SV1000 Throttle body balance.

[Mark_h]

Dear Gurus.

Firstly.

1) Yes I should have made a note of what I changed
2) Yes I should have tested my tools first

However......

Bike's been a bit lumpy of late so thought it was time to have another sync of the throttle bodies as it made a huge difference last time. So much so that I brought my own vacuum gauges last time with a promise to check them more often.

Smugly plugged into my extended hoses and found them to be a bit off. So twiddled the appropriate screw to bring them back into true for tick -over.

Lifted the revs and found they drifted miles out as the revs rose so decided (probably wrongly) to adjust the electronic screw too.

Seems I could get them balanced on tick-over or at higher revs but not at both. Twiddled both for a while to see if I could find a compromise but seems it was tickover or any other band just impossible to have tehm balanced across any decent range.

Then thought I'd just switch the gauges over to make sure they were consistent and found they were miles out!

Took the bike out for a quick run as-is. It now has a mis-fire at about 2.5k when coming in from a closed throttle and tends to pop a bit on overrun with a partially open throttle.

So.......

I need to work out how much difference there is in swapped gauges to work out how far out to adjust them (if you know what I mean) but then I need to work out at what point I should be balancing them.

Should I balance them for tickover, 3k, 5k, best compromise?

Manual says 1,200 RPM but then they are miles out higher up.

Given I've twiddled both the cable balance and the electronic balance and failed to make a note of exactly what twiddling took place I need to do my best to get it running relatively smoothly again.

If I just do it by ear then I can adjust until it sounds smoothest but messing with the secondary balance screw (the one on the electronic linkage) makes a massive difference to the tick-over speed. So I'm not sure if I should get that fairly high then balance with the cable adjuster screw or just give up and give it to someone who actually knows what they are doing.

Thoughts?

You balance them at a high tickover, I think I did mine at 3k, at idle they should still be in balance.

Are the gauges faulty?

[Mark_h]

Unfortunately the gauges are of unknown provenance and the guy I borrowed a set from last time has moved away!

My main concern is what if anything I need to do to the secondary actuators.

ah... oh... you moved them.... oh dear.

Its been a while since I played with an SV, but iirc they do a self check at bootup, do they both reach fully open?
Also did the screw have a torque mark (I'm guessing no)

If you haven't already get a set of Carbtunes http://www.bustersclassic.co.uk/proddetail.asp?prod=MVG

Suzuki SV manual (650) has the STV setup chapter 5-28.

Basically. The STV's must be level with top of TB on both sides of butterfly. IE dead flat /closed

[Bibio]

Originally Posted by Mark_h

to adjust the electronic screw too.


messing with the secondary balance screw (the one on the electronic linkage)

Thoughts?

the electronic linkage you are referring to is the secondary butterfly and should under no circumstance be adjusted. the only screw you adjust is the balance screw. i think there is a chapter in the manual that covers how to adjust the secondary link. from what i know if you adjust the secondary it throws the synchronised opening of them.

[Mark_h]

Originally Posted by Bibio

the electronic linkage you are referring to is the secondary butterfly and should under no circumstance be adjusted. the only screw you adjust is the balance screw. i think there is a chapter in the manual that covers how to adjust the secondary link. from what i know if you adjust the secondary it throws the synchronised opening of them.

Problem is I couldn't get a consistent balance across any sort of rev range with the "cable screw" so decided it must be an issue with the secondary sync and thence begun my world of pain.

I've since reset the secondaries by measuring the gap between the top of the butterflies and the top of the throttle bodies and making sure both are the same.

I have then set the "correct" screw with the revs set to 3k rpm so hopefully that should give me the smoothest response around the 2.5 - 3k range which is where it was particularly noticeable before.

Need to go collect the kids before I can take it for another test ride but will report back shortly.....

[Bibio]

what cable screw. the only cable screw is the idle adjuster.

[Mark_h]

Originally Posted by Bibio

what cable screw. the only cable screw is the idle adjuster.

Sorry, when I say cable screw I mean the balance screw that sets the off-set between the TBs on the actuator at the end of the cables. ie, the one you're supposed to adjust when balancing the TBs. The lower of the two adjuster screws with the upper being the STV balance adjuster.

Just been out for a quick ride around the block.

Backfiring on overrun sorted.
Misfire at 2.5k sorted
Blow-back through TBs sorted
General lumpiness... well it's a litre twin with 40k miles.. what do you expect?

I'm still not convinced it's all correct as the balance does not hold as the revs change. eg, I've set it this time with the idle adjuster set to 3k and it's spot-on at 3k. But at 1.5k they are miles out. Is this normal?

Given I need it to be more predictable at 2.5 - 3k than I do on tick-over it's no big deal so long as its not an indication that something more significant is wrong.

Also both the STV and main adjuster screws are both almost all the way out would this suggest another problem elsewhere or is that just how some end up?

The bike has a BMC filter with no air-box lid and was originally set up for a full M4 2:1 system by JHS racing (who also did the BMC) so there is a chance it's got some custom map that's a bit wrong now the M4's gone and been replaced with the stock headers with a pair of CCC's.

I'm considering sticking an airbox lid back on to quieten it down a bit more but not sure if that will further add to any mapping issues.

Unfortunately JHS couldn't tell me if they remapped it when they did the M4 and BMC for the previous owner as it was 7 years ago and they have no records going back that far.

Maybe I should get the lid back on then get it dyno'd to sort any mapping out but that's a couple of hundred quid I'd rather avoid spending unless I really have to.

[yorkie_chris]

Bear in mind throttle at 2.5k unloaded is much less than under load, which will show imbalance more.