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Discussion Starter · #1 · (Edited)
EDIT: I have an '01 Bird.

Alright, I thought I'd hit up you geniuses. A few months ago we went on our yearly Devil's Run which takes us up into the mountains. When leaving for the Saturday portion of the ride (starting bike at 7,000 feet), it started (bike was not warmed up, ambient temp maybe 65 or 70 degrees) then died after a few seconds. It then didn't seem to want to start at all with quite a bit of cranking. I thought I was screwed (drove hundreds of miles to get to the ride) but then decided to open up the throttle a little as I cranked it. This worked. Until it was warmed up completely I had to add a little throttle to keep it running.

Also, I've noticed lately that when I start it cold at home (ambient temp in the 80's), it idles fairly high like it should for a few minutes, then as it warms a bit it then idles at maybe 600 rpm for a while until it's completely warmed up (by that I mean temp is over 180).

Any thoughts? Seems to me that the wax unit is fine. The behavior at altitude is not good.

Thanks!
 

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Discussion Starter · #3 ·
Ahh, good point. I figured it was fine because it works for a few minutes AND a wax unit problem wouldn't explain the behavior at altitude. I figured the odds of both the barometric sensor AND the wax unit going are slim. And I guess I assumed the wax unit would be something that would either work fine or not at all.

Oh, and it might be important info: my altitude at home is 1500 feet.
 

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Does the XX have a barometric pressure sensor? I'm a carb guy so just wondering is all. Many fuel injection systems have MAS (Mass Airflow Sensor) and such. I've thought the XX FI system was somewhat less complex for some reason. (Don't know why I've thought that.) The FSM shows a altitude tweak for the carb'd machines carburetors but I've never done it for my forays to to higher altitudes of 6000ft ASL and higher. Can't say I noticed much of a performance loss given the wide range of power the XX brings to the table. Interesting problem Dave.

T.
 

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99 and 2ks have one. They eliminated it in the latter models (01 and up). Dave you may want to check sych. Mine did the same but since I've balanced it out using the home made manometer I haven't noticed it. I'll keep an ear on it over the next few days. Its been in the upper 60's to low 70's when I head out for school.
 

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it warms a bit it then idles at maybe 600 rpm for a while
as teef.au has pointed out dropping to 600 is not normal.
For info, 99-01 had a baro sensor on the rear subframe and a MAP (mean altitude pressure) sensor mounted on the fuel rail.
02 onwards lost the baro sensor.

I've only taken my 99 up mountains and had no motor related issues.
With Duck I had issues with the MAP sensor (strangely it did not like the pressure in the plenum :O) so it has been disconnected.

So whilst that doesn't answer your question directly DaveJB it tends to make me think that the MAP sensor is not at fault (when they fail/is disconnected the 'red light of doom' shows on your dash but the bike continues to run)

Does the drop to 600 happen when you are at more normal altitudes?

Personally I would pull the wax unit apart and give it a bit of a clean as a first step and to ensure that it is working well before doing anything else.
 

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Discussion Starter · #7 ·
as teef.au has pointed out dropping to 600 is not normal.
For info, 99-01 had a baro sensor on the rear subframe and a MAP (mean altitude pressure) sensor mounted on the fuel rail.
02 onwards lost the baro sensor.

I've only taken my 99 up mountains and had no motor related issues.
With Duck I had issues with the MAP sensor (strangely it did not like the pressure in the plenum :O) so it has been disconnected.

So whilst that doesn't answer your question directly DaveJB it tends to make me think that the MAP sensor is not at fault (when they fail/is disconnected the 'red light of doom' shows on your dash but the bike continues to run)

Does the drop to 600 happen when you are at more normal altitudes?

Personally I would pull the wax unit apart and give it a bit of a clean as a first step and to ensure that it is working well before doing anything else.
Thanks Brian. I'd like to get a sync done sometime for sure.

Duck, at 7000 feet it would die until it was fully warmed up. Dropping to 600 RPM is what happens when I'm back home at 1500 feet. Interesting about suspecting it's the wax unit though. Seems to me it's working great since it idles at like 1500 RPM (IIRC) for a bit like it always has then lowers to a low number until fully warmed. I don't understand how it would work perfectly for a few minutes then not work.

