R1100RT Fuel Injector and TB cleaning

[Toast]

Hey now,

 

In an effort to get to the bottom of my surge issues, i pulled the throttle bodies off last night for a thorough exam and cleaning. I was surprised at how dirty they were INSIDE, especially the left TB. Very sooty, coked up, a bit wet. My R75 carbs never looked like that. The butterfly on the left TB has black soot on it, and both BBS were in need of some love (new o-rings, general cleaning). I plan to use my small parts washer to clean all items, including the BBS's and their receptacles. My parts washer uses mineral spirits, any problems there?

 

When i pulled the right fuel injector out of the TB, i noticed that the fat rubber ring that is below the piece that attaches to the TB has a big split in it so i am assuming that it needs to be replaced. I am trying to add a picture of it, but when i click the "enter an image" icon, it pulls up a dialog box that asks me for a URL, so i don't know how to deal with that but anyways.

 

The TB didn't leak fuel before, but looking at that injector rubber ring, i think it was only a matter of time. I don't plan on "cleaning" the fuel injector per se, or even disconnecting it from the charged fuel line. Overall i think it is in good shape save for the cracked rubber ring.

 

Finally, my oil fill had a small weep, so i pulled the oil filler (the small plastic piece/o-ring that is fitted inside the cylinder head cover). This plastic piece has a small locating tab that was busted off, so i think that may be my leak source. I pulled it out, cleaned all the rocks and debris away from the hole (none fell into the cylinder head), and will install a new filler pipe today (if my local BMW dealer has the part).

 

I'm sure i'll be asking more questions on re-assembly.

 

[roger 04 rt]

Very interesting. It will be interesting to hear how your bike performs with everything cleaned up.

[dirtrider]

Morning Toast

 

The mineral spirits sure won't hurt the TB's but mineral spirits is not a very good solvent to remove coking & varnish.

 

You might spray the TB's with a carburetor cleaner first then once the cooking & varnish is loosed up with the carb clean run them through your parts washer.

 

On the rubber parts?-- definitely replace any rubber "O" rings that are spilt, swelled up, or distorted. When re-assembling use a bit of rubber lube, or silicone grease, or tire lube, or something that won't effect the rubber but will slick up the re-assembly process.

 

Now that you have the TB's removed make sure the throttle shafts are tight & not loose or worn in the end bushing areas. If the throttle plates don't consistently return to same place in the throttle bore you will never get an accurate TB balance.

 

On adding pictures to a posting?-- you need to first host the pictures on a hosting web site (like Photo Bucket or similar) then link to that hosted picture where it asks for URL.

 

[Toast]

I did inspect the TB shafts...they seem like they are tight in their bushings. I also read Dan Cata's article about replacing those bushings and i don't think my TBs are at that point yet. +1 for the advice about the mineral spirits not handling the coke deposits and for the lube on the o-rings (i always forget to do that). Will apply carb cleaner firts, then rinse with mineral spirits. Thanks guys!

[dirtrider]

Morning again Toast

 

Don't Forget-- make darn sure you don't get carb clean or mineral spirits in or on that L/H TB TPS sensor (remove sensor first).

 

[JamesW]

I think reason for very dirty TBs is the crank case ventilation. I just cleaned my TBs and was very surprised at the coking. My R100 carbs don't accumulate anywhere near as much combustion byproduct. Maybe pull the hose attached to the bottom air box compartment and vent to the open air. Yes I know bad for the environment but in the grand scheme of things not even a microscopic drop in the bucket.

[JamesW]

Oops, I got carb cleaner on the LH TPS.

[roger 04 rt]

Morning again Toast

 

Don't Forget-- make darn sure you don't get carb clean or mineral spirits in or on that L/H TB TPS sensor (remove sensor first).

 

This is probably a dumb question but if you remove the TPS to clean the sensor do you have to reajust it?

