525 and maybe the 450's jetting problems

[JC Soto]

At this point I sent my carb to the dealer. I requested for them to FIX it or replace it. After all, a $7500.00 NEW bike should work! :think: By the way, I just found my side stand bolt on the floor. It appears that the side stand bolt broke! :( (the section that goes through the rubber chain guide - any suggestions for the '03 bike stand mount?).

In my carb fix research, I inspected all the jets and found them to be the proper stock numbers (200MAJ, 100PAJ, OBDVT#3, 178MJ, 42PJ, 85 other jet??). In the many iterations, I did try an adjustable PAJ and tried 7/8 through 1 1/4 turns. This did not make much of a difference, and nothing was noticeable with respect to the number of turns I had on the Fuel Screw (FS). Could there be a leak on the choke? maybe, I did not check or know how to. I did checked and eventually replaced all the manifold clamps (they got damaged from the many on/off installations of the carb). I also did try the OCEMN and OBDVP needles. Both worked much better than the stock needle, but did not effect the FS turns. I also adjusted the valves (they were way too tight).

Could the problem be on the ignition (I think very unlikely) or the rev. limiter on the carb? I am baffled! JC

 

[Katoum]

You said your stock needle was a OBVDT than you said you tried both a OCEMN and a OBVDT and they both worked better than stock. Is there a typo there somewhere? Which was stock and which was not. What was the improvement over the stock? I will also be talking to KTM Canada about our problem. Still waiting to hear from other owners of 03's to see if they checked their number of turns out there carbs are at. if you know please post here. Thanks

 

[JC Soto]

Katoum,

Sorry about the typo. The stock needle is OBDVT. The aftermarket needles I tried were OBDVP and OCEMN. Both after market needles are a bit richer. The DVT is slightly narrower in main diameter, and the EMN had more taper (among other properties - I am using James Dean Jetting Guide spread sheet). I got some backfiring with the DVT when stopping with the engine or hesitant under 1/8 throttle; needle on #4, 170MJ, 55PJ. The EMN felt about right on #2, 165MJ, 55PJ. Also note that I live at 8400' and ride from 6500' up to 11700' (Colorado, US). Like I said in my previous posts, I set my FS at 1 3/4 to 2 turns with the 55PJ after my third or fourth carb rebuild/cleanning! It did get better after fully disassembling the midsection of the carb. Hope this helps. JC

 

[Katoum]

I must be missing something because your last post said you were taking card to dealer. My only complaint is the 3 1/2 turns to get a proper needle then having it vibrate out onto the ground. I changed to a 48 pilot but found no change in the number of turns out. Thumper talk does not seem to have anyone with problems like mine that I have found so far. In your last reply to my post you mentioned after several cleaning and dissassemblies, there was a improvement, but I take it your still satisfied. Just to confirm you know are able to idle smooth at less than 2 turns out? Thanks again.

 

[Katoum]

Please excuse all my typo's. I hope you can read between the mistakes.

 

[Smitty]

Have you checked for exhaust leaks? I know that can wreak havoc on these thumpers. I also went nuts trying to get the fuel screw set correctly saturday before realizing my choke was wedged partially open, perhaps you should find a way to check that circuit for leaks. Perhaps with WD40?????

 

[JC Soto]

Katoum,

In my carb nighmare, I had to disassemble the midsection and remove the slide/needle guide (held by 2 screws in the under side of the mid section - section is not shown on the parts catalog). I found that the PJ hole went through these two sections (the midsection and the guide), but in my case the hole in the guide was not aligned and the gaskets were not seated properly. I reassembled and noticed that I did get a response in the idling by changing the PJ's, but nothing significant until I used a 55PJ at 1 3/4 turns on the FS. This was a big improvement, but it is still wrong. These bikes should run with a 42 or 45, KTM is even bragging that they improved this circuit in the carb!

Even with this compromise, the bike would run "lean" at idling or when barely twisting the throttle (less than 1/8 throttle). So, being anal about it, I re-disassembled the carb again, but this time it got worse. This might be an indication that there could be an air leak somewhere in there. Maybe the gaskets are shot.