And now you're confusing me about the two sensors. I thought the Baro sensor was designed for altitude changes but then if there's a MAP (I thought it was called a Manifold Absolute Pressure sensor) sensor that seems redundant. :confused:
 

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Dave
Mine did the same thing. When colder ( well as cold as it can get here in the valley) it would stall unless I held the thottle partially open. The synch using the manometer seems to have cured it.
 

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Dave
Mine did the same thing. When colder ( well as cold as it can get here in the valley) it would stall unless I held the thottle partially open. The synch using the manometer seems to have cured it.

Also the 99 2k's have both unlike your redbird. The baro on mine and my son's 99 sets in the rear sub frame back by the tail light. It's open to the atmosphere. The map sets on the fuel rail like yours and is tied into the intake tract and senses off the intake track via a vacuum line.
 

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Well made, good price, fast delivery. As for using it............ never used one before, but instructions are excellent. Even me with my limited carb/throttle body skills can use one. End of October work starts on the Bird in earnest :eyebrows:. Going to do the valve clearances first though. Along with ........
Thanks beestoys for recommending it.
 

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Your welcome and yes do valves first. It will effect the sych. Hate to have you sych then find one that needs to be reshimed. Because then you'll have to check the synch again.

Dave here's a link to one being used

https://www.google.com/url?sa=t&sou...ele5fddzkpvr5wOcA&sig2=AiQ7ayg3TWL7oJi7pJH7JA

But be advised if you build one be very patient when you use it. It took me 6 hrs to get my BB settled to where I wanted it finally. And that was after I did the initial setup with a synch pro I have here.
 

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....
And now you're confusing me about the two sensors. I thought the Baro sensor was designed for altitude changes but then if there's a MAP (I thought it was called a Manifold Absolute Pressure sensor) sensor that seems redundant. :confused:
yes this confuses me as well, Honda use the same terminology (and the same part) for the sensors on the tail unit and on the fuel rail (connected to the airbox) for the 99/01 models. So whilst the one in the rear is connected to the ECM (no connection to the manifold) the airbox one is actually related to the 'manifold'!

I too love the Morgan Carbtune, been using them for many years, the rods in the tube give a decent level of damping so when a motor is well out you don't see lots of 'fluttering' that you can get with other set-ups.
 

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Duck the tail unit on the 99 2K I am figuring actually inputs the bikes altitude to the computer. As this was Mr. Honda's earlier foray into PGM FI. I am thinking they used it in the calculations, then opted out if it after they got the systems sorted out better on the later versions.
 

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Duck the tail unit on the 99 2K I am figuring actually inputs the bikes altitude to the computer. As this was Mr. Honda's earlier foray into PGM FI. I am thinking they used it in the calculations, then opted out if it after they got the systems sorted out better on the later versions.
That's is what I was thinking as well, but since as this thread shows there have been a couple of 'altitude problems' perhaps the real reason was that they wanted to use the ECM pins for the emissions 'stuff' that came in across a fair part of the world when the tail unit sensor was deleted ....
 

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That's is what I was thinking as well, but since as this thread shows there have been a couple of 'altitude problems' perhaps the real reason was that they wanted to use the ECM pins for the emissions 'stuff' that came in across a fair part of the world when the tail unit sensor was deleted ....
Suspect his issue is a synch variation. Mine exhibited the same conditions before I spent a good part of the day in the garage balancing them out. He's in the same valley as me so and mine was acting the same way.

Agree with your thinking on the removal reason.

Dave get them synched up good and I'll wager your issue goes away.
 
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All motors do that at high altitude. Its quite common,
The airs thinner, makes them hard to start, They run rough, Run at lower revs,
Untill you get them warmed up, They run like a bag of bolts,
I only know this because they talk about it on Forums to do with skiing,
And I do a fair amount of skiing,
A lot of motors wont start because of the cold and altitude,
Even my car was difficult to start when I have been up there,
The Birds have anti freeze in the radiator, So Its not a problem,
But older cars needed Anti Freeze or glycol added to the radiator or it would freeze the motor solid,
Even so, The motors were still difficult to start,
 
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