Synchronizing throttle bodies - K-Bikes.com - Excellence in Motion
 
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post #1 of 8 (permalink) Old Jan 17th, 2006, 11:43 am Thread Starter
 
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Synchronizing throttle bodies

First I must say that I'm new to the K RS (5 months) and love every moment that I ride it. Was disapointed yesterday because I had to take my FJ1200 out instead of the K RS on a 200 mile ride.

My question is, can the throttle bodies be synchronized like regular carbs? I did the throttle spring relaxation (left spring) and noticed that the idle is now between 1500 and 2000.

I poked around a little and discovered the left most throttle butterfly does not close fully after the spring has been relaxed. Pushing it close with a screw driver, the idle goes back down to normal. Just to make sure I didn't have a vacuum leak, I put the spring back to the upper tab and the idle was fine. Moved the spring back to the lower tab (relaxed), opened and closed the throttle a few times and the idle goes back up to 1500 rpm. Checked again to make sure that it wasn't the throttle cable that was causing this.

I'm thinking that the left throttle spring puts out so much tension that when it is relaxed, the left carb goes out of sync because there is less tension on the link to the next throttle body. If I coud resync the carbs, or at least the left most one, I could bring the idle back down.

Even if resynchronizing the throttle bodies may not be the solution, they are out of sync anyway. Checked it with the throttle spring on the upper tab. Can I still resync the throttle bodies like regular carbs?

Thanks.
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post #2 of 8 (permalink) Old Jan 19th, 2006, 11:35 am
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Quote:
Originally Posted by gila
........My question is, can the throttle bodies be synchronized like regular carbs? I..........
Pre '02, yes.

'02 and newer, no. Dangit.


p.s. Would somone drill off these caps on their bike and tell me if the screws are there?
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post #3 of 8 (permalink) Old Jan 19th, 2006, 12:05 pm
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Quote:
Originally Posted by gila
First I must say that I'm new to the K RS (5 months) and love every moment that I ride it. Was disapointed yesterday because I had to take my FJ1200 out instead of the K RS on a 200 mile ride.

My question is, can the throttle bodies be synchronized like regular carbs? I did the throttle spring relaxation (left spring) and noticed that the idle is now between 1500 and 2000.

I poked around a little and discovered the left most throttle butterfly does not close fully after the spring has been relaxed. Pushing it close with a screw driver, the idle goes back down to normal. Just to make sure I didn't have a vacuum leak, I put the spring back to the upper tab and the idle was fine. Moved the spring back to the lower tab (relaxed), opened and closed the throttle a few times and the idle goes back up to 1500 rpm. Checked again to make sure that it wasn't the throttle cable that was causing this.

I'm thinking that the left throttle spring puts out so much tension that when it is relaxed, the left carb goes out of sync because there is less tension on the link to the next throttle body. If I coud resync the carbs, or at least the left most one, I could bring the idle back down.

Even if resynchronizing the throttle bodies may not be the solution, they are out of sync anyway. Checked it with the throttle spring on the upper tab. Can I still resync the throttle bodies like regular carbs?

Thanks.
I've noticed the same thing on my '04KRS. Mine idles around 1100 - 1200. By taking the grip and manually returning the throttle to the idle position, the idle comes back down to normal ( about 950-1000).

I think mines probably related to a overtight throttle cable, but haven't looked into that yet. Didn't happen till after my ECU was replaced. Very possible due to "me" neetly tie straping all the vaccum lines and cables while the left fairing was off at the time. Could be pulling on the throttle or cruise control cable slightly. Hope to find out soon.

'04 K1200RS- sold
'06 R1150GS Adventure ( Final Edition ) ( Still in Crate) 4-sale
'04 Honda RC51 ( still in the crate!) 4 sale
'08 BMW HP2 Sport #43 (awsome)
'09 BMW HP2 Sport w/ABS #77 ( still in crate)
'10 Harley Davidson CVO Street Glide
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post #4 of 8 (permalink) Old Jan 19th, 2006, 9:59 pm
 
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The throttle cables are sensitive to being tied up especially on the left side where the throttle cable outer sheath clips to the upper edge of the left fan shroud.

