Apex 50cc no power

[redonkulousruntsracing]

Well, here goes. I have tried everything that I can think of to figure out what is wrong with Seth's Apex. I have had a lot of people look at it and can't figure out why it's so dead. Running the 4-6 limited class at Unadilla showed me just how off his quad was. He was 5-7 seconds a lap slower than the other 2 Apex 50's that were ordered with his and both of them are completely stock, I know both quads and families that own them. It definitely wasnt the rider, it's the quad, he had it up on 2 wheels jumping into Gravity Cavity trying to get the most out of it.
It starts and runs great on the 1st kick with no choke. Spark plug is a nice cinnamon color. We run VP C12 with Klotz R50 oil. 40:1. Off the line it takes off good and winds up to 10,500 rpm on 300 foot flat runs. On the stand in rev's to 13,500 rpm. Runs about 195 - 210 degrees on hot days after long runs (10 minutes) a normal 4 lap race it runs about 180 degrees. Here is what is on it now and every thing I have tried:

4th - new top end and piston, 165 psi compression cold.
.028" squish
21mm kehin carb, 98 main jet, 45 pilot, air screw about 1.5 turns out.
stock front variator (hetrick ground face)
3 g rollers, tried from 2.5 to 4g and the 3's seem to work best
787/16/28 belt, the stock 780/16.5/30 was 2 seconds slower per lap at Unadilla
Stage 6 clutch pack, no weights in shoes, red springs turned up to 3rd long mark, stage 6 R/T vented bell, red malossi torque spring with malossi slider. Clutch engages 7000-7200 rpm.
20 tooth front, 32 tooth rear
18" sno-hogs
new crank seals, passes a leak down test, no difference
new Stage 6 reeds w/ 4mm spacer no difference
took off rear air box set up and tried a normal intake, no difference.
stock pipe, repacked silencer, ran with out silencer, no difference.

My next thing to try is to cut the pipe in half and see how carboned up it is inside, the silener was loaded with oil and weighed about 5 lbs. The opening of the pipe into the silencer was really carboned up and a 1/2 in bolt barely fit thru it. I tried to clean it out with some gas and some 1/4 inch nuts put it all in and shook it up a few times and loads of black stuff came out. I am wondering if the pipe is plugged up causing the lack of power.... It always had black crap coming out of it where the pipe slips over the head pipe. I dont have the black stuff any more now that I have jetting right, was way off running a 115 main and a 38 pilot for 3 months.

[jerkyboy]

Not to hurt your feelings BUT it didnt sound or run well at pleasure vally ether. Get ride of that 20t front sprocket put a 19 on it stick with the 780 belt. The stage 6 clutchs are a little heavy.
try a yamasita or frc. 7000 is a little to high of a stall for a stock 50. As for jetting I ran that same carb 38 pilot 118 main. If you can get another pipe to see if that could be the problem also.
Im sure somone else will chim in with there 2 cents.

[EthansDad]

I'd agree with Jerky on the gearing, start there. your motor specs seem in line, so I would turn my attention to clutching with those rpms. is the belt diving/shifting before stall? in other words does the belt start moving up/down in the variator BEFORE the rear wheels start moving? that will sap power quickly, like always taking off in second gear.

As for the pipe, they do get loaded up and can hurt performance a little (guessing not your main problem). a quick way to clean them up is to take them to a radiator shop and have them dipped. cheap, works and a lot better than cutting the pipe open.

-EA

[redonkulousruntsracing]

No feelings hurt here, I think you mean Steel City, cuz it ran like such a turd there that I wasnt going to bother going to Pleasure Valley. At Steel City I was running only 100 lbs of compression along with the 115 main and the 38 pilot. Since then I put a new top end on that was speced out and the cylinder was cut for proper squish and the piston and rings fit to the cylinder, and changed the jetting to a 98 main and a 45 pilot, the first setup would not rev over 9500 rpm and it was blowing tons of smoke out of the exhaust and oozing black goo out the silencer and where the pipe meets the head pipe.
The first 2 practices Friday were with the 19 tooth front sprocket, I switched to the 20 and he picked up 3 seconds per lap practice 3 on friday and again looked good saturday morning.
The holeshots are a little off but the big difference in power is on long straights and up hills. I have adjusted the stage 6 to kick in any where from 6000 rpm all the way up to 8000 rpm and 7000 seems to work the best. I watched kids just drive right by Seth on the long straight that goes past the starting line. Up hill runs where it needs mid to top end power is where it is really dead.

I checked with the cover off, the variator starts to move in slightly then the shoes engage, with the belt right at the top of the rear pulley. At home I have tried 19:32, 19:35, 20:32, 20:35 and either the 19:32 or 20:32 seems to work the best. I really dont know what more to try, I appreciate the input, but no one can seem to find anything wrong with it. I like the idea of taking the pipe to a radiator shop and having it boiled out, but I really want to see how it looks inside.

