VC440 Speed Update

slonomo

I just took my cart for a high speed run and here is where I'm at:

0-20 in about 4-5 seconds, pretty quick compared to stock.

0-32 mph in about 10-12 seconds, super quick compared to stock.

32 mph at 5000 rpm (slightly uphill, almost flat road)

35 mph at 5500 rpm (slightly downhill, almost flat road)

She cruises very smoothly in the 4000 rpm range and feels very nice with good throttle response.

At 5500 rpm, she's humming smoothly, but that's all she's got. I suspect it's limited by the carb? I'm sure I could fatten up the main jet to get more, but that was creating "popping" from the exhaust the last time I did it.

Currently my setup is this:
VC440 Gen 2
billet rod
chromo pushrods
1.3 rockers
VC low/mid cam
22" tires
Stock G2 gearing
94c clutch, full shift at 3000 rpm
head ported and polished
8 deg timing key
93 octane pump gas
VC header pipe, 18" flex pipe, atv muffler

I played with the jetting a few weeks ago before I added the exhaust. Ended up backing up the jetting down to stock, 1mm I believe. I have 1.1mm and 1.2mm jets I can try. With the exhaust maybe the "popping" from the exhaust will be better.

Also to note, I set my valve lash almost to 0 to stop the "tink tink tink" sounds, which did quiet it down some. I did not notice any performance differences from the .003" and .002" settings that Geoff at VC recommended. I read online that go kart racers will often set the lash at 0. With the rockers and cam I'm guessing it's aggressive enough lift that it doesn't matter.

I'm planning on upgrading the carb to a 32mm of some variety, haven't decided yet. I'm guessing this will get the mixture better at varied rpm, prob a little better throttle response, and possibly more rpm/mph on top.

Any thoughts?

BGW

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Warlordsix

The new 32mm carb should really help your engine breath. Your stock carb is what, 24mm? That alone will make for a big difference in performance.
Ernie

Field6565

Andy...so what spring are you using in your secondary? I ended up getting mine from cart parts plus and it has amazing low end but havent found enough road at my camp to see if I lost any top end. Though looking at the clutches its looks like im getting full shift out of it.

slonomo

I hope so. The carb I'm looking at is $80, so it's worth a try. I'll be updating to this thread as we go. I'm going to try the bigger jets again with the exhaust system and see how it goes. I'll be ordering the carb this week.

slonomo

So my secondary is the Plowman's G1 machined sheaves. It was new 2 years ago or so but was on the G1 rear end. It bolted right up to the G2 rear end and works really well. I had the red spring in there, but changed it to the stock G1 gold spring because it was more low gear than I needed with the clone. I ended up selling it because I liked how the stock G1 spring was working. I have a stock G2 secondary I could try and compare, but right now it seems to be doing what I need it to.

1989Marathon

If you can get your volumetric efficiency up, I would think a 32mm carb is a little at the "beginner's" level. With a good cam, and a little porting, you should be able to achieve a pretty good VE.

What are you trying to achieve? Good low-end, good top speed, or a mix of both? What do you want for max rpm?

Field6565

Andy...what do you think of this. Im thinking about throwing my stock G1 spring back in with a shim. Just curious as to what the outcome will be? When I had it in there before it wouldnt backshift quick enough. Will it now? I'll post up if I try it.

slonomo

I like good low end, lot's of midrange power, and mild top end speed. Not trying to go 50 mph, which prob isn't possible with this gearing anyway. But I think if I could get it to run at 6000 rpm safely for short times (just for fun) then I'd be happy. I'm not interested in pushing the limits rpm wise. I know go kart engines can spin up to 8000 rpm, but they do that at the risk of catastrophe, and no low end power at all. I like to trail ride and climb hills with the occasional fire road romp.

You might be right with the size of the carb, I just don't want to go too far and risk not having low end power.

slonomo

You can put the spring in a vise and pull it to give it some more length, but it likely will return to it's original shape after a short while. You could try the shim, as long as it doesn't bind. Those springs are under some pretty good pressure. If the shim was made of metal I'd try it, but not plastic. Just don't think the plastic would hold up.

I'm curious about the UMAX spring idea. They aren't expensive, so maybe I'll try that one.

1989Marathon

Slo,
There are some guys with Vanguards spinning 11000 rpms. It takes alot of good parts to be able to do that. If all you are looking for is short bursts to 6000rpm, it shouldn't be a problem. I have absolutely no history with the clone motors, but can tell you that I have run my Vanny up past 7000rpm without issue. I am also pushing 14 pounds of boost with a supercharger. That creates alot of extra force on the parts.
Still, if you want to run at those numbers, I don't think a 32mm will do it. Minimum would be a 34mm, but better would be a 36mm. That's just one man's opinion.