You will find a clip on the left side, top center of the fan shroud. The colored section of the cable needs to go here (small sticker on the cable) . Any zip ties placed between this clip and the throttle bodies has a strong chance of raising your idle as they will be streching or pulling on the cable.

Before left bodywork is removed
1. Check to make sure cable hasn't been pulled out of throttle grip reciever.
(Place where cable goes into right twist grip) If your issue is resolved - please ride motorcycle and enjoy.

If not
When the left bodywork is removed.

1. Cut away any owner added zip ties.
(Check cable for permanent damage where outer sheath is forced into inner cable-throttle binding)(if permanent damage exists- replace cable - Super Lube 9000 will not fix this)

2. Slide the cable toward the butterflies until the idle returns to normal.

3. Turn the handle bars several times- left and right - and observe if the cable is binding up anywhere or if the idle raises. (adjsut cable by sliding towards throttle bodies )

Keep everything possible from binding the outer sheath of the cable to the actual cable inside. If it has no sharp turns and you have not bent the outer sheath to the point where it is permanently bound the cables will serve you for a long time.
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post #5 of 8 (permalink) Old Jan 20th, 2006, 11:03 am
 
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Factory sealed throttle body pack.

My 98 KRS engine developed rough running characteristics at around 12K miles. The idle through 4k rpm were affected. In short, idle to highway speed where engine roughness seemed to smoothed out. My suspicion is that it wasn't smoothing out as much as it was concealed.
The problem was so irritating that I sold the bike unable find a solution. Three shops told me to ignore the problem since it wasn't there. The last shop wanted to switch out the throttle body pack for a new one, but would not gaurantee the problem would go away. All agreed that the throttle bodies were pre set at the factory and that there was no way to adjust them properly without factory equipment. Being made of plastic may not have helped. Being sealed, made it a throw away setup, if it went bad.
I bought a Rhine chip hoping that would correct the problem. It didn't. In all, I probably spent about $2,500 more trying to correct the problem.
Before you go any further, make sure to have a leak down pressure test done. I loved my 98 KRS, but the problem finaly drove me to the ultimate solution. Any body else has or had this problem?

Vlad
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post #6 of 8 (permalink) Old Jan 20th, 2006, 1:13 pm
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Quote:
Originally Posted by vlad
..........The last shop wanted to switch out the throttle body pack for a new one, but would not gaurantee the problem would go away. All agreed that the throttle bodies were pre set at the factory and that there was no way to adjust them properly without factory equipment.........
Wrongo on the dealer's statement. Adjusting the BRASS air/fuel mixture screws with CarbStix or a good vacuum gauge(s) will DEFINATELY result in a smoother running K bike. BTDT on a K75s, K100RS, and K1100RS. Moving the steel throttle body rail screws will require a flow bench to properly readjust, but the BRASS screws are happy to be fine tuned. It's amazing what many dealers do not know.

That's why I hate the factory sealing the BRASS screws off. Our '02 has idled poorly from day one, and 4 weeks of dealer atttention didn't help the idle any. It did, however, stop trying to commit suicide in the apex of a turn at 5 grand and above, so it wasn't a totally wasted 4 weeks. New throttle bodies, new TPS, and it still idles like crap. Otherwise, it's great, and we don't idle that much. Still makes me mad when I think about it, though. BMW should be ashamed, and instead they won't even admit that a lot of RS/GT bikes have FI issues. Techron helps, but it's a design or ECU issue that we can't get to.
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post #7 of 8 (permalink) Old Jan 23rd, 2006, 10:49 am Thread Starter
 
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CABNFVR, I bet the brass screws are under that cover. Just drill one out to find out.

