Bogged down in high altitude?

hotrod1

hotrod1

Joined
Apr 30, 2014
Messages
132
Location
Las Vegas, , Nevada
Bike
94' 1100 ABS
93' 1100, Beautiful bike. 26k miles, stock. I bought it a month ago. Left Las Vegas and shot up to Mt. Charleston with the wife today. Nice ride until I hit 8400 feet, bogged down and felt like it was going nowhere at 8400 feet. Turned around and went back down to the heat of Vegas. Then continued running well. Called my mechanic brother, he said what I was thinking, restricted airflow. Tune up time!

Plan:

New iridium plugs (already have)
New air filter. ( have )
New pre air filter for carbs. (need to buy)
While I'm there, new timing belt. (have as well)
Maybe some kind of fuel cleaner.????????????????????????????????

Just ordered a vacuum synchrometer for the carbs.

Am i missing anything??????????????????????

Planning a ride in Colorado greater than 10,000 feet ASL in June with brother.

Any ideas???

Thanks, Rod
 
Can't see all that being needed for that low a mile bike.....not even close IMO.
A clean air filter, replace fuel filter(OEM,not aftermarket) and run a couple tanks with SeaFoam or Berrymans in it. Still no change.......idle mixture re-setting and re-sync would be my next choice of eliminating out of equation;).
Enjoy your riding here! My STeeds normal diet consists of 4800ft. to 12,000+ft. and everything inbetween with no issues. These ole' 11's grunt pretty good on the low-end, even at high altitudes. Plus, four air pumps always trumping two at higher altitudes makes for a given bonus:rolleyes::).
 
Winston66 ,Western Australia here.
I do not know if this is pertinent to the ST110's , but with the ST1300 on the initial start up with the ECU and the fuel injection type of system the ECU takes note of the barometric pressure at that time .
Then if there is a marked change in height above sea level whilst riding Ie. an increase from sea level to say 5000 ft the ECU still thinks that you are at sea level and keeps the initial settings for the fuel injectors. It does not keep on sensing and adjusting for the change in altitude
The way to remedy this for the ST1300 is to stop when you start to loose power (bog down).
Switch off the ignition , wait a couple of minutes and then restart.
This will allow the ECU to register that there is a change in the barometric pressure and then it will apply the correct fuel mapping for that altitude.
If you have already stopped once or twice whilst on your ride that day the ECU will adjust its mapping (readings) to the altitude when you stopped. So it is quite possible that a ST1300 rider will not even know that the fueling maps for the bike has changed at that time.
I repeat again that I do not know if this is applicable to the ST1100's
I hope this helps,
Cheers, winston66, Northampton Western Australia
 
You will notice a significant drop in power above 8000 feet with the 1100, that is normal. Also, above 9500 feet the motor wants to idle at much lower speed. At 11,000 feet it will want to idle at 300-400 RPM. Not much that can be done, just ride it out.
 
If you have an air pre-filter, like the foam cover that comes with a K&N, it will absolutely kill the breathing of the ST1100, especially at altitude. Take it off and pitch it, and remember to clean and re-oil your air filter more frequently.
 
My recollection of traveling at altitude with a carburated vehicle was somewhat similar. After that tour thru the Rockies, my research indicated that engines can be re-tuned to run better at higher altitudes, but performance decreases when you go back down.
 
Doodaa said:
My recollection of traveling at altitude with a carburated vehicle was somewhat similar. After that tour thru the Rockies, my research indicated that engines can be re-tuned to run better at higher altitudes, but performance decreases when you go back down.
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Yup......but way to much work if just visiting the area for a bit. As above stated, don't worry bout the idle if it's a bit lower. The rpm drop stated previously IS a stretch tho:rolleyes:. I can say for sure though, that vacuum operated slide carbs give absolutely no cause for any rejetting from factory. Higher altitude=less vacuum=less rise of slide/needles........works like a charm folks;).
The 3% of 'ponies' lost for every 1000ft. elev. is noticable though. I know on PC1 in Caly, across the Bigsby Bridge, my ole' 11 easily stood up and begged ALL the way across the bridge northbound from a rolling start.............not EVEN happening here at 4800ft, so don't even try. Bike is way to heavy and too tall geared, besides being extremely hard on many componets:).
 
hotrod1 said:
Nice ride until I hit 8400 feet, bogged down and felt like it was going nowhere at 8400 feet.
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Interesting, aren't the US spec models are supposed to be equipped with an "altitude control" to avoid exactly this?
Did the exhaust have a rich/raw-gas odour?
I'd consult the workshop manual on testing its proper functionality... maybe it has been tempered with in the past, or never taken care of?

