Hello and welcome. Hope you checked your valve clearances before you went nuts chasing this symptom. Tight valve or worn guides will hang idle once engine is good and warm. You may not believe what I suggest, but humor me. I've seen this complaint many times. No mention of you checking throttle free play. Should always have 3-5 mm free play at grip. If not, fix it. Your mid 2000s bikes use a really weird throttle cable routing method. Unless cables are routed exactly as shown in manual they will be too tight and hold throttle open a bit at idle. There is not enough free play adjustment to relieve tension on cables unless they are routed under tank as shown in your manual. You mention replacing fuel tank. If cables are not routed properly next to tank they will almost certainly pull throttle open when turning handlebars.

 

Thank you for the response. After thinking on it , I did add 15mm bar risers to my handle bars during the work process. I did snap the throttle open and closed, in every position imaginable and it would still move freely. Even with the bike running I would turn the handle bars lock to lock and didn’t hear any increase in rpm. I will double check the manual for cable routing and also check free play in the throttle cables. As far as valves go, I haven’t checked those yet , but certainly will. I have been procrastinating those due to the fact that I don’t have new valve cover gaskets in the event they tear or rip.

 

I bought a 2007 525 EXC back in May. I've basically rebuilt it from the ground up. My understanding is the only difference between the 450 and the 525 is the stroke length. So its basically the exact same bike.

I had cleaned my carb as one of the major needs to get it running in the first place. God knows how long it sat. And the person that bought it previously thought it was a two stroke. So the carb was gunked up to hell with 2 stroke oil. But I digress.

I put 100 miles on it, and it just started running like complete $hit. After tinkering with a bunch of things, I finally concluded that I was back to needing to re-address my carb. I bought the Tusk Carb rebuild kit, which comes with all but the air idle jet. I also bought a mid body gasket set separately. For whatever reason, RockyMountainATV.com wouldnt sell me the rebuild kit in California; which is strange since the kit came with factory default jets, and the 2007 is 50 state legal; but again I digress. I found both kits on Amazon, and they shipped to me no problem.

Spent a saturday doing a thorough teardown and cleaning. Then very carefully put it back together. RMATV does have a killer video that goes through the process step by step. Theres a bunch of nuances to putting the carb together correct. And I forgot to mention; when I opened it the first time, I saw that it was missing the splash guard that surrounds the fuel jets. So I had purchased that to install with this rebuild. Both gasket sets were a perfect fit. I'm happy to report that bike runs absolutely flawlessly now. And its actually much quieter than it had been previously. So, food for thought if your bike isnt running as well as you'd like.

If you did rebuild your carb; you might want to also buy a new accelerator pump diaphragm. Thats the only thing I didnt replace internally on the carb. I also had bought 10 feet of polymer hose, and cut brand new vent lines. The polymer hose was $7 at Tractor Supply Co.

Auggiedoggie mentioned valves. And thats also a major potential pain point. Since it had been 100 miles since I got my bike running, I had planned to re-check my valve clearances when I did the work on the carb. But by the time I was all done, I wasnt up for it. So I figured; well lets see how it runs with the carb rebuild, and go from there. It was 100% the carb in my case. So I'll put the valves off for another 100 miles. But if you havent done yours, you definitely need to do that as well.

I'll throw links below for the parts I bought, as well as the youtube video. Obviously you'd need to doublecheck the compatibility for you exact model. But if its a Keihen FCR-MX carb (mines a 39mm), it should work well. Just confirm your jet sizes in the service manual for a 450. I just check my manual, and the table for 2005 models (which is the max my service manual goes to) shows the 450 and 525 having identical jet sizes.

Good luck man!