Guess I'm fortunate to have a '98 in this case.

I put the throttle spring back to the original position and decided to live with the tight throttle. No the idle is back to normal. I do not have cruise so it's not as tight as others. Still it would be nice to have it like all my other Jap bikes.

Didn't do any carb sync. yet since searching the archives, some people say that the carbs are factory synced and they should not be messed with. Their other argument was that in a non-fuel injected bike, what goes through the carb is a fuel air mixture. In a fuel injected, only air goes through the throttle bodies.

Now I'm confussed. I thought the purpose of synchrozing carbs is to make sure that the different cylinders do not "fight" each other as in the case of them getting inconsistant amounts of fuel/air combination. Assuming that the fuel injectors put out the same amount of fuel for the 4 cylinders, wouldn't the amount of air/fuel combination be controlled by the amount of air entering the cylinders?

So why would it be o.k to sync a non-fuel injected bike and not o.k. to sync a fuel-injected one? After all, the vacuum gauge(sync gauge) does not care if it is fuel injected or not. It just measures the amount of vacuum in each cyclinder.

I'm not and do not claim to be en expert on the subject so that's why I'm looking for answers. I've always synced my non-fuel injected jap bikes and it helps the rough idle a lot.
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post #8 of 8 (permalink) Old Jan 23rd, 2006, 11:12 am
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Quote:
Originally Posted by gila
CABNFVR, I bet the brass screws are under that cover. Just drill one out to find out.
But what if we're wrong? I'd rather someone else do it.

Quote:
Guess I'm fortunate to have a '98 in this case.
Yep.

Quote:
I put the throttle spring back to the original position ..... Now the idle is back to normal. ........it would be nice to have it like all my other Jap bikes.
I don't think anyone at BMW has ridden a Jap bike or Duc in 20 years. Why should they? (said with sarcasm)

Quote:
.......the carbs are factory synced .....what goes through the carb is a fuel air mixture. .......I thought the purpose of synchrozing carbs is to make sure that the different cylinders do not "fight" each other as in the case of them getting inconsistant amounts of fuel/air combination. .......wouldn't the amount of air/fuel combination be controlled by the amount of air entering the cylinders?
If you have a nice smooth idle and throttle response, don't touch it. If you'd like it "better", sync it. Variances in compression, injector spray (quantity and quality of pattern), and sycn between the throttle bodies (the "don't touch" steel screws) all affect low rpm (idle) smoothness. If BMW dealers could "fix" FI problems I'd gladly let them, but ....

Quote:
So why would it be o.k to sync a non-fuel injected bike and not o.k. to sync a fuel-injected one? After all, the vacuum gauge(sync gauge) does not care if it is fuel injected or not. It just measures the amount of vacuum in each cyclinder.
The first FI Ducati's had a wonderful potentiometer in the ECU that was accessible by anyone. Some fine tweaking produced purrrfectly running Ducs. The EPA tightened the rules, and bye-bye to adjustability. Yes, it's OK to sync a FI motor.

Isn't it totally ironic that BMW tells us K-bike owners that you can't sync the throttle bodies AT THE SAME TIME that they are telling the FI twin owners that they have to have theirs sync'd every 6k ?

Quote:
I'm not and do not claim to be en expert on the subject so that's why I'm looking for answers. I've always synced my non-fuel injected jap bikes and it helps the rough idle a lot.
I'm no expert, either. Unfortunately I can tell if my dealer and the Southeastern BMW service rep is, and they are not. They can set it spot on to factory specs, and if that doesn't work ... :wtf You will not hurt a thing by syncing with the brass screws, and I'd bet you get a better idle.

p.s. Trivia note for thse bored and reading all of this.... above 3000 rpms none of this matters at all. Screw up the air/fuel idle circuits and there's so much air (cfm) flowing at highway speeds that the engine won't know a thing about it. IOW, you won't hurt the engine playing with this, but it is best to sort of know what's happening in there. :think:
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