Briggs Opposed 18HP & Comet 780 in TXT - Super slow!

[tommywilder]

I am desperate for a quick solution, as the annual golf cart mud drags are happening this weekend!

I just took the Predator 420 out of my TXT and dropped in a 18HP Briggs Opposed Twin in the quest for more torque. Kept the same old Comet 780 that I've been running for a year or so.

It's running good, from what I can tell, although the top end RPM is not where I want it, but that's just an adjustment/governor thing I believe. (Only hitting about 3k right now.)

I am about 1.5" longer center to center on the clutches than I was before, so I bought a belt that was 3" longer, thought it was too loose, so I also bought one that was only 2" longer. The 2" longer belt is too tight, not crazy tight, but will make a little squeal trying to keep the cart sitting still.

The dilemma - this thing is SUPER slow. At about 3k RPM, I'm only getting around 9-10MPH, from a guess, haven't GPS'ed. I was running mid 20's or better with the 420. I did get the 780 stuck twice, being dumb, revved the engine without the belt. Popped it back closed both times without issue. Did I screw it up? I can't think of anything else to check.

The only other oddball thing right now is that I have the shift cables off waiting on longer ones. I have clicked it into forward and don't hear any racket indicating that it's popping out of gear, nor does it ever quit pulling.

What am I missing? Please help!

[slonomo]

Sounds like your clutches aren't fully shifting. When it's in neutral do the clutches fully shift when you give it full throttle? You are looking for the primary clutch to close all the way squeezing the belt all the way to the top, and the secondary to do the opposite with the belt all the way at the bottom.

As far as rpm, is your throttle opening all the way? Check the cable to make sure you are getting full travel.

[tommywilder]

Definitely not getting full travel on the throttle, but I think that's only part of the equation. I'm getting to about 3k, I think this motor is really only supposed to run up to 3600, with 4k being the absolute max on stock internals.

I am expecting break-neck torque out of this thing off the line (which is where I need it for the mud drags); specs show it around 28ft lbs compared to the 17ft lbs of the Predator 420. The predator you could crack the throttle and the cart would lunge pretty good, this one - nothing, total weak sauce!

The primary squeezes all the way shut, but it seems slow getting there. I may try to get a video uploaded when I get home of how the clutches are behaving. The driven clutch appears to be behaving properly as well, wondering if I need to crack it open and play with the spring settings on the rear.

[raydhd]

Just remember the opies aren't rpm engines.

[tommywilder]

I took apart the Comet clutch last night and everything looked to be fine. Cleaned it out while I was in there, but I don't think the clutch is the culprit. Not expecting any fast speeds out of this thing, but where's the torque everyone raves about?

The power went out last night, so that cut my investigation short. Any more insight from anyone would be appreciated!

[raydhd]

In have a modded VC 460 in my golf cart and a 18 HP B&S twin ii with 20 hp heads and a rejetted carb in my lawn tractor. There is no comparison in any way that the twin ii is in the same power league with the VC 460. Not throttle response, not rev limit , not HP. The 460 even with 24" tires pulls so hard off the line it could easily lift the front wheels off the ground. Don't believe every thing that some people post here.

[TheNewGuy]

Originally Posted by raydhd

In have a modded VC 460 in my golf cart and a 18 HP B&S twin ii with 20 hp heads and a rejetted carb in my lawn tractor. There is no comparison in any way that the twin ii is in the same power league with the VC 460. Not throttle response, not rev limit , not HP. The 460 even with 24" tires pulls so hard off the line it could easily lift the front wheels off the ground. Don't believe every thing that some people post here.

LOL....I agree.

[raydhd]

Well in this case I own both, modded both, researched every source I could find and actually built both. Anyone needs pics they are both still here and being used.

[slonomo]

Originally Posted by raydhd

Well in this case I own both, modded both, researched every source I could find and actually built both. Anyone needs pics they are both still here and being used.

But have you had both engines in the same cart?

[tommywilder]

Well, for what its worth, I abandoned the opposed twin and threw the Predator 420 back in. The difference in power, speed, and the whole shebang is night and day different. Sold the opposed to a guy for his Cub Cadet tractor a couple days ago. The saga has ended.

But I did pick up a VC460 for $100. I will start a new thread for that.