Speed question

gray horse · 04-05-2013, 07:14 AM

I've got a Predator 346cc motor in my 84 G1 with a G2 rear. The head has been milled .050, heavy springs, 6 degree timing key, bigger jet in the carb, Robertson exhaust and K&N style air cleaner. Running 22x11x10 Sahara AT tires, 6" lift, stock drive/driven clutches (rear is new), torque spring from CPP and a HD drive belt (double cog). GPS'd on flat road with one person it runs 23mph @ 4700rpm. With 2 people in it that drops down a bit. It will also slow down when pulling hills, not a lot but noticeable. Seems to be running a little rich. Is this about par for this setup? If not, any ideas on what I should do to improve performance? Not looking at a speed demon, would just like it to maintain a steady rpm/mph loaded or not.

geoffw · 04-05-2013, 05:28 PM

Take the cart for a long full throttle blast and cut the ignition, pull the plug and see what it looks like...then post it.

I personally dont have much experience with the 346cc engines as we use the 420/440s exclusively, but, Im going to make an educated guess and say you should be able to see 5500 out of it....especially on flat ground.

Engine wise, did you port the head? what springs are in it?

sho305 · 04-05-2013, 08:33 PM

Should go faster I ran 31gps and I doubt the 420 clone was above 5100 rpm, in a G9 with stock clutches (rebuilt with new alum sheaves, cut secondary, otherwise stock) on 22" trailpro tires. My clone is likely faster and I cant' get over 5200 in the room I have to run straight. Make sure the belt runs to top of primary at high speed.

It may have less power and get to speed slower, but I ran 30 gps with the stock engine in my G9 on pavement and 28 on dirt, both flat roads. It ran around 5K rpm I forget exactly. The clone takes about 1/4 the distance to do that same speed. My tires measure 23 tall, but even if yours are little less that is way less mph you still would do 27 or better.

Pitbull Joe · 04-06-2013, 07:14 AM

Subscribing. Good luck on the outcome.

gray horse · 04-06-2013, 08:04 AM

The head was milled and then smoothed out on the inside, nothing major. The springs are from NR Racing. I purchased one of their kits. Pulled the plug and it is tan in color so it's not running rich. Will be checking clutches today to see if the belt is climbing up like it should. Could the exhaust be causing the problem? Too restrictive? I know on my bagger I had to go to different, less restrictive mufflers to get it to run right with the Sputhe 104 in it.

sho305 · 04-06-2013, 06:46 PM

Take the muffler off and try it, though may not be good to run nothing on the head if you don't have a pipe. Mostly you need to take out the cutter marks from when they cut the valve seats in, and do the short radius. But not sure it does much with the stock cam anyway as it does not flow the air larger cams do.

geoffw · 04-06-2013, 07:14 PM

Porting and Milling on the stock cam make a huge difference. Its still a dog after 5000rpm because there just isnt enough duration on the stock cam, but theres definately a drastic torque and mid range increase.

Something isnt right in your setup though. Im beginning to think its a clutching issue.

-Geoff

sho305 · 04-06-2013, 08:48 PM

I have yet to run mine against the stock clone, it feels pretty good but then the stock one is pretty torquey too. Don't think the stock one was as easy to spin the tires at speed, but would on takeoff.

geoffw · 04-06-2013, 09:02 PM

Sho, how much quench are you running?

Did you lap the valves?

sho305 · 04-06-2013, 09:27 PM

I don't know lol, had a speed shop do the head who does build lawn engines...but I think he just decked it .050 and cleaned out the ports pretty nicely. I did lap the valves after, it was new and not run (except at the factory) before that. I think maybe you are right and the gx200 'dual' springs are not getting it done. Trying to find some other stuff right now the lash caps, jet, etc.

04-05-2013, 07:14 AM	#1
gray horse Gone Wild Join Date: Aug 2012 Location: Colona, Illinois Posts: 473	Speed question I've got a Predator 346cc motor in my 84 G1 with a G2 rear. The head has been milled .050, heavy springs, 6 degree timing key, bigger jet in the carb, Robertson exhaust and K&N style air cleaner. Running 22x11x10 Sahara AT tires, 6" lift, stock drive/driven clutches (rear is new), torque spring from CPP and a HD drive belt (double cog). GPS'd on flat road with one person it runs 23mph @ 4700rpm. With 2 people in it that drops down a bit. It will also slow down when pulling hills, not a lot but noticeable. Seems to be running a little rich. Is this about par for this setup? If not, any ideas on what I should do to improve performance? Not looking at a speed demon, would just like it to maintain a steady rpm/mph loaded or not.

