lifted club cars - lifted ezgo
Home FAQDonate Who's Online
Go Back   Buggies Gone Wild Golf Cart Forum > Modified Golf Carts > Big Block Talk! > Clone Engine Swaps


Post New Thread  Reply
 
Thread Tools Display Modes
Old 07-08-2024, 10:02 AM   #1
BaselessEarth12
Not Yet Wild
 
Join Date: Jul 2019
Posts: 49
Question VC 625 Refuses to Idle, Considering a Mikuni 34mm Carb Among Other Things...

Howdy, folks! Been a while since I posted anything, but I've been pretty busy with work the past few years...

Anyway, this thing is in its final stages! However, after coming out of storage this time around she refuses to idle... Opened the carb, and both of the jets that I could find and see were completely clogged with shmoo. After cleaning and reassembly, it seems to be leaking out the front of the carb, and running VERY rich. It will only start with about 1/4 throttle, and dies if you let off. Once it's running, though, it has no problems to speak of other than the occasional popping if letting off the throttle at speed. I have also completely replaced 90% of the fuel system: new fuel cell, primary filter, and all new fuel lines. I'm at a total loss as to what the actual problem is, but I have a few theories: either I missed the idle circuit and it's still thoroughly clogged, the float needle is sticking open and effectively "drowning" it at low throttle input, the larger fuel line is allowing the pump to flow more fuel than the carb can actually handle, the check valve after the fuel return line is preventing the flow of fuel to be properly diverted from the carb back to the tank, or some variation/combination of the other 4.

Instead of diagnosing the actual problem, my buddies are trying to convince me that I need a 34mm Mikuni kit on it... While technically an option, the actual benefits are wasted without a billet rod to handle the higher RPMs. Would it even be worth it, even with the 3800rpm electronic limiter still in place? I'm more concerned about the diagnosing of the current carb's problem, as it is both right in front of me, and is a lot cheaper than a 34mm kit. As always, any and all input and insight is greatly appreciated!
Attached Images
File Type: jpg 20240707_130302.jpg (467.0 KB, 0 views)
File Type: jpg 20240704_142253.jpg (433.8 KB, 0 views)
File Type: jpg 20240703_144323.jpg (337.8 KB, 0 views)
BaselessEarth12 is offline   Reply With Quote
Alt Today
BGW

Golf car forum Sponsored Links

__________________
This advertising will not be shown in this way to registered members.
Register your free account today and become a member on Buggies Gone Wild Golf Cart Forum
   
Old 07-09-2024, 01:53 PM   #2
raydhd
VC 460 CLONE GONE WILD
 
raydhd's Avatar
Yamaha
 
Join Date: Oct 2014
Location: Ray BY The Bay NJ
Posts: 10,803
Default Re: VC 625 Refuses to Idle, Considering a Mikuni 34mm Carb Among Other Things...

Did you look a vegascarts tuning of the stock 625 carb ?
raydhd is online now   Reply With Quote
Old 07-10-2024, 06:31 AM   #3
slonomo
Searching for The Way
 
slonomo's Avatar
Yamaha
 
Join Date: Oct 2009
Location: Medina, Ohio (NEOHIO)
Posts: 11,549
Default Re: VC 625 Refuses to Idle, Considering a Mikuni 34mm Carb Among Other Things...

Adding a 34mm Mikuni is not just an upgrade at high rpm. Motorcycle carbs will allow a ton of tuning so you can get it to idle at 800 rpm and it will rev effortlessly and smoothly without popping etc. While not "easy" to tune, they are fairly simple if you know what to do. I recommend watching a ton of tuning videos and reading some Mikuni literature.