Links:

Amazon.com: Tusk Carburetor Rebuild Kit For KTM 525 EXC 4-Stroke 2006-2007 : Automotive

Buy Tusk Carburetor Rebuild Kit For KTM 525 EXC 4-Stroke 2006-2007: Carburetors - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

Amazon.com: 26-1512 Racing Carburetor mid body gasket Kit Compatible With For KTM EXC 450 2007-2011，EXC 525 2006-2007, EXC 530 2009-2011，Replacement EXC-G 400 2006 : Automotive

Buy 26-1512 Racing Carburetor mid body gasket Kit Compatible With For KTM EXC 450 2007-2011，EXC 525 2006-2007, EXC 530 2009-2011，Replacement EXC-G 400 2006: Carburetors - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

 

Thanks for the info /

I bought a 2007 525 EXC back in May. I've basically rebuilt it from the ground up. My understanding is the only difference between the 450 and the 525 is the stroke length. So its basically the exact same bike.

I had cleaned my carb as one of the major needs to get it running in the first place. God knows how long it sat. And the person that bought it previously thought it was a two stroke. So the carb was gunked up to hell with 2 stroke oil. But I digress.

I put 100 miles on it, and it just started running like complete $hit. After tinkering with a bunch of things, I finally concluded that I was back to needing to re-address my carb. I bought the Tusk Carb rebuild kit, which comes with all but the air idle jet. I also bought a mid body gasket set separately. For whatever reason, RockyMountainATV.com wouldnt sell me the rebuild kit in California; which is strange since the kit came with factory default jets, and the 2007 is 50 state legal; but again I digress. I found both kits on Amazon, and they shipped to me no problem.

Spent a saturday doing a thorough teardown and cleaning. Then very carefully put it back together. RMATV does have a killer video that goes through the process step by step. Theres a bunch of nuances to putting the carb together correct. And I forgot to mention; when I opened it the first time, I saw that it was missing the splash guard that surrounds the fuel jets. So I had purchased that to install with this rebuild. Both gasket sets were a perfect fit. I'm happy to report that bike runs absolutely flawlessly now. And its actually much quieter than it had been previously. So, food for thought if your bike isnt running as well as you'd like.

If you did rebuild your carb; you might want to also buy a new accelerator pump diaphragm. Thats the only thing I didnt replace internally on the carb. I also had bought 10 feet of polymer hose, and cut brand new vent lines. The polymer hose was $7 at Tractor Supply Co.

Auggiedoggie mentioned valves. And thats also a major potential pain point. Since it had been 100 miles since I got my bike running, I had planned to re-check my valve clearances when I did the work on the carb. But by the time I was all done, I wasnt up for it. So I figured; well lets see how it runs with the carb rebuild, and go from there. It was 100% the carb in my case. So I'll put the valves off for another 100 miles. But if you havent done yours, you definitely need to do that as well.

I'll throw links below for the parts I bought, as well as the youtube video. Obviously you'd need to doublecheck the compatibility for you exact model. But if its a Keihen FCR-MX carb (mines a 39mm), it should work well. Just confirm your jet sizes in the service manual for a 450. I just check my manual, and the table for 2005 models (which is the max my service manual goes to) shows the 450 and 525 having identical jet sizes.

Good luck man!

Links:

http://[URL]https://www.amazon.com/dp/B09MMPF96N

[/URL]

http://[URL]https://www.amazon.com/dp/B0DZCB6DM8

[/URL]

hints.

I bought a 2007 525 EXC back in May. I've basically rebuilt it from the ground up. My understanding is the only difference between the 450 and the 525 is the stroke length. So its basically the exact same bike.

I had cleaned my carb as one of the major needs to get it running in the first place. God knows how long it sat. And the person that bought it previously thought it was a two stroke. So the carb was gunked up to hell with 2 stroke oil. But I digress.

I put 100 miles on it, and it just started running like complete $hit. After tinkering with a bunch of things, I finally concluded that I was back to needing to re-address my carb. I bought the Tusk Carb rebuild kit, which comes with all but the air idle jet. I also bought a mid body gasket set separately. For whatever reason, RockyMountainATV.com wouldnt sell me the rebuild kit in California; which is strange since the kit came with factory default jets, and the 2007 is 50 state legal; but again I digress. I found both kits on Amazon, and they shipped to me no problem.