P.S. Seth rode for 2 hours staright today and it sound good, but I can see it going up hills that it's dead, oh well he had fun tearing up mthe yard.

[jerkyboy]

I still feel that the stage 6 clutch is too heavy for a stock 50. Id try putting the old clutch back in with red molossi springs. Also
this is a new cylinder correct. Has it been ported if so that might be one of your problems. Not to put down your engine builder but somthing isnt wright.

[fomospede]

all these guys are pretty sharp on these 50cc machines . no where do you mention ignition timing.i had put alot of time and testing in and thought that are 50 was a dog as well,then i picked up an adjustable cdi and the difference is unreal
we also run 18'' tires
18-32
stage6clutch and vented bell ,red springs stall 6000 rpm
3.5 rollers
stage 6 cyl, 155 psi
this may seem minor but have you balanced your tires? this also makes a suprising difference in performance
have you checked that every thing spins freely
oh yeah i found my s6 clutch bell was out of round by .014 too that really helped out check that for sure!
good luck

[jerkyboy]

fomospede its a stock limited 50 and hes not allowed to change the timing or cdi box.

[redonkulousruntsracing]

Jerkyboy- I gave up on my 1st engine builder. He had 2 tries. This top end is from Shawn Dean of DS Modz out of Rochester NY and it was on one of the fastest limited 50's around last year. It is a proven setup that worked well last season. I was at his house 2 weeks ago and we worked on Seth's quad for hours. He took parts right off his kids quad and tried them on Seth's to try and figure it out, but really couldn't find much wrong with it. I felt pretty good about it until we went to Unadilla then I watched kids on other 50 limited bikes just cruise right by him, it was so noticeable that after 1st practice I checked the carb to be sure it was opening all the way. I really feel horrible about putting Seth out there on a turd machine, I can see him shaking his head when he gets passed, he's trying his hardest out there. He would hold it wide open from the gate all the way thru Gravity Cavity and not lift until the 180 corner at the top. Hell I could have zip tied the throttle wide open and he still could have rode it and gotten passed by just about everything out there.
As for the timing, the Apex has an adjustable stator plate. It's set in the middle, I can advance it a little more but it just makes the quad run hotter and not any performance gain.
And maybe I am not under standing, but you keep saying the stage 6 is too heavy for a 50? Are you referring to the weight of it or the way it engages?

[jerkyboy]

The weight of the clutch. I feel that its to much for a 50 to turn.
some may not agree but thats my opinion. Im not sure if you can use a smaller carb on it and still be leagal but try putting a 16mm
carb on it.

[edwardsp&b]

I sure am glad that im done with 50's! They are a huge headache!
bryan

[fomospede]

actually there must be a call out of where the timing should be stock and from what you are saying advancing it would be wrong that would give you bottom end and take from the top ,you would have to retard the timing to gain topend performance, as for the clutch being heavy are you going to notice it at 10,000 rpm?
im sure you have squared the machine and checked toe in as well?

that gear combo seems really steep id drop to a 19-35 or 18-32

i had ran a 18-28 when we changed to a 18-32 it was quicker off the line wound out faster and the top speed was very close to the same!

have you looked at all the static loss possibilities ?

[redonkulousruntsracing]

yup, the alignment is good, all wheels roll freely, bearing are all good. I have the timing in the middle. there is a slot in the stator plate and you can rotate it about a 1/2 an inch. It comes all the way retarded, and I advanced it half way whan I bought it last year. It ran fine there all last year, I tried advancing it the rest of the way but it just caused it to run hot.

[fomospede]

if you are like me you get frustrated and walk away for a bit and vent it out here:)
well looking at what others have jetted at ,as well as mine
and where you r at with yours makes me wonder if your stator is going south ,ive seen it posted that if you start leaning out to run good something is wrong with the sparky side of things!
seeing that your jetting is 20 points less than most ,makes sense why your top end speed is off

[redonkulousruntsracing]

i know it was jetted 108 main and 45 pilot when it was bone stock last year and I ran 50+ races on it with out even changing a spark plug. this year after a few rebuilds and some port work and the compression bumped up, I upped it to a 112 main and a 45 pilot and It ran decent, but was gutless, blew smoke and black crap out of it every where, it wasnt buning the fuel. When I took the cylinder off the last time there was oil every where, the silencer weighed a good 5 lbs. Shawn was the one who tried changing the jetting. One of the othe Apexes that was bought with mine also has the 21mm carb and he runs a 98 or 100 main in his and his kid can ride circles around Seth. Like I said before with the 112 main it wouldnt rev over 9500rpm and was sputtering and puking unburnt gas and oil out of it, and with the 98 in it it revs to 13500rpm and every thing cleaned right up, but it's been gutless all year!!! My son wants to keep racing but I don't want to take him anymore because I cant bear to watch him out there. I think I see a PVL in my future... I dont care about the 50 limited class anymore, so.....