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High RPM Problem, Help needed

kmartin

kmartin

Cruisin' Guzzisti
Joined
Oct 3, 2009
Messages
292
Location
SoCal Mountains
By New Stelvio, which I've been anticipating for several weeks, has a high RPM bog problem. For the first 100 mi, I had the shift light set down around 7000 rpm in an attempt to be gentle. As I passed about 6500 RPM, the engine would bog, felt all the world like an RPM limiter, so I assumed that was it. Next time out I set it up to 8500 or so, same result. I've found that at full throttle, it's pull ok up to 7000, but at reduced throttle, bogging starts about 6500. I can't get it much past 7000 in any case. Cold starting has been hard, requiring up to a minute of hand on throttle to keep it going.

Gas mileage has been around 25 mpg as reported but the computer.

I just received my VDSTS the other night, so went out this morning to check things out. After I figured out how to jumper the cable (I'll have to fix it later, it's not correct for the Stelvio), I carefully balanced the carbs and reset the TPS per instructions found here.

I was really hoping that would fix my problem. Alas, no change. I also checked the plug caps to ensure good contact, they looked good.

Any ideas? I'd really like to fix it myself, it's be a real pain to take to a dealer.

Keith
 
Start simple. Pull the top off the airbox and make sure there isn't something plugging the intake.
Pull the covers off the spark plugs and verify that there is no arcing to ground in there. The caps can get damaged easily.
 
Keith, do you know if the sending dealer did a true pre-delivery? With that fuel mileage, I'd be curious what the valves and TPS are set at, in addition to what Wayne posted above. Post your findings here.
VDST is plug in, no need to modify ever. Are you sure you're trying to plug into the correct plug?
 
Correct plug, Todd, 2 wires on VDSTS cable on outside positions of a 3 conductor connector, 2 wires on bike side, one in the middle. I made it work using jumper wires and clip leads. I'll fix it myself if I can figure out how to work the connector.

I did a careful balance and TPS reset. TPS was a 5.0 before the reset, 4.8 after. Airbox is clean, dealer claimed to have don the cam recall. I checked plug wire seating.

I have NOT checked the valves, maybe tomorrow. I couldn't imagine the valves causing these symptoms.

It feels for all the world like a rev limiter, but varies slightly with throttle. I haven't been able to check cold start since the balance and TPS. Fuel mileage in the mid 20's seems excessive.
 
Will email you for details on the VDST. 20's is excessive, but what is the daytime temp highs?
The rev flasher is not a limiter, just a visible indicator/reminder. Keep us posted.
 
Keith,
I might be very wrong here but......I have a feeling there's some trick factory setting in the system that means you can't really change the rev limit until the basic running in mileage has been done. You can do the re-set but it won't actually work until the electronic brain is happy the bike has done the initial running in mileage.
 
Just as a comparison. I picked up my Stelvio about 6 weeks ago and have been riding in almost the same temps. I have appx 2200 miles on her now. The flashing red light is set low "out of the box" and as others posted, it is more a shift point reminder that you can adjust, it is not a rev limiter in my experience. When I make a cold or hot start, I never touch the throttle, just turn on the key and give her a moment to complete the electronic wake up and then push the button. She has always fired right up and quickly settled in to a nice idle. I did have a couple tanks in the 33-35 m.p.g. range, but I found she quickly settled in to 38-39 (via computer and doing the math) and that is with smooth/aggressive mountain riding that always includes some runs against the rev limiter and a few 100+ MPH blasts. I weigh appx 250 LBS, add some camping gear and it's giving her a load to pull too. After reading owner reports for problems I checked her over (and continue to inspect her nooks and crannies :eek:) , so far, I found some body panel screws askew and one of the foam pads on the air intake had come off it's glue and was resting on the air filter. You will have some great advice here. Hope it is something simple like an air leak/electric connector or some terribly bad gas working out of the system.

Good luck, she is worth sorting out for the fun to be had.

