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Discussion Starter · #1 ·
So my bike suffered a serious accident last year when the frame snapped (too many wheelies). I've restored what was left and installed it all in a new frame with lots of new and used replacement parts. Last week, when installing the new throttle cables, I noticed that the tab that connects the throttle connected to the first two tb's to the right two tb's was broken, so I fabricated a little adjustable tab to reconnect them.

Anyhow, come Friday, once everything was wired up and I tried to fire the bike, it wouldn't start. Finally got it running with starting fluid, but it runs HORRIBLY. Drained and replaced the gas, inspected fuel filter and checked spark just to rule them out (no FI indicator either).

Finally hooked up a set of balancing vacuum gauges to the tb's... One and two were at about 10 psi, three was spiking between 10-30, and four was holding at 30. Adjusting the air screws on three and four didn't do a damn thing. I'm thinking that the whole throttle body is just toast, and I'm trying to source one locally before I turn to feeBay.

Any thoughts?
 

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I don't think your post is being ignored, but for me, I just don't have any input. You have done so much to the bike there is no telling what is going on from a post over the interweb.

I'm not sure how how a throttle body becomes "toast". There is really is not much to them.

Maybe if you narrowed it down to only one problem at a time?
 

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Alpha Canuck
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My first thought is your fabricated tab is the common denominator, it is the link between 1&2 and 3&4. I am not familiar enough with this to tell you what to do to balance them but maybe sourcing a factory part to sort it out before you spend much more time and money is a wise idea.
 

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1995 GSX-R 750
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If you worded this correctly, you said you are turning the AIR screw to make the balancing adjustment? To vacuum sync, you need to be adjusting the butterflies, not the A/F mixture screws. I wasn't aware throttle bodies even had air screws.
 

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If you worded this correctly, you said you are turning the AIR screw to make the balancing adjustment? To vacuum sync, you need to be adjusting the butterflies, not the A/F mixture screws. I wasn't aware throttle bodies even had air screws.
Some throttle bodies have solid shafts between the butterflies so you can't adjust the relationship. In that case they provide an air bleed screw between the two sides of the butterfly so the cylinders can be balanced.
 

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1995 GSX-R 750
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Thank you for the clarification, John. That is interesting to learn. Seems to be a stupid design, but maybe it works better than adjustable butterflies? In light of that info, I would agree with Tin, that your "engineered" tab is likely the cause of the imbalance. I would see if you can tweak your tab to where 3 & 4 are open a touch more.
 

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I don't have a service manual for your bike so I'm hoping that this is relevant. Starting from scratch, close all air screws and check how 1 & 2 compare with 3 & 4. Use the center adjustment screw to get them into rough alignment. Then turn the air screw on either 1 or 2 until they match (turn the screw on the one with the highest vacuum to bring it down to the other). Do the same thing for 3 & 4. Then readjust the center screw so that 1 & 2 match 3 & 4. You might need to slightly readjust the air bleeds to get 1 & 2 to match again. Ditto 3 & 4 as well as the center screw. But the adjustments should be small by then. Note that this will result in you ending up balanced with one air bleed being closed on 1 & 2 and on 3 & 4.

One thing that bothers me is your stating that 3 was jumping around so much. That shouldn't happen. You might have an air hose leak or some other issue. Finally, with regard to the center screw and your fabricated tab, the screw/tab is spring loaded such that there's no slop between 1/2 and 3/4. I wonder if your tab isn't correctly fabricated or the spring is missing. Also I have the K6 600 manual and in it the center balance screw is mentioned as (4) but there's no (4) in the pics.

In another thread here I showed a tool that installs in place of the fan relay to allow the fan to be manually controlled. I find it to be a godsend for things like TB balancing where you're running in the garage for an extended time. With it you can let the engine warm up to the thermostat temperature, turn the fan on, and the temperature will just sit there.
 

