Ignition Not Advancing...???
05-13-2008 | 11:41 PM
#1
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Ignition Not Advancing...???
In my long and very annoying quest to stomp out the gremlin in my bike I decided to run some test's on my TPS. History
As per the Honda service manual, if you start the bike with the TPS unplugged then keep the rpm's above 3,500 and plug the TPS back in the rpm's should rise. How much I do not know... but mine do not rise at all.
I've tested for continuity from the TPS coupler back to the converter unit and that came back good.
I calibrated my TPS to 500ohms dead nuts (from 860ohms), no difference.
I swapped converter unit's and ICM from a good running 2001 VTR, no difference.
I swapped carb assemblies from my buddies VTR (TPS and all), no difference.
I took it for a short ride with the TPS plugged in, then stopped, turned the bike off, unplugged the TPS then started riding again.... it made absolutely no difference. How much of a difference should there be?
Does it sound like my ignition is not advancing for some reason... is there something I'm forgeting to check?
Video...
As per the Honda service manual, if you start the bike with the TPS unplugged then keep the rpm's above 3,500 and plug the TPS back in the rpm's should rise. How much I do not know... but mine do not rise at all.
I've tested for continuity from the TPS coupler back to the converter unit and that came back good.
I calibrated my TPS to 500ohms dead nuts (from 860ohms), no difference.
I swapped converter unit's and ICM from a good running 2001 VTR, no difference.
I swapped carb assemblies from my buddies VTR (TPS and all), no difference.
I took it for a short ride with the TPS plugged in, then stopped, turned the bike off, unplugged the TPS then started riding again.... it made absolutely no difference. How much of a difference should there be?
Does it sound like my ignition is not advancing for some reason... is there something I'm forgeting to check?
Video...
Last edited by inderocker; 05-15-2008 at 01:02 AM.
05-15-2008 | 09:43 AM
#6
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He's got a '98 so his won't plug into my harness. He is buying a new wire harness soon, so i may lay his new harness over my bike and plug in all the engine connections then use his converter unit and icm and see if that works. I did swap mt icm and converter unit with a set I won on eBay, but it made no difference.
05-16-2008 | 04:13 AM
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inderocker,
I've had a quick look through your history and this thread but I don't see any mention of how the bike runs on the road? Apart from the tick over issue does this problem affect the performance of the engine when riding the bike?
Chris.
I've had a quick look through your history and this thread but I don't see any mention of how the bike runs on the road? Apart from the tick over issue does this problem affect the performance of the engine when riding the bike?
Chris.
05-16-2008 | 01:23 PM
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This echoes a problem I had with a built, (big pistons and cams, BUB exhaust and pumper carbs), R 100 RS. I pulled my hair out thinking I had checked everything twice, but I had been in error on three items. The ignition was set too far advanced, the valves were too tight and the throttle cables were binding.
Perhaps apples and oranges, but where is your ignition set and did you check for vacuum leaks?
Perhaps apples and oranges, but where is your ignition set and did you check for vacuum leaks?
05-16-2008 | 01:39 PM
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I'm in the vacuum leak camp. In order for the idle to be high, there has to be air and fuel to burn. If the throttle plates are closed, there can't be air unless it's getting in some other way.
05-16-2008 | 04:04 PM
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What is the air cutoff valve? Either I'm forgetting about it, or it was added in later years.
I know on cars, a valve was added to provide air to burn the extra fuel pulled into the engine when the throttle is closed abruptly. My integra had a vacuum actuated shuttle to allow air to bypass the throttle plate until the vacuum dropped. On another car there was a solenoid acuated rod that would briefly prevent the throttle from closing completely for the same reason. It caused the idle to hang briefly for lower emissions.
I know on cars, a valve was added to provide air to burn the extra fuel pulled into the engine when the throttle is closed abruptly. My integra had a vacuum actuated shuttle to allow air to bypass the throttle plate until the vacuum dropped. On another car there was a solenoid acuated rod that would briefly prevent the throttle from closing completely for the same reason. It caused the idle to hang briefly for lower emissions.
05-16-2008 | 04:08 PM
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I was too, but I've unloaded the better half of propane bottle to try and find one.
05-16-2008 | 04:12 PM
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What is the air cutoff valve? Either I'm forgetting about it, or it was added in later years.
I know on cars, a valve was added to provide air to burn the extra fuel pulled into the engine when the throttle is closed abruptly. My integra had a vacuum actuated shuttle to allow air to bypass the throttle plate until the vacuum dropped. On another car there was a solenoid acuated rod that would briefly prevent the throttle from closing completely for the same reason. It caused the idle to hang briefly for lower emissions.
