A friend of mine asked me to service their bike for them with a view to maybe selling it on after as they aren't using it, it turns out to be a 2002 KTM 400 EXC four stroke in pretty good condition, apart from the fact it hasn't been started for nearly three years now.
We poured some fresh petrol into the tank, only to find it pouring straight out of the bottom of the float bowl, there is a drain pipe there, so I guessed the carb was blocked up with gelled fuel, cleaning time!
Once I'd got the bike home, it was strip down time and out came the usuals, spark plug, air filter, oil filters, oil, coolant, and all the brake fluids and the clutch fluid. I now learned a few things about these bikes, something I was keen to do as I've heard nothing but good things about this engine and these KTM's.
Clutch Stuff
The Magura clutch uses hydraulic mineral fluid instead of the usual Dot 4 or 5 brake and clutch fluid, you don't bleed it in the same way as the other bikes either, you force the fluid uphill through a syringe to remove the air, it's a pig to do the other way, as I found out... I also changed the Master Cylinder seals and piston as they didn't seem to good.
I found this behind the Slave Cylinder, so not sure what happens here, but it needs investigation me thinks!
This was on the KTM forum when I did a bit of a search around for info, I've not come across this before so thought I'd better check up on it before doing anything...
"Standard problem on bike of that era, history;
2000 model had a clutch that spun on a bronze bushing (needed lots of oil) so the routed oil pressure passage into the cavity between the slave and the left side mainshaft bearing so oil would flow thru the main shaft and into the clutch. The oil pressure build up at revs simply pushed the slave cylinder back in so all the fluid in the system flows backwards to the master cylinder, then when you pull the clutch the lever is floppy.
2001 they changed the clutch to a needle bearing which does not need the oil but did they change the oil system, uh not until 2003. Welcome to how KTM deals with problems.
Good news is we have a fix, un-bolt the slave and set it aside, looking in you will see an orange plastic ring, that is the seal of a sealed one side bearing. All we need to do, I use a ice pic, just peal back an edge of that seal, go in with needle nose pliers and rip it out. Now the oil flows into the trans, no pressure build up, clutch works like its supposed to. Done many of 'em"
Not sure how accurate this info is so I'll go and speak to my local dealer and see what they say just to be sure, it is definitely the seal for the bearing, so I thought to do as said above but now have no tension in the clutch lever at all, so I'm guessing it's not right or the seals on the Slave Cylinder have gone as well.
After a lot of chat, I've now pulled out the orange bearing seal and had a pig of a job bleeding the clutch, eventually found it worked best by using the slave cylinder as a pump and kept filling it with a syringe. There is now a lovely working clutch, whoop whoop!
Update: July 2016
The last couple of rides I've been having an intermittant clutch problem, one minute I have one, the next it's gone, then it's back again, today on the ride out it went altogether despite several re bleeds and changing a cracked pastic washer in the master cylinder.
It is fine when I'm doing off road stuff, but within 10 minutes of being on the road finds me with no clutch again... what a pain..
I've ordered another master cylinder service kit, cleaned and replaced the seals in the slave cylinder and all of the connection points, the hydraulic hose has a wear point where it's been rubbed by the cable on the pressure release lever. So if all else fails I'll replace that. Looking on the blogs/forums this seems a normal problem with bikes of this one's age, so I'll keep on playing to see if I can resolve it.
Oil Change
There are two paper oil filters and 2 mesh inline filters, the inline ones have never been removed off this bike at a guess and they do not move at all!
The paper ones have a smaller one, which the oil passes through first, then a larger second one that filters the oil a bit finer before it passes onwards around the system. They are easy to get at and easy to change, including the O rings in the outer casing. Happy days...
The rear brake fluid cylinder is in a very protected place and much better than the newer versions sticking out above the footpeg.
Carb Clean
Both the fuel tank and the Carb were a bit green and again smelled terrible, so lots of cleaning and soaking in fresh petrol followed. The tank got several washes and the internal petrol filter has had a scrub too.
With the carb rebuilt and some seals & O rings changed, now it was time to check all the settings were normal and then run it to see how it goes, it may need a sonic clean etc, we'll see.
Next up was that when I hit the starter, there was nothing, not a squeak out of the bike, so I tried to kick it over, still nowt... mmm, turns out the 'new' battery has no charge and wouldn't charge, so swapped it with another one and hey presto she fired up on the 3rd attempt... so a new battery on order now, next up just gotta set the carb up correctly to get her to tick over nicely and off we go for an MOT.
I'm struggling to get the bike to idle nicely at the moment, she runs great on choke, no worries but as soon as she's warm, I knock the choke off and she dies. I've set the carb up as per the manual so now it's investigation time again.
