Carb Re-jetting

[Bongo111]

Can anyone offer advice on the following ...?
I'm interested in buying a 2001 790cc Bonnie, which has had TOR silencers fitted and the A.I. removed, but the current owner didn't change the jetting on the carbs. Is the jet upgrade essential, or just a prefered option ? Would this have caused any damage to the valves or anything else ?

 

[Aussie_T100]

Can anyone offer advice on the following ...?
I'm interested in buying a 2001 790cc Bonnie, which has had TOR silencers fitted and the A.I. removed, but the current owner didn't change the jetting on the carbs. Is the jet upgrade essential, or just a prefered option ? Would this have caused any damage to the valves or anything else ?

Standard main jet is 110 which is usually upgraded to 115 when fitting TORs, the change is not entirely essential but strongly recommended, I can't see Triumph shipping the 115 main jets with TOR's if they didn't recommend they be fitted. It is however unlikely that any serious damage would occur to the engine unless it has been ridden really hard for lots of miles in a hot climate.

My recommendation would be to fit 115 main jets and pull the intake snorkle from the airbox.

 

[SCBonneville]

Can anyone offer advice on the following ...?
I'm interested in buying a 2001 790cc Bonnie, which has had TOR silencers fitted and the A.I. removed, but the current owner didn't change the jetting on the carbs. Is the jet upgrade essential, or just a prefered option ? Would this have caused any damage to the valves or anything else ?

The 110's are quite lean as standard... with the TOR's even the 115's are fairly lean...

On my '02 I found that the following set up worked well: 3 to 3 1/2 turns out on the "air screws", either 1 of the aftermarket (thick) shims or 2 of the Keihin (thin) shims under the needles and 125 main jets.

The above set up was with the "snorkel" pulled and a Uni filter installed. Also, for me, the stock needles worked better than the Thruxton profile needles, which ran fairly rich when I tried them...

 

[Aussie_T100]

The 110's are quite lean as standard... with the TOR's even the 115's are fairly lean...

Is it possible for you to point me to a dyno chart with A/F graph that confirms that or have you run an A/F gauge on a bike so equipped?

I know it is commonly thought that Bonnie's run lean from the factory but I have seen Pieman post to the contrary and I tend to believe him considering the amount of dyno hours he has put in with these bikes.

My own 2008 T100 is currently running Norman Hyde Toga's, no snorkle, stock filter and 115 mains with no other mods and I'm at sea level. The bike consistently returns between 140 to 160 miles to reserve (230 to 260k on 13 litres depending on riding style) which is exactly what it returned when it was dead stock. I'm not seeing any obvious indications of lean running such as high engine temps, pinging or white exhaust pipes and the bike pulls strongly all the way to the rev limiter.

Damn, I must find the time to finally fit that A/F gauge that's been sitting in the cupboard for months now.

 

[jphickory]

Is it possible for you to point me to a dyno chart with A/F graph that confirms that or have you run an A/F gauge on a bike so equipped?

I know it is commonly thought that Bonnie's run lean from the factory but I have seen Pieman post to the contrary and I tend to believe him considering the amount of dyno hours he has put in with these bikes.

My own 2008 T100 is currently running Norman Hyde Toga's, no snorkle, stock filter and 115 mains with no other mods and I'm at sea level. The bike consistently returns between 140 to 160 miles to reserve (230 to 260k on 13 litres depending on riding style) which is exactly what it returned when it was dead stock. I'm not seeing any obvious indications of lean running such as high engine temps, pinging or white exhaust pipes and the bike pulls strongly all the way to the rev limiter.

Damn, I must find the time to finally fit that A/F gauge that's been sitting in the cupboard for months now.

+1

I've seen Pieman's dyno charts on stock bikes and they do not indicate a lean factory condition exists.

 

[SCBonneville]

Is it possible for you to point me to a dyno chart with A/F graph that confirms that or have you run an A/F gauge on a bike so equipped?

I know it is commonly thought that Bonnie's run lean from the factory but I have seen Pieman post to the contrary and I tend to believe him considering the amount of dyno hours he has put in with these bikes.