Anyway, I gave up and sent it to the dealer. I paid for a working new bike, and after more than 40 hours dicking with it, I give up. Let them repair it or KTM replace it. After all it is a very expensive new bike. Let me know if you need any help. JC

 

[endoquest]

Good for you JC, after that many hours I would have done the same thing. I hope your dealer is helpful.
Katoum, I'm going to try to get to Terra Nova this weekend, ever heard of it? Got any info or flyers?

 

[jeb]

The fuel screw on my USA G spec 03 450E was 1.5 out from the factory. I run it at 1 out with the EMN# and 172 mj and it runs and idles fine.

BTW, you can edit your own post if you find typos, etc. There's an Edit/Delete selection at the bottom right of all the post. You can only edit your own, of course.

 

[Bonehead]

Recap
Plugged casting on the right side of the carb. (Top air vent, under brass fitting vent) Fixed with a .074 drill.
Ran better for 5 min. (AIRSCREW WAS AT 1 3/4 TERNS OUT)
Tried the carb off my 00 520 and it ran better.
Went to a 62 pilot jet, what the hell go big and work back, 182 main, raised the needle 1 clip, ran better on the stand.
Went 0ut rode for 30 min. on MX track wouldn't start after hot but ran fine
Went to a 48 pilot, clip back to stock, 182 main, 1 1/2 terns out on the airscrew.
Took the carb. Apart 5 or 6 times by now.

I found that the voltage regulator was loose and fixed.
It runs better but very hard to start now

And yes I paid $8,400.00 out the door $860.00 tax and licence

 

[JC Soto]

Bonehead,

Katoum is telling me that there are five of us now with this probblem. We should all keep in touch so that if we have to talk to KTM USA we can do it as a group and have more leverage to get our carbs replaced if nescesary. ;) My email is elcabraloca@hotmail.com.

I think your hot start problem is because the 62PJ is too big. Try a 58 or the 55PJ and set the adjustable PAJ to 1 1/8 turns. I did noticed my bike a bit starved when running below 1/8 throttle (somewhat hesitant and misfiring), but otherwise it would run just fine and start when hot. JC

 

[JC Soto]

You have to love the guys at CYCLE ZONE KTM! Mike Kruger is the manager and he has been very proactive in resolving my problem with the carburetor. Mike's mechanics found the same problem we have been diescribing on these postings, and he was unable to get it to work either :ugg: . So, he talked to KTM and they want to check the carb and either fix it or replace it ;) . He is giving me one of his new bike! That is service and dealer backup :thumb: .

Oviously this problem will be addressed and resolved. I will post the problem as soon KTM knows (and passes down the info) on what the heck is causing this. I would suggest for anyone who's got this problem to talk to their dealer. Cheers, JC (CrazyGoat, also know as the OldSlowGoat).

 

[Blackie Dave]

Bonehead;

Blackie Dave, here. I know this is off the subject, but was the easiest way I could think of to contact you.

I picked up a dozen of those buckle anchor plates for the RC5's. Let me know if you'd like a few. They only cost about $1.25 apiece.

 

[endoquest]

Hi JC Soto, it's been a week or so, any verdict on the carb? You ARE running the stock exhaust, correct? Bonehead's is stock. Mine is stock.
Once you get this figured out you're going to love this bike, the forks are better than my '01(which were GREAT already) and the motor (with the right jetting) has more hit off the bottom even though it's the same motor. Steering is GREAT and the bike is very balanced in a standing position. I'm not going to change any valving or springs in the front for the time being. My stock #2 rear spring sagged way too much with the 8mm of preload but static and race sag work GREAT at 16mm of preload(about 4 full turns). I weigh 170lb and am "competitive", anyone heavier might want a #3. Notice how many times I've said GREAT in this post, this bike rocks. Good luck

 

[endoquest]

Anyone else read the latest Cycle News article about the National Hare and Hound? Curt Casselli couldn't race because his brand new 525MXC "popped and spit and refused to respond positively to jetting changes". His crew gave up, blaming electronics. He didn't even start! I think we'll be finding out the real problem soon. It's in the latest issue #42 on page 9.