Update: OK so I've spent a fair bit of time on this carb now, it's had a new float needle in it as I reckon the old one was hard and the tip wasn't pointed anymore, when I reassembled it, it kept peeing out fuel, so I've taken the float bowl off a few times now until I finally sorted the issue, the seal was crimping as it was reloaded and as there is about 5 bits to line up each time you do it, it takes some practice! There was also a massive difference in the gap between where the float sits and the standard spec, gap should be 9mm, it was about 13mm, so adjusted that too... I've also re-routed two of the breather hoses into the airbox so it doesn't drag water into the carb in the winter...
It now runs fine and will run OK once it is fully warmed up, however the tick over still needs a tiny adjustment in the air mixture to get it as good as can be. This turned out to be the idle jet, it was blocked with more gooey old fuel, I've cleaned it twice now, but I'm going to put a new one on it anyway as god know what else there is gummed up inside it. The tick over is a bit better but still not a hundred percent, so keep at it! Part code for the idle jet is: 590.31.607.048 as it's the 48 that is standard on these carbs.
One other rhing that hapened on this is that I cam e to put the bike on reserve to get to a garage after I deliberately ran it low to see how far it would go and found that the petcock had perished inside, so no reserve... err stuck on the roadside in the dark, at least it wasn't raining! A replacement after market one ordered which now works fine and is much cheaper than the KTM version.
A little bit of the RFS Engine History
I found this description of the RFS engine on Thumper Talk forum, thanks to a guy called Dave Hopkins for this knowledge, I don't know him, but it sounds like he knows his stuff from reading this...
RFS was introduced in 2000, based upon the Husaberg which was based on Husky was much lighter than prior 4 strokes, is single overhead cam, kinda racy but not up to supercross level.
2000-2002 it was 400 & 520
2003 250, 450, 525 and both 450 # 525 has SX models that where more hopped up
I believe 2004 the 400 cam back
2006 there was a small production of 560 SMR
2007 was the last year in KTM MC lineup
2008 the 525 was still in quads2009 I believe the only RFS production is for engine sales to other manufacturers, other than that KTM has replaced the RFS with the XC4, still single cam but a bit more modern slightly more racy combo with smaller combustion chamber, shims in place of threaded adjusters, Ti valves and the big improvement ball bearings on the mains. Two items I do not like are a hydraulic chain tensioner and the crankcase oil system. They dropped the ball on us big time
I've not even ridden this bike yet and I like it for some reason, I'm sure it's fab off road as are all KTM's, but what's it like on the road? What's it like to live with? A mate in the Northumbria TRF has one and loves it to bits, so maybe I'll have a play on it once it's all sorted...
Airbox Design
It has the same really stupid airbox design that I really dislike on all the KTM's I've worked on so far, I can't see the point of not having the intake under the saddle and putting a decent filter up there too, it'll make these bikes so much more usable in the UK all year round and other countries too, hey ho... KTM logic I guess...
Summary
I've now ridden this bike on the road and I reckon they are a bit of a beast... not a beginners bike for sure, this one is very lively, it's got much more poke than Lucy's 2007 250 EXC-F as you would expect, once it's warmed up and running, it's nice to just move around and do the technical stuff on, the clutch is a bit fierce at the moment, so maybe it'll soften with a bit of time or maybe I need to bleed it again...
Update: October 2015 - This bike has now done about 6 trail riding days of around 80 - 100 miles each day, the bike is performing much better now it's had a few tanks of fuel through it and I've done another oil change/air filter clean after 20 hours.
- The stand has done the usual with KTM stands, it doesn't work, so I need to sort a replacement washer for the inside as the copper one in there has broken.
- The fuelling still runs on a little so a new set of throttle cables may well be the order of the day, as the other option is to replace the carb needle and I dread to think how much one of them will cost... otherwise it's running pretty well, and it is a joy to ride both on the trails and the road!
- I find the rear brake quite tame, sometimes you don't know if its even working, not very confidence inspiring on a steep downhill, but it maybe that I just need to get a bigger footpeg on it so I know I'm pressing it...
Total Costs of the Parts:
The parts for this came from various places including Triple D in Kendal, our local KTM dealer, Wemoto & a KTM dealer in Newcastle that I have forgotten the name of...