I know on cars, a valve was added to provide air to burn the extra fuel pulled into the engine when the throttle is closed abruptly. My integra had a vacuum actuated shuttle to allow air to bypass the throttle plate until the vacuum dropped. On another car there was a solenoid acuated rod that would briefly prevent the throttle from closing completely for the same reason. It caused the idle to hang briefly for lower emissions.
05-16-2008 | 05:19 PM
#18
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The throttle doesn't need help to cut rpm.
$10 says it opens to burn unused fuel when the throttle is closed and causes the idle to hang briefly.
I think I misstated slightly. It burns unused fuel, but also prevents very high vacuum which pulls fuel out of the float bowls. so it decreases the amount of raw fuel and burns what is there.
$10 says it opens to burn unused fuel when the throttle is closed and causes the idle to hang briefly.
I think I misstated slightly. It burns unused fuel, but also prevents very high vacuum which pulls fuel out of the float bowls. so it decreases the amount of raw fuel and burns what is there.
Last edited by RCVTR; 05-16-2008 at 05:37 PM.
05-16-2008 | 08:49 PM
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From ninja250.org:
COASTING ENRICHER - Feeding a Closed Mouth
You're blasting down the road and you see a hairpin coming up, so you close the throttle. This closes the butterfly valve. You and your 400 lb. baby (the bike, not the other love of your life), are still rolling with inertia, keeping the engine revs high. Now it can't get the mixture it's trying to suck in because the butterfly valve is closed, blocking the air flow.
To compensate for this there's an air jet in the lower diaphragm chamber that transfers ambient pressure to one side of the coasting enricher's spring-loaded cut off valve. The excess vacuum in front of the butterfly valve is transferred to a drilling that leads to the other side of the cut off valve. This sucks it open, allowing the pilot jet to feed more fuel to the engine, preventing an overly lean condition. (Pop. Pop. Pop.)
COASTING ENRICHER - Feeding a Closed Mouth
You're blasting down the road and you see a hairpin coming up, so you close the throttle. This closes the butterfly valve. You and your 400 lb. baby (the bike, not the other love of your life), are still rolling with inertia, keeping the engine revs high. Now it can't get the mixture it's trying to suck in because the butterfly valve is closed, blocking the air flow.
To compensate for this there's an air jet in the lower diaphragm chamber that transfers ambient pressure to one side of the coasting enricher's spring-loaded cut off valve. The excess vacuum in front of the butterfly valve is transferred to a drilling that leads to the other side of the cut off valve. This sucks it open, allowing the pilot jet to feed more fuel to the engine, preventing an overly lean condition. (Pop. Pop. Pop.)
05-17-2008 | 01:25 AM
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http://www.cyclewareables.com/pages/.../aircutoff.htm
"AIR CUT OFF VALVES PREVENT "AFTER BURN" GENERATED WHEN THE THROTTLE IS SUDDENLY CLOSED WHEN THE THROTTLE IS SUDDENLY CLOSED, THE VALVE TEMPORARILY CLOSES THE SLOW-JET PASSAGEWAY---CREATING AN INSTANTLY RICHER MIXTURE AND THUS REDUCES "POP" SOUNDS UPON DE-ACCELERATION"
"AIR CUT OFF VALVES PREVENT "AFTER BURN" GENERATED WHEN THE THROTTLE IS SUDDENLY CLOSED WHEN THE THROTTLE IS SUDDENLY CLOSED, THE VALVE TEMPORARILY CLOSES THE SLOW-JET PASSAGEWAY---CREATING AN INSTANTLY RICHER MIXTURE AND THUS REDUCES "POP" SOUNDS UPON DE-ACCELERATION"
05-17-2008 | 02:13 AM
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Not wishing to sound as if I'm knocking your mechanical capabilities here, but only trying to help.
I feel this problem must be something that's been missed, considering all the different things you've already tried!
Can you explain the procedure you used when you checked the valve timing?
Chris.
I feel this problem must be something that's been missed, considering all the different things you've already tried!
Can you explain the procedure you used when you checked the valve timing?
Chris.
05-17-2008 | 03:25 AM
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Chris.
05-17-2008 | 09:32 AM
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Don't remember how far the turn was, but if your suggesting that the cam timing was checked on overlap, and it looked to be in time, then the bike wouldn't even run.
