TB air screws

[catfish]

I replaced the throttle bodies on my 650k7 today (long story) and not surprisingly the new-to-me ones were out of sync. Way out of sync, so much that as soon as I cranked the engine with my homemade manometer hooked up fluid was moving REALLY quick toward one cylinder. Since I know that one cylinder is pulling fluid quickly, which way should I turn that cylinder's air screw (in or out) to slow the pull? Would it be just as safe to turn the other cylinder's air screw to equalize the fluid levels? Thanks!

[johnofchar]

I'd try the ones that's pulling in & the other out the same amount. A little at a time.

[catfish]

#1 cylinder was pulling ATF fluid so I turned that air screw in and #2 out and the pulling seemed to get worse. Basically, through trial and error, I found that the only way to get fluid to stop moving toward #1 was to have #1 air screw out a lot (possibly to its maximum) and to have #2 air screw ALL the way in. And the fluid levels are still a couple of FEET off, and I obviously can't improve that because my air screws are already at their maximums. Something doesn't seem right. However, the engine seems happier than it did with the old TBs. Any ideas?

[greywolf]

I've got to wonder if the linkage is adjusted properly to start with if the throttle bodies were never on a bike before or may have been played with if they were on a different bike. The air screw adjustments for a TBS assume the linkage relationship is correct. I'd be looking for a dealer practiced in using the SDS system to get things set up right to start with.

[catfish]

The TBs are off of another bike. I know from experience that the linkage screw isn't very tight so it may have accidentally been turned, all I can say is that the line of white paint on the screw and "spring" line up. I do think taking it to a dealer mechanic is a good idea (I'm about due to have the valves checked anyway) but I worry 1) they won't want to help me when I tell them I replaced the TBs and 2) they won't know how to properly adjust the linkage, which I read isn't even discussed in the service manual. So the linkage being off may affect the TB balance (as on older stroms)? All I've heard is that messing with it is bad, which doesn't help me understand what its there for on k7s and up.

[greywolf]

Right. All the manual says is the linkage is adjusted at the factory and shouldn't be touched.

[catfish]

Right. All the manual says is the linkage is adjusted at the factory and shouldn't be touched.

Which means its begging for me to touch it.

[johnofchar]

Since it would probably be hard to screw it up any more, I'd give the primary mechanical linkage adjustment a try.

Mechanical adjust for primary throttle plates: You need two of something fairly small and round & long enough to hold on too. A couple pieces of bare 14 gage solid copper wire or a couple of same size drill bits, etc. Tape a string onto these just in case of a drop. You need to place these between the throttle body and the primary plates on the side that lifts up when you roll on the throttle. Not the side that looks like clear plastic. Adjust the leakage screw so the drag is the same on both pieces of wire. They should actually be clamped in place with both being equally hard to move when it's right.

After mechanical adjust set both air screws to mid range & use your manometer & air adjust screws. When adjusting TBS keep the engine at 3 bars on the temp gage using large fan on radiator, etc.

But think before I did anything, a check for vacuum leaks would be good.

[catfish]

The bike doesn't have any symptoms of a vacuum leak, like the idle is pretty constant, but I can see how if there was one it could affect the pull at the vacuum ports. I'm confused about how to "place the wire between the TB and the primary plate". Do you mean with the plate (throttle) slightly open put the wire between the plate and the TB? So when the throttle (plate) closes it hits the wire? And both plates should hit the wire at the same time?

[johnofchar]

Yep.

[catfish]

Good thing I now have a spare set of TBs to practice on!

[catfish]

I'm hoping this weekend to check my throttle plates, but I also want y'all's opinion on something. Several months ago I was checking my TB synch and curiosity about the linkage screw got the best of me and I played with it a little. I turned it to see what would happen (making sure I knew where to turn it back to). Turning it caused the rpm to increase a little and the TB balance (homemade manometer) to shift. Yeah, the bike idled rougher too. When I put my "new" TBs on the rpm was high (~1600) and the balance was off (like when I messed with the linkage screw on my old TBs), and maxing the air screws out fixed the rpm but I can't get the balance anywhere close to even. It seems to me that adjusting the linkage screw may just be another way to get the rpm and TB balance to normal, like a major adjustment, and the air screws a minor adjustment. Do you guys think this is possible and would I screw something up permanently if I 1) turned the air screws to a medium position 2) turned the linkage screw to see if I can get the TB balance and rpm to a roughly normal range and 3) used the air screws to fine tune it? This would be after checking for a vacuum leak and seeing if the throttle plates are equally closing. And of course I would know where to turn the linkage screw back to.

[greywolf]

It's not really a coarse/fine adjustment in the way you describe it. Do it the way John said if you can't find a vacuum leak. Really check for one first rather than make any assumptions. Spray starter fluid around all the joints and connections on the throttle bodies. If there is a leak, the engine operation will change when spraying on the leaky area.

[catfish]

Thanks greywolf. Spray the starter fluid around the throttle bodies with the engine at idle, right? And the rpms should increase if there is a leak? That doesn't damage anything does it?

[greywolf]

Any changes would indicate a leak. Without a leak, the fluid spray will have no effect. It's harmless.

[catfish]

Regarding checking the throttle plates, just to make sure I do it right, I open the plates (throttle), insert wires/drill bits into opening (they're tied with string or something to keep them from falling into the engine cause that would be bad), close throttle, and they would either both be held against the wall if things are adjusted right, or one wouldn't be held against the wall if things aren't adjusted right. Thats what I get from John's instructions and this post in another thread... "Yes, with the wires inserted the plates will be at an angle and should be the same after adjustment, as far as I know, this being all a bit of guess work. Insert both wires and one should be held by the plate and the other not. Adjust until they are the same."  Sorry for the million questions, but thanks!

