won't run, advice please

Vic Madrid · Posted: Sun Jul 23, 2006 2:45 pm Post subject: won't run, advice please

Hey guys, having a bit of trouble. My motor just up and quit on me during a practice session, just died under full throttle, nothing spectacular to speak of. I thought it was fuel starvation, as it had been running for 20 minutes (not continuously) just fine. But a quick fill of the tank, repriming, checking the plug, changing plugs, and lots of pushes I couldn't get it to fire. The only thing different from the last 2 years of running this thing is that I finally got around to washing out the air filter just prior to the practice session. (it was really, really dirty!)

I towed the kart home and it sat for 2 weeks. I went out to start it up and it fired right up. I parked it, thinking I just had a fouled plug, or maybe a flooded carb (running a pump-around, though), and went to the next event 2 weeks later (this past sunday). At the event, the kart started right up, idled great, revved fine (didn't try full throttle) on the stand, and I shut it down.

Time to run- sitting in grid, motor idling just fine, warming up for 3-4 minutes. Time to go, I jump in, give a few full throttle blips in neutral, only to find it won't rev past about 8 or 9k, then after another couple full throttles it dies. Can't get it started. Thankfully got a co-drive w/ Mike Kline. BTW, ambient temp about 90 and humid, but I've run in hotter conditions just fine.

I just went out today, a week after the failure. It starts up on first pull, sounds great, idles great, after a brief warm up the first couple blips have nice response, then a full throttle blip kills the motor again. Ambient temp is about 80, and dry.

Is this a jetting problem? Is it too rich? It has been using the richest jet in the box that came w/ the kart, but that's what I've been running since I bought the kart 2.5 seasons ago, and never had trouble. Running rich seems counter intuitive if I'm getting more air through a cleaner filter, and today's cooler temp would seem to counter the hot and humid conditions of last week. But I do think there's more smoke than nl. Could this be a fuel pump issue? (not delivering enough at full throttle?) Or does this sound like something internal, like a blown ring? (only 3 autocrosses and 2 brief practice sessions on current ring)

Before I start dismantling everything I thought I'd ask here first. If I've omitted any pertinent info, please let me know (and forgive my ignorance, hehehe Embarassed

)

Thanks for any help! Hope to get this sorted out so I can start thinking about Topeka and meet the rest of you guys. (despite what Garfield has said about you all Wink

)

Vic
_________________
- Vic
- SCCA/WDCR F125 #54
- 2006 Tony//Kart Krypton 125

Andrew. james · Posted: Sun Jul 23, 2006 3:38 pm Post subject:

When you say the biggest jet in the box what size is that? I have no idea if thats actually your problem or not but being to rich will make it die when you go full throttle. It's been in the mid 90's lately in Atlanta and I've been using low 160 main jets most of the time. If you're using like a 180 or something I could totally see that being a problem.

Vic Madrid · Posted: Mon Jul 24, 2006 5:29 pm Post subject:

just checked, it's a 182. But it's also a 41mm PWM, I assume that a bigger carb will need correspondingly begger jets? The box that came w/ the kart has jets ranging from 160-182. So, I'm guessing I'm running rich. And have been w/o problems for the past 2+ years. Why the sudden sensitivity? Does it have any relation to cleaning out my air filter? Should I just try 2 sizes leaner as a start? more?

thanks for any more thoughts.......
_________________
- Vic
- SCCA/WDCR F125 #54
- 2006 Tony//Kart Krypton 125

Scott Nagler · Joined: 07 Mar 2006 Posts: 44

Well I know of a boo-boo I made once... I did a bunch of runs with the choke on and it fouled a plug in a hurry and was getting loaded up to the point of barely running WOT. I doubt your making the same mistake as you seem to know more about it than I do, but thought I might throw that out there... maybe choke is sticking somehow?? I was also smoking like a banshee but thought maybe the oil had settled a bit.
_________________
Still a noob, but can't wait to be "on the pipe"

Vic Madrid · Posted: Tue Jul 25, 2006 4:55 am Post subject:

good thought, but the choke's not on. In fact, I've never needed to pull the choke to start. Is that fact a sign of the potential problem?
_________________
- Vic
- SCCA/WDCR F125 #54
- 2006 Tony//Kart Krypton 125

Scott Nagler · Joined: 07 Mar 2006 Posts: 44

nah, mine'll start n run with the choke off too, I just use it outta habit. Its strange that it runs fine cold but not warm... just outta curiousity have you done a compression check cold vs hot? Have you verified that your getting spark... but usually when a coil fails its just dead forever.
_________________
Still a noob, but can't wait to be "on the pipe"

Mike Rodriguez · Joined: 05 Jun 2005 Posts: 59

Are you saying that you've never changed jetting in the time you've run your kart?

