Throttle Synchronization?

Hi all! New 1250s owner here - bought from a nice fellow locally with 4K on the clock - all stock standard, black.

The bike seems to run great and I'm pretty happy with it. Will need a new set of tires soon.

Here's the thing though - it does seem to me to vibrate quite a bit around 50 mph and higher - quite the buzz (seems more on the right side handlebar than the left) - I was surprised by that given the rubber mounted engine and counterbalancing shaft. Is this "normal" or do you all think I need to synch the engine? I'll check the TPS reading first I guess, but if that is not on spec, is there a good description anyone can point me to to do the TBS procedure? I sure wouldn't trust a Suzuki dealership to do it for me.

Thanks in advance!

p.s. El Bandito - you're The Man! Thanks for sharing so much of your work.

My first guess on this buzz is that it's coming from the windscreen or faring, not the engine. I had this same thing, many others have reported it as well. Mine disappeared when I removed and reinstalled the windscreen making sure the rubber grommets were properly in place and the screen was tightened adequately.

Some have used s a little silicone to make sure things are all sung and quiet.

twist said:

My first guess on this buzz is that it's coming from the windscreen or faring, not the engine. I had this same thing, many others have reported it as well. Mine disappeared when I removed and reinstalled the windscreen making sure the rubber grommets were properly in place and the screen was tightened adequately.

Some have used s a little silicone to make sure things are all sung and quiet.

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I'll check that screen, but maybe I should have said "major mechanical vibration" felt in the handlbars and footpegs while above 4k rpm.

platypus said:

I'll check the TPS reading first I guess, but if that is not on spec, is there a good description anyone can point me to to do the TBS procedure? I sure wouldn't trust a Suzuki dealership to do it for me.

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I'm with you on not trusting a dealership - good ones are few and far between. Get yourself an electronic copy of the factory manual - they're all over the place including on eBay. Instructions for the throttle sync are on pages 1D-15 to 1D-17. I should be able to give you more detailed instructions tomorrow as I'm doing mine tonight for the first time, but I expect someone else will come along with details before then.

Basically you put the bike in dealer mode, disconnect the IAP (Intake Air Pressure) sensor, connect up your gauges and you're up and away. Adjustment is on the air screw on each throttle body. That's the theory, anyway - I'll find out later whether the reality matches up.

TPS can be checked simply by going inot dealer mode with the key on and on/off switch on. Plug is located on the right side of the bike behind the sidepanel. The plug is white with a black rubber cap. As your looking at the plug straight on the far right two pin holes are the ones to jump with a paper clip to put the bike in dealer mode. Once you have done this turn on the key and on switch wait a second and look for -C00 on the dash. Anything else like htis _C00 or bar above the C and your TPS is off. To set it correctly is quite a job the throttle bodies must come off to access the TPS adjusment screw. Do the dealer mode thing 1st and if your off I can walk you through the TPS adjustment procedure. I have already had to do it on my bike. Throttle sync will follow suit after TPS adjustment.

platypus said:

I'll check that screen, but maybe I should have said "major mechanical vibration" felt in the handlbars and footpegs while above 4k rpm.

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ouch - that don't sound good (bad grammar intentional)

Well the experts here are already helping you out with advice, so I will just watch and learn...

That "bad vibration" is not normal. One of the characteristics of the Bandit has been how smooth it runs.

I, too, will stand aside and read the expert's advice. (It's issues like this and the throttle body syncing that make me really appreciate TWTex.com)

Throttle bodies out of sync and it will vibrate. Especially between 3500 ~ 4000 rpm's. I have been through all this and it was a pain in the butt to get it all evened out. I spent alot of time and a little money making this bike run smooth. Good set of sync guages are a must. I bought a motion Pro snyc Pro but make sure you get it from Motion Pro because there are alot of vendors out there who have the outdated model which will not work on a large I4 multi. The vacum is off on them. I found out the hard way.

If your TPS is correct then go straight to the balance procedure layed out in the service manual, any further questions just hollar here.

Roy said:

Throttle bodies out of sync and it will vibrate. Especially between 3500 ~ 4000 rpm's. I have been through all this and it was a pain in the butt to get it all evened out. I spent alot of time and a little money making this bike run smooth. Good set of sync guages are a must. I bought a motion Pro snyc Pro but make sure you get it from Motion Pro because there are alot of vendors out there who have the outdated model which will not work on a large I4 multi. The vacum is off on them. I found out the hard way.

If your TPS is correct then go straight to the balance procedure layed out in the service manual, any further questions just hollar here.

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Sounds like the "Go" Roy! I just checked the TPS via Dealer Mode and got a nice -COO reading, so synch procedure is next. Thanks!

platypus said:

Sounds like the "Go" Roy! I just checked the TPS via Dealer Mode and got a nice -COO reading, so synch procedure is next. Thanks!

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Consider yourself one of the lucky ones. There are alot of them out there that are set wrong from the factory mine being one of them.

