KLX250S (EFI) Big Bore Kit

Discussion in 'Technical & Motorcycle Services' started by johnnysneds, Jan 12, 2011.

  1. rickypanecatyl

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    Just curious if there was any progress stories out there tuning the BB 351 with FI?

    FWIW I now have well over 100,000KM on my BB351 cc kit here in Malaysia. The bike itself has about 200,000 KM. I am thinking of selling it and getting a new one. Mine is 2008 (like the US 2007 but with KLX450 speedo) and is carbed. The new ones are of course FI.
    The bike has never let me down, but at the same time as it gets older I'm finding it's hard to maintain it to be running at 100%. Something is always close to needing replacement... swing arm bearings, frayed wires, leaking seals, blown shock etc. I've never got the BB TM 33 to 34mm jetting down very well and my mileage is horrible as well as it runs pretty rough at higher rpm's. Super tough to gets jets here, I'm not that clever with that sort of stuff nor do I have much time and while the mechanics here can afro engineer anything and get it running fine tuning isn't there specialty.

    I'm on the fence between getting a new bike and putting a new 351 on or doing a complete rebuild of the old one. If there was one mechanic you know of in Bangkok who could do an excellent job of dialing in the FI with the 351cc I'd be happy to take a ride up there and leave it with him.

    Any thoughts?
     
  2. TonyBKK

    TonyBKK Ol'Timer

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    I'm not aware of any fuel injected 351cc KLX's

    As I understand it the stock fuel injector, even if tuned to maximum, can not supply enough fuel for 351cc.

    I imagine one could install a higher capacity injector, but I haven't heard of anyone going down that road. I would wonder if the stock fuel pump provides enough pressure for a higher flow injector?

    One of the big advantages of going with a carb is it allows you a much larger aftermarket tank.

    I imagine range must be very short on a 351 with tiny stock tank...

    As far as having your Mikuni TM33 tuned here in Thailand, I don't think there are many mechanics here who are familiar with this carb, so probably best to try and figure it out on your own. That's what I've had to do!
     
  3. KLX331 Crazy

    KLX331 Crazy Active Member

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    Hi Beau,

    I am running a similar setup but using Kustom Kraft cylinder and Beet cams, same exhaust with mega bomb. If you want I am willing to share my maps. Forget to mention its a KLX250S, not a D-Tracker
     
  4. niro28

    niro28 Member

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    Hi klx331 Crazy!
    I have just installed bb 331 kit with autotune and pcv and have this problem...
    Can you please give me some more info about adjusting the throttle position sensor

    Thx in advance!

     
  5. niro28

    niro28 Member

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    Hi all! Can anyone give me some detailed info about adjusting TPS? I have installed BB331 kit + PCV&Autotune. Everything is fine except this problem

     
  6. TonyBKK

    TonyBKK Ol'Timer

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    The installation instructions that come with the PCV explain how to reset the TPS. Don't have them handy but it's quite simple. Probably you can find them also on the dynojet website?
     
  7. niro28

    niro28 Member

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    Hi Tony, I thought it's about rotating the tps on the bike )

    Actually now i understand that i'm running lean on any rpm and it is very sad... i cant understand what is the problem. My map is already heavely trimmed, even on idle with 0% throttle autotune suggests +40 trim in order to have 14 AFR. If i start to increase rpm i see AFR 15-16 (on trimmed map!!) Even 16+ so that autotune cant work under this condition (it works only if AFR <16)

    I checked intake and exhaust leaks twice, i even cleaned the injector... no result. I'm confused and would be grateful for any advice

     
  8. KLX331 Crazy

    KLX331 Crazy Active Member

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    Hi niro28, have you blocked off the PAIR valve?? If this is not blocked then you will get fresh air into the exhaust system and the AFR will be lean.
     
  9. KLX331 Crazy

    KLX331 Crazy Active Member

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    Hi niro28, the PAIR valve is part of the pollution control and allows fresh air into the exhaust to help to burn off the unused fuel that exists the exhaust system. It is located beside the cylinder head exhaust port and has to small bolts holding it to the head, I had a plate made to blank it off but one of the other guys just filled the valve with silicone. If you use silicone remember to give it time to set before starting the engine. Hope this helps
     
  10. KLX331 Crazy

    KLX331 Crazy Active Member

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    Hi niro28, the PAIR valve is part of the pollution control and allows fresh air into the exhaust to help to burn off the unused fuel that exists the exhaust system. It is located beside the cylinder head exhaust port and has to small bolts holding it to the head, I had a plate made to blank it off but one of the other guys just filled the valve with silicone. If you use silicone remember to give it time to set before starting the engine. Hope this helps[/QUOTE]
     
  11. niro28

    niro28 Member

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    Hi Crazy, thx for reply!
    PAIR valve is blocked since 250cc.

    Today i cleaned all the wire clamps with contact cleaner, tightened exhaust clamp, even checked my pair valve hose still blocked... no result
    to lllustrate that's how my map looks now:
    2wegaiw.

    as you can see it's heavily trimed and still have high AFR
    I did not check my compression after the installation, because i have no compressometre. I think i should find it and check

    [/QUOTE]
     
  12. TonyBKK

    TonyBKK Ol'Timer

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    Your map looks a bit crazy mate... I recently built a Kustom Kraft 330 KLX for a mate and didn't have to add nearly as much fuel as you have to reach target AFR. I'd share my fuel map created using an auto tune, but it's on my laptop in Thailand and I'm in the US right now.
    No idea your location but the tool shop next to Veera Siam in Khlong Tan, Bangkok sells compression gauges for just 900 baht. I'd say you should definitely check your compression as something isn't right. A leak down test might also be in order but no idea where to buy a leak down tester in Thailand...
    good luck!
     