A bad coil could give you those symptoms of not running over a certain RPM but most of the time when it's dead it's dead. I had a dying coil on my old Honda Transalp (twin cylinder 4 stroke w/two separate coil packs) They were both running then one would quit and I couldn't rev over a certain RPM. Unfortunately I don't know of a way to test coils except get a new or used one that's known to be good.

Did you see if you had cracked a reed in the reed block?

How did the plug look when you were first having these problems. Typically if you're running rich @ WOT you'll get a missing feeling. At least that's what I get when I'm running rich (like this last weekend...grrr)
_________________
cheers!

-m.

Vic Madrid · Posted: Tue Jul 25, 2006 5:05 pm Post subject:

[quote="Mike Rodriguez"]Are you saying that you've never changed jetting in the time you've run your kart?quote]

yup. Embarassed

I've got good spark (when grounded, priming the carb, I can see it fire). I've got a couple extra coils, but unfortunately they're a different length and I'll have to fabricate a new mount somehow.

And the plug was wet after it died, so I'm guessing it is the main jet. I peeked in at the reeds, look fine at a glance, will check closer on saturday when I have more time.
_________________
- Vic
- SCCA/WDCR F125 #54
- 2006 Tony//Kart Krypton 125

Ryan D Thompson · Posted: Tue Jul 25, 2006 6:31 pm Post subject:

Definately sounds like the main jet is too high. I had the same problem with mine and it won't run past 8-9k when the main jet is too high. I'm still being conservative and a little rich right now just scared of damaging the motor being lean.

Vic,
you have the banke motor right? Maybe his motors won't rev high when rich. Since we both have the same motor builder and symptoms. I've been fine once I leaned out the needle clip, main, and pilot jet. Start learning what each change does and start changing your jets to get it to run better. I change jets pretty much every time I run the kart and even between runs. I'm still working on getting the jetting right so I'm changing more than most people will.

Mike Rodriguez · Joined: 05 Jun 2005 Posts: 59

[quote="Vic Madrid"]

Brian Garfield · Posted: Wed Jul 26, 2006 6:14 pm Post subject:

Although I have less knowledge Vic, I was thinking about a few things:

1) You say all that's changed was cleaning the filter. However, this is the first time your motor ran in THAT kind of heat/humidity since it was redone by Banke.

2) That same day, I didn't clear mine out at the line and had to short shift for 75% of the course before it cleared out, and it was smoking A TON! First time I've had that problem. Meaning what Ryan just said above, I was too rich and it wouldn't rev above around 8k.

Brian

Vic Madrid · Posted: Wed Jul 26, 2006 7:34 pm Post subject:

the motor wasn't redone, just got it replated by Millenium.

I just changed the jet from a 182 to a 175. I'm just hoping all the fuel that dumped out onto the floor of my wooden shed doesn't lead to a fire Shocked

_________________
- Vic
- SCCA/WDCR F125 #54
- 2006 Tony//Kart Krypton 125

Scott Nagler · Joined: 07 Mar 2006 Posts: 44

that'd be the icing on the cake for ya... hope that gets you goin the right direction bud
_________________
Still a noob, but can't wait to be "on the pipe"

Alan Sheidler · Joined: 09 Aug 2001 Posts: 471

Guys,

When an engine just stops running while you are driving as Vic's has, look to the ignition system. A bad connection, coil, or electronic box (or rotor/stator) may refire and then run erratically later.

This is not symptomatic of an incorrect jet or fuel-based problem.

Alan

Vic Madrid · Posted: Sun Jul 30, 2006 7:44 pm Post subject:

Bingo. After taking off the carb and reed cage, only then did I see the broken wire off the coil. After I get a new coil, and mount it anywhere other than the motor, I'll confirm here if that solved the problem.

THANK YOU for all the other opinions, at the very least it got me consciencious about jetting.
_________________
- Vic
- SCCA/WDCR F125 #54
- 2006 Tony//Kart Krypton 125