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Discussion Starter · #8 ·
I don't have a service manual for your bike so I'm hoping that this is relevant. Starting from scratch, close all air screws and check how 1 & 2 compare with 3 & 4. Use the center adjustment screw to get them into rough alignment. Then turn the air screw on either 1 or 2 until they match (turn the screw on the one with the highest vacuum to bring it down to the other). Do the same thing for 3 & 4. Then readjust the center screw so that 1 & 2 match 3 & 4. You might need to slightly readjust the air bleeds to get 1 & 2 to match again. Ditto 3 & 4 as well as the center screw. But the adjustments should be small by then. Note that this will result in you ending up balanced with one air bleed being closed on 1 & 2 and on 3 & 4.

One thing that bothers me is your stating that 3 was jumping around so much. That shouldn't happen. You might have an air hose leak or some other issue. Finally, with regard to the center screw and your fabricated tab, the screw/tab is spring loaded such that there's no slop between 1/2 and 3/4. I wonder if your tab isn't correctly fabricated or the spring is missing. Also I have the K6 600 manual and in it the center balance screw is mentioned as (4) but there's no (4) in the pics.

In another thread here I showed a tool that installs in place of the fan relay to allow the fan to be manually controlled. I find it to be a godsend for things like TB balancing where you're running in the garage for an extended time. With it you can let the engine warm up to the thermostat temperature, turn the fan on, and the temperature will just sit there.
Your tool sounds like a good idea. You're description of the procedure matches the fsm. As for the jumping needle, that was caused by the adjuster on the vacuum gauge manifold for cylinder three being misadjusted. As for my misfire problem... I'm a fucking idiot, and accidentally installed coil pack one in cylinder two and vice versa ???.

As for the center linkage adjustment piece that I fabricated being insufficient, I believe you are correct; I ordered a nasty-looking tb from fleabay for $22 and already took the linkage out of it and am going to swap it with the bits on my old throttle body.

Hopefully I can finally get this damn thing rideable tomorrow; I'm beyond sick of driving, and this Bay area traffic is horrible for the commute from my day job to my night job on 4 wheels.

I'm currently probably about $2500 deep into a bike that probably wouldn't sell for $3500 on a good day no matter how clean it is after going through damn near everything, considering that the motor has close to 72k on it. Lol.
 

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2005 GSX-R600 Anniversary Edition
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Most TB sync tools I've seen have some sort of valve on the lines to smooth out the pulsations. I would agree with a previous assessment that you need to rule out your tool. Hook the tool up so that you swap 3&4 and see if the problem moves to #4. That will prove if the issue is with the tool or the TB. Another possibility is since I assume you had the TB off the engine, you might just have a leak between the TB and the engine.

BillV is correct. Ideally, one of the air screws on 1&2 will be shut, and one on 3&4 will be shut. Then you open the air screw on the higher vacuum cylinder from each pair to balance it with it's mate. Then you adjust the screw on the shaft to balance the pairs together.
 

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Discussion Starter · #10 ·
Most TB sync tools I've seen have some sort of valve on the lines to smooth out the pulsations. I would agree with a previous assessment that you need to rule out your tool. Hook the tool up so that you swap 3&4 and see if the problem moves to #4. That will prove if the issue is with the tool or the TB. Another possibility is since I assume you had the TB off the engine, you might just have a leak between the TB and the engine.
Yes, there was an adjuster on the tool; my buddy loaned it to me and I'd never used one before and there weren't instructions so I didn't realize that I had to adjust the tool to get an accurate reading.

A vacuum leak between the TB and cylinder head was the first thing that I looked for.

Luckily I have that spare throttle body that I can swap out the linkage on... Going to do that right now. Probably going to have to flame the seller for his ridiculous description of the throttle body on eBay though; he called it "good, usable condition" when the butterflies were completely galled shut and it's had the stva removed and everything else. Luckily I bought it just for the linkage and had paid accordingly though.