[Toast]

I pulled it off and don't really see that there is much to adjust. The butterfly shaft has a "tenon" on the end that fits into the TPS. Its a snug fit...maybe the TPS memory gets wiped out and has to be reset? I did notice that the electrical connection had a bunch of grit in it when i disconnected it. I'll be sure to hit that with dielectric grease on reassembly.

 

Went to my local dealer to get the o-rings etc that i indicated in my previous post. Not my favorite place to go because the owner is somewhat, um, ostentatious. I prefer to get my parts online, but that old instant gratification thing beat me up this time. He was less than enthusiastic about the RT and even commented about whether or not i could maintain it. What a punk. He told me i would NEVER fully eliminate the surge problems, i probably wouldn't even be able to minimize it. Then he commented on the Hall sensor probably going to fail soon as the bike has 95K on it. Total doomsday conversation. Like i said, i prefer not to go there. Once i went in there with a brass part that i had mangled for my r75 carb. He clapped his hands and rubbed them together and said "i LOVE it when guys try to work on their own bikes." See what i'm talking about? I turned around and walked out and ordered the part online...but everytime i go in there (and believe me it's not often) i recall that bad experience.

[dirtrider]

Morning Roger

 

Yes it would need re-adjustment. You can mark the position before removal but that would only get it close at re-install.

 

Even if not removed just the fact of cleaning the TB's would probably alter the base air flow enough to require a re-adjustment of the base idle settings to get the idle RPM correct. To do it correctly & set the BBS air flow properly would probably then require a little tweak on the throttle stop screws & that could drive a TPS re-adjustment anyhow.

 

[dirtrider]

I pulled it off and don't really see that there is much to adjust. The butterfly shaft has a "tenon" on the end that fits into the TPS.

 

 

Afternoon Toast

 

 

If you look closely at your TPS sensor you will see the mounting screw holes are slotted. Those slotted holes allow the sensor to be rotated enough to significantly change the base voltage output.

 

That TPS output voltage (between pin #1 & pin #4) with wire harness hooked up & key on (choke OFF) needs to be set to .385-.390 volts with the base idle RPM correct & the BBS screws adjusted to 1-1/2 turns out from seated.

 

[roger 04 rt]

Toast, sounds like a pretty painful dealer experience but if you need it quickly ...

 

DR, I wouldn't have guessed that cleaning the TBs would result in readjusting the throttle stops. I was under the impression that they were set at the factory and should be left alone. I haven't had to got there yet so I haven't looked too closely.

[dirtrider]

Afternoon Roger

 

You are correct in that the throttle stops are pre-set using either air flow or a pre-set angle at the Bing factory.

 

That is just peachy for a new bike using new TB's.

 

After some miles the engine idle patristic drag changes, the throttle plates wear, the throttle plate bushings wear & that all effects the base idle air settings to keep the engine idle RPM near specs.

 

But even (if) all the above is still perfect he will probably remove the CCP. On the 1100 that most certainly richens the idle fuel/air mixture & that will raise the idle RPM (sometimes significantly)

 

If (when) the idle RPM increases that means the idle RPM will have to be lowered & re-balanced. One of the things that need to be strived for is to keep the BBS screws about even as far as turns out from seated & close to the desired 1 or 1-1/2 turns out from seated (at least as a starting point)

 

Once Toast is assured that BBS passages are squeaky clean, the throttle plates & throttle bores are clean he can then preset the BBS screws to 1-1/2 turns out from seated then use the base idle screws to set idle RPM & balance the base TB air flow delta.

 

On the 1100 personally I use 1-1/2 turns out form seated if the (factory) CCP is still in place or 1 turn out from seated if the CCP is removed as a starting point.

 

[biometrics]

Has anyone here ever used Pine Sol as a Throttle Body cleaner? I used to own a 1983 Honda Nighthawk 650, and the forum for those bikes has a good thread on cleaning scrungy carburetors...

 

http://nighthawk-forums.com/index.php/topic,4472.0.html

 

I don't see why this wouldn't also work just as well on filthy throttle bodies...

