Argon Posted July 16, 2007 Share Posted July 16, 2007 Do any of you ever touch the thottle stop screws on the 1150RT? I have a 2003 RT with about 30K. When it was new, the tach would read around 1100 rpm at idle. After about 6K miles, I noticed the rpm at idle had dropped to around 950. I have tried to adjust the idle rpm with the brass screws, but I can't get it to increase. I have had the dealer do the tune up at 6K and 18K and they claim that the rpm on their instrument is reading the proper 1050, but that tach is reading low. I don't completely buy that because of what I saw from the tach when the bike was new. The bike runs fine so it is not a big deal, but I have stalled on occasion when coming to a stop which I blame partially on the low idle rpm. I think the trottle stop screws might have bent or worn slightly, lowering the idle rpm, but I have not touched the screws as I understand that is supposed to mess up the TPS setting. But it seems a slight adjustment wouldn't hurt anything-has anyone adjusted these screws? Link to comment
steve.foote Posted July 16, 2007 Share Posted July 16, 2007 Andy, I'm pretty sure the repair manual specifically says to leave them alone. It is possible that the tach has become inaccurate over time, and since the bike is running well, I wouldn't give it another thought. Link to comment
Ken H. Posted July 16, 2007 Share Posted July 16, 2007 You normally should not adjust the stop screws. Especially the left one. Doing so will mess up the TPS (Throttle Position Sensor)calibration. I will sometimes adjust the right one to improve idle sync, but never the left one. There is little control of idle speed available on the 1150 series, but what little there is can be made with equal adjustments of the large brass air bypass screws. Link to comment
ShovelStrokeEd Posted July 16, 2007 Share Posted July 16, 2007 The throttle stop screws are set at the factory to provide a specific air flow past the, almost closed, throttle plates at a specific differential pressure across the plates. Things like shaft bushing wear and small accumulations of dirt/crud on the mating surfaces can change that. As it all works out, on a brand new engine, with the big brass screws adjusted about 1.5 turns out, the idle speed will be about 1050 RPM. You no longer have a brand new engine and chances are there is some wear in the bushings although there shouldn't be very much at your mileage. The tachometer is driven by a pulse stream from the CPU but is a magnetic coil device depending on average voltage of that pulse stream to drive the needle around the face. It is quite possible that the connections between the CPU and the tach have deteriorated due to light corrosion and your tach is reading a bit low, especially at low RPM. The stalling thing is odd, though, they normally don't stall. I would reset the CPU's memory by disconnecting the battery negative post for a minute or so and reconnecting. Then, key on but don't start, wind the throttle from full closed to full open and back twice and then go for a long, high speed ride and see if things have improved. Some other things that can effect this are valve adjustments, condition of spark plugs and plug wires, recent driving habits. My version of an Italian tuneup involves about two tanks of gas at freeway speeds, maybe running in 5th gear for most of the first tank. On the second tank, run the bike through the gears and through the RPM band, starting at lighter throttle openings and progressing to full throttle, red line shifts in at least the lower 3 or 4 gears. Watch out for the PoPo. The idea here is to avoid glazing any deposits on the spark plugs with instant heat from full load running. The first tank is to give the deposits a little time to burn off normally. My Blackbird will pick up 50 RPM at idle after the second tank of gas on a nice long trip. Doesn't go any further, thank goodness. as a good days ride for me involves about 4 tanks. Plugs on that bike have about 45K miles on them and it is probably time for a change. They are iridium and expensive as heck at about $15 each. PITA to get to as well. I figure they will last me till I get 1500 or so miles home and then the 'bird goes down for a major and I'll be riding my VFR for awhile. Link to comment
T__ Posted July 16, 2007 Share Posted July 16, 2007 Do any of you ever touch the thottle stop screws on the 1150RT? I have a 2003 RT with about 30K. When it was new, the tach would read around 1100 rpm at idle. After about 6K miles, I noticed the rpm at idle had dropped to around 950. I have tried to adjust the idle rpm with the brass screws, but I can't get it to increase. I have had the dealer do the tune up at 6K and 18K and they claim that the rpm on their instrument is reading the proper 1050, but that tach is reading low. I don't completely buy that because of what I saw from the tach when the bike was new. The bike runs fine so it is not a big deal, but I have stalled on occasion when coming to a stop which I blame partially on the low idle rpm. I think the trottle stop screws might have bent or worn slightly, lowering the idle rpm, but I have not touched the screws as I understand that is supposed to mess up the TPS setting. But it seems a slight adjustment wouldn't hurt anything-has anyone adjusted these screws? Andy, when the brass idle air by-pass screws seem to have little effect it is usually due to the either the screw tips & or their seats in the throttle bodies starting to coke (carbon) up.. That is usually also accompanied by a drop in idle RPM.. You might MARK both L & R brass screws for position then remove them & use carb cleaner to clean BOTH the screw tips & their related seats in the throttle body.. My guess is that will return the idle to 1100 or so & allow the brass screws to again function properly… Twisty Link to comment
