Predator 420 Setup Questions

jrv97240

Many of you have probably seen my build thread with a Predator 670 and Yamaha G2. Many of you have probably also seen my thread about all the struggles I had trying to make that engine run right. I finally decided enough was enough, and pulled the 670 (for sale if anyone is interested. Im in Kansas City, MO). I purchased a new Predator 420 with warranty this time in case i have any issues. Install was pretty easy and I was able to re-use almost everything from my old setup. I did remove the governor and install 35lb valve springs from Vegas Carts. I took it on its first drive last night and I was very impressed. I do however have a couple questions.

1. The engine is very hard to turn over sometimes. When the engine stops in a certain position my electric start can't turn it over, and its is very difficult to pull start as well. If I rotate the crankshaft by hand from the clutch end, and get past the "difficult spot" The electric start will turn it over and it starts right up. Could this be related to the heavy valve springs I installed?

2. How is the predator charging system connected to the batter? Since I am re-using the wiring from the 670 that is already in place they do not match up 1:1. I have a wire coming from the ignition switch that went to a regulator on the 670, I assumed this should be connected the wire coming from the stator on the 420? Or can I just connect the wire from the stator directly to my battery?

3. What setting on the secondary clutch will give maximum torque? I know i will not have the same torque as the 670, and I am fine with that. But it seems at the current setting it is shifting out too fast. This is a Yamaha G2, with an aftermarket secondary clutch. I think I am at B2 right now but I cant remember.

Thanks in advance!

BGW

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raydhd

My engine is a little more built up than yours but I have the umaxx spring set on B 1 and it works perfectly. On the starting are you using the carts S/G or the starter from the predator? Another thought since you installed the valve springs is the lash set correctly? If there is too much lash the compression release will not function making starting much harder.

jrv97240

I am using a stock Yamaha spring. I originally installed a "high torque" spring but that was way too much and the engine would never fully shift out. How much difference is there between the UMAX spring and the stock spring? I will check the valve lash again. Is there a better method for finding TDC than removing the spark plug and using a dowel pin to see when the piston is all the way to the top? I am also using the predator starter, I no longer have the starter/generator from the cart.

raydhd

I get a nice smooth shift with the umaxx.My stock spring had seen better days along with the old ramp shoes.I was going to try other settings but this worked so well I have not fooled with it.

sho305

Umaxx is between the huge ebay springs that don't work well and the stock spring. Even a new stock spring will work better because they get old and lose tension (if yours is old), but the umax is ideal for lifted carts or if you tow/etc. B2 is the stock setting for the stock spring. Setting it tighter will make it rev more iirc B3 is tighter then C1, C2, etc. You have to rotate it more each setting for more preload on the spring before you push the sheave on all the way. I'd highly recommend a umax, and they don't cost much either. They are a yamaha part for the umax utility model cart.

Set your valve lash very low 0-.004 max. If you can just slide the rocker around on top of the valve you have enough, with your fingers, easily. All you have to do is turn the engine over and watch the rockers push the valves open. The intake goes first then both shut on power stroke where you adjust them, then the exhaust opens and back to the intake. Make sure you turn it the correct way it runs. If you turn the crank each way and nothing moves then adjust them there. Someplace in there one valve bumps up a little for the comp release, don't adjust it when that is happening.

jrv97240

Thanks Sho, do you have a part number for the umax spring? Also any ideas on how to wire the stator charge to my battery? Can I just run it directly to the battery? I know its not much of a charging system but I would like to keep my battery topped off as best I can. I will try adjusting the valve again tonight.

jrv97240

I adjusted the valves again tonight, set them at .0015 for the intake and .003 for the exhaust and the fixed the hard starting issue. I also found a rectifier diode inside the old ignition switch housing and I wired that inline between the stator and battery to solve that issue as well. I tested before i put the diode in and I was getting AC current, after the diode I know get DC. I need to get the umax spring ordered, but all in all it was an easy swap and i am very pleased with the 420 motor. I just wish i would have gone this route over the 670 in the first place.

sho305

Yes the diode makes it DC, there is no voltage reg because its low enough power it wont overcharge. Should put a fuse on that wire or usually they run it through the breaker in the key start box on a clone.

The umax number in this post http://www.buggiesgonewild.com/gas-y...tch-uh-oh.html

Really wish the 670 would have worked out for you, though I know sometimes you dont have the time or need the trouble figuring out a difficult setup on a project. My clone running well so far, has good power and revs for higher top speed. If I got the cart I wanted right now it would be a limo lifted with 25s minimum, so a 670 would be ideal, but not seeing that project any time soon with my list of things to do. At least our snow is melting today and it should warm up next week.

jrv97240

Thanks Sho, I got the clutch spring ordered. I wish the 670 would have worked out for me too. I spent alot of time and alot of money trying to make it right. New ignition coils, new carb, countless amount of plugs. But I had to draw a line. My wife and I enjoy going to garage sales on the weekend and that was the purpose of building the cart. So when April came around and I was still in the same place I was last fall I decided enough was enough. I really like the 420 so far, much quieter, plenty of power and speed for me. I was also able to unload the 670 on craigslist this weekend. I took a loss on it but was able to cover the costs of the 420 and its upgrades so I'm happy.

sho305

Well that is good. I look for improvements to come for the 670 but they are not here quite yet. Yeah you can get some nice top end with a clone and power is not bad at all.