 

You just have to rinse everything really well and make sure it's dry before assembly.

[dirtrider]

Afternoon biometrics

 

I might just work OK as well as Simple Green or other type degreasing cleaners.

 

How well it would work is anyone guess & way too much work to do it over again if the Pine Sol doesn’t get all the crud out of the insides.

 

Probably make them look good on the outside anyhow as it should get the grease & crud off.

 

Carb cleaner & even brake clean does work, is pretty cheap, & has a proven track record for removing stubborn coking & baked on varnish.

 

[Toast]

I did inspect the TB shafts...they seem like they are tight in their bushings. I also read Dan Cata's article about replacing those bushings and i don't think my TBs are at that point yet. +1 for the advice about the mineral spirits not handling the coke deposits and for the lube on the o-rings (i always forget to do that). Will apply carb cleaner firts, then rinse with mineral spirits. Thanks guys! [/quote

 

Well, well, well, I took a closer look at the right side TB and the butterfly shaft is indeed loose. I took off the round piece and spring and the bushing is TOAST (Haha on that pun, i've gotta get some laughs or i'll just cry all the time). Sooooo, i guess i need to press out that bushing and spend some $ on new ones. The left TB is much tighter, no wiggle at all. It looks like the spring has worn the right TB bushing down to pretty much nothing, the shaft has LOTS of play. At least the TBs are clean now! I spent a whole can of carb clean, didn't even get any on the TPS because i removed it first and bagged it (+1 toast).

 

I also was able to press in the new oil filler pipe with new o-ring and that's the end of that leak, so the day wasn't a total loss. After 10+ years of wrenching on my old r75 and now several weeks on this "new" RT1100, i have come to realize that motorcycling isn't all about the ride, at least for me. It can be frustrating as hell but it's really like solving a puzzle. Each piece goes in a special way (or not), and when i learn a new technique or trick, it's awesome. I am looking forward to solving this puzzle, because even though i just said it's not all about the ride, you all know that's not really true, is it? It IS about the ride, and this community of helpful folks. I always wonder about the other bikes (HD,japs, dukes, etc) i see tooling around and wonder if the riders would be able to fix them if they broke down. One time i was riding my r75 to work and the head gasket failed and pissed oil out all over my boot. I parked the bike in a parking lot of a heavy machinery garage, hitched to the dealer, got the part, hitched back, and fixed the bike right there with my on-board tool kit, kicked it over and rode away. The guys in the shop couldn't believe it and gave me a standing ovation as i hit the throttle. Okay enough tooting my own horn, back to sulking about this bushing.

[dirtrider]

Morning Toast

 

If the shaft is loose in the bushing there is a good chance you have as much wear on the shaft as the bushing. Take it apart & look closely (or measure with a precision mike or caliper). Seldom do you get just bushing wear without significant shaft wear.

 

[cpayne]

I did inspect the TB shafts...they seem like they are tight in their bushings. I also read Dan Cata's article about replacing those bushings and i don't think my TBs are at that point yet. +1 for the advice about the mineral spirits not handling the coke deposits and for the lube on the o-rings (i always forget to do that). Will apply carb cleaner firts, then rinse with mineral spirits. Thanks guys! [/quote

 

Well, well, well, I took a closer look at the right side TB and the butterfly shaft is indeed loose. I took off the round piece and spring and the bushing is TOAST (Haha on that pun, i've gotta get some laughs or i'll just cry all the time). Sooooo, i guess i need to press out that bushing and spend some $ on new ones. The left TB is much tighter, no wiggle at all. It looks like the spring has worn the right TB bushing down to pretty much nothing, the shaft has LOTS of play. At least the TBs are clean now! I spent a whole can of carb clean, didn't even get any on the TPS because i removed it first and bagged it (+1 toast).