4wheeldog Posted July 16, 2007 Share Posted July 16, 2007 Do any of you ever touch the thottle stop screws on the 1150RT? I have a 2003 RT with about 30K. When it was new, the tach would read around 1100 rpm at idle. After about 6K miles, I noticed the rpm at idle had dropped to around 950. I have tried to adjust the idle rpm with the brass screws, but I can't get it to increase. I have had the dealer do the tune up at 6K and 18K and they claim that the rpm on their instrument is reading the proper 1050, but that tach is reading low. I don't completely buy that because of what I saw from the tach when the bike was new. The bike runs fine so it is not a big deal, but I have stalled on occasion when coming to a stop which I blame partially on the low idle rpm. I think the trottle stop screws might have bent or worn slightly, lowering the idle rpm, but I have not touched the screws as I understand that is supposed to mess up the TPS setting. But it seems a slight adjustment wouldn't hurt anything-has anyone adjusted these screws? Andy, when the brass idle air by-pass screws seem to have little effect it is usually due to the either the screw tips & or their seats in the throttle bodies starting to coke (carbon) up.. That is usually also accompanied by a drop in idle RPM.. You might MARK both L & R brass screws for position then remove them & use carb cleaner to clean BOTH the screw tips & their related seats in the throttle body.. My guess is that will return the idle to 1100 or so & allow the brass screws to again function properly… Twisty +1. I don't clean these everytime, but if the idle is off, this is the first place I would go. I have my R1150RT set to idle at 1000 rpm at home, because home is at 7200'. When I go down to 5000', idle is up to 1100. I expect if I ever get back to sea level, it wil be more like 1300. I can live with that. Link to comment
Argon Posted July 16, 2007 Author Share Posted July 16, 2007 Thanks for all the input. I did try the cleaning of the brass screws when I did a TBS at about 16K. The screws were dirty, but cleaned up easily, but it didn't have any noticable effect on the idle RPM. I did spray carb cleaner in the holes, but maybe not enough. I will try again when I do the next TBS. Ed, I have read about your Italian tune up before, and that might be helpful for this bike. I don't run it very hard, rarely getting above 5K RPM, so I probably have some carbon deposits. Link to comment
ShovelStrokeEd Posted July 16, 2007 Share Posted July 16, 2007 Poor bike, take it out and give it some love. Just not tough love. The ride it like you stole it crowd are full of bovine digestive byproduct, gaseous or solid, take your pick. Best medicine is a long, moderate load, run. The higher the speed the better as the aerodynamic drag will produce a really nice load on the motor. I'm not advocating that anyone break any laws here but, 85 to 100 mph true, in top gear, for a couple hundred miles, is just what the Dr. ordered. 'Sides that, it is fun! Link to comment
tomk99r11 Posted July 16, 2007 Share Posted July 16, 2007 Now, this confirms that this Ed guy knows his shit! Link to comment
AndyT Posted July 16, 2007 Share Posted July 16, 2007 Ed's advice is spot on. I tended to bog the 1150's engine too much and after following his advice along with a really good self tune up and throtle sync including a set of Auto Lite 3923's the engine has run much smoother and idles at 1050 to 1100 where as before I had a low 900 to 950 idle which was annoying (after the dealers tune up from purchase)! Good luck! AndyT Link to comment
4wheeldog Posted July 17, 2007 Share Posted July 17, 2007 Poor bike, take it out and give it some love. Just not tough love. The ride it like you stole it crowd are full of bovine digestive byproduct, gaseous or solid, take your pick. Best medicine is a long, moderate load, run. The higher the speed the better as the aerodynamic drag will produce a really nice load on the motor. I'm not advocating that anyone break any laws here but, 85 to 100 mph true, in top gear, for a couple hundred miles, is just what the Dr. ordered. 'Sides that, it is fun! +1. It isn't RPM that cleans things up, it is load. And load is defined by how wide open the throttle is. Anywhere in the fat torque part of the range (4500 to 6000) with a good handfull of throttle is what generates high combustion pressure and cleans out the carbon. Also seats the rings if you have a young motor. A long, steep mountain is what these motors really need. Link to comment
philbytx Posted July 17, 2007 Share Posted July 17, 2007 You can adjust the RH throttle stop screw to balance them out but don't mess with the LH one! You can then fine tune the idle with the LBS's. Link to comment
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