used in time trials,reducing air resistance is more productive than increasing power.
 
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dui, I need to keep my motorcycle helmet.

If I move my front basket to the rear, that should streamline some.
 
40 is a good speed for peaks when you need it. If you can get 40, you will probably beat cars, as many people drive slow, and it's nice to go past them.

In say a 30mph zone with no bikelane or sidewalk, I find it MUCH safer to go 30-35mph in the lane like a regular vehicle. It sure beats riding at only 20 and nearly getting hit by cars or having to ride in the grass.
 
I think the easiest way to hit 50 is get a smaller friction drive...

Reduce the RPM on both engines.... since you have 2 you probably have plenty of power anyways for acceleration.

If you reduce the RPM you will also help the engines last longer.
 
40 is a good speed for peaks when you need it. If you can get 40, you will probably beat cars, as many people drive slow, and it's nice to go past them.

In say a 30mph zone with no bikelane or sidewalk, I find it MUCH safer to go 30-35mph in the lane like a regular vehicle. It sure beats riding at only 20 and nearly getting hit by cars or having to ride in the grass.

I hear ya, Znsane.

I try not to drive below the speed limit, unless of course if the flow of traffic is below the limit. If I claim the lane there's a buffer zone so cars shouldn't have to zip by closely.

macarollo, I'm shooting for 40mph, not 50. Another 1.5" roller will definitely benefit the engine and might push for higher top end.

Maybe a combination of oversize roller, relocation of front basket, more tire pressure, less cargo.
 
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