 

I also was able to press in the new oil filler pipe with new o-ring and that's the end of that leak, so the day wasn't a total loss. After 10+ years of wrenching on my old r75 and now several weeks on this "new" RT1100, i have come to realize that motorcycling isn't all about the ride, at least for me. It can be frustrating as hell but it's really like solving a puzzle. Each piece goes in a special way (or not), and when i learn a new technique or trick, it's awesome. I am looking forward to solving this puzzle, because even though i just said it's not all about the ride, you all know that's not really true, is it? It IS about the ride, and this community of helpful folks. I always wonder about the other bikes (HD,japs, dukes, etc) i see tooling around and wonder if the riders would be able to fix them if they broke down. One time i was riding my r75 to work and the head gasket failed and pissed oil out all over my boot. I parked the bike in a parking lot of a heavy machinery garage, hitched to the dealer, got the part, hitched back, and fixed the bike right there with my on-board tool kit, kicked it over and rode away. The guys in the shop couldn't believe it and gave me a standing ovation as i hit the throttle. Okay enough tooting my own horn, back to sulking about this bushing.

Would it be possible to take photos of your procedures and post them to photobucket? This would be a great learning tool for newbies like myself.

[Toast]

Hey now. I am planning to buy one of Dan Cata's repair kits, they come with a new spindle shaft and he has a good write up with photos on his website, I think it is this:

 

http://boxer-upgrades.m.webs.com

 

But if not, google him and you should find his repair kits page. Looks like good stuff from Romania.

[NJNeal]

http://boxer-upgrades.webs.com/apps/webstore/

 

So, my question, after reading his tutorial, is that it appears that after the overhaul you'll have to reset the throttle plate opening by eye as it will no longer have the factory setting. Is this right?

 

[Toast]

I thought the throttle plate "base" opening was controlled by the idle screw with the paint on it? If all i am doing is replacing the spindle and bushing, and re-attaching the butterfly valve, i would think that it would re-set to the "base" because the idle screw hasn't been turned? Or maybe (probably) i am wrong...I'll find out. Dan sent his parts this morning, so we'll see when they arrive from Romania...Maybe Dan can chime in if he's reading this....

[Toast]

When i pulled the right fuel injector out of the TB, i noticed that the fat rubber ring that is below the piece that attaches to the TB has a big split in it so i am assuming that it needs to be replaced. I am trying to add a picture of it, but when i click the "enter an image" icon, it pulls up a dialog box that asks me for a URL, so i don't know how to deal with that but anyways.

 

 

Here is a picture of the cracked rubber block. Is this just a block for stabilizing the fuel injector in the TB? Should i be overly concerned about replacing it? Sources? Also, i did not see any o-rings on the fuel injector (the end that fits into the TB, although the schematic indicates that one should be present. The ones i bought are rather fat and fit over the yellow part of the fuel injector, is that where it is supposed to go?

[dirtrider]

I thought the throttle plate "base" opening was controlled by the idle screw with the paint on it? If all i am doing is replacing the spindle and bushing, and re-attaching the butterfly valve, i would think that it would re-set to the "base" because the idle screw hasn't been turned?

 

Morning Toast

 

The "throttle plate "base" opening (IS) controlled by the idle screw with the paint on it".

 

(BUT)-the amount of air the throttle plate allows by using that factory set stop screw is dependent on the below.

 

 

Assumes the throttle shaft is in the "very same" position as on the original, assumes the new throttle shaft has EXACTLY the same throttle plate position on the shaft as the original, assumes the new assembled TB has the throttle plate in the EXACT same position within the throttle bore as the original, assumes the throttle plate has no wear from contacting the TB bore due to operating with worn bushings, assumes the throttle plate is clocked on the throttle shaft the exact same way as on the original.

 

If you are 100% convinced ALL the above is exactly the same as on the original then the factory painted screw position will probably be real close.

On the other hand if ANY of the above things are not back to exactly the same as on the original then the factory screw setting will probably off enough to need to be re-set.