Tip of the day, when you sync the throttle bodies do not let the engine get hot to the point the cooling fan is on. Reson being the manual states 176~212 degrees to sync. The Bandit has no temp guage so this can be kind of difficult to perform. I used a laptop that had Suzuki's SDS software on it and was able to monitor my cooling temp live. Once it gets hot the fluid range on the guages is all over the place. Have a big old fan blowing directly at the radiator. Sync your guages to intake #1 before proceeding to perform the actual sync process. Take your time and make sure your guages are sync'd good it pays in the long run. Don't panic if your idle jumps up a few minutes into the procedure its totally normal. you can use 2x4 blocks of wood to support the tank while doing the job. A close to empty tank makes it easier.

Roy said:

Consider yourself one of the lucky ones. There are alot of them out there that are set wrong from the factory mine being one of them.

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And, as I discovered last night, mine being another. I'm really annoyed with myself - I had the throttle bodies off the bike a couple of weeks ago but didn't realise at the time that the TPS could be adjusted only with them off the bike. If I had it would have taken only a couple of minutes extra to adjust it. Instead I left it until last night to check and found it was reading _C00 so now the bodies have to come off again to adjust that before I can do the sync

And time is running out before my appointment with Mr Dynojet......

sproggy said:

And, as I discovered last night, mine being another. I'm really annoyed with myself - I had the throttle bodies off the bike a couple of weeks ago but didn't realise at the time that the TPS could be adjusted only with them off the bike. If I had it would have taken only a couple of minutes extra to adjust it. Instead I left it until last night to check and found it was reading _C00 so now the bodies have to come off again to adjust that before I can do the sync

And time is running out before my appointment with Mr Dynojet......

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Its not that bad sproggy only a few pinched fingers and skint knuckles here and there Remember to plug everything back up when you lay them in there to adjust the screw. I also found it way easier to go ahead and just remove the airbox completely then lay them in there and plug it all up gives you more room to work with with the airbox out. Leave the throttle cables attached no need for extra work. But make sure you not pulling on the cables when you set the screw they could pull enough to open the butterflies which is read by the TPS sensor on the end. With the bar in the middle of the C you should have 27.9 degrees if you were to look at it on a laptop with SDS. Also play with it up and down to achieve the middle of the road setting as close as you can. The guage on the dash is pretty accurate for doing this. Check the throttle body sync afterward.

Roy said:

Its not that bad sproggy only a few pinched fingers and skint knuckles here and there

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It's not that I mind doing it so much as I mind doing it twice in the space of 2 weeks just because I didn't plan ahead! I'll just put last time down as a practice run

Roy said:

But make sure you not pulling on the cables when you set the screw they could pull enough to open the butterflies which is read by the TPS sensor on the end.

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I always adjust all of the play out of my throttle cables - it makes on/off throttle riding smoother. When I first checked the TPS setting last night I was happy to see it at -C00, but then I introduced some slack into the cable....... _C00 So yes, they could definitely pull enough to affect the reading.

Roy said:

Also play with it up and down to achieve the middle of the road setting as close as you can. The guage on the dash is pretty accurate for doing this.

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Yes, I'd planned to find the point at which it went to _C00, then find the point at which it goes high, and then split the difference to find a happy medium. I suspect that will give a fairly good approximation of 27.9 degrees, but having it spot on is probably more important when you're using the factory fuelling map than it is with a custom map which will make allowances for the TPS setting being slightly different. I'd rather not put that theory to the test, though.

Thanks for the advice.

Here's a picture of the TPS adjuster for anyone having trouble finding it. What a bu**er of a job to get to for such a quick adjustment.....



Mine was just over a turn away from where it should have been.

And this is what the throttle balance looked like before I touched it



I also adjusted the balance screw between RH and LH pairs of throttle slightly because at higher revs cylinders 1 and 2 were reading higher than 3 and 4. It only needed a slight tweak but it's smoother now (in the garage - I haven't ridden it yet).

Sproggy, how did you determine when the TPS position was "correct" since I assume you can't read the "-COO" indicator with the thing apart like that.

I will be very interested in your ride experience after the balancing. As I said in my first post, I am surprised how much vibration I have at highway speeds. I have a Motion Pro Synch tool on order which should arrive next week. Hopefully it will be the updated version as warned by Roy. If not, I'll be further delayed while swapping that for an updated one.

platypus said:

Sproggy, how did you determine when the TPS position was "correct" since I assume you can't read the "-COO" indicator with the thing apart like that.

I will be very interested in your ride experience after the balancing. As I said in my first post, I am surprised how much vibration I have at highway speeds. I have a Motion Pro Synch tool on order which should arrive next week. Hopefully it will be the updated version as warned by Roy. If not, I'll be further delayed while swapping that for an updated one.

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You can read the dash readout once you plug eveything up to the throttle bodies then turn on the key. The readout -C00 is on the dash in the tripmeter location when your in dealer mode. you must have all plugins connected to the throttle bodies before turning the key on or your throw a bunch of codes to teh ECM. That is the reason you remove the airbox so you will have room to do all htis with the TB's hanging there in your hands.

You should be okay with the new motion pro sync pro. I like the old mercury guages better but those are not sold anymore. The new glycol guages can be finicky to use.

platypus said:

Sproggy, how did you determine when the TPS position was "correct" since I assume you can't read the "-COO" indicator with the thing apart like that.

