883 to 1200 conversion gone bad???

Discussion in 'Sportster Models' started by DavesKystoms, Feb 21, 2010.

  1. DavesKystoms

    DavesKystoms Member

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    I've got a 2002 883 receintly converted to 1200. My problem is a lean condition at about 2000 rpms. Weisco pistons with stock bored cylinders large valves and ported heads. 175 main jet 48 pilot jet with two .050 washers under the needle (started with 45 pilot jet also started with a 175 main jet but have had everything in it up to 200) If I run the bike at 2000 rpms (no load) for about 3-4 minutes the pipes start glowing, if I go above this it cools off abit. Oh I also have a different tapered needle which is supposed to allow more fuel at this low rpm. initial timing is at 10* BTDC @ 950 rpms ful advance is 28* BTDC @ 3500 rpms VOES was recailibrated to get it to switch at a higher rpm. What should my next move be??
    Thanks
    Dave
     
  2. prodrag1320

    prodrag1320 Account Removed

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    recheck your timing,jetting seems in the ball bark
     
  3. Chopper

    Chopper Senior Member

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    Are you sure you're not over jetting making it too rich? I have always used the dynojet tuners kit so not much help on your jet sizes and needles, as prodrag said timing could be your problem.
     
  4. Hoople

    Hoople Account Removed

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    You really need to measure the actual A/F ratio with some type of wide band (such as Innovate) A/F ratio meter or CO infrared. The VOES toggle point is dependent on intake manifold vacuum (engine load) and is not really a function of RPM point so I don't understand. Do you still have centrifigal advance along with voes? If so, what amount of centrifigal advance do you have & what is the VOES advance. Would you know at what in/hg your voes toggles?
     
  5. DavesKystoms

    DavesKystoms Member

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    Vacuum is affected by rpm more rpm=more vacuum. The VOES was set to toggle at 4 in. making it advance at 2450 rpms, we set it at 6 in. now it advances at 3500 rpms. its not a too rich problem my plugs are white after a run at 2000 -2500 rpms. Do you use an A/F ratio meter on all the engines you build? I should be able to get it close enough to keep my pipes from glowing without one. After all im not loking for 10ths of hp I just dont want the pipes to glow. These things are not that complicated. Ive built hundreds of engines for all types of racing applications in the past 25 yrs(very succesfully). This is the first cv carb Ive ever messed with and at first was not worried about figureing it out. I'm starting to think it needs to be tossed in my aluminum pile. Any other imput would be greatly appreciated.
     
  6. prodrag1320

    prodrag1320 Account Removed

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    the jets youve got are not going to make the pipes start glowing,either you have a MAJOR intake leak or you timing is way off
     
  7. Hoople

    Hoople Account Removed

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    Yes vacuum does increase with RPM assuming the load remains constant and is low. Example: Hook up a vacuum gauge to your intake manifold. While riding down a level road in 2nd gear, gradually increase your rpm until your engine is going 3500 RPM. Hold that RPM. Your engine vacuum will of course be high. Probably somewhere around 23 in/Hg. so what you said is True. But now quickly open your throttle to 100% and see what happens to your vacuum. It will fall like a rock to probably 10 in/hg. Why? It was at the same RPM but your vacuum gauge read a way different vacuum readings due to the load on the engine when you nailed the throttle. Want to see an even more dramatic example. When you were at your constant 3500 RPM in 2nd gear, shift into 3rd and nail the throttle to 100%. Your vacuum reading will be close to 3 in/Hg and you only dropped your RPM by maybe 500 RPM.
    Performing the 1st part of this example (holding throttle at 3500 and snap it to wide open) with the bike in neutral is meaningless since you did not apply any real load to the engine which is what makes the vacuum fall on its face. And unless the mass of the rollers on an inertia dyno are large enough to extend the pull times out where they should be, you won't see it happen there either. Hence the need for actual road testing or an eddy current dyno.

    Another good example of how RPM does not track with vacuum is in how a power valves works in a performance carburetor (old school Holley). They open when they sense low vacuum which equals to more load which equals to needing more fuel or needing a lower A/F ratio. Of course vacuum will change with RPM but power valves don't open and close based on RPM. They open and close based on Load demands and that is recognized through vacuum levels.

    I asked but you did not say if your sole means of spark advance is your VOES. I have seen some aftermarket setups that have Base timing along with some additional electronic advance plus VOES.
    I take it your total advance is 28 degrees with a base of 10 so the VOES is 18..(?) Since you have the toggle point of VOES set at 6 in/Hg, that would mean at cruise speed under light loads you have 28 degrees of advance. That is well within the ballpark and is by no means on the edge. I can not see how that would cause the pipes to glow. Since you can increase RPM and past through the glow point, I would continue looking at the carb or a vacuum leak.

