Fine tuning Carbs and Idle after installing a new/used set.

[ST1100Y]

...first start up after un-run for more than half a decade...

Well, frankly the old '94 I'd refurbed in 2011 is also a bit reluctant after firing up, unruly idle while on choke and also requires its aid for a long time (longer that I'm used to on the '00 ST...).
Sure, by now probably again staled fuel, hasn't been on long rides/usage for quite a while, but once fully warmed up, very quick and lively on the throttle... I should really get it out on the road more...
I noticed that STs don't like being grounded for a while or used for short commutes, cause out on a long haul with >300 miles/day the engine-sound changes to a real smooth and contented hum after like a week, zero vibes, rock solid idle... one could stand a coin on its edge on that engine ;-)

So quite possible that also yours will "clean out" if you take it on a two week ride
I'd confirm that everything is roadworthy, pack and head out on it...

 

[mznyc]

If it is a blockage in the one or more of the jets,I'll try to let the SF do it's job.Those carbs are not original.They were a clean set I got off Ebay,pulled float bowls and diaphragms and looked cleaned inside.
One thing I did not do when syncing was check sync at higher RPM (I use 4k for my Guzzi) which is required on my other bikes in addition to a sync at idle.Try to get both as close as possible,usually a compromise somewhere,...

 

[Brant]

No compromise needed. The sync is to be set with ALL intake as it runs in place.....period. Syncing carbs together is worthless unles you FIRST set idle mixtures......to highest in. vacuum....sync........re-set idle mixes to a T, and resync again. ANY varience of idle, as in 'floating around a bit at idle means carbs are NOT properly synced, which includes proper idle mixture settings.......with all intake in place.

BTW, that all IS to be done at lowest rpm it runs smooth at..........7-900rpm......and goes for ALL multi carb bikes.

 

[Brant]

Remember to also run a cooling box fan in front of motor during this process. REason being, when bike cooling fan comes on, the charging system increases load on motor, which changes vacuum which iterfers with correct syncing and idle mixture settings. The process HAS to be stopped if the bike cooling fan comes on. The extra fan in front of motor enables you to prolong the process without having to shut bike off so many times waiting for it to cool before continuing sync process. No such thing as a 10min. sync....period.

 

[mznyc]

Ok may have found the problem.
Spray carb cleaner into the boots and revs go up,slightly on two,noticeably on the other two.
Thoughts?

 

[Brant]

Ok may have found the problem.
Spray carb cleaner into the boots and revs go up,slightly on two,noticeably on the other two.
Thoughts?

Pull the fuel tank.......carb bank(no need to remove enricher or throttle cables), replace carb boots noting location of each clamp(specially the upper ones, and replace ONE boot at a time so that indexed(notch that keeps clamp stationary) of new boot is EXACTLY the same as old one. OEM boots...not aftermarket.

 

[mznyc]

They're new boots Brant so don't think think it's the boots but the orientation of their position.I was aware of the notches and they were aligned with the cut out in the boot,but something is awry.
The question is,,..Is a change in idle with the application carb cleaner prove that i have unacceptable amount leakage at the boot?
I want to confirm this before I pull them,...
Thanks
Michael

 

[JEST]

Hi, Michael

Check the boot clamps, mine had stretched and wouldn't tighten firmly enough to prevent vacuum leakage. Also, these are special clamps with limited clamping to prevent collapsing or damaging intakes.

Johnny

 

[Brant]

They're new boots Brant so don't think think it's the boots but the orientation of their position.I was aware of the notches and they were aligned with the cut out in the boot,but something is awry.
The question is,,..Is a change in idle with the application carb cleaner prove that i have unacceptable amount leakage at the boot?
I want to confirm this before I pull them,...
Thanks
Michael

Not being able to physically be there makes it a somewhat of a guessing game so to speak, but, as has been suggested, the clamps themselves MAY be the cause. Since I ONLY offer suggestions based on my own experiences with these scoots, along with some knowledgable backround in the automotive high performance world, I definitely would be interested as to what you find as the issue. Definitely an intake vacuum leak though with your testing. As to the actual final cause........definitely could save someone else a repeat if you'll post your final findings.

 

[Bigmak96]

The clamps are pretty stout and I would doubt they are stretched. Even the OEM boots when new do not clamp up as tight as I would have thought they would. I did get a set from Canada a few years back that were knock offs. At least they did not come in Honda packaging, and these were a bit larger OD. They snugged up nice with the original clamps.

 

[Brant]

Tottally agree with Bigmak96 on the clamps. Can't comment on the aftermarket boots since I used Honda OEM boots. They also allowed the clamps ALOT of tightening pressure.....least in my scoots case. Possibly 'shelf' life from manufacturing time could be the deciding factor as to any varience associated with 'drying out'/shrinkage.

 

[mznyc]

So the increase in idle is proving that I have an unacceptable amount of leakage there?

 

[Brant]

So the increase in idle is proving that I have an unacceptable amount of leakage there?

Sounds like you pretty much got it isolated.

 

[mznyc]

***Update.***
Pulled carbs.Came out easily,maybe too easily.Boots are new,but even with loosening screws and grease leftover from installation,seemed too easy to come out,so were probably not installed with proper orientation.Should have given more resistance.
Starting over with new insulators,bands and screws (as they were started to get worn).
Report back with results when new boots come in,probably a week or two.

 

[Bigmak96]

I have given the bands some thought.
I think the next time I deal with them I will make some shims to make them tighter.
I think a guy could cut some parts out of pop can with little tabs on them that can wrap around the bands to keep them in place. I think the added thickness would give them just a bit more clamping.

