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Discussion Starter · #1 ·
Have an 09 525xc. Only purchased cause a dealer had it for a pretty good deal. Always heard they were monsters and beat 450s easily. So I took it home and raced my 2010 yfz450x. 450x has a full dasa, fci and vortex. Stock otherwise. The 450 was winning every race from a roll to a dig. Pavement or grass. So I took it to a shop and had them do the carb mods I read about. Definitely improved performance but still not enough. Now they're dead even til 5th then the 450 still slowly walks away. Had the mechanic go over the whole quad when he did the carb work and he said it's all good. Valves, leak down etc. Am I missing something or is this pretty typical? Not trying to build it to be faster then my 450 just caught off guard.
 

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Is your 525 XC stock? I have a 525 XC too. Like all machines they are a bit corked up from the factory. Mine really woke up after I installed an Akrapovic silencer and header--especially the header. You might also consider the Fuel Customs air intake and KTM's higher profile cam. I forget which one it is (maybe 806), check this website. The RS engine is not really a high rev engine if that is what you are after. It's more of an old school torque engine, designed for XC. At that it excels. If you are looking for a rev happy KTM, find an SX. I have the 505 SX. That machine is a rocket ship. It's designed for motocross.
 

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Discussion Starter · #3 ·
It has an fmf slip on, uni air filter and the Ranchero64 carb mods. It's a torque monster for sure. I knew it wouldn't be a beast up top but still figured it would beat my 450 in a race. I ride my banshee when I'm looking for some serious speed. I just wanted something all around fun. I like the quad a lot just figured it would be able to beat my 450 in a drag race.
 

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My experience a few years ago between my XC and a YZF: 450 XC Performance

The RFS engine platform used in the XCs isn't a fast revving engine so drag racing isn't its forte'. Get in a situation where you need torque like sand or hill climbs and it's all over for that 450. That being said I've pulled plenty of good starts with my 525 against lighter guys on 450s racing MX. The 525 needs more air even in the stock configuration. Adding the KTM 806 cam, a SX intake with stiffener, opening up the airbox are relatively easy bolt-on things to do. Boring the 39mm carb to a 41mm helps too.

The SX intake boot is the stock part from any year, but the stiffener that goes in it is from 2010+ model years available in Europe. Do some searching here to find the part number. To open up the airbox take the cover off the left side (two screws up from the bottom) and put two 2" to 2-1/2" holes through the side of the air box and cover them with prefilter material or something. Then you can put the plastic cover back on in muddy or wet conditions. KTM designed the airbox to be opened up this way. I've used these in the side of my SX airbox before for a quick and clean install: Flow-Rite™ Intake Kits part 14-194 specifically.
 

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Discussion Starter · #5 ·
My experience a few years ago between my XC and a YZF: 450 XC Performance

The RFS engine platform used in the XCs isn't a fast revving engine so drag racing isn't its forte'. Get in a situation where you need torque like sand or hill climbs and it's all over for that 450. That being said I've pulled plenty of good starts with my 525 against lighter guys on 450s racing MX. The 525 needs more air even in the stock configuration. Adding the KTM 806 cam, a SX intake with stiffener, opening up the airbox are relatively easy bolt-on things to do. Boring the 39mm carb to a 41mm helps too.

The SX intake boot is the stock part from any year, but the stiffener that goes in it is from 2010+ model years available in Europe. Do some searching here to find the part number. To open up the airbox take the cover off the left side (two screws up from the bottom) and put two 2" to 2-1/2" holes through the side of the air box and cover them with prefilter material or something. Then you can put the plastic cover back on in muddy or wet conditions. KTM designed the airbox to be opened up this way. I've used these in the side of my SX airbox before for a quick and clean install: Flow-Rite™ Intake Kits part 14-194 specifically.
Awesome thank you! Yeah I like the power delivery on the ktm but it's totally opposite of everything I've ever ridden. Always had yfz or banshees. Ill look into the intake. How much jetting will I need to change? It runs great but it's hard to cold start. It pops on decel still but doesn't hesitate at all when I give it some gas. Should I still be running the stock pilot jet? I believe it's a 42 right now. I'm at 1300ft asl.
 

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Might have to open up the main jet by 1 step with the intake and open airbox maybe, if at all. More airflow can pull more fuel with it to a degree. Should be able to run stock pilot still. Most of the popping is probably from air being sucked between the head pipe and the flange on the head. The head pipes are too long and hit the welds on the flange before the pipes can seal together internally. Pull the head pipe and cut 1/8" off the front of the head pipes (don't trim the flange). look and see if there are goobers hanging inside the pipes from the spring tabs being welded on as well. Mine did pretty bad and I reached in with a dremel tool and ground them away.
 

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Discussion Starter · #7 ·
Might have to open up the main jet by 1 step with the intake and open airbox maybe, if at all. More airflow can pull more fuel with it to a degree. Should be able to run stock pilot still. Most of the popping is probably from air being sucked between the head pipe and the flange on the head. The head pipes are too long and hit the welds on the flange before the pipes can seal together internally. Pull the head pipe and cut 1/8" off the front of the head pipes (don't trim the flange). look and see if there are goobers hanging inside the pipes from the spring tabs being welded on as well. Mine did pretty bad and I reached in with a dremel tool and ground them away.
Cool. Ill give that a try when I get some time off work. Thanks for the help!
 

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What gearing are you running on your 525? I have found a 15t front Sprocket best. I run 15/39 for the dunes but you would be good with 15/38. Your Yamaha 450 has probably 7-10 HP over a stock unit with your Big 3 on it. Is your Vortex both fuel and ignition or just fuel? You have one of the best Big 3 setups available. Full Dasa systems are one of the top of the line exhausts for HP ratings. You put a KTM Bills Pipe on your KTM with the FCI or SX Intake in conjunction with your carb work, spot on jetting and gearing upgrade and your 525 is faster than your YFZ. A bone stock KTM 525XC vs bone stock KTM 450 XC has about 3-4 HP gain.
 

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Discussion Starter · #9 ·
What gearing are you running on your 525? I have found a 15t front Sprocket best. I run 15/39 for the dunes but you would be good with 15/38. Your Yamaha 450 has probably 7-10 HP over a stock unit with your Big 3 on it. Is your Vortex both fuel and ignition or just fuel? You have one of the best Big 3 setups available. Full Dasa systems are one of the top of the line exhausts for HP ratings. You put a KTM Bills Pipe on your KTM with the FCI or SX Intake in conjunction with your carb work, spot on jetting and gearing upgrade and your 525 is faster than your YFZ. A bone stock KTM 525XC vs bone stock KTM 450 XC has about 3-4 HP gain.
Stock gearing for both. Vortex is both fuel and Ignition. I've been debating putting a 15t sprocket on the ktm but I do enjoy the wheelies lol.
 
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