 

[JC Soto]

Endoquest,

Got a new carb from Cycle Zone KTM, Mike Kruger (the manager) came through for me. I sent him the original carb back (mailed it!) and he was also unable to make it work. KTM wanted the carb and wrench it to make it work or replace it. Mike sent it, but he was so cool that he took one of his floor bike. How cool is that! He figured that I had gone through enough pain that I did not warrant the wait. Anyhow, I installed it and guess what...the darn machine would still sputter and run rough. Well, I ended removing a grossly fouled plug and replacing it (the previous carb ruined the plug). The bike immediately changed into a purring manchine! :thumb: The original carb is definitely faulty, so far I have not heard from Mike, but he should know as soon as KTM figures it out.

A few weeks ago James Dean suggested I use a OBDVP needle so I installed it and it rocks. I have the following setup for 8400' (40-50 F, dry air) 42PJ, 1 1/2 turns on the FS, 165 MJ, 100 PAJ, 200 MAJ, 85 SJ (startjet), and stock acceleration pump (stock exhaust). The bike is now predictable and runs as expected. I have not started messing with optimizing the carb, but that will come latter. I just want to ride before the white stuff falls!

Regarding suspension, I am going to install Chuck Wagoneer's kit on the front and replace the rear springs for something stiffer. I am 190 on my b-day suit and I think a bit too heavy for the back shock.

I am also curious to know what the heck is wrong with some of the carburetors. It usually takes a lot of noice to make the manufacturers respond to a problem, but when PR kicks in things seem to move a bit faster!

I do have a few questions for you (or anyone that might know the answer), I know that the BK mod allows you to adjust the amount of squirt you get from the accelerator pump, but why adjust it? I mean, what is the effect of the squirt on the initial throttle twist (i.e. pilot jets/initial needle movement)? How do you know how to adjust the squirt amount or the timming of the squirt actuation, to a given needle type (i.e. Dxx series vs Exx or vs Fxx series)? If you know, let me know. I would like to understand how the BK mod affects the carb and its effects on carburetion before I do it to my new carb. Thanks JC

 

[cbm4stroke]

If you could get by without a pump and only run on the carburetor metering circuits it would be best. However, to get excellent off idle response the pump is used as a gap filler to transition from idle to the needle circuits on rapid throttle openings. Unfortunately the pump blasts a basically uncontrolled shot of raw fuel into the intake. Since the pump operates during all throttle movements not just the rapid ones and it is not a very well metered shot you want the pump squirt to be as short as possible to bridge the gap between the METERED carburetor circuits. This helps prevent the engine from loading up, conserves fuel and will improve engine response. With the second generation Kehin FCR you have a adjustment screw to control the pump start point and with the BK mod a second screw is added to control the stop point--giving complete and easy adjustment to the pump "Squirt" start and duration.

Consensus says about 1 second of squirt starting as soon as the throttle slide moves is a good start point. Depending on your pilot circuit and needle selection you should experiment from there to get a optimum performance for your situation (location, altitude, needle, PJ, PAJ or setting of the Adjustable Pilot Air Jet (APJ) if used, etc.).

Cheers

Clark

 

[JC Soto]

Clark,

Thanks for the response. It is just weird that KTM has not address the added BK mod screw onto the new bikes. How easy is it to just request Keihin to add the adjustability to the ACP (of the squirt amount). Not to mention that they have set the squirt period too long, for about 3 seconds. Is there a reason why they do that?

I did do the mod (to the new carb) and did noticed an inmediate responce change. I did some posting reading and set the squirt time to ~ 3/4 turns in from the point were the actuating cam just contacts (and takes the play) the rod of the diaphram. This was recomended by "James Dean" at TT, as a good strating point (BTW, this seems to match the initial KTM setting by +/- 1/8 turn). I did set the squirt duration to 1 second (it is really easy when you pull out the carb of the engine, and set it next to the tank to constantly have a fuel feed).I am satisfied with the results. I will leave it at that; for a while. :cool:

Generally speaking, do you increase the actuation time (early on vs. later on) with needles having more taper (i.e. E or F series vs. D series) and when using smaller pilot jets? And, do you reduce the squirt amount (i.e. 1/2 sec from 1 sec) with richer needles and pilot jets? (it kind of makes sence to do it that way....) Thanks for the lesson.