 

I doubt very much that you can depend on that factory screw setting to be correct after a new shaft & bushings are installed.

 

[Toast]

Thanks D.R. I kinda figured on having to reset that screw. Doesn't hurt my feelings too much to have to break the paint, especially since i won't be going to my dealer for help, this board provides everything i need and more. Loving it!

[NJNeal]

With respect to the paint, from my personal rotten experience at a BMW dealer I won't return to, if the paint indicates that anyone has touched the screws, they won't even attempt to balance the TBs, or do any other work to that system, unless you buy new TBs. They stated that BMW policy is if the paint indicates anyone messed with the system, they won't touch it at all. Clearly not a warranty issue, as the bikes are ALL out of warranty. Just a way for the dealer to avoid doing real work and instead just making a lot of money selling parts.

[tallman]

Neal,

That sounds more like a dealer decision, not BMWNA policy.

 

It wouls be more likely from my experience a customer would be told, looks like someone has messed with the set up, may be easier, or much harder to deal with so there may be additional time.

We never turned away a bike based on that issue.

[nrp]

Speculating, it may also simply be a consequence of EPA emission certification since the air flow balance between the throttle stop and the big brass screws determines the mixture function vs the throttle position sensor as seen by the CPU.

 

Surely it wouldn't be a big deal to come up with an equivalent orifice for the throttle stops which could be set in the field with two pressure gauges - if the EPA would allow it.

[dirtrider]

Afternoon NRP

 

Bing sets those throttle stop screws well before BMW even sees the throttle bodies. On some they use an actual measured throttle plate opening angle & on others measured air flow.

As long as they are all the same & the BBS screws are mid travel then BMW has a TB that will work & allow BBS adjustment as needed for balance over the normal life of the TB.

 

I'm betting the base air flow or plate angle as supplied is set according to BMW's requested specs.

 

For 1100 non cat emission idle Co compliance there was a Co pot to adjust the hot engine idle Co emissions. For all the other (cat equipped) 1100's & all 1150's the 02 sensor & cat automatically handled the idle Co compliance.

 

[philbytx]

DR,

IIRC I saw information that the R1150 TB plate baselines are at 5 degrees and the R1100 TB plates are at 10 degrees.

 

I know I saw it posted somewhere, can't remember if it was on here or ADVRIDER.

[nrp]

Afternoon NRP

 

Bing sets those throttle stop screws well before BMW even sees the throttle bodies. On some they use an actual measured throttle plate opening angle & on others measured air flow.

As long as they are all the same & the BBS screws are mid travel then BMW has a TB that will work & allow BBS adjustment as needed for balance over the normal life of the TB.

 

I'm betting the base air flow or plate angle as supplied is set according to BMW's requested specs.

Air flow is easy to measure. Throttle plate angle would be very difficult to measure accurately, and not really the item of concern assuming airflow with a given pressure differential is what is desired.

 

A small round hole in an air fitting (like a differential compression measurement scheme used for aircraft) would be logical using lower pressures.

Maybe someone wants to take a brand new throttle body & make an equivalent hole orifice and offer a throttle body resetting service. There's a free business idea!

[NJNeal]

What does Bing do in their overhaul service? At the bottom of this page: http://bingcarburetor.com/pdf/throttlebodykits.pdf they offer a rebuild service for $155 for the pair plus the cost of the rebuild kit or about $355 all in. I'd like to think they restored the TB to the build spec. Anyone ever go this route? Far cry from dealer new cost.

[roger 04 rt]

...

 

Air flow is easy to measure. Throttle plate angle would be very difficult to measure accurately, and not really the item of concern assuming airflow with a given pressure differential is what is desired.

 

...

 

That's an interesting comment that I've read elsewhere. One of the benefits of Closed Loop operation and adaptation values is that the Motronic learns its errors over time and makes some level of adjustment.

