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Old 08-09-2010, 04:03 PM   #41
sho305
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Default Re: The CLONE engine setup & specs thread

That appears to be the easiest solution. Wow you have a lot of room in there, mine is packed with stuff. I did find out this is actually not a copy of the GX390 Honda that is 12hp, it is a stroked and bored version. In the manual it says 15hp though its supposed to be 16hp. The Honda was a GX420....but everyone calls this a 390 clone.
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Old 08-09-2010, 04:33 PM   #42
bordin34
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Default Re: The CLONE engine setup & specs thread

Yeah, its technically a 420 but we call it a GX390 clone because Honda does not make a GX420.
Also, my return line sure returns alot of fuel at idle and I added a clear fuel filter just to make sure my pump was working right.
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Old 09-06-2010, 04:37 PM   #43
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Default Re: The CLONE engine setup & specs thread

Just an update I bought a carb rebuild kit for $14 on ebay it has all the jets and gaskets for bowl. Took the .050" hogged jet out and put the stock one in, ended up hogging that one to .044 and it runs better, no missing at low speeds. I put the new idle jet needle in an it promptly broke off, beware of that thing. It is set close to what it needs to be. It was still losing power lean when you took a corner and hammered it, so took the float out and replaced the spring I had stretched out. It was better. Sometimes it takes a second to bring the power at low rpms, otherwise its right there. Might have to go larger just a hair but leaving it for now. I have medium to light brown color on the plug now so going to let him run it some and see what it does, it had not been run that much on that plug. I also feel the clutch engages kind of low so it leans under that load, at higher rpm it is spot on. I don't know how to make it richer initially since it has no accelerator pump lol. Anyway its close and running pretty good. This did make it a little cold blooded, you can't go past 1/3 throttle until it runs for a minute or so. What it could use is more ramp on the secondary so it revs when you gas it, or weights, but you can't change the stock primary very easily. Still trying to get a spring for it that will fit.
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Old 09-19-2010, 09:50 PM   #44
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Default Re: The CLONE engine setup & specs thread

Ran this for a while today, with this jetting it seems to run well but for a few things. If you hammer it from stop or low speed it might take off good or it might miss some. But if you hammer it from higher speed say over 10mph it always takes off hard. If you use half throttle or less at low speeds its fine. I know its lean under high load and low rpm, so I'm going to see if I can find some info on the E tube in the carb and tuning it. All in all it is running well and the miss is not that bad or that often, you can let up and back down it stops doing it, it still speeds up when missing. I think it misses and upsets the signal to the carb. It might be a little lean yet but unfortunately I did not get time to check the plug, gps it, or video it due to rain and other stuff I had to do. When it was too rich it did not have this issue, it always took off hard from any rpm when you floored it. It might wind out a little faster now wish I would have been able to check it and see if top speed was better. Thing is a load of fun to run, I was leaving peel marks all over the place, lot of sand drives and trails there and it rained the day before. I also noted that like my stock cart, the last 1/3 of throttle seems to do little if anything except maybe when rpm are quite high. It still lays down at high rpm just like a governor almost. But even half throttle it takes off harder and digs up the dirt, its a hoot compared to stock power.
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Old 09-19-2010, 10:12 PM   #45
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Default Re: The CLONE engine setup & specs thread

I'm pretty new around here sho, but ive been reading the play by play on your work with the clone engine. I think when u do the one for your cart you are gonna want the the parson's racing stage 1 kit and the 32 mikuni carb. That would have to be a hoot in one of those clone motors. Just a thought it, it could be a cure for the power dying out on top end and the throttle response issues
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Old 09-19-2010, 10:14 PM   #46
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Default Re: The CLONE engine setup & specs thread

These clone motors seem to be the ticket for repowering on a budget
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Old 09-20-2010, 07:18 AM   #47
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Default Re: The CLONE engine setup & specs thread

Quote:
Originally Posted by TenaciousT View Post
I'm pretty new around here sho, but ive been reading the play by play on your work with the clone engine. I think when u do the one for your cart you are gonna want the the parson's racing stage 1 kit and the 32 mikuni carb. That would have to be a hoot in one of those clone motors. Just a thought it, it could be a cure for the power dying out on top end and the throttle response issues
I totally agree with you, but then you have the same cash into it as a V twin so why bother? I don't need the smaller engine like a Kart does to fit on it, and a V twin sounds cooler and has an oil pump.

I guess what I am looking at is maybe a larger/better carb, I did find larger PZ carbs for like $40 that should work well they are for 250cc motorcyles I think. Pretty sure I read these are 21mm internally? So a 26mm or something should be good but some use the outside measure not the venturi. Then advance the timing about 6 degrees maybe 8 since its still low compression. I'd really like to change to a CDI that advances but maybe later. Then I could shim the springs or get better, but I don't think they are floating now it really feels like the cam has died and if they use the 13hp cam I can see why it would with a stroker like this. All that leads me to wonder if I could find a mild cam that went 1K higher in powerband, put a good rod in, springs it needed and timing advance, possibly larger carb, would that work and how much would it cost? I've read they can run 6K with stock flywheel that is all I need. As it is now the last near 1/3 of throttle does nothing really, so I don't think a larger carb would help at all without some other mods (but may run better overall with a better carb). Remember the gokarts are not pulling 600lb of cart on 22 ATV tires, they wind higher as they have no load. I'll keep trying to figure out the right combination, but even the cams I look at they don't say what rpm they run at and just how radical they are. I also have to look at durability issues I don't intend to take it back out of the cart for years its not just a toy that can break.

