apex top end cut out

[Christiansdad]

06 apex 70, with stage 6 intake and cage, 20mm keihin carb, main jet 100, pilot 58, bando coil, new airsal 50cc cylinder kit. Ngk br8es

Thing ran great until we changed the cylinder kit over from a stock 50 drr cylinder kit to a airsal kit. Has a real bad sputter like not leting it rev up past a certain spot(similar to a rev limiter). It is engaging about 6200 rpm and a few more thousand it cutts itself when it gets to the gravy point where it wants to start to pull more..and it feels like it has more. Buddy at the track said it is to rich so i swapped the jet from a 100 to 95..it sounded better on the stand but pulled the same once set on the ground. I moved the needle up and down from rich to lean..nothing still has the sputter..from a dead stand still..gas it, just starts to break the tire's loose then starts the sputter..you can ride it easy and it rolls out fine. It idle's and everything. .

[redonkulousruntsracing]

Sounds like it needs more fuel. I run 100 main in our stock 50. The pilot seem high, that is probably what its running on. Once you get past 1/4 throttle it starts transitioning to the main jet.

[Christiansdad]

i put a new plug in and changed the fuel filter. The fuel filter didnt fill up right away, i kicked it over and it started to suck the gas threw the filter (almost like when it needed it) I havent changed the lines yet but the seem to flow ok at the end's of the line. As far as the carb, i ordered new from hetrick,slapped it on, ran great then. The carb isnt but 3 months old at the most. I run 110 gas with about 3.5 onces of ams oil dominator when he races...other than that we have been running non ethonal 93 pump gas with same mixture.

[redonkulousruntsracing]

Is this a PE 20 or a PWK carb?

[Nichols Atvs]

Go up 10 points on your main jet . if it will take it. if it does and runs better great then try another 10 and come down till plug is a nice chocolate brown ! Rich dosent hurt lean can blow up.

[Christiansdad]

its a PE carb..when i got the carb from hetrick, they said it was pretty close and didnt need much jetting required. But i did change the reedcage,intake, and the airsal kit on it. My cvt stuff stayed the same pretty much. 3 grams on the front, 1000 max rpm spring, and my clutch is a 107 stage 6 adjustable with the white springs..which are real light...but have them adjusted almost all the way out. It does catch about 6200 rpm.. friend at the track had a tach...i am ordering one for $85 from g force and a jet kit to see what happens. What is the highest jet you need for a 50 with the carb i have.

[fastrnrik]

Your pilot seems too big and main seems too small.

Try a 42 pilot and 110 main, or something close to that to start with, then get your needle & air screw adjusted properly. Different motors like different stuff, but that should give you somewhere to start with

Just my $.02

[redonkulousruntsracing]

Kinda what I was thinking .
my guess would be a 42-48 pilot and main in the high one teens to low twenties.

[Christiansdad]

alright... I ordered jets 108 to 120 main jets. And a kit for pilots from 40's to high 50's. A hand held tach tool. A guy named mike from g force gave me a setup on the clutch what should be on there and the pushed me on buying the tach, also a good friend at the track said the same.

[o4twinpeaks]

on our airsal 70 ac kit with wrh pipe we were 115 main 50 piolt with the 20 pe carb


NOT saying this is what you need but just letting you know where we were at.

[Christiansdad]

thanks any info would help out...this quad use to be a 70 when we got it before..

[selbygirl]

it seems like wen every somthing happens to a bike every one goes for the carb not saying its not the carb but check all your electrical the gound s the factory conection from the cdi to the coil check the color of the plug when ever i had electrical problems the plug is on the blackish side in color afew weeks ago one of our bikes was acting funny and we all thout it was a carb issue come find it was one of the shoe springs went bad and some times those kill switchs will give you a fit if you took the motor apart retrace your steps you may for got somthing i no i forget a lot espescially when i have all the kids in the trailer playing and they keep bugging you can i ride can i ride or are we ther yet good luck hope you get it

[Christiansdad]

got this thing figured out now..i say about 2 gallons of gas and throw a match to the whole thing...problem solved...at a 110 main jet the plug looked brand new still..so i went to a 112 looking somewhat the same but getting darker...then went to a 115..rode it for 2 mins or so..coming back to the pits to check the color of the plug, bogged down,shut off..i tinkered with it for ever..guys at the track threw a compression tester on it 30 psi...they said it wouldnt do nothing until over 90 or so depending..piston looks like it just come out the box. Has about 1 hour race time on it, if that..it did run a little warm cause of the heat saturday...does anybody know where i can order a ring for it