 

 

[dirtrider]

Morning Roger

 

That is true on the fueling side but unlike the 1200 with the BMS-K system the Motronic 2.2 & 2.4 has no ability to apply adaptation valves to change the TB air flow. Even the 1200 with the BMS-K can only alter the air flow at idle & very low throttle openings.

 

 

[dirtrider]

Afternoon NRP

 

Bing sets those throttle stop screws well before BMW even sees the throttle bodies. On some they use an actual measured throttle plate opening angle & on others measured air flow.

As long as they are all the same & the BBS screws are mid travel then BMW has a TB that will work & allow BBS adjustment as needed for balance over the normal life of the TB.

 

I'm betting the base air flow or plate angle as supplied is set according to BMW's requested specs.

Air flow is easy to measure. Throttle plate angle would be very difficult to measure accurately, and not really the item of concern assuming airflow with a given pressure differential is what is desired.

 

A small round hole in an air fitting (like a differential compression measurement scheme used for aircraft) would be logical using lower pressures.

Maybe someone wants to take a brand new throttle body & make an equivalent hole orifice and offer a throttle body resetting service. There's a free business idea!

 

 

Morning NRP

 

Obviously having all the vendor supplied TB's used by a certain make & model motorcycle come in with the same air flow or same throttle plate angle makes the initial assembly & initial build faster & end of line adjustments much faster.

When 20 or more bikes an hour are coming off the end of the assembly line the less that needs to be adjusted the better.

Same at dealer level, all most dealers want to do is throw on a matched set of TB's, do a quick balance, & grab your money, then push you out the door.

 

Personally I don't see that having the TB's at a certain throttle plate angle or precise air flow as being that big of a plus for the home tuner or home TB re-builder. That is unless they are in big hurry to get-er-done & out the door.

 

For a long time now a lot of us home tuners have been tweaking the factory base throttle stop screws to get even air flow & perfectly even throttle plate lift off.

 

On the ones I work with I really don't care what throttle angle or air flow the TB's were built with as long as the final balance gives me an even air flow delta at hot curb idle with the BBS at very close to the same turns out from seated & to desired specs, that the cross side balance delta tracks smoothly from closed throttle to about 1/2 throttle, & most importantly to me that both throttle plates lift off the stops at the exact time with even cross side delta during the lift off.

As an added it makes me smile if both side throttle cams hit the WOT stops at the exact same time also. If they don't then I either did something wrong, or for some reason the engine is not pulling even vacuum side to side, or there is something wrong with the TB's or throttle plate position within the TB's.

 

Then once the air flow is even side to side from idle all the away to WOT the fueling needs to addressed to also be very even side to side from hot curb idle all the way to WOT road load (good luck with this one). Or at least made rich enough that a bit of fueling difference side to side isn't that big of a deal (easiest way out)

 

[roger 04 rt]

Morning Roger

 

That is true on the fueling side but unlike the 1200 with the BMS-K system the Motronic 2.2 & 2.4 has no ability to apply adaptation valves to change the TB air flow. Even the 1200 with the BMS-K can only alter the air flow at idle & very low throttle openings.

 

 

As you know, I am in complete agreement with your observation. My point there was more subtle. Assuming for a minute that there is a reasonable balance between cylinders, if the TPS and the Motronic's interpretation of its throttle angle were not a good marker for the VE due to miscalibration, wear or design, when the Motronic starts running its Closed Loop program, its integrative adaptation function quickly gets the combined fuel to match the air/VE.

 

Then over time, to some as yet unmeasured extent, the Motronic creates block adaptations and applies them to Open Loop, all helping with the small-throttle-angle versus VE problem that NRP described. I had a good lesson in this over the weekend.

 

After two months of riding my motorcyle with Closed Loop fueling set at 13.8:1, and making many test rides where the sole purpose was to evaluate how the bike was running, I replaced my battery on Saturday morning. With the richer mixtures, my 04RT had a good strong idle. After replacing the battery, at startup, the idle was rough and uneven. After a few trips and an overnight cooldown, the next morning's start was quick and smooth, as it had been. Also immediately after the reset event, I noticed for a while that the motorcycle "felt" different. Since I've only made a few short trips, there are a lot of TPS/RPM areas/blocks for the Motronic to relearn.