"repowering on a budget" - Oh and then some. You can stay under $400 with the adapter and using the cart starter and clutch, I think, if you are careful how you do the intake and exhaust. 0 to 25mph it pulls way harder than the stock cart. I'm trying to get a race on video just to show how it walks the stock cart but it rained last weekend I didn't have time. Even better is how they tear up hills and spin the tires some, no comparison to stock.
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Old 09-20-2010, 04:41 PM   #48
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Default Re: The CLONE engine setup & specs thread

I agree, the performance parts u find for the clones are mainly directed at the go kart market. I admire that u have been putting in some serious time in trying to figure out what is the perfect combination for least amount of dollars spent. I will keep buying lotto tickets so i can hopefully send some research money your way. It seems to me when most folks put a twin or upgrade there golf kart motor that the rev kit seems like the first addition and maybe the timing advance key. The gx clones would have to benefit as much as the twins from the same mods. A question i have is, how much would the motor benefit from say just the basic rev kit and file the key a few degrees?
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Old 09-20-2010, 06:27 PM   #49
sho305
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Default Re: The CLONE engine setup & specs thread

Problem it is will not rev, while a vanguard will until it valvefloats...so you put a rev kit in and you are good. Think a rev kit is only pushrods and spring shims? I forget, but this does not seem to be floating. What the deal is, is they copied the honda GX390 13hp and bored and stroked it. They use the same (actually very close but not same) head on both the clone 13 and 16, though the 16 actually says 15hp in the manual and home depot now has them as a 15. Anyway, a stroker does run out of rpm faster if you use the same cam(?)/head/etc. It makes sense, as it has a very healthy bottom end and midrange, the power just pours on and you think you have more than 16hp...its the torque it has down there.

Issue #2 is they say the flywheels blow up over 6K some say get a billet one before that (places that sell them of course). I don't know if this is for 16hp or 6.5hp, they don't really blow up, the magnets fly out they are not glued in that well...and it depends on what brand clone you get. The flywheel itself is good for more rpm than 6K. Don't know what a Honda wheel costs.

I just have a feeling timing and springs or shims are not going to do much, but I could be wrong. Most times float you will hear the clicking, the exhaust note changes, it can surge....this does none of that its smooth and quiet. I ran it with no rear body 2' from the motor. I saw some dyno runs on other clones and they show only a small increase on the topend from more timing so it helps, but this seems to need more than that. I think it needs a cam, but nobody will say what rpm their cams run or how they run compared to stock. They don't say when you need a better rod, they say get a $800 kit and I say screw that I will get a vanguard. I'll keep looking into it. I don't want a huge radical cam that causes problems either. Anther issue yet is this has a lot of side load on the piston, in the mod ones they use a shorter piston and longer rod. Thinking it would not be an issue at 6K but have to look into it more. To balance that out I don't run max rpm much, I mean even on the road I wind it up and go back to half throttle I don't keep it hammered.

I really just don't need that much more so its starting to PO me a little. I only need another 1K rpm, just that other than full on mod engines few have done anything with them. You can get any setup for a 6.5 you want from cheap 10hp to way more. I even considered putting a pair of them in my cart but I don't see the room to do it, 20hp at 6K would be sweet for not much cash either. You can get 6.5 for $100.
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Old 10-12-2010, 06:33 AM   #50
sho305
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Default Re: The CLONE engine setup & specs thread

Update, we ran it till now and it got cooler weather out was missing some times when you stomp it at low speeds, but fine at higher rpm. So I took the jet out and went from .044 to .046 and it seemed perfect. One time around a corner it went a little flat but didn't miss and just for a couple seconds, otherwise pulled hard. Next day it got really strange lost power missing...look around and find the pipe came loose from the airbox. I told him to put a nut in there but we thought it was ok. It was welded and it came loose. Have to redo it now take the shocks off and drop the cradle just to get at it. Going to look for a intake to move it, problem is I'd have to build all new linkages for it. We might make a box to go on the carb and pipe into that. Put a bungee on it to hold it in and it ran fine again.

It does seem to go faster now with leaner jetting and break in, but didn't check it w/gps. I can tell it pulls more up there now. Talked to a guy at Precision Cams that makes cams for gokarts he says he has a cam that is mild and would give 1K more rpm with no other mods really (maybe valvetrain stuff like a rev kit of course) and said it would have about 15% more power if you also worked the head for more flow. I plan to do that with mine and advance the timing, not sure I will bother with the head I don't need power up there just rpm...unless it makes more power lower too. Seems like it would with a cam anyway.

I think the carb is good now, if not I'll end up going to a motorcycle type carb and screw this thing. You also have to pull the rear body to check the plug or mess with carb, though its pretty easy on the G9.

The clutch is weird, it works like stock and takes off smooth. You think its bogging, but when you put a hill in front of it or trailer on/etc to load it, it revs more and off you go. We climbed a grass ditch around 6-8' tall and very steep. With two people starting at the bottom it was spinning the tires as it lofted the front end up in the air going off the top. My stock cart crawls over it with one person barely moving. It just takes a few seconds to get going from a dead stop, I tried to power brake it but his brakes are not good and will not hold the power.
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