Hear is the deal.

Got a 1999 Sport from someone who had a bunch of work done. It had been Ported (guessing top end for the dunes), has Carbon Reeds, 38 Flatside Mikuni, FMF pipe and silencer. Within a few months, the piston burned up just crusing along in the midrange. Had to have it resleved and clean up the ports again. Burned up again. Now it is at .20 over. Found the carb had a 420 main jet, increased to 470 and put a EGT gauge on the bike. Started running good, but seemed slow. The primary clutch spring was green, changed it to brown and now it seems faster, but still lacks something. The bike tops out at 55 mph on the GPS. EGT is at 1100 in the midrange, lower on top end. The bike is a monster in the low and midrange, but I get left behind in the drags about 40 mph and just can't get any real top end speed.

That said, here are the questions:
I do not know if it has had any clutch work, or how to tell if it has. Are there any identifying marks for fingers, helix, etc?

What are the changes I should make to start getting the top end speed?

 

If the quad burned out in the midrange, then changing a main jet won't help. Try raising the needle. That actually controll the midrange more than the main jet does. Also, the next time you rebuild, have Swaintech coat the piston for you. Use ceramic on top and poly-moly on the sides.

 

How far is the egt gauge from the piston face?? If it is like mine and 7" or close, midrange sounds right, your main is way too big in my opinion. Your gauge should read around 1300 on top end,(if it is 7"). Check for airleaks. Spray all around the motor, head, base, intake, airbox, reedcage, etc. and listen for changes in idle. If it changes the idle, you have found your airleak. Fix asap or you will lose another piston. You have a quick response probe or heavy duty on the EGT gauge?? What pilot and needle are you running? Where is the airscrew. how many turns out? Best thing to do is get rid of the FMF pipe and silencer, sell it on ebay. Get either an Aaen top-end pipe or HPD trail pipe. Any head mods that you know of?? Race port or trail port?? My carb with my set-up, close to yours, I am running a 410 main. Helix is more than likely stock, not identifiable really if it isn't. I am running a teflon coated from Aaen,44-36/ green spring should work well unless it also has blue marks, then get an Aaen green or red. I am running s58 weights in the primary, you can identify those, they have the weight # on them. I am running an Aaen blue secondary spring. Like I said I am trail mod, so if you are the same, you should be close. Also, what needle clip position are you in??

 

NCScrambler, here is the info you asked about. I had forgotten to list that this bike had a HotSeat Head also, but unsure of the porting. No airleaks to speak of, plus the bike always idles down nicely.

Mikuni TMX 38 Flatslide
470 Main
32.5 Pilot
Airscrew 1 ½ turns out
Needle 6EJ12-58 (3rd down from leanest in series)
Clip on the bottom (5th down)

EGT from HPD
Probe is 7 inches from head

Clutch
HPD Brown Spring
S55 Weights
Blue Secondary Spring

After getting all of this info written down, it looks like I could go to a size or two smaller on the needle to fatten up the midrange.
Thanks for taking an interest!

 

You've gotta kinda tune out that EGT focus. That's what I used to do as well. Read your jetting primarily by the plug color, and use that info, coupled with kinda watching the EGT to keep it in the ballpark. Start at the 0-1/4 throttle, that's controlled by your pilot screw. Anything more than 3 turns out is probably not gonna have an affect. Change one thing at a time, and in small increments. Hold the machine at 1/4 throttle for about 1/4 mile (concentrate on very steady throttle) use your kill switch on the left bars to kill the ignition. Coast to a stop and check your plug. Don't get me wrong here, still watch your EGT so it doesn't go ape$%^%, but the plug color is what your looking for. Black is rich, white is lean, and cocoa brown is in the zone. Repeat for 1/2 throttle, and 3/4 throttle: those are adjusted by the needle position. Then do it for wide open throttle (WOT), that's controlled by your main jet. Has the oil injection tank been removed from the front of this machine? Are you supposed to be pre-mixing the fuel? Also if the oil injection is still installed, there is a filter for the oil as well as the fuel on the left side of the fuel tank.

 

You sound way too rich to me, you are extremely close to my set-up with mods. I am running a 410 main, same needle with clip in middle, 35 pilot, could probably use a 32.5 but I make it work. I totally agree with Modquad about the plug along with egt. Just for your info though, my egt heat ranges from, 1/8 throttle ideal temp is from 800-1000, 1/4 throttle from 1000-1100, 1/2 throttle from 1100-1200, 3/4 throttle 1200-1250, and full throttle from 1250-1350. That is the guide I got with my gauge 7" from the cylinder. I am also leaning towards Modquads thinking that you may have an oil problem. You are running so rich everywhere except idle-1/4 that it can't be getting oiled right?? If you still have oil injection, check the setting of the oil pump, you may also want to bleed the system and replace the inline oil filter. Also, check the hoses and everything well, check valve may also be bad. If you are running a mix what ratio are you using? If you need info as how to adjust anything or check the check valve, let me know and I will answer those questions. Here is a real good page on jetting that I refer to often that you may want to read. Carb Tuning Here is another excellent article on tuning and problems that may arise. Eric Gorr It is alot of reading, but it will help you learn alot about jetting and problems therein. You may see something also that we may have missed. Hope this helps you out.

 

If I may throw this in, the brown spring and s-55 weights will produce about 6500-6700 RPMs, which is probably not going to be good for the FMF pipe. The best thing you need to do before anything else is definitely ditch the pipe and get a good one first. You just might be very surprised..........

 

put that FMF pipe in the thrash,you will never have a decent top end power with those pipes on a polaris,with a 38 tmx it should pull the s-55 weights pretty easely,your mains sound too rich,i don't remember the 42mm specs on the top of my head and wasn't that rich either tough...
i run a digatron with egt's and digital tach,but the better fine tuning come from the color of the spark plug at all throttle opening,i've put a dial-jet on some time ago to get and little edge on jetting whenever the temp is.

 

Modquad, the oil injection has been removed. Premix 100LL AVGas at 32-1. I am planning a trip next weekend. I will take an assortment of carb parts with me and make the suggested runs at 1/4, 1/2, 3/4 and WOT. I had been doing WOT runs and coming up with cocoa, but have not done the other runs. NCScrambler, thanks for the links, I will read up! To everyone else, yeah, I figured I would get a few votes to trash the FMF. Honey, I'm gonna need about $300! Thanks for all the help. I will update when I make some progress.

 

OK, if you are running premix, then ixnay on the oil pump crap. You must be running a race port or 14:1,15:1 compression to be running that 100LL av gas otherwise, you are throwing money out the window. Do you have a hard time getting racing gas in your area? Just wondering why you are running avgas? I am not knocking it, I know Modquad runs it in his, but here, take time to read another interesteing article. Race Gas vs. Av Gas Just click on the appropriate link. Sounds like you are doing things right. Just be patient and it will all come together.