80 Marathon Engine swap. Goes like hell, but need some advice. (video inside)

[Greg-J]

Short video:

1980 EZGO Marathon with 500cc Arctic Cat engine - YouTube

1980 EZGO Marathon with 500cc Arctic Cat engine - YouTube

I have a 1979 Pantera 500cc motor in my 80 Marathon with the fuel tank above the motor and a Mikuni pulse pump feeding it. I'm not a 2 stroke pro, so I could really use some help with this issue.

• The good:
  The motor starts immediately and idles very well. If I get in and go immediately after starting it, it goes like a champ. If I had to guess, I'd say it accelerates slower than expected, but it goes and goes pretty decent.
  
  
• The bad:
  If it is left to idle for even a short while (less than a minute), there is no throttle response. You can hear the tone of the motor lower with the throttle wide open, but it doesn't rev a lot higher than idle, and it's inconsistent.

I cleaned the carb and it looks great. Everything moves freely and it is free of grime on the inside. I put a 4-7lb. fuel pump in place of the pulse pump to see if it wasn't getting enough fuel and that didn't change the behavior at all. I just ended up with fuel spitting out of the pulse pump nipple in the crank case and out of what I imagine is an overflow hole in the carb.

I don't know what a motor behaves like or sounds like when it's flooded, so I don't know if it's getting too much fuel or not enough. It has good compression, and there's definitely spark.


ANY help is appreciated. I'm at my wits end trying to figure it out.

[racin161]

I would think it's a jetting problem when it does act up try applying some choke and see if this helps. If it's worse or stalls you may have to lean it out with jets or moving the needle on the slide. Another piece of advise ROLL BAR & HELMET unless you have a DEATH WISHYou may also want to visit the BIG BLOCK FORUMS and post there there some crazy guys over there.

[Herm715]

I wud guess a jetting prob as well. There not made to run in warm temps. Ul burn up ur motor. Dido on the helmet n roll bar quote LOL its crazy fast!! Nice work!

[Greg-J]

Well, it looks like it was a jetting problem!

In that, the jet was clogged. Somehow missed that after taking the carb apart several times. Cleaned it out with wire and so far so good.

The motor is about 1/4" offset though, so now I'm chewing through $70 belts.

Anyone know of a site that I can order the golf cart /snowmobile style belts by length?

We have been wearing a helmet when riding now as well. The roll bar is next to go on after we decide if we can change the steering wheel geometry to set the seats down a good 5". I'd really like to lower the center of gravity with us on it.

[Greg-J]

Well, it looks like it was a jetting problem!

In that, the jet was clogged. Somehow missed that after taking the carb apart several times. Cleaned it out with wire and so far so good.

The motor is about 1/4" offset though, so now I'm chewing through $70 belts.

Anyone know of a site that I can order the golf cart /snowmobile style belts by length?

We have been wearing a helmet when riding now as well. The roll bar is next to go on after we decide if we can change the steering wheel geometry to set the seats down a good 5". I'd really like to lower the center of gravity with us on it.

[1fast67]

And racing seats with 5 point harnesses. That thing is stupid fast! I want to drive it!

Sent from my LG-P999 using Tapatalk 2

[Greg-J]

The fastest we've got it to is 40mph, and that's with a medium sized belt. I think we've opted to go for more torque, less speed. The front end on these things scares the hell out of me at high speeds.

[Heliarc]

OMFG!That thing rules LOL!

Also, check out a NAPA store.You should be able to get a Gates belt in the size you want.

[BrewCityMusic]

I WANNA RACE !!!! (Not that I'd have a chance in HE** of winning, but once I lost you'd likely feel bad and let me drive it, hahahahaha) ...

Adjusting your toe-in will help that front end - mine does a whopping 23mph and until I dialed in the front end was one scary SOB at speed (especially on 22X11 tires) - I kicked her in just a wee bit pigeon-toed and it really helped keep her on course at speed.

Then again, at 40, you're sorta on your own, LOL

[Greg-J]

When you're on it, 40mph doesn't seem all that fast. We were hoping to hit 60, but that does seem a bit silly now.

If I lift it and put 22s on it, I'll get as small a belt as I can fit around the pulleys. If I lower it and modify the seats/steering however, I would love to hit 60.

We'll see.