Spark Plug: CR8EK £7.49
Float Needle £17.50
Carb Diaphram £20.52
Carb float bowl O ring: £13.74
Carb float bowl needle £17.30
Clutch Master Cylinder kit £28.44
Rear Sprocket: £39.00
Oil Filters, Paper: £12.10
10/40 Synthetic oil: £14.00
Hydraulic Oil: £4.73
Syringe £6.15
Carb Cleaner: £6.50
Chain DID: Not yet bought
Front Sprocket: Not yet bought
Battery: £24.56 MOT £29.00
Fuel Petcock £24.00
Tyres £47.50
Various postage: £8.00
Total so far: £320.53
31 July 2016
Rocky Mountain ATV FILM of top end rebuild
We poured some fresh petrol into the tank, only to find it pouring straight out of the bottom of the float bowl, there is a drain pipe there, so I guessed the carb was blocked up with gelled fuel, cleaning time!
Once I'd got the bike home, it was strip down time and out came the usuals, spark plug, air filter, oil filters, oil, coolant, and all the brake fluids and the clutch fluid. I now learned a few things about these bikes, something I was keen to do as I've heard nothing but good things about this engine and these KTM's.
 |
| mmm nice! |
The Magura clutch uses hydraulic mineral fluid instead of the usual Dot 4 or 5 brake and clutch fluid, you don't bleed it in the same way as the other bikes either, you force the fluid uphill through a syringe to remove the air, it's a pig to do the other way, as I found out... I also changed the Master Cylinder seals and piston as they didn't seem to good.
I found this behind the Slave Cylinder, so not sure what happens here, but it needs investigation me thinks!
 |
| Damaged bearing seal |
This was on the KTM forum when I did a bit of a search around for info, I've not come across this before so thought I'd better check up on it before doing anything...
"Standard problem on bike of that era, history;
2000 model had a clutch that spun on a bronze bushing (needed lots of oil) so the routed oil pressure passage into the cavity between the slave and the left side mainshaft bearing so oil would flow thru the main shaft and into the clutch. The oil pressure build up at revs simply pushed the slave cylinder back in so all the fluid in the system flows backwards to the master cylinder, then when you pull the clutch the lever is floppy.
2001 they changed the clutch to a needle bearing which does not need the oil but did they change the oil system, uh not until 2003. Welcome to how KTM deals with problems.
Good news is we have a fix, un-bolt the slave and set it aside, looking in you will see an orange plastic ring, that is the seal of a sealed one side bearing. All we need to do, I use a ice pic, just peal back an edge of that seal, go in with needle nose pliers and rip it out. Now the oil flows into the trans, no pressure build up, clutch works like its supposed to. Done many of 'em"
Not sure how accurate this info is so I'll go and speak to my local dealer and see what they say just to be sure, it is definitely the seal for the bearing, so I thought to do as said above but now have no tension in the clutch lever at all, so I'm guessing it's not right or the seals on the Slave Cylinder have gone as well.
After a lot of chat, I've now pulled out the orange bearing seal and had a pig of a job bleeding the clutch, eventually found it worked best by using the slave cylinder as a pump and kept filling it with a syringe. There is now a lovely working clutch, whoop whoop!
Update: July 2016
The last couple of rides I've been having an intermittant clutch problem, one minute I have one, the next it's gone, then it's back again, today on the ride out it went altogether despite several re bleeds and changing a cracked pastic washer in the master cylinder.
It is fine when I'm doing off road stuff, but within 10 minutes of being on the road finds me with no clutch again... what a pain..
I've ordered another master cylinder service kit, cleaned and replaced the seals in the slave cylinder and all of the connection points, the hydraulic hose has a wear point where it's been rubbed by the cable on the pressure release lever. So if all else fails I'll replace that. Looking on the blogs/forums this seems a normal problem with bikes of this one's age, so I'll keep on playing to see if I can resolve it.
Oil Change
There are two paper oil filters and 2 mesh inline filters, the inline ones have never been removed off this bike at a guess and they do not move at all!
The paper ones have a smaller one, which the oil passes through first, then a larger second one that filters the oil a bit finer before it passes onwards around the system. They are easy to get at and easy to change, including the O rings in the outer casing. Happy days...
The rear brake fluid cylinder is in a very protected place and much better than the newer versions sticking out above the footpeg.
Carb Clean
Both the fuel tank and the Carb were a bit green and again smelled terrible, so lots of cleaning and soaking in fresh petrol followed. The tank got several washes and the internal petrol filter has had a scrub too.
With the carb rebuilt and some seals & O rings changed, now it was time to check all the settings were normal and then run it to see how it goes, it may need a sonic clean etc, we'll see.
 |
| Very shiny after a clean! |
 |
| Float bowl was full of goo!! |
 |
| KTM 400 EXC 2002 Carb Manual |
Update: OK so I've spent a fair bit of time on this carb now, it's had a new float needle in it as I reckon the old one was hard and the tip wasn't pointed anymore, when I reassembled it, it kept peeing out fuel, so I've taken the float bowl off a few times now until I finally sorted the issue, the seal was crimping as it was reloaded and as there is about 5 bits to line up each time you do it, it takes some practice! There was also a massive difference in the gap between where the float sits and the standard spec, gap should be 9mm, it was about 13mm, so adjusted that too... I've also re-routed two of the breather hoses into the airbox so it doesn't drag water into the carb in the winter...