 

[John OoSTerhuis]

I have given the bands some thought.
I think the next time I deal with them I will make some shims to make them tighter.
I think a guy could cut some parts out of pop can with little tabs on them that can wrap around the bands to keep them in place. I think the added thickness would give them just a bit more clamping.

Hmmm... a simple wrap of electrical tape around the boot/under the clamp might be just enough...

 

[mznyc]

I have given the bands some thought.
I think the next time I deal with them I will make some shims to make them tighter.
I think a guy could cut some parts out of pop can with little tabs on them that can wrap around the bands to keep them in place. I think the added thickness would give them just a bit more clamping.

Cool idea.I would like to see what you come up with Mark even though it may be too late for me as I'll probably have them back on next week.

Hmmm... a simple wrap of electrical tape around the boot/under the clamp might be just enough...

No problem with the heat of the block to electrical tape John?

Whilst waiting for the boots to come in and have the carbs out I figured I would look at the jets.Before I installed them I removed the float bowls,adjusted floats,removed diaphragms and cleaned.Looked very clean so didn't bother with jets but figured I will now as I hope not to do this again.
Couple of questions,

I have heard many people refer to the Idle jet when trouble shooting or tuning.Clymer calls this the "pilot jet" and Honda refers to it as a "slow jet". Assuming calling it slow jet is correct? Also they both refer to the the pilot screw as "screw" not "jet".
In Jack Smith's excellent write-up, http://koczarski.com/ST1100/CarbRebuild/Carbs.htm, I'm assuming he's incorrect by saying "Reinstalling the jets and holders. Keep everything numbered so you don't mix up the parts. The paper shown shows the number of turns on the idle screws for each
carb."
When removing mine these jets(slow/Main) they were seated completely in..This is correct? Only the "pilot screw" is set to a certain turn ratio?I haven't removed mine as I left my Honda D-socket at the garage.
Thanks
Michael

 

[Brant]

First off......no grease on those boots before installation! It'll eventually rot the rubber. A shot of silicone spray is what's needed.
The term 'slow jets' is referring to pilot jets. Main jets are exactly that...main jets, or sometimes 'high speed' jets.
Lastly, there is NEVER a set number of turns for idle mixtures, not on ANY multi-carb bike. Those need to be set individually, using either a multi-vacuum gauge set-up, mercury manometer, or MorganCarbTune......with ALL intake(airbox, ect.) in place.
Same for sync.......sync reasonably close first......set idle mixes to highest in.vac.........re-sync.......double check mixture settings....re-sync.
Run a box fan in front of motor while doing this. It will prolong the time before cooling fan comes on. When fan comes on, stop process, shut motor down till it cools.
Reason being, the charging load of alt. from fan coming on changes vacuum AND fuel mixtures when motor is under even the slightest load.
FWIW, there's no such thing as a 10 or 15min. sync., not if CORRECTLY done. Anything short of that is just time wasted and not a noticable difference. Those that defer to 'above idle, sync makes no difference' are assuming just another urban myth....at best.

 

[Bush]

FWIW, there's no such thing as a 10 or 15min. sync., not if CORRECTLY done. Anything short of that is just time wasted and not a noticable difference. Those that defer to 'above idle, sync makes no difference' are assuming just another urban myth....at best.

Just can't leave it alone, can you?:BDH:

 

[mznyc]

First off......no grease on those boots before installation! It'll eventually rot the rubber. A shot of silicone spray is what's needed.
The term 'slow jets' is referring to pilot jets. Main jets are exactly that...main jets, or sometimes 'high speed' jets.
Lastly, there is NEVER a set number of turns for idle mixtures, not on ANY multi-carb bike. Those need to be set individually, using either a multi-vacuum gauge set-up, mercury manometer, or MorganCarbTune......with ALL intake(airbox, ect.) in place.
Same for sync.......sync reasonably close first......set idle mixes to highest in.vac.........re-sync.......double check mixture settings....re-sync.
Run a box fan in front of motor while doing this. It will prolong the time before cooling fan comes on. When fan comes on, stop process, shut motor down till it cools.
Reason being, the charging load of alt. from fan coming on changes vacuum AND fuel mixtures when motor is under even the slightest load.
FWIW, there's no such thing as a 10 or 15min. sync., not if CORRECTLY done. Anything short of that is just time wasted and not a noticable difference. Those that defer to 'above idle, sync makes no difference' are assuming just another urban myth....at best.

Thanks for the thoughts Brant,unfortunately,you've kinda gone off course here and didn't answer the questions.
The sync is something that comes after assembly,I did read and understand your earlier response,but just trying to make sure the re-assembly is correct before buttoning up.
I did spend 15-20 mins on my sync but believe my issue was a vacuum leak at the boots,not how long it took.On my FI bikes the check of sync at the higher revs is a general practice by tuners and owners and used in many write-ups.Don't know about carbed bikes such as the ST,but once again this isn't part of my inquiry here.
The grease issue I guess is a personal choice,I used silicone grease,many use,oil,grease,plumbers grease,etc. Don't know how that relates to jets.

1) The "slow" jet that is what Honda calls it,just passing it on, as three different names can confuse noobs.
2)What I was asking was ,Are the "Pilot screws" the only screws/jets that are turn specific? Ie; Slows,mains,all the way seated?,Pilot screws,set to a specific amount of turns?
3) Was Jack Smith incorrect in saying he recorded the " number of turns on the idle screws for each
carb." .He should have said Pilot Screws.Correct?

Just can't leave it alone, can you?:BDH:

Hey,I like Brant's passion!