Spent a saturday doing a thorough teardown and cleaning. Then very carefully put it back together. RMATV does have a killer video that goes through the process step by step. Theres a bunch of nuances to putting the carb together correct. And I forgot to mention; when I opened it the first time, I saw that it was missing the splash guard that surrounds the fuel jets. So I had purchased that to install with this rebuild. Both gasket sets were a perfect fit. I'm happy to report that bike runs absolutely flawlessly now. And its actually much quieter than it had been previously. So, food for thought if your bike isnt running as well as you'd like.

If you did rebuild your carb; you might want to also buy a new accelerator pump diaphragm. Thats the only thing I didnt replace internally on the carb. I also had bought 10 feet of polymer hose, and cut brand new vent lines. The polymer hose was $7 at Tractor Supply Co.

Auggiedoggie mentioned valves. And thats also a major potential pain point. Since it had been 100 miles since I got my bike running, I had planned to re-check my valve clearances when I did the work on the carb. But by the time I was all done, I wasnt up for it. So I figured; well lets see how it runs with the carb rebuild, and go from there. It was 100% the carb in my case. So I'll put the valves off for another 100 miles. But if you havent done yours, you definitely need to do that as well.

I'll throw links below for the parts I bought, as well as the youtube video. Obviously you'd need to doublecheck the compatibility for you exact model. But if its a Keihen FCR-MX carb (mines a 39mm), it should work well. Just confirm your jet sizes in the service manual for a 450. I just check my manual, and the table for 2005 models (which is the max my service manual goes to) shows the 450 and 525 having identical jet sizes.

Good luck man!

Links:

Amazon.com: Tusk Carburetor Rebuild Kit For KTM 525 EXC 4-Stroke 2006-2007 : Automotive

Buy Tusk Carburetor Rebuild Kit For KTM 525 EXC 4-Stroke 2006-2007: Carburetors - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

Amazon.com: 26-1512 Racing Carburetor mid body gasket Kit Compatible With For KTM EXC 450 2007-2011，EXC 525 2006-2007, EXC 530 2009-2011，Replacement EXC-G 400 2006 : Automotive

Buy 26-1512 Racing Carburetor mid body gasket Kit Compatible With For KTM EXC 450 2007-2011，EXC 525 2006-2007, EXC 530 2009-2011，Replacement EXC-G 400 2006: Carburetors - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

thanks for the response. I will try what auggie suggested first in terms of the throttle play and the routing. If that doesn’t work I will try valves , and last but not least the carb rebuild. It’s frustrating as I took this bike on a long ride the week before and had none of these issues, not saying valves couldn’t have moved during that time. But I just find it unlikely. The bike did sit for a while before I bought it, got it from an older gentleman who probably put 600 miles on it in 7 years of ownership. I will report back with what I find.

 

Thanks for the info /

hints.

thanks for the response. I will try what auggie suggested first in terms of the throttle play and the routing. If that doesn’t work I will try valves , and last but not least the carb rebuild. It’s frustrating as I took this bike on a long ride the week before and had none of these issues, not saying valves couldn’t have moved during that time. But I just find it unlikely. The bike did sit for a while before I bought it, got it from an older gentleman who probably put 600 miles on it in 7 years of ownership. I will report back with what I find.

I hear you man. Every time I've thought things were good to go; something new cropped up. I love my bike. But its definitely a queen in some regards. My carb issue was a one day it worked, and next day it was jacked up. An easy way to tell, is to just take off the float bowl. You'll have a very good idea of whats up with the carb, just visually from that. If the gasket were to rip; the gasket needed to be replaced anyways. But honestly, it probably wouldnt, since they're rubber. It'll just looked like melted goo, if its old. It should re-seal up though.

If you havent checked your valves though; thats a must do job. If you've done it already, then its probably not critical. But if its never been done, I would make that my first project. Its not super hard to do. The only real pain in the *** is finding TDC on the right stroke. Once thats done, the adjustment isnt too bad at all.