[selbygirl]

i use marc at hot quads best way to get ahold of him is email him just check out ther web sight hotquads if they dont have it he can point you in the right direction well at least you got it i was wondering if you checked your compesion take care tommy

[Christiansdad]

i called marc..i didnt know his email. he did point me toward a company named ''MHR moped hospital'' out of south flordia. They sell all the stuff for airsal still..alot cheaper than those other cylinder kits thats out there on the market.one more question on the jetting..when you change the pilot. What purpose does it do or what will happen if its not right..i know now what the wrong main jet will do just curious what the pilot does.

[redonkulousruntsracing]

Your quads idles and takes off on the pilot jet when you adust the air screw, that is how too tell if your pilot is off. You should be at 1 1/2-2 turns out. If less, you need a larger pilot, if more then you need a smaller pilot. When you hit the gas the needle comes out of the main, transitioning from the pilot to the main.

pilot jet - low end
needle - midrange
main - top end

Apex has a great carb tuning guide on their Tech section of their website.

[selbygirl]

end when the pilot jet is to small seems hard to start nice bike are you guys racing district 13 we do a few d13 races mostly d7 but with gas prices so high we bin doing a lot of backyard racing

[Christiansdad]

thanks for the compliement..here is what i have now..122 ran ok but sputtered when it got to top..i changed it to a 120 and it blister's shi# everywhere on top end..but before it had a small sputter until it got to the top..so needle adjusting right...my pilot is a 150..about 2 turns to the left from the bottemed right(air screw)...o forgot to metion the ring snaped in two..the cylinder look fine..just the ring. The outer ring on top of the piston had spots around it that match the head..if that sound like it was running lean..also i noticed that it had a different type crank when i pulled the head to put a ring in. The crank had some plastic stuff built to the crank.it was on both sides of the rod going both ways???

[mmsoup]

I am assuming that the plug is new and only had a run or two on it. When you say it burbled on top did it behave sort of like a rev limiter? or did it just stumble? Like if it hit the top of the range it suddenly acted like it lost fuel and then caught back up OR just bumped rapidly and with some force? I'm thinking it is leaning out still. When the head cam e off was there any aluminum on the plug?

The crank is what is called a stuffer crank, designed for a higher primary compression rate in the case which supposedly flows better than an OEM crank. Be curious to know what the stroke is.

Did the piston have any scuffing on it? was there any melting on the crown or maybe the edge of the crown on the exhaust side?

What was the compression on the cylinder B/4 it blew?

Again, just curious.........

Have you done a leak down test on the motor? If you have a leak or two that may be contributing to the motor leaning out at the top end. You mentioned that you replaced the cylinder so I am curious if you developed a base leak in the process. Need to check the intake for leaks as well

Also, just for clarification, Did the motor have the stumble with a 122 main and then burn up after you went to the 120?
The reason I am asking is that you leaned it up going down in main jet. Pilot makes very little difference at the top end as far as durability is concerned.
I burned up a shid ton of motors before I finally got it through my head that rich is cheaper lol. Motor rarely stumbles when I jet it rich either by the way.
Good looking Apex, good luck getting it to the front of the pack, these things aren't that complicated but can be frustrating. Sorry for writing a book but thought I would ask the questions that I would ask myself

[Christiansdad]

it hit more like a 4 stroke rev limiter...the stroke on it i am not sure...i use a sh.. Load of gaskets to clear the head and piston. But before it lost its compression it was at a 105 main..i didnt pay much attention to the plug then until it started to not rev all the way out...just reved it up on the stand figured it was ok..this plug color?? Now it changes from dark to white..cant get a established color..i even put a 130 just to see it get dark..it came out running like a turd and still having a ghost type plug...the exhaust header has oil dripping from where it meets the pipe..so its rich but the plug aint showing it..marc said check on the type of plug..its a br8es..he said use a br9es..what is a common 50 plug size..i recken everyone uses ngk i guess..just the 3 dollor plug..i dont wana get nothin exspensive until i get the color of the plug right...here is what my piston looked like when i tore the topend off .if thats hits a lightbulb for anyone..plus another thing..my brother bought a apex..same as mine..same kit put on and new carb just like mine, except his doesnt have a crank..his is doing the same thing.nothing happens this week its going on a road trip to marc at hotquads..this lean b@st@rd has way to much money in her now two take a dump on us again.

