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Re: Lets get back to oilheads... throttle body question

Hi Bob and Andrew,

Well, I started out this morning thinking I had better do a zero=zero.  
What I found when I started taking the left throttle body "stuff" off 
was that the throttle body clamp to the cylinder head was loose and 
passing crud (and probably air...hidden from sight by the plastic 
injector cover) and that the GS intake tube had a broken o-ring 
connecting to the throttle body.  To me that means that the left side 
was actually the weaker side as the right had more vacuum (as borne out 
by the TwinMax...replaced its cracking hoses today to eliminate that 
source of leakage).  So, zero=zero is on hold while I get a replacement 
o-ring. Hopefully, that will solve the BBS imbalance, and life will be 
good once again. I did find the existing TPS to be a bit low at .340 but 
I'm not going to change anything until the o-ring is installed and 
another balance attempted (I think I'll start swearing if I have to 
adjust the throttle stop!). This bike has never annoyingly surged (well, 
once when the Hall Effect unit went south).  Left throttle cable still 
has .5 mm free play...right has none at this point but hopefully that 
will change at next balance.  I'll keep you posted.  Thanks.

John Van Deren
Montpelier, VT
No ride today!

Bob Hadden wrote:

> John,  Just a thought, but I may be going to Parkers on Monday 
> morning.  Perhaps we could hook up to deliver the part if needed?
> Bob Hadden
> On Sep 3, 2005, at 7:57 AM, John Van Deren wrote:
>> Hi Bob,
>> Yeah, I'll check TPS voltage too...haven't done that in a looong 
>> time.  I was hoping to ride on this beautiful morning but I guess I 
>> have some work to do.  Thanks for your thoughts (and replacement TPS 
>> if I need it!).
>> John Van Deren
>> Montpelier, VT
>> Bob Hadden wrote:
>>> John,  The setting of the tps affects the idle speed.  Perhaps, with 
>>> the mileage on your bike, the throttle stop has loosened up or the 
>>> tps is wearing and not getting down to the proper level.  You should 
>>> check the throttle stop to be sure it is not loose, and check the 
>>> tps voltage to be sure it is still where you want it.
>>> Incidentally, I have a tps new in the plastic if you need it.
>>> Bob Hadden '05R12GS, '62R27
>>> On Sep 3, 2005, at 7:37 AM, John Van Deren wrote:
>>>> Thanks, Andrew,
>>>> I wish we could post photos.  If the 28 feet of tubing are in a "u" 
>>>> shape on the four foot board (using what sounds like about 10 feet 
>>>> of the tubing), where is the remainder of the 28 feet?  I'm having 
>>>> a little trouble visualizing what your vacuum gage looks like.  
>>>> Anyway, I'll test for air leakage w/carb cleaner.  The tube clamps 
>>>> are tight. I do have an old Carb Stik w/mercury that I never 
>>>> liked.   I may break it out and see if I can adjust the throttle 
>>>> stops as you suggested.  I've never removed the BBSs and cleaned 
>>>> them so I'll do that too.  I had done a careful valve adjustment 
>>>> (OVAD).  The engine runs smoothly, but I'd like to determine why 
>>>> the BBSs are so uneven in their setting and get the idle down a 
>>>> bit.  Thanks for your ideas.
>>>> John Van Deren
>>>> Montpelier, VT
>>>> andrew johnson wrote:
>>>>> At 1:46 PM -0400 9/2/05, John Van Deren wrote:
>>>>>> Hi listers,
>>>>>> Today I was adjusting the throttle body synch on my 94 RS (110K 
>>>>>> miles) and noticed that the right brass air bypass screw needed 
>>>>>> to be almost closed (clockwise) to attain balance on the Twinmax. 
>>>>>> The left screw is a couple of turns out.  I cannot get the idle 
>>>>>> low enough to suit me...about 1400 rpm is as low as I can get 
>>>>>> it.  Does this indicate that the right throttle body has a 
>>>>>> problem (wear)?  Do I have an air leak perhaps on one side?  Any 
>>>>>> wisdom from the pros out there would be greatly appreciated.  
>>>>>> BTW, I use GS tubes.
>>>>>> John Van Deren
>>>>>> High and dry in Montpelier, VT
>>>>> Could be an issue with your throttle body, the butterfly shaft can 
>>>>> wear and allow air to pass through its bore in the cast body. 
>>>>> Conventional wisdom says squirt carb cleaner on the throttle body 
>>>>> near the shaft's bearing points and see if any change in idle.
>>>>> I finally tossed the TwinMax. It had developed a preference to 
>>>>> lean off to one side, indicated by swapping hoses and seeing a 
>>>>> whole different reading from the last set zero. I was also looking 
>>>>> for something better for adjusting the throttle stop screws.
>>>>> I made up a water gage, about 28 feet of 3/16 I.D. vinyl tubing, 
>>>>> in a "U" shape along a four-foot wood board, with exactly the same 
>>>>> lengths from bottom of "U". I filled it with colored water to half 
>>>>> the height of the board. When I attach this to the vacuum ports I 
>>>>> get a very clear and stable indication of whether the engine is in 
>>>>> balance or not.
>>>>> My adjustment process is as follows:
>>>>> 1. Valves dead-on, cold, OVAD style with four guages, engine set 
>>>>> at TDC with home-built TDC flywheel locking tool.
>>>>> 2. Remove and clean the Big Brass Screws (BBS) and their bores 
>>>>> with carb cleaner. A faint dab of silicone grease on the O-ring, 
>>>>> then back in.
>>>>> 3. With engine fully warmed up, and throttle cables slack against 
>>>>> their adjustment barrels, the BBS are fully and gently seated 
>>>>> (turned in clockwise until they stop).
>>>>> 4. Engine running (roughly and slowly) I adjust the right hand 
>>>>> side throttle stop screw until I have perfect balance in the water 
>>>>> tubes (or TwinMax). The water tubes take a while to settle, be 
>>>>> patient. When the engine is balanced at this stage, you will feel 
>>>>> and hear a discernable relaxing of the roughness, even though it's 
>>>>> idling at 600 RPM.
>>>>> 5. I back both BBS out two full turns, then adjust for balance at 
>>>>> idle (throttle cables still slack).
>>>>> 6. I finally adjust for off-idle balance by moving the right hand 
>>>>> side throttle cable adjustment barrel, as needed. Take it to 1500 
>>>>> RPM for basic measurement, higher if you wish.
>>>>> This is what I do. The left side throttle stop is fixed, TPS is 
>>>>> set at 0.390 volts, I don't mess on that side except BBS.
>>>>> Bike runs so smooth now, the water gage helped me get the throttle 
>>>>> stops in perfect balance, as never before.


End of oilheads-digest V2 #204