 

Some further thoughts below.

 

 

Afternoon NRP

 

Bing sets those throttle stop screws well before BMW even sees the throttle bodies. On some they use an actual measured throttle plate opening angle & on others measured air flow.

As long as they are all the same & the BBS screws are mid travel then BMW has a TB that will work & allow BBS adjustment as needed for balance over the normal life of the TB.

 

I'm betting the base air flow or plate angle as supplied is set according to BMW's requested specs.

Air flow is easy to measure. Throttle plate angle would be very difficult to measure accurately, and not really the item of concern assuming airflow with a given pressure differential is what is desired.

 

A small round hole in an air fitting (like a differential compression measurement scheme used for aircraft) would be logical using lower pressures.

Maybe someone wants to take a brand new throttle body & make an equivalent hole orifice and offer a throttle body resetting service. There's a free business idea!

 

 

Morning NRP

 

...

 

Then once the air flow is even side to side from idle all the away to WOT the fueling needs to addressed to also be very even side to side from hot curb idle all the way to WOT road load (good luck with this one). Or at least made rich enough that a bit of fueling difference side to side isn't that big of a deal (easiest way out)

 

It sounds like you have a meticulous approach to getting the air balance as close as it can be. And you've described in other places how one might get that air balance refined through on-the-road adjustment. Given that the two injectors have different flow-rates and different turn-on-times, I can't think of a way (short of using a PowerCommander on one of the injectors but not the other or slightly reducing the power at the richer of the two injectors) to compensate the side to side fueling other than to buy very carefully matched injectors--matched for flow rate and turn-on time for pulse widths between 2 and 5 mS where most of the action is.

 

So I end up in agreement with you on running a richer mixture. Once the mixture is rich enough that O2 is depleted and there is a slight (4-6%) excess of fuel in each cylinder, adjusting airflow on the right side, under power, can yield an exact power balance, at least over a range of TPS/RPM. Then the motronic's value adaptation function can fine tune further over time--provided you have maintained a Closed Loop function.

 

Lastly, I want to point out that running a richer mixture gives a small "accelerator pump" function compared to a stock bike. My reasoning goes like this: if you're cruising with a warmed-up stock bike and open the throttle, there is no excess fuel in the mixture and the immediate effect is that the mixture gets leaner from the increased airflow--and power drops/hesitates. If you are running 6% rich, you open the throttle, airflow increases and consumes some of the "excess" fuel of the richer mixture and power immediately increases.

 

All very interesting.

 

[nrp]

I agree completely that the engine etc can be used to set the throttle stops & that it not necessary to buy new throttle bodies if the old one has been tinkered with. It just takes a knowledgeable mechanic - like DR.

[Toast]

Well folks upon closer review of my right TB I saw that the plastic spring shim was gone and the spring action had worn away half of the boss. The left side looked ok just a bit cruddy so a good cleaning and back on. Decided to replace the TB. It was so shiny out of the box! Re-installed the RTB, got the choke and throttle cables figured out and sync'd, bike runs sweet now, no discernible surge, it's awesome! So glad I bought this bike. Thanks to all who have co tributes to this discussion

[Twinsig]

has anyone successfully repaired one of these TBs with the spring-groove worn into the boss?

 

 

[Toast]

DR indicated very doubtfully that i could MAYBE get a machine shop to create a "slip-on" over the failed boss, but that kind of mickey mouse action at such a critical point in the fuel delivery system didn't excite me as much as opening the box of my NEW TB. The results are obvious (to me), and the bike is running smooth, strong, and sofa king much more fun than my old R75/5....

[Toast]

Also, with a slip on over the failed boss, i think i would need a larger diameter throttle return spring....with NO source for that...