 

I always try slamming handlebars lock to lock when idle hangs and I suspect throttle cable problem. It sometimes will be intermittent. Check carefully before chasing other issues. Your throttle free play should remain constant clearance with bars turned both ways and idle speed should not change when bars are turned. Valve clearance issue is possible but is usually accompanied by hard starting or other low speed performance complaint.

 

Ok. Thanks man. Going on a long ride tomorrow with a buddy. I will try the bar lock to lock trick and see if that helps. Just a thought, If the idle circuit is running too lean could that be causing the intermittent high idle? Would it be worth turning out the pilot screw and try giving it some more gas if the throttle cables aren’t to blame ?

 

Nice photo in your first post... looks like some good technical rock climbing there, lol.

 

Thanks, lots of fun riding up here.

 

Just general info on setting idle mixture - I'm not experienced with your KTM carb, but have rebuilt & tuned many carbs, and they are all similar. Don't confuse it with the speed screw - that happens. You may know all this, just saying, so hang with me.... If the mixture screw is behind the slide, it's an air adjustment, so in cuts air and makes it richer, out leaner. If it's on the engine side of the slide, it's a fuel adjustment, opposite effect, in is leaner. Turn it in till it seats lightly while counting the turns, for a baseline. Turn one way or another 1/8 of a turn and listen for the idle change - give it 10s to settle. Set it to the middle of where it starts to drop either way, going in/out. So if it drops at 1-1/8 in and 1-7/8 out, 1-1/2 should be right, the highest idle. I'd always err on the side of richer and check plugs for color.

 

Thank you for your response, I am aware of the difference between idle speed screw and pilot/fuel screw. But thank you for explaining it just in case I didn't/someone else that reads this in the future doesn't know. I have the pilot screw currently set to about 1.5 turns out maybe just a tad under that, 1.4 turns out from seated. I have not taken this carb apart to look at jetting, however I am up at 6k+ elevation and am curious if there is different sized pilot/main jetting installed by previous owner or service center that touched it before me. I rode the bike with a buddy of mine today and we did about a 70 mile loop, going from 6k all the way up to 9.5k above sea level. Something I didn't consider or factor into my decision making process was that carb adjustment (idle and pilot) may just be so sensitive on my bike that cranking it even a 1/4 turn may be too much at one time. The past week trying to track down this issue I often turn the idle screw 1/2 turns at a time to get the desired rpm. The pilot screw I'm more carful with adjustments, but even 1/8th turn on that screw could have a big effect? On the ride up today, the bike was idling okay, at a stop light after it was warmed up I turned the idle screw maybe 1/8th rotation to increase the idle speed as the bike seemed like it wanted to die. No major issues for the rest of the ride on the way up. When we reached the turn around point, the bike was wanting to idle high again, nothing like before, but certainly enough where I wanted to turn it down just a bit. I'm estimating 2.5-3k rpm and I turned it down closer to 1.5-2k. I did not touch the fuel screw on my ride today at all, just the idle speed screw. It rode fine, great throttle response, no bogging, no backfiring or anything like that. Got roughly 48mpg on this ride today which is pretty consistent with what I normally get. Going to check the valves next week and see if that changes anything, if not I am going to take the carb out and rebuild It I think.

 

A leak at the rubber intake boot will cause a hanging idle, that's also easy to check. Some people say to shoot starter fluid on it, but that seems sketchy. A spray bottle misting water on it works. Not sure you're describing a hanging idle though. I tend to work on banks of 4, old Japanese bikes, and that's their nemesis, among other things.

As some wag once said "when I pass, put my ashes in the fuel tank so I can go through that carburetor one more time"

 

Ha, thats funny. I dont think its a vacuum/intake leak. I have pulled the seat and tank off it and ran the bike and sprayed carb clean every which direction all over the carb its self and both of the intake boots. NO change in rpm what so ever. If/when I get that carb off ill closely inspect them to make sure there are no cracks or anything. Yeah, these carbs can be quite a pain in the *** im finding out.