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As Roy said, you have to connect everything back up. I didn't remove the airbox and this makes it rather more difficult to get the wires to meet up but it is possible.

platypus said:

I will be very interested in your ride experience after the balancing.

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All I can say is, I thought it was good before - now it's fantastic, particularly from low revs. The torque pulling away is hugely improved, and it's SO much smoother. The fuelling is clearly well out, though (the result of fitting cat-less headers and removing the secondaries while using an inapporopriate map) so I'll reserve judgement until after tomorrow when it's been mapped properly. But so far I'm happy - everyone should check their setup - don't trust the factory and don't trust the dealer.

sounds like a nice modification...

sproggy said:

everyone should check their setup - don't trust the factory and don't trust the dealer.

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I been syaing this all along, the factory assembles bikes but they don't tune them they intrust the dealers to do that if there is a problem. I suspect there alot of 1250's out there with a bad TPS and throttle sync. If your mileage is poor and I mean poor chances are your affected. Its a simple test but a rather involved job to correct. If your good with basic hand tools you can do it. I stated in another thread I randomly checked a new bike on the floor and the TPS was off on it so they are out there.

Roy said:

If your mileage is poor and I mean poor chances are your affected.

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I don't think it's as simple as that, Roy - my fuel consumption has been very good even though everything was out of adjustment. I guess it depends how much it's out and in which direction.

sproggy said:

I don't think it's as simple as that, Roy - my fuel consumption has been very good even though everything was out of adjustment. I guess it depends how much it's out and in which direction.

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Your fuel is different than the crap we call fuel. most I have heard that had poor mileage here did indeed have a TPS issue. My bike was just not right from the get go and the longer I owned it I knew something was just not right. It had alot of vibration around 3500 rpm's. Either way its a simple check for even the most challenged individuals. Correcting it takes a certain degree of skill like me and you happen to have. We are lucky

Just got back from a 600 mile weekend trip after owning the bike for about 10 days now. Overall I am very impressed with the bike (i've owned about 10 bikes over the years). Rock solid cruising around 80 MPH. I averaged 48 mpg, cruising 70 to 80 with occasional 100 mph bursts (so easy to get there on the Bandit engine).

I've certainly got a noticable vibration at 3.5 to 4,000 rpm which I'm currently attributing to out of synch TBs. Sync tool is on its way and I'll report back on the result after synching up but I expect it will smooth the bike out in that rough area.

On another note, let me put in a "plug" for the stock muffler setup. I've gone the path in the past of "hotting" up my bikes with straight through pipes etc. and don't intend to do so on the Bandit. First off, it has plenty of pep and a few added HP from mods is not going to amount to a hill of beans. I'll grant you there is some satisfaction to be had knowing an engine is all that it can be. But, on the other hand, the thing runs very CLEAN and that appeals to my sense of planet preservation - every bit helps. So, my desire to have the most "pure" running engine is overridden by my stronger desire to have the most "green" engine I can and the stock fits the bill there.

Oh, also, at idle and low revs one gets that lovely hair dryer sound, and at highway speeds, no sounds at all from the bike - I wear ear plugs and can hear myself think - much less stress.

p.s. thanks Roy for all your advice and pointers about how to do the TB sych - very helpful!

platypus said:

But, on the other hand, the thing runs very CLEAN and that appeals to my sense of planet preservation - every bit helps. So, my desire to have the most "pure" running engine is overridden by my stronger desire to have the most "green" engine I can and the stock fits the bill there.

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That all depends upon what you call 'green'. A vehicle with a catalytic converter creates more CO2 (your "greenhouse gas") than one without. Sure, other emissions are lower (CO, for example), but you don't get anything for nothing.

The cleanest engine is the one that runs most efficiently, and better breathing will make for improved efficiency.

I'm not saying you're wrong to want to keep the bike stock, just pointing out that there is another side to the argument.

The Motion Pro Synch tool arrived today. After checking with the Motion Pro Tech Support team and confirming that I had the "good" model (I do - the serial numbers include a "B" which stands for Billet. Apparently the fluid chamber is now a billeted piece rather than extruded.) I went ahead and synched up the TBs.

Interestingly, #s 2,3 and 4 chambers (reading right to left) were almost exactly one turn out from fully closed, but #1 was 2.5 turns out - both before and after the synch. They were not out that much - about an inch or two max from lowest to highest fluid chamber on the tool.

It only takes the slightest turn of the screw to make a noticable difference on the respective levels - no wonder many bikes could be out, even if they were set right at the factory (which they probably weren't in all cases).

I added some removable thread locker to the tops of the screws after adjustment to hold them in place a bit better.

Went for a short highway ride and the thing is certainly smoother in the 3.5 - 4K rpm range - astoundingly smoother? - like butter? - no, but smoother enough to warrant doing the job and buying the tool IMHO.

Your mileage may vary.

I think my bike is done for now - I'm just going to ride it as much as possible for the rest of the year.

Thanks again Roy and Sproggy for your advice - made it all very easy and quick to do!

How much did the Motion Pro Synch Tool cost and what is the model number? I'm thinking I may need to get this on the tool shopping list.