If I remember right, the rear cylinder fires first then the front fires 180 degrees later... either that or the front fires first but only 180 degrees after the rear.
If I remember right, the rear cylinder fires first then the front fires 180 degrees later... either that or the front fires first but only 180 degrees after the rear.
Last edited by inderocker; 05-17-2008 at 10:23 AM.
05-17-2008 | 09:56 AM
#26
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Ahhh... yes.
I'm forgeting my carburetion fundamentals. The idle/low speed inlet is just upstream of the throttle plate. It sits perpendicular to airflow. High air velocity creates low pressure, which pulls fuel through the pilot jet. Vacuum has nothing to do with it, except that it causes high velocity at the gap above and below the throttle plate. Is there a second port further forward that comes past the idle screw? I think so.
Anyway, now the air cutoff makes sense. My car had an air bypass, but that was for car emissions standards on a fuel-injected car.
However, I still maintain that it is the change in state of the valve that causes the idle to hang, then unhang. I don't believe my '00 49 state carbs had the valve installed, but I think I remember the location on the carb body where they would go. I put a bigger pilot jet in to get rid of lean decel popping.
I would temporarily disable the valve by plugging the vacuum port. MY $10 is still on the table.
I'm forgeting my carburetion fundamentals. The idle/low speed inlet is just upstream of the throttle plate. It sits perpendicular to airflow. High air velocity creates low pressure, which pulls fuel through the pilot jet. Vacuum has nothing to do with it, except that it causes high velocity at the gap above and below the throttle plate. Is there a second port further forward that comes past the idle screw? I think so.
Anyway, now the air cutoff makes sense. My car had an air bypass, but that was for car emissions standards on a fuel-injected car.
However, I still maintain that it is the change in state of the valve that causes the idle to hang, then unhang. I don't believe my '00 49 state carbs had the valve installed, but I think I remember the location on the carb body where they would go. I put a bigger pilot jet in to get rid of lean decel popping.
I would temporarily disable the valve by plugging the vacuum port. MY $10 is still on the table.
Last edited by RCVTR; 05-17-2008 at 10:03 AM.
05-18-2008 | 02:37 PM
#27
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Don't remember how far the turn was, but if your suggesting that the cam timing was checked on overlap, and it looked to be in time, then the bike wouldn't even run.
If I remember right, the rear cylinder fires first then the front fires 180 degrees later... either that or the front fires first but only 180 degrees after the rear.
If I remember right, the rear cylinder fires first then the front fires 180 degrees later... either that or the front fires first but only 180 degrees after the rear.
If you do decide to re-check it make sure the cam lobes are facing in the right direction for each cylinder at TDC. Also that the engine is turned over the correct amount of turns for checking the second cylinder.
As I said earlier I feel something has been missed here and you have to start somewhere.
Chris.
05-18-2008 | 08:42 PM
#28
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Cam timing was checked back in November of last year, then again in January of this year when I rebuilt the heads. I have enough faith in my mechanical abilities to to be completely satisfied with the results. As the assistant service manager at the local Honda/Kawasaki/Suzuki dealership, I work on bikes, quads and utility vehicles on a daily basis. I feel rather competent with almost all aspects of motorcycle diagnosis and repair... with the exceptional exception of major electrical diagnosis (gremlins 
). For me to tear the valve covers off again to check the cam timing would just be like beating a dead horse. It is a very simple procedure that any motorcycle owner would benefit from knowing (i.e. valve clearance check and adjustment). I definitely appreciate all suggestions, just thought I'd give some background info.
). For me to tear the valve covers off again to check the cam timing would just be like beating a dead horse. It is a very simple procedure that any motorcycle owner would benefit from knowing (i.e. valve clearance check and adjustment). I definitely appreciate all suggestions, just thought I'd give some background info.
05-18-2008 | 09:27 PM
#29
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inderocker, I think I know what the problem is. You're running lean at idle. Try putting the #45 pilot jets back in and adjust mixture screws to 2 turns out. Then do a good carb sync. Keep the mains and the needles where they are. Raise idle speed to 1300.
05-18-2008 | 09:41 PM
#30
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I'm actually running #45 pilot jets with the mixture screw either 2 or 2.5 turns out. I still get some sputtering on take off. The #42 pilot jets were too lean with the new 178/180 main jet combo. If I remember correctly, the #48 pilot jets seemed boggy plus it died at idle once it got hot, but I'm gonna give those another shot after the memorial weekend ride. I went on a 200+ mile loop to the Tonto Natural Bridge and got 42MPG... A new record for me, YAY!!