It now runs fine and will run OK once it is fully warmed up, however the tick over still needs a tiny adjustment in the air mixture to get it as good as can be. This turned out to be the idle jet, it was blocked with more gooey old fuel, I've cleaned it twice now, but I'm going to put a new one on it anyway as god know what else there is gummed up inside it. The tick over is a bit better but still not a hundred percent, so keep at it! Part code for the idle jet is: 590.31.607.048 as it's the 48 that is standard on these carbs.
One other rhing that hapened on this is that I cam e to put the bike on reserve to get to a garage after I deliberately ran it low to see how far it would go and found that the petcock had perished inside, so no reserve... err stuck on the roadside in the dark, at least it wasn't raining! A replacement after market one ordered which now works fine and is much cheaper than the KTM version.
A little bit of the RFS Engine History
I found this description of the RFS engine on Thumper Talk forum, thanks to a guy called Dave Hopkins for this knowledge, I don't know him, but it sounds like he knows his stuff from reading this...
RFS was introduced in 2000, based upon the Husaberg which was based on Husky was much lighter than prior 4 strokes, is single overhead cam, kinda racy but not up to supercross level.
2000-2002 it was 400 & 520
2003 250, 450, 525 and both 450 # 525 has SX models that where more hopped up
I believe 2004 the 400 cam back
2006 there was a small production of 560 SMR
2007 was the last year in KTM MC lineup
2008 the 525 was still in quads2009 I believe the only RFS production is for engine sales to other manufacturers, other than that KTM has replaced the RFS with the XC4, still single cam but a bit more modern slightly more racy combo with smaller combustion chamber, shims in place of threaded adjusters, Ti valves and the big improvement ball bearings on the mains. Two items I do not like are a hydraulic chain tensioner and the crankcase oil system. They dropped the ball on us big time
I've not even ridden this bike yet and I like it for some reason, I'm sure it's fab off road as are all KTM's, but what's it like on the road? What's it like to live with? A mate in the Northumbria TRF has one and loves it to bits, so maybe I'll have a play on it once it's all sorted...
Airbox Design
It has the same really stupid airbox design that I really dislike on all the KTM's I've worked on so far, I can't see the point of not having the intake under the saddle and putting a decent filter up there too, it'll make these bikes so much more usable in the UK all year round and other countries too, hey ho... KTM logic I guess...
Summary
I've now ridden this bike on the road and I reckon they are a bit of a beast... not a beginners bike for sure, this one is very lively, it's got much more poke than Lucy's 2007 250 EXC-F as you would expect, once it's warmed up and running, it's nice to just move around and do the technical stuff on, the clutch is a bit fierce at the moment, so maybe it'll soften with a bit of time or maybe I need to bleed it again...
Update: October 2015 - This bike has now done about 6 trail riding days of around 80 - 100 miles each day, the bike is performing much better now it's had a few tanks of fuel through it and I've done another oil change/air filter clean after 20 hours.
- The stand has done the usual with KTM stands, it doesn't work, so I need to sort a replacement washer for the inside as the copper one in there has broken.
- The fuelling still runs on a little so a new set of throttle cables may well be the order of the day, as the other option is to replace the carb needle and I dread to think how much one of them will cost... otherwise it's running pretty well, and it is a joy to ride both on the trails and the road!
- I find the rear brake quite tame, sometimes you don't know if its even working, not very confidence inspiring on a steep downhill, but it maybe that I just need to get a bigger footpeg on it so I know I'm pressing it...
Total Costs of the Parts:
The parts for this came from various places including Triple D in Kendal, our local KTM dealer, Wemoto & a KTM dealer in Newcastle that I have forgotten the name of...
Spark Plug: CR8EK £7.49
Float Needle £17.50
Carb Diaphram £20.52
Carb float bowl O ring: £13.74
Carb float bowl needle £17.30
Clutch Master Cylinder kit £28.44
Rear Sprocket: £39.00
Oil Filters, Paper: £12.10
10/40 Synthetic oil: £14.00
Hydraulic Oil: £4.73
Syringe £6.15
Carb Cleaner: £6.50
Chain DID: Not yet bought
Front Sprocket: Not yet bought
Battery: £24.56 MOT £29.00
Fuel Petcock £24.00
Tyres £47.50
Various postage: £8.00
Total so far: £320.53
31 July 2016
Rocky Mountain ATV FILM of top end rebuild