04-05-2013, 05:28 PM	#2
geoffw Gone Wild Join Date: Jun 2012 Location: Las Vegas, NV Posts: 961	Re: Speed question Take the cart for a long full throttle blast and cut the ignition, pull the plug and see what it looks like...then post it. I personally dont have much experience with the 346cc engines as we use the 420/440s exclusively, but, Im going to make an educated guess and say you should be able to see 5500 out of it....especially on flat ground. Engine wise, did you port the head? what springs are in it?

04-05-2013, 08:33 PM	#3
sho305 Vegas modded 420 Join Date: Jun 2009 Location: West MI Posts: 15,445	Re: Speed question Should go faster I ran 31gps and I doubt the 420 clone was above 5100 rpm, in a G9 with stock clutches (rebuilt with new alum sheaves, cut secondary, otherwise stock) on 22" trailpro tires. My clone is likely faster and I cant' get over 5200 in the room I have to run straight. Make sure the belt runs to top of primary at high speed. It may have less power and get to speed slower, but I ran 30 gps with the stock engine in my G9 on pavement and 28 on dirt, both flat roads. It ran around 5K rpm I forget exactly. The clone takes about 1/4 the distance to do that same speed. My tires measure 23 tall, but even if yours are little less that is way less mph you still would do 27 or better.

04-06-2013, 07:14 AM	#4
Pitbull Joe Gone Wild Join Date: Feb 2013 Location: Plant City, FL Posts: 2,212	Re: Speed question Subscribing. Good luck on the outcome.

04-06-2013, 08:04 AM	#5
gray horse Gone Wild Join Date: Aug 2012 Location: Colona, Illinois Posts: 473	Re: Speed question The head was milled and then smoothed out on the inside, nothing major. The springs are from NR Racing. I purchased one of their kits. Pulled the plug and it is tan in color so it's not running rich. Will be checking clutches today to see if the belt is climbing up like it should. Could the exhaust be causing the problem? Too restrictive? I know on my bagger I had to go to different, less restrictive mufflers to get it to run right with the Sputhe 104 in it.

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04-06-2013, 06:46 PM	#6
sho305 Vegas modded 420 Join Date: Jun 2009 Location: West MI Posts: 15,445	Re: Speed question Take the muffler off and try it, though may not be good to run nothing on the head if you don't have a pipe. Mostly you need to take out the cutter marks from when they cut the valve seats in, and do the short radius. But not sure it does much with the stock cam anyway as it does not flow the air larger cams do.

04-06-2013, 07:14 PM	#7
geoffw Gone Wild Join Date: Jun 2012 Location: Las Vegas, NV Posts: 961	Re: Speed question Porting and Milling on the stock cam make a huge difference. Its still a dog after 5000rpm because there just isnt enough duration on the stock cam, but theres definately a drastic torque and mid range increase. Something isnt right in your setup though. Im beginning to think its a clutching issue. -Geoff

04-06-2013, 08:48 PM	#8
sho305 Vegas modded 420 Join Date: Jun 2009 Location: West MI Posts: 15,445	Re: Speed question I have yet to run mine against the stock clone, it feels pretty good but then the stock one is pretty torquey too. Don't think the stock one was as easy to spin the tires at speed, but would on takeoff.

04-06-2013, 09:02 PM	#9
geoffw Gone Wild Join Date: Jun 2012 Location: Las Vegas, NV Posts: 961	Re: Speed question Sho, how much quench are you running? Did you lap the valves?

04-06-2013, 09:27 PM	#10
sho305 Vegas modded 420 Join Date: Jun 2009 Location: West MI Posts: 15,445	Re: Speed question I don't know lol, had a speed shop do the head who does build lawn engines...but I think he just decked it .050 and cleaned out the ports pretty nicely. I did lap the valves after, it was new and not run (except at the factory) before that. I think maybe you are right and the gx200 'dual' springs are not getting it done. Trying to find some other stuff right now the lash caps, jet, etc.

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