  13. niro28

    niro28 Member

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    Tony, can u tell please what compression reading should be on 331cc? Won't the KACR fake the readings?
     
  14. KLX331 Crazy

    KLX331 Crazy Active Member

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    Hi niro28, where is your O2 sensor mounted in the exhaust system and are you running the Beet oversize injector? What is your target AFR table set to?
     
  15. niro28

    niro28 Member

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    Hi! idle set to 14, and 13.5 for 2-100% tps. Lambda mounted before muffler, same place then in stock. And it worked good on 250cc. I'm pretty sure now that the problem is in faulty installation, but i don't know what exactly... i used new torque wrench, everything according to manual and DIY guides. Rings were oriented properly, timing was good..Theoretically what can cause running lean? Bad gasket? I think first step i'll test my compression, then acording to results i'll start disassembling
     
  16. KLX331 Crazy

    KLX331 Crazy Active Member

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    Hi niro, I would check your inlet manifold gasket / oring for correct fitting and the throttle body for air leaks. I don't think you have an issue with compression. When you removed the original O2 sensor, did you insert the bypass plug into the original O2 sensor connector?
     
  17. niro28

    niro28 Member

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    I didn't touch the inlet manifold, i think there is a gasket only between manifold and Head... And i have O2 bypuss plug inserted. Anyway i'll try to check at weekend!

    What do you mean "throttle body leaks"? I tried to listen for any leaking sounds. did not find anything... I checked all the clamps - everything was good

    Thx for trying to help

     
  18. TonyBKK

    TonyBKK Ol'Timer

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    As far as I know compression should remain the same with the Bill Blue 331 (which is why you don't need to switch to high octane fuel) but you're right that the compression release on the exhaust cam will make it challenging to get an accurate reading. You can remove it, but it would add a fair bit of work to your troubleshooting...
     
  19. TonyBKK

    TonyBKK Ol'Timer

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    A manifold leak could certainly explain the lean running engine. Are you 100% sure that the o-ring that seals your throttle body to the head is correctly seated? That's given me problems in the past! Certainly before you pull the head off best to check the "simple" stuff first! I don't think you'd be able to hear a leak with the engine running...

    Here's a very easy way to check for intake manifold leaks, shown on a car, but this test will work just fine on your KLX intake manifold too:
     
  20. KLX331 Crazy

    KLX331 Crazy Active Member

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    Niro, when you removed the head, you had to remove the throttle body from the inlet manifold, make sure that it has been reinstalled correctly otherwise there may be an induction leak there. Also try tuning without the air filter installed.
     
  21. niro28

    niro28 Member

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    visually everything on its place, clamps are tightened. Today i sprayed some carb cleaner on junctions as shown on video - no result.
    I think i'll test my compression, then remove cam cover to see what's going on there
     
  22. niro28

    niro28 Member

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    Hi everyone!

    Yesterday i checked my compression - 149 psi!!
    Now i'm pretty sure that the problem is in my fuel sprayer..

    Also i checked my service codes but i have problems with reading it. Can anyone help me? ) Is it 12?? :confused:

     
  23. KLX331 Crazy

    KLX331 Crazy Active Member

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    Hi Niro,

    Did you remove the secondary butterfly and rod from the throttle body?? Inside the throttle body (carb) there are 2 butterflies, the primary and secondary, the primary has the throttle cable connected to it and the secondary is operated by a samll servo motor. if the rod has been removed for the secondary then the FI light will show an error code and the fuel injection will go into limphome mode (will not inject full fuel). I noticed from your video that I could not hear the servo motor working. If removed, reinstall the rod into the throttle body, be careful to make sure it is syncronised to the main butterfly. When you turn the key on you should hear the servo motor cycle and the FI light will go out. Once this is done, run the engine and recheck the autotune maps.

    With the FI light is showing an error code, you will never tune the engine.
     
  24. heilong

    heilong Ol'Timer

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    Don't use carb cleaner anywhere near rubber parts, if you still care about them! It's not safe for plastic, either. Brake cleaner is much milder to rubber, but not great either. Starting fluid or WD-40 would be safer to use for this kind of test.
    That's why when you use carb cleaner to clean carbs or parts, you should completely tear down the carb / remove all rubber and plastic parts first!

    As was already suggested, try take off the throttle body holder (the plastic part bolted down to the head) and check the condition of the o-ring. According to the manual, this o-ring should be replaced with a new one on reassembly. When I did a top end rebuild recently, my old o-ring had a little damage on it, I've heard from a mechanic friend before in this area you don't want any damage or wear whatsoever, he said just replace it if any doubt. Put a thin coating of grease on this o-ring as well (according to the manual).
     
  25. niro28

    niro28 Member

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    Hi guys, I'm back with my "lean" problem =)
    Does anyone have proper PCV map for 331cc?
     
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