Fitting & synchronizing carbs with Carbtune

[MtheTiger]

I got my carbs clean and reassembled and will be fitting them this weekend. I've synchronised them as good as it gets on the bench with feeler gauges but to do it properly I will use a carbtune unit :D
Because I do not have a manual with the unit I have some (stupid?) questions:

1. Does the setting of the pilot screws influence the vacuum reading ?
2. If so, what do I do with the pilot screws to adjust the butterfly valves first?  (close them alltogether?)
3. Can I use carbtune for the pilot screw setting also after the butterfly valves are synched?

In the online Carbtune manual that I found on the interweb there's nothing about any pilot of air screw settings.....

A step-by-step guide would be appreciated.

thx a lot.

[iansoady]

All carbtune or any other vacuum device will do is to allow you to set the slides / butterflies so that they open at the same time. They won't help with the pilot screws. Mustang or someone else will be along shortly to tell you how to do them. :)

[Mustang]

what Ian said the carbtune only syncs the butterflys so they all work at the same vacuum setting

the proper way to set the pilot screws is with an O2 sensor screwed into the bungs on the header pipe , but they cost lots of $$$$$$$$ so either you set them with  engine running till it sounds happy happy at idle , which you are only going to be able to do if you are experienced .

Hey that sounds like the title to a Jimi Hendrix album ...................Are you Experienced ?

 

You have Mikunis  .just set the pilot screws at 1 1/2 turns out from lightly seated  .....works very well

with the carb tune hooked up  and bike idling you will be setting the vacuum on # 1 and # 3 to match #2 which has no adjustment
the adjustment screws are on the throttle linkage  for # 1 and # 3

It makes a huge difference in how the bike idles and does throttle pulls under load .
The exact vacuum reading doesn't matter as long as all three are the same

and you should set the carb sync as the last thing you do because any changes you make to the carbs and even valve adjustments can affect the vacuum readings .

[MtheTiger]

All carbtune or any other vacuum device will do is to allow you to set the slides / butterflies so that they open at the same time. They won't help with the pilot screws.

That's too bad...I was hoping for a bit more. Now I have to get colortune I guess. Or do some plug pulling after a mile of 1/4-1/2 throttle.

Hey that sounds like the title to a Jimi Hendrix album ...................Are you Experienced ?

I prefer Electric Ladyland myself though...

and you should set the carb sync as the last thing you do because any changes you make to the carbs and even valve adjustments can affect the vacuum readings .

Will do that. Valves are checked & OK, new airbox, all orings renewed aswell as the petcock, tank cleaned...tigger is gonna be one happy puppy again.
If she still runs on two when she hotting up it's coil replacement time.

Thx guys

[iansoady]

You'll struggle to see a colortune down those holes even if you can get one down there. I'd have thought seat of the pants would be good enough.

When I had twin carbs on my Commando the best way to set them was to disconnect the plug on one side and set the other up as a single, then do the same for the other side, then balance the slides. I don't know if you could do that with a Tiger?

[MtheTiger]

I'd have thought seat of the pants would be good enough.

I could live with that also......my only concern here would be getting a too lean mixture with piston holes in the wrong place as a consequence...
(I experienced this with my first bike Suzuki GT 250...a two stroke I know but the danger exists with four strokes also I assume) ... and I don't wanna travel up that road again.

[iansoady]

Normally you're only setting the slow running (pilot jets) which won't result in any holed pistons even if it's way out. It's main jets that are usually the main factor there, ie when the bike's pulling hard on a wide open throttle.

But what do I know being a Girly and Velo rider.......

[Mustang]

Ian's right even if he is a Girly rider  

the bike will not run lean with the pilots set at 1 1/2 turns on the mikunis
if you have the standard pilot jets still in place 1 1/2 is just about perfect in the mikunis

[MtheTiger]

Thx 'Stang & Iansoady for these reassuring words :D
I got the stock pilot jets allright and will go with 1,5 turn out.
Indeed I beat the piss out of the Suus before experiencing the holes, i.e. full throttle for about 250 km with a passenger and luggage....guess her main jet wasn't up to scratch :(

Any "secret" tricks for fine adjusting the three pilot screws relative to each other when idling?

[Mustang]

secret trick ..........just set em at 1 1/2 turns and forget about it  :D

[nightrunner]

A late comment here but as stated above the only thing to make sure of before syncing is the valves are adjusted properly, as that will affect vacuum.   You can sync with mercury sticks or vacuum gauges, but its not very precise to compare the full vacuum readings to each other.   I'm not familiar with the carbtune but presumably it compares the vacuum between two carbs, which of course you should adjust to zero.  You can build one using some clear vinyl tubing, a small reservoir, and a valve to act as a damper.  Partly fill the tube with water or oil and hang it up so you can compare the levels.  Adjust the one carb until the levels are equal.  I think there are several threads on Advrider with pics of poor-mans-syncs that folks have made.

I'm surprised that the Miks are okay at 1.5 turns with stock jets.  The Keihins on the 98's are very lean at 3 turns (which is effectively all the way out).  They run fine at 1.5 turns with the next size larger jet.  And yes, unfortunately the only way to fine-tune the screws is to measure O2 or CO at the little sampling ports that Triumph thoughtfully put there.  The manual calls for 1% CO on the U.S. models and 2.5 - 4.5%CO on the UK models.  Mine was running at 0.1% CO in stock form, which explains why it was so damn cold-blooded.  I'd wager most US models were in reality leaned out to well below 1% as well.

[Mustang]

A but its not very precise to compare the full vacuum readings to each other.  

:icon_scratch
that's the only way you can set them #2 is what it is and you match #1 and # 3 to # 2 at idle speed of 1200-1400 rpm

I'm not familiar with the carbtune but presumably it compares the vacuum between two carbs, which of course you should adjust to zero.

It allows up to 4 carbs to be compared to each other and uses no mercury and no you don't set anything to "zero"
on a proper engine that is setup correctly at idle you should see between 5 and 6 HG of vacuum according to triumph  . again #2 is not adjustable and you set the other carbs to match #2 on a triple

 

I'm surprised that the Miks are okay at 1.5 turns with stock jets.  The Keihins on the 98's are very lean at 3 turns (which is effectively all the way out).  They run fine at 1.5 turns with the next size larger jet.

the mikunis are very happy with stock pilots and 1  1/2 turns to 2 turns out  .

also to be noted is that the mikunis came stock with 105 main jets and the keihins had .98 mains
105's in a keihin make a world of difference

the pilot screws on my 98 with keihins were just about screwed shut , in fact 1 of them was from the factory

the 95 with mikunis were all three set at almost exactly 1 1/2 turns
 from the factory and the 95 has purred like a kitten since day 1

[MtheTiger]

secret trick ..........just set em at 1 1/2 turns and forget about it

Amen Bro !...works fine for me.