CDI Rev Limiter retrofit for DAX Titan?

ByronRACE

New Member
Jan 11, 2012
3
0
0
Gilroy, CA
Hey Guys,

It has 2 wheels; so is it a bicycle?

I'm apparently the first guy to put a DAX Titan bicycle kit engine on a Goped GSR, and I have to say...it's a great powerful stealthy quiet option for those of us that would rather not be making unmuffled chainsaw noises and smoke around the neighborhood. I'm really pleased with it.

Some video if you're interested:

GopedTitan - YouTube

I only am having one problem with the conversion. Rev limit. There is no way to prevent over-rev on this engine other than gearing up to the point where the engine can physically not push into it's rev limit. That works, as long as you're OK doing 35mph and don't have hills to climb. Let's say you prefer 20mph with more hill climbing prowess, and gear it accordingly. When under-geared like this, you can't WOT down the road on flat ground without over-revving the engine. I've tried restrictor plating with limited joy. I've tried throttle stopping, but then you have no power for hill climbing.

There's no indication of over rev. It doesn't stumble. The power band doesn't fall off. The noise it makes is not that much different at 7500rpm than it is at 6500rpm. People are used to winding Gopeds to 12000+, so there's no inhibition there either. So, "rider mitigation" is dicey, at best.

Is it possible to fit a CDI rev limiter to one of these engines? Has anyone done this? I'd be perfectly happy with an ignition cut limiter at say 7K as a means by which to give the rider feedback that they need to back off. Are there CDI limiters that will work without an onboard DC power system?

Thanks in advance,

Byron
 

ByronRACE

New Member
Jan 11, 2012
3
0
0
Gilroy, CA
I've never seen a $12 tachometer, can you point me to one? Is it battery powered or magneto powered?

Do you think there's a market for a tiny magneto powered shift light / ignition-cut rev limiter? I'm an embedded systems engineer; I could design such a thing if I thought it was a worthwhile endeavor and had broader application than my scooter project.

Byron
 

rohmell

Active Member
Jun 2, 2010
1,533
1
36
New York
You could build up a circuit like that quite easily;
Some turns of wire around the spark plug lead as am input for an op-amp with its output feeding a relay with contacts in parallel with the kill switch.
 

Mr. Minecraft

Visionary
Jan 13, 2012
349
0
0
San Diego
Hey, Did you ever figure out a way to do this? Im putting a Super Titan on a new MB and just noticed i could over rev it and break the connecting rod.
 

ByronRACE

New Member
Jan 11, 2012
3
0
0
Gilroy, CA
Hey, Did you ever figure out a way to do this? Im putting a Super Titan on a new MB and just noticed i could over rev it and break the connecting rod.
So this engine is produced by a machine shop in china that takes the general purpose F142 weedwhacker/blower/pump motor from the manufacturer and customizes it a bit. I've had multiple conversations with the maker about importing these motors in volume with several modifications so they would be more appropriate for use in GoPed scooters. For example, a pumper carburetor with and a rev limiter ignition would be appropriate so you could use the factory goped fuel tank and not have to worry about blowing it up by over-revving it when you gear it such that it's capable of spinning to the moon.

Both of these options are off-the-shelf parts, and DAX could order them. I'm not going to pursue importing these motors because of the myriad of smog laws and legal obligations that surround being an engine supplier in the lovely state of California. So, encourage DAX to dig a bit and get the parts people want into his motor design.

By the way, the pumper carburetor also has a mixture adjust screw on the idle circuit and main circuit so you can tune the air/fuel ratio and eek out even more power. Also, these guys can make these motors as large as 58cc.

It would be awfully nice to see DAX offer a 58cc, pumper carb, rev limited motor. All these parts are ready now; there is no invention here...just order it from the manufacturer. I'm also surprised GoPed isn't interested in offering this motor on their scooter as an option. Perhaps they will after I visit their factory this fall and show them what it does.

I'm presently using the standard DAX offering and added the pumper carb and dealt with the rev limiter issue by buying a cheap ebay tachometer and limiting rpm with gearing and a throttle stop. Once you do this, the only way to over-rev is by being stupid downhill; and fortunately I have a brain and can remember not to do that.

Also, I've got a lot of miles on this motor now and have had ZERO issues. It's the nicest and most powerful small 4-stroke motor I've ever owned. It's not as powerful as a 46CC CY 2-stroke, but I really don't care. I'm not the neighborhood jackass anymore...I go unnoticed; which is just the way I like it.
 

Bohemian_Lady

New Member
Feb 7, 2013
110
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0
Hawaii
I know this is old, but how would you use a tachometer to determine over rev1? I get the whole just wrap the wire around the spark plug lead but what readings on the tachometer indicate over rev? What numbers would I be looking for?
 

MotorBicycleRacing

Well-Known Member
Jul 28, 2010
5,845
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SoCal Baby!!!
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I know this is old, but how would you use a tachometer to determine over rev1? I get the whole just wrap the wire around the spark plug lead but what readings on the tachometer indicate over rev? What numbers would I be looking for?
The Honda GXH50 has a redline of 7800 rpm.

A Titan is a Huasheng Tai Shan Chinese clone of the Honda more or less so it has the same redline.

Dax just sticks a Titan sticker on a Huasheng motor, actually they do it at the factory.

You can get away with about 8500 rpm but if you want to be safe stay under 8000 rpm.