My own 2008 T100 is currently running Norman Hyde Toga's, no snorkle, stock filter and 115 mains with no other mods and I'm at sea level. The bike consistently returns between 140 to 160 miles to reserve (230 to 260k on 13 litres depending on riding style) which is exactly what it returned when it was dead stock. I'm not seeing any obvious indications of lean running such as high engine temps, pinging or white exhaust pipes and the bike pulls strongly all the way to the rev limiter.

Damn, I must find the time to finally fit that A/F gauge that's been sitting in the cupboard for months now.

White exhaust pipes???? Never heard of that one... Are they blue? Beyond the first bend? If so, you're lean... Have you pulled your plugs and checked the color? They should be a cocoa tan... shading to white and you're lean...

The maximum hp will be developed in a very slightly lean mix... in the 14.5 to 1 range.

The best range for running (particularly an air cooled engine) is a slightly rich mixture... in the 13.5 to 1 range... cooler running and not as taxing on parts...

I never did a dyno run on my '02 (wrecked) that had an A/F ratio done on it... just a quick hp/torque run...

On my '03 that has the air box carved/pod filters thruxton needles and one Keihin shim, 138 mains with EPCO peashooters, I ran lean above 5500 rpms and went WAY lean above 7k rpms... This was verified on a dyno... I have since moved to 145 main jets... oh, and I have/had NO bluing on my headers after doing the things I've listed...

If you want to KNOW what your state of tune is and dial it in, book some dyno time....

If you want get things close, use what the bike is telling you... it's there for you to see... pipes and plugs...

If Triumph is shipping bikes that are not jetted lean (and they were... to meet emissions limits)... why do you see so many bone stock bikes with the headers blue down to and past the second bend? Even with the air injection pulled...

 

[Aussie_T100]

White exhaust pipes???? Never heard of that one... Are they blue? Beyond the first bend? If so, you're lean... Have you pulled your plugs and checked the color? They should be a cocoa tan... shading to white and you're lean...

The maximum hp will be developed in a very slightly lean mix... in the 14.5 to 1 range.

The best range for running (particularly an air cooled engine) is a slightly rich mixture... in the 13.5 to 1 range... cooler running and not as taxing on parts...

I never did a dyno run on my '02 (wrecked) that had an A/F ratio done on it... just a quick hp/torque run...

On my '03 that has the air box carved/pod filters thruxton needles and one Keihin shim, 138 mains with EPCO peashooters, I ran lean above 5500 rpms and went WAY lean above 7k rpms... This was verified on a dyno... I have since moved to 145 main jets... oh, and I have/had NO bluing on my headers after doing the things I've listed...

If you want to KNOW what your state of tune is and dial it in, book some dyno time....

If you want get things close, use what the bike is telling you... it's there for you to see... pipes and plugs...

If Triumph is shipping bikes that are not jetted lean (and they were... to meet emissions limits)... why do you see so many bone stock bikes with the headers blue down to and past the second bend? Even with the air injection pulled...

No major problem with bluing pipes on my bike, blue to the first bend and gold almost to the next:-

I have a theory about pipe bluing on these bikes - to me it seems to be worse on bikes from cold climates - dunno, it's just a theory.

What I'm referring to with white exhaust pipes is internal colour not external colour - medium to light grey is good, black is too rich and very light grey to white is too lean.

Dunno about max power at 14.5 A/F most of the guru's around the forums seem to think that 12.8 to 13.2 is best for max power on these bikes. Various opinions exist about the value of plug readings with modern fuels as well.

No doubt that an A/F gauge or dyno run is the only way to dial in a bike exactly but lean running to any serious degree is pretty obvious to anybody that's been tuning engines for a while.

The opinion that Triumph shipped these bikes running on the lean side to meet emissions is commonly held but is apparently a fallacy from what I've seen reported by very knowledgeable people who have actually checked it out.

 

[derby boy]

Much of the jetting is subject to altitude. I live in a very hot climate and I ride between 2500-7000 ft above sea level and I was always lean. Here is a picture of my pipes when the bike was stone stock with less than 500 miles on it. They were the most discolored pipes I'd ever seen.
Since that point it has been heavily intake / exhaust modified. I'm running 142 mains, stock pilots 3 turns out with 1 shim. My performance has really improved especially above 3500 rpm which was verified by 72 rear wheel hp on the dyno with 56ft/lbs of torque. I still average 45-47 miles to the gallon on my daily commute. I'm at 141 miles on this tank of gas and not on reserve yet.