With that said, the stock carb can probably use a good ultrasonic cleaning. If you've been using ethanol fuel, I'd ditch that and go to non-ethanol or at the least use a fuel stabilizer. Ethanol, especially if left in the carb over winter, can wreak havok on a carb. Those carbs can be tuned IIRC. See if you can find some videos on that etc. The stock carbs on these clone engines are typically made for tractors or equipment and aren't designed to idle then go full throttle then back again, so they are not perfect for this application, keep that in mind. Getting it to run "ok" is about the best you can do. The fuel atomization is not that great and they sometimes are "adjustable" but not really fully "tunable" like a motorcycle carb.
slonomo is offline   Reply With Quote
Old 07-10-2024, 05:00 PM   #4
raydhd
VC 460 CLONE GONE WILD
 
raydhd's Avatar
Yamaha
 
Join Date: Oct 2014
Location: Ray BY The Bay NJ
Posts: 10,803
Default Re: VC 625 Refuses to Idle, Considering a Mikuni 34mm Carb Among Other Things...

The modded 625 carb has both the idle circuit and main jet are adjustable. The 625 carb is a 3 circuit carb. It has the extra circuit for better atomizasion. The mikunis don't have any more tuning ability than that. In the case of big block clone go kart racers running 7500-8500 rpm and the mini bikes running up to 10,000 rpms no doubt about it is a plus. In a golf cart particularly with the 625 the RPM limit is at best 5000 and more likely 4000 if you want it to live at all.
raydhd is online now   Reply With Quote
Old 07-15-2024, 09:02 AM   #5
BaselessEarth12
Not Yet Wild
 
Join Date: Jul 2019
Posts: 49
Default Re: VC 625 Refuses to Idle, Considering a Mikuni 34mm Carb Among Other Things...

Quote:
Originally Posted by slonomo View Post
Adding a 34mm Mikuni is not just an upgrade at high rpm. Motorcycle carbs will allow a ton of tuning so you can get it to idle at 800 rpm and it will rev effortlessly and smoothly without popping etc. While not "easy" to tune, they are fairly simple if you know what to do. I recommend watching a ton of tuning videos and reading some Mikuni literature.
A lower idle RPM would be nice. It currently, well, formerly idled at around 12-1300. When I first started this project almost a decade ago, I had a 340cc Suzuki motor from a '79 Arctic Cat sled with a HUGE Mikuni on it that was pretty straightforward to tune... GoPowerSports.com has a complete 34mm kit for the GX390/HF420, but would I really need a 34mm?

I'm pretty sure that the ethanol is what killed the current carburetor. I took it apart again, cleaned it again, and it's still refusing to idle while overflowing the bowl. I'll be adding stabilizer at every fill up, but will have a proper fuel shutoff from the tank so that I can run it completely dry before storage this year, too.
BaselessEarth12 is offline   Reply With Quote
Old 07-15-2024, 09:06 AM   #6
BaselessEarth12
Not Yet Wild
 
Join Date: Jul 2019
Posts: 49
Default Re: VC 625 Refuses to Idle, Considering a Mikuni 34mm Carb Among Other Things...

Quote:
Originally Posted by raydhd View Post
In a golf cart particularly with the 625 the RPM limit is at best 5000 and more likely 4000 if you want it to live at all.
That's what I kinda figured... If I could adjust the RPM limit to 4500RPM, I'd just go ahead and do that. Only need a tiny bit more top-end to hit 25mph again. Ultimately doesn't need more power, just needs to be able put it down more efficiently and effectively.
BaselessEarth12 is offline   Reply With Quote
Old 07-19-2024, 06:46 AM   #7
slonomo
Searching for The Way
 
slonomo's Avatar
Yamaha
 
Join Date: Oct 2009
Location: Medina, Ohio (NEOHIO)
Posts: 11,549
Default Re: VC 625 Refuses to Idle, Considering a Mikuni 34mm Carb Among Other Things...

People think 34mm is huge, it is not. And the difference between a 32mm and 34mm is....2mm, I mean we're splitting hairs here. Yes a smaller carb will work too. I'm just going by what I've actually used. I've also used a 44mm Mikuni and it runs great too, yes 44mm is probably too large, but it ran good, idled like a dream.

And in the world of Mikuni carbs, it's not so much the size of the carb as it is the tuning. If any carb is over jetted it will run like garbage and foul the plugs. A well tuned 30mm Mikuni will out perform a poorly tuned 34mm Mikuni on the top end any day. But if both carbs are perfectly tuned, the 34mm will obviously flow more air so it has more hp potential. Mikuni carbs have multiple circuits and a tunable needle so you can literally make them run perfectly at any rpm. And when you need more power as you upgrade an engine, you can rejet and retune.

