Yamaha Drive EFI Speed Limiter Bypass

Reply

  #1  
Old 07-22-14, 06:44 AM
Member
Thread Starter
Join Date: Jul 2014
Location: USA
Posts: 3
Question Yamaha Drive EFI Speed Limiter Bypass

I recently traded a 2012 Yamaha (carb engine) for a 2014 Yamaha Drive (EFI engine). The 2014 has an 8 to 1 rear gear set, 23 inch tires and the final drive pulley is from the 2012 (it is slightly smaller in diameter when compared to the 2014 Drive). The cart presently has a top speed of 28 to 30 mph. The tach is displaying around 750 rpm on top end. The Yamaha mechanic said to double the rpm reading because the 2014 engine fires every other cycle, and not every cycle like the 2012, which would tach around 2200 to 2300 rpm and also travel around 28 to 30 mph. The 2012 also had the 8 to 1 gear. The Yamaha mechanic could not "turn up" the 2014 due to some type of rpm limiter. Can anyone verify the firing cycle and also let me know how to defeat/bypass the speed limitier. Thanks.
 
Sponsored Links
  #2  
Old 07-22-14, 12:17 PM
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 16,915
Every Yamaha gas golf cart made in the last 30 years (OK, it's actually 29 years since the G-2 was introduced) has had a four stroke engine. The ignition fires on every other revolution of the engine. Your tach is set incorrectly and I bet your rpm is actually 3'000 (4 x 750 = 3'000) but even that sounds too slow. It should turn 3'500 from the factory.

If you want to make your EFI cart go faster the easiest thing to do is sell your cart and buy a carbureted model which has a mechanical governor in the rear end that can be easily defeated or disconnected. EFI's in addition to the mechanical speed sensing governor also have engine rev limiting built into the engine's controller. Removing it basically means chunking the EFI system and converting it back to a carburetor.

Another option is to replace the engine altogether. Hondas are great engines but their electronic ignition includes a built in rev limiter that kicks in at 4k. Briggs engines are great for souping up and you can turn it up as high as you want and your wallet can afford.
 
  #3  
Old 07-24-14, 01:59 PM
Member
Thread Starter
Join Date: Jul 2014
Location: USA
Posts: 3
Pilot Dane, thanks for your reply. I can't consider changing engines yet, as I only have around 1.5 hours of operation on the 2014. I traded in a 2012 carb engine for the 2014 EFI. The scenario I don't understand is the 2012 turned around 2300 to 2500 rpm, but the same tach is only showing around 700 - 750 rpm on the 2014. I understand the X4 factor on the 2014, but why was the 2012 taching 2300 - 2500. Does this have something to do with the EFI. Do you know of a tach that will give me a true reading. I just ordered a TTO tach to verify the existing tach. Please inform if you hear of some way to defeat the speed limiter, other than converting to carb. I guess for now I will be happy with the 30 mph. Again, thanks for the info.
 
  #4  
Old 07-25-14, 05:53 AM
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 16,915
Well, you have not yet said what tach you are using. If it's one of those cheap digital hour meter/tachometers with a wire you wrap around a spark plug wire... they are notorious for not retaining the engine mode setting. They are also very slow to respond and require the engine to be held at a stable rpm for many seconds for the display to stabilize. The TTO might be better but it works on the same technology.

You said "defeat the speed limiter". There are two limits on the cart. A speed sensing arm sticking out of the rear end gearbox and the engine's rev limiter. Have you adjusted, removed or bypassed the mechanical speed sensor (zip tie trick)? The electronic rev limiter of the EFI controller basically can not be defeated unless you have the ability to access and hack it's firmware.

I also think there is a high speed gear available for the rear end. It does nothing for engine power or rpm but does provide higher speeds at the expense of less torque and acceleration.
 
  #5  
Old 07-28-14, 05:40 AM
Member
Thread Starter
Join Date: Jul 2014
Location: USA
Posts: 3
Yamaha EFI Speed Limiter

The tach is one of those cheap digital tachometer/hour meters with the wire that wraps around the spark plug. It worked fine on the 2012 Drive and on a Honda 420. When I check the rpms I am going down a paved road and the engine has been wound up for more than ample time for the tach to settle down and display a constant rpm.The 10 mm nut on the mechanical governor is screwed almost all the way in. The cart already has an 8:1 final gear and a slightly smaller than stock final drive pulley. The mechanical governor has been defeated, my concern is the speed limiter in/on the engine. It appears there must not be an easy way to defeat the electronic limiter.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
'