 

[derby boy]

Pic didn't come thru??

 

[TC_Dick]

Pic didn't come thru??

my pipes looked like that when I rode it as stock. Blued all the way to the crossover pipe.

 

[Aussie_T100]

Since that point it has been heavily intake / exhaust modified. I'm running 142 mains, stock pilots 3 turns out with 1 shim. My performance has really improved especially above 3500 rpm which was verified by 72 rear wheel hp on the dyno with 56ft/lbs of torque.

Did you achieve those figures with only intake & exhaust mods? Stock carbs, stock head, stock bore & stock cams? Reprogrammed ignitor?

Which filters are you using and what exhaust exactly?

The reason I ask is that is the sort of output I'm aiming for but I have gone for Hi-comp pistons and cams as well as the intake & exhaust mods and reprogrammed ignitor.

 

[dr_cerebro]

Pic didn't come thru??

I love that windscreen. What brand is that?

 

[B06Tang]

I love that windscreen. What brand is that?

I think it is a parabellum? You can find it here though:

http://www.bellacorse.com/bcc056.htm

 

[Keith Harding]

Guys,
I'm trying to get at the internals of my carbys to check my jetting. Removed the seat and side covers. Disconnected the heaters, loosened off the band at the airbox and the two connecting the carbys to the engine. I couldn't get the carbys loose from the airbox or engine to swing them up to the left and get at the main jets.
Have I missed loosening something?

 

[BlueJ]

You didn't mention disconnecting the fuel line or the throttle cable. Possible to do it w/o the throttle cable disconnect, but not much room.

Actually possible to do it without disconnecting anything except fuel, but you need to already know where everything is, as you're putting the jets in blind, once you take off the bowls at the bottom.

You did order replacement float bowl screws, right? Those babies are really soft crappy metal, OEM. Easy to strip the heads.

With the airbox intact, you really need to wrestle the carbs a bit to get them unseated from either the intake manifold side or the airbox, before you can lever them out.

 

[bluesforchallah]

Forgive me as I'm going off memory from 4 years ago....

If memory serves me correctly, the carbs disconnect from the airbox much easier if you unbolt from the frame under the seat and slide the air box back as far as it will allow.

 

[Keith Harding]

Thanks for your quick response guys.
No - I didn't disconnect the fuel line or throttle cable.
The idea of sliding the airbox back seems like a good one. The next chance I get will probably be the Christmas holidays - no problems about the weather then as the temperature here in Western Australia will be up around the 90-100 mark.
As for the replacement float bowl screws I asked about them when I was last in my Triumph dealer and he'd never heard of them. I worry a bit about that dealership...

 

[whyme]

I used a video on line when I did my ARK...can't remember from who but the carbs were just slid out to the side a bit and I could get to the bowls for removal. I also bought the replacement screws at newbonneville.com....$6.

 

[Keith Harding]

Thanks for that Whyme. I tried to buy a velocity stack from Jenks Bolts in the UK - the cost of the stack wasn't too bad at all but the freight to Australia was insane - three times the price of the part itself.
I'll have a look at New Bonneville but I have a feeling in the back of my mind that they don't deliver to Australia, something about distribution rights over here. I'd be very pleased to be shown to be wrong about this!

 

[Baltobonneville]

Guys,
I'm trying to get at the internals of my carbys to check my jetting. Removed the seat and side covers. Disconnected the heaters, loosened off the band at the airbox and the two connecting the carbys to the engine. I couldn't get the carbys loose from the airbox or engine to swing them up to the left and get at the main jets.
Have I missed loosening something?

I used the pics in the Jenks manual and an inspection mirror to change jets the first time, to avoid having to do all this. It's slow and fiddly the first time, but not too bad once you've done it once or twice. It's easier if you have the bike on a lift.

And yes, by all means replace the screws the first time you do it.