[mmsoup]

It's running lean most likely because you have an air leak and by the sounds of it a major one

I am assuming that you don't have a leak down test kit?

Are you familiar with how one works?

You could be leaking air from either crank seal, the base gasket, the intake gasket(s) the carb boot, the case half section join or a combination thereof

I burned more than my fair share of motors up before I finally understood how important gas (not oil) is to the cooling function of these cylinders.

I posted on a thread in the Apex section a couple of months ago titled Quick??? by Hooligan
It is a little over halfway down the first page of the Apex section
I posted photos and a description of our home made leakdown kit. Parts cost around $25 and it has already saved me twice.

We have two full mod CVT's that we race GNCC with and couldn't afford to have anyone else maintain them for us the way we want them maintained. Took us a year and change to learn the motors inside out and we still learn hard lessons from time to time

Biggest challenge recently was a friends 70 that was running like a terd the night before a GNCC. Took us 2 1/2 hours but we found a couple of leaks, a clutch shoe dragging and a bad carb. Watching his kid fighting for third on the holeshot the next morning.............PRICELESS

[Christiansdad]

i am the same way on saving what i can and what to spend $ on. I did get my tach in the other day. I got a max rpm reading of 10,500 average while on the stand. The plug is looking like choclate darkish...lovin it too...i got a gun to measure the temp on the head,water etc...i got about 210 to 212 in the middle of radiator..the head was about 170 to 180, whats the temp they(cvts)usually run at ? The needle in the slide is set on the middle...i may want to move the clip to see if it takes that sputter away...it happens when you gap back on it hard..but say you give it more than 3/4 thottle at take of it spits at ya some till it gains some speed...my 5 year old son trust daddy a little better now working on his quad since its ran for more that 2 hours. He's trusting it more and more he rides..here is his first time with a little air

[bulldogfallon]

A leak down test would be the ideal way to check for an air leak....If you have one then you can rejet all day and not get a desired result.

You can build one pretty cheap..just do a google search for "how to 2-stroke leak down tester"

It is a valuable tool to have for any mini racer....

When we get motors sent to us for rebuild or for HP kits to be added we check for leaks....I would say more than 50% have leaks that led to the demise of their engine and added frustration to parent and rider.

Also---Get your fuel down to about 100 octane...anymore than that and you are hurting your performance.

The temps are a little high, but that could be due to air in the system, small Apex radiator, jetting, ignition timing etc

Most Apex stators come slotted so they can be adavanced, but I think the slot is too aggressive in size...you can try to retard the stator if it is slotted..to see if the temps change at all.

Needle adjustments on the carb are have a huge impact on how a quad runs....I see pilot info and main jet info, but have tried moving the needle around as well?

I suggest a leak down test right away to see if there are any issues there.

What pipe are you running?

[FISH ON!]

Hey Chris..............

I don't have any time this week but if you don't get it figured out, I'll be back on the 16th and would be glad to leak check your motor and help you figure out what's going on. I'm home today and if you have it together with just the pipe and carb off I could do a leak check today. Just can't spend much more time than that on it being Mothers day.......

Todd

[Christiansdad]

I think i got this thing actin right somewhat. Its frustrating when you go to bed that night the next day he's on it for 30 min it starts to do the same thing over again and again. ONE day good next day a retard. I messed with the main so much i didnt think about the pilot to much...i did the idleling it up and turning the air screw to one and half turns once or twice..didnt get the big picture then..the 48 pilot sounded about right but when i dropped it back to a 42 then 45..which i may put the 42 back in it..that thing snatches you head back and keeps pulling and pulling. now its just getting little man to hold it there. going towards suspension part now i belive..on the lookout for so 12in shocks and i think the rear is 10in...............another thing i have noticed about the carbs on 50's..the 21mm pwk keihin seem to work better on that...my brother slapped his stock carb that he had when it was a 70..changed the main one size and the pilot down two sizes and done deal.



i will be sending the motor off to g force in the future to get refreshin and just out of curiousity how much that little boy puts out on the dyno....anyone have a stock drr 90 pipe laying around. Gary at g-force said that was pretty much the ticket for all the motor you could get out of a 50

[bulldogfallon]

There are other 50 pipes out there, but most are double the price of a new drx90 pipe.