HELP: Throttle Body Adjustment Screw Specs - Yamaha R6 Forum: YZF-R6 Forums
 
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post #1 of 6 (permalink) Old 01-07-2017, 11:37 AM Thread Starter
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HELP: Throttle Body Adjustment Screw Specs

I have a 2005 R6 and I'm trying to sync the throttle bodies. Problem I'm having is that TB1 has considerably less vacuum than TB2, TB3, and TB4. I was able to get 2 and 4 pretty close to 3, as the service manual states TB3's air screw should not be touched and used as a standard reference point. The issue is that now I have TB1's adjustment air screw screwed all the way in(creating the most vacuum possible) and it is still out of sync. It's as if I need more adjustment room, to create more vacuum in TB1 to get it to equal TB3. The service manual states that each TB should have a vacuum pressure of 180mmHg at idle, and that the difference in vacuum pressure between any two TB's should not be greater than 10mmHG. I don't have an accurate vacuum gauge but I measured how many turns out my TB3 air screw was; 1 5/8 turns out. I bought the bike used so I don't know if anybody has messed with TB3's air adjustment screw.

Does anybody know how many turns out Throttle body #3's air adjustment screw is on a 2003-2005 R6, or any R6S straight from the factory?

I know there is a lot of variability in the TB's vacuum pressures overtime due to wear in parts, but according to the manual, TB3 is the standard and is never to be adjusted. All other TB's are to be synced to #3. So what I figure is that TB3's air screw should always be the same, or at least close to it's factory setting. Valve clearances were adjusted on my bike at 25,800 miles about a month ago. Now it has 26,400 miles, idle RPM when warm is about 1,400-1,350, and she's all stock except for a Akroprovic slip on. The bike has been running OK, except for cylinder 1 being more rich than the others(darker plug) and the idle loping a little(which I've heard is common and normal for the R6) which I think may be attributed to the lower vacuum pressure.

If anybody knows or could check how many turns out there TB3 air screw is, it would be greatly appreciated. Just thought I'd ask before investing in a quality vacuum gauge. I just need to rule out if my reference TB has been messed with or not before I start looking for vacuum leaks.

Thanks

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Last edited by Dr.smr; 01-07-2017 at 11:43 AM.
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post #2 of 6 (permalink) Old 01-08-2017, 12:11 PM
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Re: HELP: Throttle Body Adjustment Screw Specs

sounds like the engine may have a mechanical issue. do a compression check
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post #3 of 6 (permalink) Old 01-08-2017, 01:45 PM
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Re: HELP: Throttle Body Adjustment Screw Specs

^^^ Yup.


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post #4 of 6 (permalink) Old 01-09-2017, 11:50 AM Thread Starter
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Re: HELP: Throttle Body Adjustment Screw Specs

I went ahead and pulled the throttle bodies and their lower mounting boots. I cleaned and inspected both for areas of possible vacuum leaks but didn't find anything obvious. Reset all air screws to 2 turns out, put everything back together, and re-attempted to sync the TB's. Strangely, this time I was successful in getting all throttle bodies to pull a similar amount of vacuum. However, TB1's air screw is still screwed in all the way while the other 3 are about 1.5-1.75 turns out.

I also performed the compression test, once the bike was warmed up, and got pretty uniform readings across the cylinders. I tested each cylinder three times and these are roughly the averages:
Cylinder 1 180PSI
Cylinder 2 175PSI
Cylinder 3 180PSi
Cylinder 4 175PSi
The service manual states that the standard compression reading is 220PSI, max 246PSI and the minimum is 191PSI. My compression tester is only a few months old but I only paid around $40 for it off Amazon, so I can't attest to it's accuracy. Even if my compression is low, it seems like all cylinders have similar wear, not as if one is far more or less than the others. The bike starts up easily and runs well, has plenty of high RPM power. Cylinder 1 spark plug still looks darker than the rest, and the TB1 air screw is still screwed in all the way. If low compression was the cause for TB1's vacuum being low, wouldn't all the throttle bodies have the same issue?
Intermittently, the bike will smoke a bit on start up out of the exhaust, but clears up after a few seconds. Usually does this when its been sitting overnight, and it is cold in the mornings. Could this be a valve stem seal starting to go bad? Could all other issues I'm having be related to that?

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post #5 of 6 (permalink) Old 01-09-2017, 01:12 PM
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Re: HELP: Throttle Body Adjustment Screw Specs

did you try it with a teaspoon of oil? this can tell if its low because of valves or piston rings. it could be the valves are slightly open since it was recently adjusted. also check the timing. if you can't get all the alignment marks to match up then the chain is stretched. I had to replace mine around 30k miles. it's only $25 or so.

what kind of synch tool you using?
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post #6 of 6 (permalink) Old 01-10-2017, 01:05 PM Thread Starter
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Re: HELP: Throttle Body Adjustment Screw Specs

Against my will, I took my bike to a shop for the valve adjustment. I can't vouch for the work done because it was the first time I did business with them. Also, the oil burning/sparkplug#1 fouling problem started happening when I got it back from the shop.
The sync tool I'm using is a homemade manometer, with six feet of tubing per throttle body and restricting couplers(to dampen the vacuum pulses) installed in each hose, filled with two stroke oil. I have borrowed my friends sync tool in the past, one with for dial faces, and got the same results; TB#1 was low on vacuum.
I'll try the compression test again tonight when I'm off work, but with the addition of oil. Hopefully I'll be able to figure out if the low compression is due to valves or the rings.

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