The EC spec model doesn't have the altitude thingy, but mine performed absolutely well this w/e when riding at/> 8400ft, also on the highest mountain pass road in France (~10.000ft) I had no issues whatsoever... idle drops a bit, a little less "omph" accelerating out them hairpins in 2nd gear, but overall still running perfect, especially no trouble, like misfire, stalling or refusing to fire up again like many of them German Beemers showed up there... :lol:
 
A friend and I were riding 1100's up Beartooth pass (approx. 11,000 feet) a few years ago, he had a stock air filter, I had a K&N without the prefilter. His bike was bogging down and started to misfire near the top, mine had no problems. My guess is restricted air flow. You may not have to go the K&N route, but make sure the stock filter is in good shape.
 
For those riding in the mountains or at elevation that have naturally aspirated vehicles. Typically for every 1000 foot rise in elevation you could experience up to 5% loss in HP. So at 8400 feet you could have as much as a 42% loss in HP. This is why we have gears. I ride at 6700 feet and up every day. May be I am just accustom to the elevation changes and ride accordingly. Electronic fuel injected and carbureted motors act differently.
 
Yeah, but if idle it is i.e. set too rich to begin with (there are some threads about that), the low air-density at altitude "enriches" the mix further till it literally stalls the engine (like having the choke ON)... even while you're closing the throttle for shifting and such...
Effects of course worsen with clogged/wrong air-filter and/or other setting issues...
 
ST1100Y said:
Yeah, but if idle it is i.e. set too rich to begin with
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Okay you have thrown me for a loop. "Idle set too rich". How is this done. On the US models there is an air pilot screw which is typically factory set (requires special wrench to turn), the jets which require removing the carbs and increasing or decreasing jet size and the idle sync which provides equal vacuum on each cylinder.

So how would you set the idle to rich? Please tell me.
 
Grabcon said:
Okay you have thrown me for a loop. "Idle set too rich". How is this done. On the US models there is an air pilot screw which is typically factory set (requires special wrench to turn), the jets which require removing the carbs and increasing or decreasing jet size and the idle sync which provides equal vacuum on each cylinder.

So how would you set the idle to rich? Please tell me.
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You've got it: the Pilot Screw Adjustment procedure in the manual. And if riding above 6,500 feet ASL continuously, the High Altitude Adjustment procedure. Both require the Honda special tool, as mentioned.

I've had my 91 at altitude many times, including 14,000' and while there was a noticeable loss of power, it certainly performed OK. [edit: w/K&N air filter] The OP's report didn't seem 'normal.'

John
 
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John Thanks for clearing that up for me. I have no idea how mine are set, but living a 6700 feet as I mentioned earlier I am like you there is a power loss but if the rpms are kept up when very high (in altitude) the bike performs well. Although it may not win many races at above 10000 feet.

I have 5 carbureted bikes and they all act the same at these high altitudes.
 
While in N.M. a few years ago, I rolled over 190K miles at a GPS indicated 9000 feet and 90 mph. The 1100 didn't struggle to get there but it had work more than around home. Home is a considerable lower altitude of about 100 feet. I would guess my carbs were fairly clean due to the year around use at 15-18,000 miles.

As mentioned above, I'd look at the plugs, air filters, carb sync. and run carb cleaner every tank until you trip. I've used Seafoam with good results.
 
Like John O, I have ridden my '91 (had silver sides:bow1:) over 10K feet. There was some lost power, but nothing dropping a gear didn't cure. Still no problem hitting the ton. Could it be that '91s are the best?
 
John OoSTerhuis said:
Besides the obvious... pinhole in the Auto Fuel Valve diaphragm...?
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Well, could be a possibility... lower air density plus steep uphill passages requiring lower gears, thus higher revs...
What about worn spark plugs? A too wide gap with "rich" mixture might contribute as well...

BuddingGeezer said:
Could it be that '91s are the best?
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All pun aside: quality wise '91 and '92 were the beST production years by Honda, all across the model range...
But also my taken care of '00 model runs fine at altitude... might be more a service issue or lack of though...
 
Took the bike apart this morning. To my amazement, the air filter was filthy. The carb pre-air filter was so old it was disintegrating. I was surprised because the PO looked like he kept good care of the bike. Going to buy a fuel filter since its apart. Also going to use some Seafoam, I'm sure with the torn up carb filter, there is some crud down there. Thanks for all of the replies, will keep you posted. Rod
 
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