I know this is were I should by playinbg around with this stuff, but it sure would be nice to have some guidelines. JC

 

[James Dean]

JC,

Your suggestion to adjust the pump duration in relation to the needle taper sounds good in theory but is difficult to choose in real world riding and setup. To be practical, I would suggest getting the pump at about the 1 second duration and leave it.

The clip position is more often set a step richer when reducing the pump time from 2-3 seconds down to ~1 second. When you have a needle that is working good, a few varied clip position tests with fuel screw adjustments are the most worthwhile things to check.

The needle tapers are usually selected for a steady acceleration and longer periods where it could be many seconds to minutes when going up long climbs. They also affect jetting a little higher up at mid throttle. The Dxx(.75 degree) needles are leaner at mid-throttle than Exx(1.0 degree). The Keihin "standard" taper needles for the FCR carb are Exx taper.

James

 

[JC Soto]

James,

Thanks for posting and shedding some light to my question. Is there a book or manual that I could get hold of, so that I could understand better how the FCR carburetor works? I been scanning the webs and I been piecing together the information to get a general idea of how the individual jets interact, but as a mechanical engineer I would like to get into the core of things. Thankc, JC

 

[JC Soto]

This is an old thread, but the answer to this carb problem might have been found! Per Mike (at Cycle Zone KTM), he got the carb I sent him back from KTM USA. The problem KTM found with the original carb was on the slide assembly. KTM claims that there is a plate on the slide assembly that was installed backwards. KTM reversed the orientation of this plate and the thing works as it should!

It kind of makes sense, if the slide is not fully seating and sealing the air intake, you would need a lot of fuel to get a better fuel/air mix (i.e. therefore the increase pilot jet to a 55 to get some response).

This is an indication that a few badly assembled carbs from Keihin slipped :scream: ; as there has been about 6 bikes that I know of with this problem. I can say that because I did not remove that slide from the original carb, and it would not work when it came on my brand new bike.

So, if this is the problem it is an easy fix. For those who have this problem, try changing the orientation of the slide cover. :thumb:
JC

 

[Bonehead]

Thanks JC Ill let you know what I find on my slide
BH

 

[Bonehead]

Well if I could get the slide out I could flip the plate over NOT!!! The screw that holds the slide is so tight that it wont budge
Looking at the manual it looks like it is in backwards It has a M stamped on it and the plate has ridges on the side faceing the intake. In the manual it looks like the flat side of the plate goes to the intake side.
Looks like I will take it in and let the shop try and get the slide out!

JC Do you remember what the slide looked like?

 

[Katoum]

Problem solved! No more 4 turns out on idle screw. Thanks to JC Soto and Mike at Cycle Zone the elusive idle fuel screw problem has been solved.
Page 23 Part 21 Gasket Plate Throttle Valve was installed upside down. Check orientation in manual and you will see the a there is a small hole in plate which has to be as in picture, which is hole to bottom of carb. Mine was upside down, causing the idle circuit to run extremely lean regardless of jetting changes.
It incredible that this part goes together either way and one can see how a factory worker could have made the mistake in assembly. It's also easy to see how we all missed problem on inspection of carb. So if anyone out there has modified their 03 RFS's to make them idle by richening pilot circuit to correct lean idle please check by looking in bore from the rear of carb, and there should be a 1/4 hold in plate near bottom of plate, if you see half a hole in plate at very top of bore then yours to is upside down.
After correcting we turned idle speed wheel right back and turned fuel screw to 1 turn out and bike fired up immediately and purred like it should.
funny how the simple things are the ones that go undetected for the longest.

 

[Katoum]

Bonehead, plate will not go on backward, only upside down, read my previous post and I explain how to check without taking carb apart.