Okay so there's stuff I'm doing now that isn't covered in the fsm or elsewhere online, probably, so I'll write about it. The manual shows the tb's as one solid piece, but they're joined in the center by two bolts. Once those bolts are removed, along with the fuel rail (which I stripped the head of one of the screws on, yay me ?), the tb's can be rotated which allows access to o the center linkage pieces. Then the butterflies on the left side must be removed to allow the shaft to be removed. This is the only part that makes me nervous for reassembly; if the butterflies don't re-seat just like they are now, then I'll be hosed, so I'll just make some match-marks and hope for the best.

Thanks for all of the input, everyone, and wish me luck.
Auto part Engine Automotive engine part Carburetor Automotive super charger part
 

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Discussion Starter · #11 ·
Okay so the drill is already dead lol. I'm going to let it charge back up and drill the hole bigger so that I can use my second-smallest extractor rather than the smallest one; learned a new level of suck when I broke an extractor off inside the right side motor mount bolt earlier in this project so I'm not taking any chances. No shortage of other work to do on this bike in the meantime...
 

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2005 GSX-R600 Anniversary Edition
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TIP: A heat gun to heat up the entire throttle plate, shaft and screws for a given runner make the screws that hold the plates to the shaft easier to remove. If you don't have a heat gun, a 150W soldering iron on the screw works, but takes a long time to get it hot enough. Also, use thread locker when reassembling so you don't destroy an engine when a screw falls out.

And FWIW, that STVA looks like I might have have had my hands on it at some point, so it should be good to go.
 

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Discussion Starter · #13 ·
Okay so I swapped everything out. Now I can't get the bike to idle at 1200 because the secondaries aren't closing at all... So the stva might be toast. It opens fully then backs to 95% like it's supposed to when priming the ignition, but then it doesn't move at all when the bike is running, so it's holding the idle too high. It's supposed to move quite a bit depending on load and rpm, correct? Also, what makes you think that you handled this particular stva?
 

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Discussion Starter · #14 · (Edited)
TIP: A heat gun to heat up the entire throttle plate, shaft and screws for a given runner make the screws that hold the plates to the shaft easier to remove. If you don't have a heat gun, a 150W soldering iron on the screw works, but takes a long time to get it hot enough. Also, use thread locker when reassembling so you don't destroy an engine when a screw falls out.

And FWIW, that STVA looks like I might have have had my hands on it at some point, so it should be good to go.
Chuckster, found some of your other posts on the TB system... So yeah, swapped the stps and that didn't do anything; ignition prime opens the secondaries then backs to 95% like it should, a few seconds after starting the bike, the secondaries shut about halfway, jerk a bit, the fully reopen.

Thoughts?
 

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Sounds like the STPS wasn't installed correctly. Have you checked the open and closed resistance values? Are you sure you don't have the harness connectors for the TPS and STPS reversed?
 

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Discussion Starter · #16 · (Edited)
Hmm... I only checked closed resistance on the stps. Set to 1.6. I thought that the connectors were keyed differently? And it's not throwing any code.
I just went ahead and removed the fast idle screw so that it would idle so that I could sync the tb's somewhat better, but I'd like it fixed right... Because as it sits now, the secondaries don't budge at all after the bike has been running for a few seconds. Also, can't get the bike started when it's cold without starting fluid...
 

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Discussion Starter · #17 ·
Sounds like the STPS wasn't installed correctly. Have you checked the open and closed resistance values? Are you sure you don't have the harness connectors for the TPS and STPS reversed?
So I see that the connectors can be reversed, but when they are, the stv shuts instead of opening on priming the bike, and the fi light comes on...
 

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"I thought that the connectors were keyed differently?"
On my K6 1000 one is by Sumitomo and the other by Yazaki and there's no way that they would interconnect.

There is some other misconnection possibility but I've forgotten the specifics. It's a 3 pin connector that might be associated with the GPS or the EXCVA.
 

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Discussion Starter · #20 ·
Do you have a powercommander on this bike?
Yeah, I do. It came with the bike. Guess I should look into removing it to rule it out; as I've never installed one, I'm not quite sure how to rewire the injector wiring to stock.

I was wondering if it might not have lost its programming from being disconnected from power for 5 months...
 
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