Midas

[KartFab]

spark plug reading?

Put in the biggest jet .046"

https://www.ombwarehouse.com/jet-kit-for-gx340-390-and-predator-420cc-1.html

Put in New plug after warming up engine.

Ran at WOT for about1 min under full load.

This is the result.

Can anyone read this?

 

[KartFab]

Well. Here's my conclusion.

Battery added a good bit of weight in front of engine.
Starter added another good bit of weight in front of engine.
Flywheel is heavier with ring gear so more rotational mass at start.

Shaving head with port job did get more flow (I hope) but I haven't jacked around with jetting enough to know what I'm even doing. So maybe I'll just have to do like a more exhaustive test with a set distance to measure acceleration and take pics of plug readings.

How the kart feels is basically the same at start. It will only do baby wheelies when I'm on it.

Changing the carb might wake it up some more but I'm fine with it the way it is. I'm trying to add a tachometer right now, then a cheap little bicycle speedometer. Maybe put some stickers on the tank and forget about the kart for a while.

 

[bob58o]

Can anyone read this?

BPR6ES? LOL

The mark on the strap looks to be in the right spot. I dunno?? I cut up lots of plugs trying to look deep inside. And I still don't really know.

 

[KartFab]

I'm sure I increased performance a little but, but it wasn't enough for my fat butt to wheelie. I'm just coming to terms with that right now and am kinda bummed out.

 

[Denny]

Looks a little lean by the ground strap. Cut plug or look down with lighted magnifying glass for tan or black.


Denny

 

[KartFab]

Looks a little lean by the ground strap. Cut plug or look down with lighted magnifying glass for tan or black.


Denny

Its weird because that jet was the biggest one in the kit for the gx270 -predator 420 kit. I just don't get why (or if) it is running so lean.

Does shaving the head affect rich/lean?
Does porting affect rich/lean?

I have a set of drill bits and i can drill the original jet out (because its too small) after I dial it in, I hope to be able to just hang up the towel on this one and work on another project.

 

[Denny]

Porting will for sure, no doubt about it, positively affect mixture. If it is done right it will lean it out.


Denny

 

[KartFab]

Got a tachometer on there. Not sure if it is accurate at the low rpms, but its pretty stinkin close. It is perfectly accurate at max rpm (tested with another tachometer that is actually accurate).

Set it to setting #5.

Regeared the kart with a 10t jackshaft sprocket.

So with 40 series torque converter, 18" tires, 10t jackshaft, 54t axle, and 5500 max rpm, how long will it take for me to crack my jackshaft keyway? Top speed is now 54.5 mph @5500 RPM according to my calculations. Previous top speed was 43 mph at 5500 rpm. Unmodified top speed was 32 mph at 3600

Touched up a few paint spots and its ready to roll. Yeah buddy!!!!

 

[Kartorbust]

Seems pretty easy to install after glancing at the instructions. Long as it's accurate enough at around valve float, should be fine.

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