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Can anyone tell me the relationship between the two small holes in the top of each bore of the throttle body and the air bleed screws on the face of the throttle body? I have read that the bleed screws need to be turned out 1-1/2 turns and the small bores can be cleaned with carb cleaner.
The holes do clog due to the breather system eating it's own chit from the head breather, I've never looked into how the small holes work but cleaning them can help the idle.
Usually the engine temperature sensor fails in the M&M sending the ECM false readings, messes with cold start, ISC motor, fuel changes, can go lean or rich depending on which way the sensor reads.
Setting the throttle position sensor helps due to wear, need to remove the air cleaner base to gain access to the idle screw and something simple like pulling the ECM fuse for 10 minutes allowing the ECM to reset fixes issues, also need to pull the fuse if you make any adjustments so it goes into the relearn procedure.
Last edited by 1997bagger; Feb 20, 2022 at 09:13 AM.
Thanks for that info. I have seen the video you posted and have done the TPS adjustment (.275VDC) changed out the whole linkage and small bearing on the cable side of the throttle body, added a new front head temp sensor, ISC actuator and adjusted both cold and fast idles to their respective rpm's. My issue is, after starting, the motor wants to fast idle (ISC has extended) but it starts about 850 and slowly creeps up to 1200 then after the temp has risen sufficiently, it backs off to 950-1050 which is correct. That's why I believe there is some correlation between the bleed screws and the small holes on the throttle body. When I get back north I'll dig out the epoxy on the bleed screws, determine what position (turns in or out) they are in, remove them and try cleaning through the bleed screw openings and see if it runs thru the small holes in the bores.
I have upped my bike to Stage 1 with the air cleaner, added true duals and Rush Big Louie mufflers. Currently I'm getting close to 50MPG and most tankful's in the 47 - 49 MPG range with average riding.
1998 RK Classic - 52K miles - original owner, purchased new in January of 1998
The IAC should just move out and pull back into a cold start idle up position @ key on, the ECM locks in a cold start(pre determined fuel) mode which also applies the IAC, after warming up the cold start mode releases the ECM back to the programmed map to alter fuel. I don't understand why it would start out at 850 and go to 1200, the IAC isn't moving. You might be onto something by richening the screws up allowing the cold start more fuel based on your mpg, that's great mpg but signs your lean, the engine may not be getting enough fuel at first start up cold when it needs it, your stage 1 could be allowing more free flow than what was programmed in the locked cold start mode.
Kept the MM with a stroker kit and head work eventually just started using the throttle lock for warm up backing the fast idle screw off, when leaving with a group, sometimes didn't have time to let the cold start mode release, trying to put a Evo in gear at 1200rpm is a little rough.
Thanks for the response! Yes, the IAC is working as you describe. As far as running lean, temp at full warm up is right in the ballpark and plugs are not discolored as they would be if lean. The other thing I'm noticing is that my fuel pump makes the same noise at ignition on that indicates possible air in the lines. It's the original pump and I may change that out to a new Quantum pump, filter, regulator and screen. I'll get to the bottom of this whole thing one way or another. The bike has never been down and I have all the original parts that have been removed and replaced with factory accessories. Not sure there are many bikes left around that are in the condition as mine.
Thanks for the response! Yes, the IAC is working as you describe. As far as running lean, temp at full warm up is right in the ballpark and plugs are not discolored as they would be if lean. The other thing I'm noticing is that my fuel pump makes the same noise at ignition on that indicates possible air in the lines. It's the original pump and I may change that out to a new Quantum pump, filter, regulator and screen. I'll get to the bottom of this whole thing one way or another. The bike has never been down and I have all the original parts that have been removed and replaced with factory accessories. Not sure there are many bikes left around that are in the condition as mine.
There is 2 check valves in the fuel ports in the bottom of the tanks, job is to keep pressure in the lines, no air but a fuel pump whines when it is getting weak.
Can't judge plugs by today's gas, 50 mpg is going to be on the edge of lean is the only reason it was mentioned plus the free flowing items installed. Target: why does it only idle 850 at start up cold and raises the idle to 1200 while warming up - answer fuel, the ECM is only programmed to put a certain amount of fuel in at cold mode lock, no O2 sensors to adjust it. Richen up those screws and should be repaired.
I have pretty much the same bike (although mine isn't nearly as clean). I have a similar issue with cold idle temps. My theory is that the head temp sensor is breaking down and sending the wrong temps to the computer. My head temp sensor is getting fairly old and I have a spare on hand for when it goes completely south. Before you go digging the epoxy out of the air bleed screws, you might try doing nothing other than replacing the head temp sensor to see if it cold idles like it should. I know you just replaced yours. Sometimes they are bad right off the bad. If you have a spare on hand, it's about a 30 minute job (you already know that).
I've read a lot about those air bleed holes. I think that it's mostly twin cams that have a problem with them clogging up. I've also read it's best not to adjust them and if you do, they are very sensitive. That doesn't mean I'm right, either.
Also, the next time you adjust your hot/cold idle screws, pull them all the way out and put some blue locktite on them so they don't creep.
Post up your results, regardless of what you do. For my money, I don't care much about the cold idle. The hot idle is very consistent.
I think we may have hit on something here. My fuel pump makes a clicking sound when ignition turned on. You would figure that once everything is at proper pressure, if the ignition is turned off that it would come back on and the pump would be primed sufficiently. Not the case for me, Everytime the ignition is turned on, I get the same clicking sound from the pump! I think an order from Quantum may be in order!
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