    To answer your question about A/F ratio meters. I don't build engines but yes, I always use both an Innovate wide band A/F ratio meter and a Bear/Marquette dispersive Infra-red exhaust analyzer. The Innovate I mount to the bike and data record while riding it. The Infra-red gas analyzer is a shop roll around tool I use while stationary tuning. Without them, everything is just a guess. It is not too bad with carburetors because carbs feed both cylinders with somewhat of the same mixture or A/F ratio. On fuel injection I can set the A/F ratio on each cylinder independently so I probe each tail pipe before the cross-over pipe. This is what I do and this is how I tune my bike.

    I probably can't help you very much because I don't understand HD carbs to any great degree. I thought I may be of some help if you felt it was a spark advance issue. It sounds like your on the right track.
     
  8. BUBBIE

    BUBBIE Well-Known Member

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    DAVE,,,

    I hope your 3 to 4 min of running at 2000 rpm IS NOT with bike STANDING STILL WITH NO WIND COOLING THE MOTOR DOWN...

    If you run a motor (air cooled) at the RPM mentioned for that long SERIOUS over heating CAN an WILL do a lot of damage to those wiesco pistons rings and cyld. walls...

    The GLOW might be a LEAN at 2000 rpm and causes listed by above others...
    I would put a large fan in front of motor and YES blowing on exhaust pipes.. while performing these checks for glowing pipes..

    THEY are AIR COOLED ALSO..

    the jetting falls in line with MY knowledge of 1200 but INTAKE air LEAK is a possible cause...

    DOES IT BACK FIRE when you let off the bike in any gear above 2000 down to idle speed on compression??? and if so it is probably that LEAK...

    I NEVER allow any of my bikes to run without benefit of air cooling REGARDLESS of what i'm trying to accomplish
    .... 2000 RPM will heat and WAY over HEAT any air cooled motor....3/4 min? WAY TOO LONG...

    GLOWING pipes are not ab-normal at FAST idle at 2000 rpm IN MY BOOK...

    JUST MY OPINION and suggestion.
    signed....BUBBIE
     
  9. DavesKystoms

    DavesKystoms Member

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    Vacuum leaks is the very first thing I checked for after noticing this, no vacuum leaks.

    Hoople, I understand what you are saying about vacuum with load, and also understand the venturi affect on vacuum, and agree with what you are saying. And yes VOES is the sole means of advance. At a steady rpm no load is where I've tested this for now. With fuel injected engines you wouldnt need your A/F meter, you should be able to look at the numbers on the PC. On carbed engines how are you installing your sensor? I have wideband A/F meters but for me to use these I would need to drill holes in my pipes and I'm not to excited about that. Shouldnt I be able to get it close without monitoring A/F?
    I mean my pipes are glowing.

    BUBBIE, yes the bike is standing still but it has been 10* outside.(Therefore i havent been able to ride it) If you idle too long with fresh rings in the holes they will not seal properly. It has been my experiance that 2500 to 3000 rpms (after adequate oil pressure is reached) is optimal for sealing rings(loaded or not) There is no damage done as im holding 99% leak down. The 1% I'm losing is going by the valves.Not any air cooled engine will be hurt by doing this either. I think Harley is one of the only air cooled engines I have seen without its own blower setup to keep it cool. I've never let my head temp get above 420* and that shouldnt hurt anything. What I was hoping to hear is hat you said though, this may be a normal condition. As far as backfireing or popping it does neither, throttle response is sick (as my son would say)
    and have no other problems with how it runs. When we first fired it after the conversion, we established oil pressure and began to seat rings bringing the rpm up. This is how we noticed this problem.
    I would like to see how many others think this may be normal. Everything Ive read says glowing pipes are not normal. According to the chart i found on this web site at that rpm with the throttle position it looks like it may still be running on idle circuit. Should i try a 50 or 52 pilot jet? Thanks again guys
     
  10. DavesKystoms

    DavesKystoms Member

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    As far as I can tell the slide is working properly. I have no experience with these carbs, so not sure how to test other than moving it with my finger, it slides easy. The diaphram looks good and it worked fine before conversion. The needle and seat is not stuck, tested by putting a clear tube on the drain to see what level was. Kinda funny I remember my dad showing me that trick several years ago when i was a kid, then read about it on here lastnight, maybe he did know what he was doing! lol!! Yes stock 883 cams for now. What do you think I should do? I think I'm going to try a 50 and or 52 pilot and see what happens, doesnt cost anything to try, right? One thing that I question which way would you turn the pickup to advance timing? Reason I ask this is because when I set timing I moved it counter clockwise to retard the timing. On the right side on the engine where the pickup is shouldnt counter clock wise be advanceing the timing? Or does the pickup run off of the cam running the opposite rotation of the crankshaft? (Maybe my timing light needs calibrated?) I like this forum you guys are great!! Thanks again for your help!