Bob
 
Keith: Flashing triangle is not rev limiter, shift point reminder that can be passed if it is set low. Try checking connecters for loose pins. Could be related to vibration frequency. I had a problem earlier this year that was caused by a pin in the connecter for the immobilizer moving around and breaking contact,was occuring at low engine rpm. Caused extremely poor mileage, missing, bogging, detonation and ultimately shutdown of the ECU. Pin was locked into place properly in the connector and that was it problem solved. Worth a look.
FBC
 
Update, and a few comments.
I understand that the shift light is not a limiter, my intent was to show that the behavior felt so much like a limiter, that I was fooled.

Spark plug caps are in perfect condition.

Wayne, I appreciate your suggestion to check the air box. My initial thought was "tell me something useful", but I looked anyway. Just as bobw did, I found a piece of foam, but more importantly, when feeling around in the airbox, I found a large piece of flashing that would have eventually come off and lodged somewhere.

Will, I've never read about a progressive limiter before, but I think its a good idea. I'd love to find out that there is such a thing there.

Now for the update:
After telling everyone that I didn't think a valve adjustment could be the problem, I checked them. I've never found easier valves to adjust, just over 1/2 hour, no pain involved. I've also never seen anything so far out.
The left side intakes were >0.50 mm, exhausts were right on, 0.15 mm. The right side intakes were >0.60 & >0.65, the exhausts were ZERO. The selling dealer claimed to have done the cam recall, so it must be them.
The result? Little to no change in high RPM behavior, still dies by 7000 RPM. Everything below that, however, feels great. I almost never run near red line, I just felt this was an indication of a problem. Maybe not. I'll have to take a long ride to check mileage, but for now I think I'll be happy.

Thanks for the help,

Keith
 
Hey Keith, I am no technician but I think I had a similar problem....I found when riding and as soon as I would hit 7,000 RPM' it would bog as if it hit red line but if I kept on the throttle it would pick up speed again and pull forward......As soon as I changed the muffler and replaced it with the one that Todd made for me, the problem went away...Good Luck!!
 
kmartin said:
Will, I've never read about a progressive limiter before, but I think its a good idea. I'd love to find out that there is such a thing there.
Click to expand...
There is no built-in progressive limiter based on mileage on the ECU.
Keith, so on Gigio's words, there you may have it. I ran a Press Stelvio for a week up and down the Coast, and I didn't notice such thing, however if you both are experiencing it, we may be on to something. He replaced both the muffler with a GT-Sx megaphone and has my PC-V/ECU/AT running currently as well. His bike runs phenomenally, as I got the spend some time with it, as my first test bike I installed the full kit on.
 
Todd,
I'm afraid it's not quite right. Based on Gigio's comment, and now yours, I hope it normal variation in units causing mixture to be lean at high RPM, even though your plots in the PCV thread don't indicate that. I'm hoping that the PCV will correct it.

I was initially concerned that there was an ECU problem, and didn't want to spend money on a reflash on a suspect unit. I'm not so concerned now, and feel it may just be a tolerance stack up working against me.



It just occured to me. I recall the last digits of the ECU version being something like 18. I didn't write it down and don't have time to look again, but I know it was a low number. Another thread here says the latest map is 52. Could this be part of my problem? Could it be a combination of slightly off TPS, way off valves, and old ECU mapping?

If so, I assume a reflash / PCV will take care of any remaining issues?


Keith
 
I may do a PC and exhaust mod down the road, but I tend to put some miles on my bikes prior to buying a bar, seat, etc., and I also like to make sure the baseline is as good as possible prior to any performance "upgrades", be it a filter, pipe or tune, etc., but that's just me. Your valves being way out of adjustment and an old fuel map are perfect examples of this. Any better shops available than the selling dealer? Prior to any mods I still would want to double check the recall work was done (properly) based on your findings to date.

Good luck!
 
kmartin said:
Todd,
It just occured to me. I recall the last digits of the ECU version being something like 18. I didn't write it down and don't have time to look again, but I know it was a low number. Another thread here says the latest map is 52. Could this be part of my problem? Could it be a combination of slightly off TPS, way off valves, and old ECU mapping?
Click to expand...


Flashing mine from 18 to 52 did nothing except eliminate the surging at cruising speeds. but it is a touch harder to start on hot days now. Oddly.

TPS has little impact at wider throttle openings. BUT, you had mention cold idle issues. Those could be TPS related.
 
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