[johnofchar]

Sounds good.

[catfish]

Last night I looked at the throttle plates on my old/now spare throttle bodies and practiced aligning them so I don't screw up the ones that are on my bike now.  I tied and taped fishing line to two same size small drill bits and inserted the bits between the open throttle plates on the sides that rise up then closed the throttle plates. As expected, if the linkage screw is turned counterclockwise the rear throttle plate opens and the drill bit becomes loose and falls out. Turning the linkage screw clockwise closes the rear throttle plate and the drill bit remains firmly clamped by the plate. Turning the linkage screw 2-3 additional turns clockwise didn't have an effect on how tightly either plate held the bits and I couldn't tell/didn't check if the rear plate continued to rotate around or if the front plate was ever affected by the linkage screw. Here's my new question: Do you guys think I should find a point where the rear plate doesn't securely hold the drill bit and then turn the linkage screw until it just does and then stop?

[johnofchar]

Your adjusting the rear to match the front as you found out. With bits inserted, adjust so the rear just gets some drag on the bit and stop.

How far off were the old bodies?

[catfish]

I didn't think to check the old ones before I started tinkering with them, so the linkage screw was turned before I checked the plates. Would've been really nice to know if they were misadjusted from the factory. I will say that when I just got equal drag on front and rear, the white line painted on the linkage screw at the factory didn't line up, was maybe a quarter turn off.

[catfish]

On Saturday I checked the throttle plates on my new TBs with drill bits as described by John above. The good news, if you want to call it that because it could explain my bikes pulsing/surging, was that the linkage screw needed two full turns to get the rear plate to hold its drill bit. I turned the air screws to a medium position, hooked up my manometer and I was happy to see that the fluid levels were off but were at least stablized, and I was able to get them even without having to turn the air screws too far away from each other. I checked the TPS and needed to adjust it even though I had done this the previous week. The bad news is my bike seems no better and may even be worse. Sigh. I was amazed at how sensitive the bike is to quite minor TPS adjustments.  I'd read adjusting it so the bar (-C) would move up at 1500-1600rpm was optimal, but I tried for 45 minutes and couldn't get it less than 1800rpm without it moving up at idle. The idle isn't currently smooth. Its definitely rideable and acceleration seems fine, its just still got the aggravating 3-4k rpm low throttle surge/pulse and inconsistent engine brake when decelerating through 4-3k rpm. I guess I'll be taking the plastic off again in the near future to see if I can get things smoother. Any ideas would be appreciated.

[catfish]

I forgot to add...when checking the TBS I noticed that barely cracking the throttle caused a huge vacuum increase at the rear cylinder. I know that off idle the ATF fluid levels will change some, but this was quite a lot.

[johnofchar]

Remember I said when we started this that manual syncing of the throttle bodies was just an educated guess procedure. My K9 is spinning like a top. I did check the TBS using the SDS and it was very close. I should have my bike apart later in the week & I'll check the factory setting on the primary valves.

How much is a lot? Don't forget, with the home-made manometer, 7-8 inches is only one inch of mercury. So 3-4 inches is no biggie.

[catfish]

I think the procedure is fine, as supported to my actually being able to balance the ATF fluid levels after adjusting the linkage screw. One question would be how much does say a quarter turn of the linkage screw affect things. When I said that cracking the throttle moved the fluid a lot I mean I got uncomfortable with it moving as fast as it was toward the rear cylinder, so it never stabilized and when I closed the throttle it was maybe 48+ inches off? It went back to even at idle. This may be normal for all I know.

[johnofchar]

No not normal, something is still amiss.

[PeterW]

That large a difference off idle is almost certainly a leak of some sort.

Front throttle body boot cracked or blown off, one of the vacuum port caps cracked or leaking somehow ?
A leak in the vacuum sensor line ?

I'd suggest going back to the traditional methods of finding leaks - a can of engine start (ether) and spray small amounts over anything connected to the cylinders at idle. When you get to the leaking area the idle will increase.

Pete

[greywolf]

The leak test has been mentioned a couple of times now. It's vital. Did you ever do it?

[catfish]

I sprayed starter fluid around the TB boots and the vacuum ports and what hoses attached to the TBs I could see with the tank raised. When sprayed around the boots the rpms increased 200rpm, to 1500. I didn't think much of it since I'd read somewhere the engine would rev if there was a leak, but maybe I overestimated what "rev" meant. Would a 200rpm increase be enough to indicate a leak? The rpm went up when the fluid was sprayed around both the front and the rear boots. The TBs looked well seated and the clamps are tight, but I didn't look for problems (cracks) in the rubber. Spraying that stuff around a hot engine made me a little anxious...

Thanks guys. I really appreciate your ideas and your time. Hopefully I'll get this figured out.

[johnofchar]

The RPM increase depends on how big the leak is. If it raises at all there is some kind of leak, unless some is getting in the intake. You will need the airbox off to really investigate properly. Could be a bad manifold or just bad seal at TB.

Remove TB's and clean both the bottoms of the TB's & inside the manifolds well using alcohol, reinstall and test.

[PeterW]

....
 Spraying that stuff around a hot engine made me a little anxious...

Thanks guys. I really appreciate your ideas and your time. Hopefully I'll get this figured out.

The reason ether is used for this is that although it burns real easy, it also burns cold and fast.
You might lose an eyebrow but it's unlikely to hospitalize you. (Wear eye protection).

I've seen a 0.5x0.5x5m long SQUARE flame of ether from an error of judgement in a chem lab - impressive as all hell. A few people needed a change of underclothing afterwards, but no damage done - Just WHOOOOOMPH and gone.

Cheers
Pete