Like I said I've never used the engine you are using, but it's a large displacement Vtwin. I've run several similar engines. The stock carb is the limiting factor on that engine, they were designed to run at constant rpm while meeting EPA standards, so they are not tunable for that reason, EPA doesn't want people adding more fuel and blowing a hole in the ozone layer with hydrocarbons etc
slonomo is offline   Reply With Quote
Old 07-19-2024, 07:51 AM   #8
raydhd
VC 460 CLONE GONE WILD
 
raydhd's Avatar
Yamaha
 
Join Date: Oct 2014
Location: Ray BY The Bay NJ
Posts: 10,803
Default Re: VC 625 Refuses to Idle, Considering a Mikuni 34mm Carb Among Other Things...

The 625 is a single cylinder engine. The big brother of the other single cylinder clones. It has exactly the same carb mounting studs and intake gaskets as all the other 390-460 clones.
raydhd is online now   Reply With Quote
Old 07-19-2024, 10:07 PM   #9
slonomo
Searching for The Way
 
slonomo's Avatar
Yamaha
 
Join Date: Oct 2009
Location: Medina, Ohio (NEOHIO)
Posts: 11,549
Default Re: VC 625 Refuses to Idle, Considering a Mikuni 34mm Carb Among Other Things...

Yamaha Grizzly 660cc is a single cylinder engine and it uses a 44mm Mikuni. A Yamaha Warrior 350cc is a single cylinder engine and it uses a 36mm Mikuni. So I know they will work on singles as well as vtwins. As I said, I have no experience with the 625 engine, but its the same principle.

An adjustable clone carb would be better than what you have now. You definitely don't need to swap to a Mikuni, I was just stating my experiences with them. Adding more fuel isn't always better, but adding fuel where you need it is the key. When tuning a carb you have to remember that fuel comes in at different points in the rpm range. Each range needs tuned. In my experience small changes can make a huge difference in how it runs and how it feels.
slonomo is offline   Reply With Quote
Old 07-20-2024, 07:58 AM   #10
raydhd
VC 460 CLONE GONE WILD
 
raydhd's Avatar
Yamaha
 
Join Date: Oct 2014
Location: Ray BY The Bay NJ
Posts: 10,803
Default Re: VC 625 Refuses to Idle, Considering a Mikuni 34mm Carb Among Other Things...

For the OP If I am giving you more info than needed please let me know. The 625 is a Zongshen unit imported briefly by Vegascarts. The weak point turned out to be the connecting rod even though it was pressure oiled. For an even briefer period VC produced a billet connecting rod to remedy the situation. For whatever reason VC stopped selling the engine and spare are scarce to nonexistent. As it sits now neither the billet nor stock connecting rod are available. IMHO if have one of these engines caution is the order of the day about over revving one. P.S. As far as I can find a substitute connecting rod has not been found. P.P.S. The starter motor is also a failure point that again it does not appear that a substitute has been found. There is a 625 owners group on facebook that really shares the info out there on what's available.
raydhd is online now   Reply With Quote
Reply
Go Back   Buggies Gone Wild Golf Cart Forum > Modified Golf Carts > Big Block Talk! > Clone Engine Swaps


Thread Tools
Display Modes


Similar Threads
Thread Forum
34mm Mikuni on a 670 on a lifted club car. Clone Engine Swaps
carb tuning mikuni or eBay CV carb Clone Engine Swaps
Carb rebuild kit for 97 Mikuni carb. Gas Columbia ParCar
Mikuni 34mm carb jetting on Predator 420 Clone Engine Swaps


All times are GMT -5. The time now is 09:05 AM.


Club Car Electric | EZGO Electric | Lifted Golf Carts | Gas EZGO | Used Golf Carts and Parts

Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
This Website and forum is the property of Buggiesgonewild.com. No material may be taken or duplicated in part or full without prior written consent of the owners of buggiesgonewild.com. 2006-2017 Buggiesgonewild.com. All rights reserved.