Triumphrat

mr_badda_bing

Took the bike in for a dyno run, it ran lean on the Left Cylinder and rich on the Right. The tech could not explain why it had the big drop at the 32 to 38 mph area on the Right cylinder. Something about an accelerator pump?



He suggested a change from the 122's to a 115 on the right side and a 127 on the left.

I have no idea, the Triumph Service Manager at Big Twin in Boise said he had never heard of jetting different sizes like this. They are booked until October, so I cannot get it in to them for another month or so.

I am very dissapointed right now.
Anyone else have any ideas what is going on?

Stats of the bike are in my signature.

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2006 Thruxton - Zoe Yellowbike
125 main jets, 42 pilots, 1 shims, 2 turns, HARK (homemade airbox removal kit) EMGO Reverse Cones, 17T sprocket. 4700 Feet Above Sea Level

sweatmachine

I've heard of people running different sized mains in each carb before on the bonnies. I wouldn't worry, looks like once you get the a/f ratio sorted you'll be pulling good #s.

You don't have an acclerator pump btw.

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Macgruber!


Click for a picture of my slightly modified Bonnie

mr_badda_bing

I forgot to add this info, not sure of it will help.

At a 20% load...

A/F Ratio A/F Ratio
MPH Left Side Right Side
50 15.1 13.7
60 14.8 13.1
70 15.1 13.3
80 14.7 13.3


Correct A/F is 12.5 - 13.3? so the Right side is very close to what I want, but the left needs help.

Do I change the right, or leave it alone when I change the left?

Could the balance (or lack) of the carbs be causing the discrepancy?

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2006 Thruxton - Zoe Yellowbike
125 main jets, 42 pilots, 1 shims, 2 turns, HARK (homemade airbox removal kit) EMGO Reverse Cones, 17T sprocket. 4700 Feet Above Sea Level

RedBird

That sounds like a lot of discrepancy for carb balance to resolve, IMHO. I would recommend balancing the carbs, first. Next, I would do a compression check (both wet and dry) for both cylinders and compare them.

Also, how did the dyno tech determine the difference in the two sides? With a crossover pipe in the header, it is difficult to use a sniffer in the end of the silencer and determine which side is which. Did he use the header holes before the crossover for his EGA probes? More than a few have reported that one side silencer is hotter than the other side and this is probably a result of the crossover being where it is--a bad location--too far from the exhaust port, IMHO.

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Larry
2003 T-100 (790cc), NARK, NH Togas, 8100 rpm rev limiter, 158 main jets, 42 pilot jets (less than 1 turn out on pilot screws), stock needles--no shims. 13 A/F ratio from 1100 rpm to 4000 rpm; 12 A/F ratio from 4000 rpm to 6000 rpm; 13 A/F from 6000 rpm to 8100 rpm.:D
2007 Tiger 1050--White:D--SW-Motech crashbars, Skidmarx rear hugger/chain guard, Calsci +7 windscreen.

mr_badda_bing

The Tech slid a sensor in until it hit the bottom bend in the headers.
That is the reason there are three runs, two without the baffles in and one with.

The baffles did add a bit of H/P and dropped the torque a bit. I am happy with the HP and Torque, the A/F is what is the main concern.

I guess I will load the bike and haul it the 3 hour drive to the dealer and see what they can tell me.

__________________
2006 Thruxton - Zoe Yellowbike
125 main jets, 42 pilots, 1 shims, 2 turns, HARK (homemade airbox removal kit) EMGO Reverse Cones, 17T sprocket. 4700 Feet Above Sea Level

JMV2006

I only managed to have my T100 running well after 3 dyno runs.
Here is the sequence:

Stock:
Max. Torque: 45.8Lb.ft / 62.1Nm (73.03 Nm) at 4,700 RPM
Max. Power: 57.0 rwhp (69.8 shp) at 6,900 RPM
Average fuel consumption: 42 mpg (5.60 litres/100km)

1st Modification
- AI (Air Injection) removed.
- Baffle removed.
- Added a .020" (0.51mm) shim under each needle
- Opened the low speed mixture screws about 1/4 turn.
Results:
Max. Torque: 49.7Lb.ft / 67.4Nm (79.26 Nm) at 6,062 RPM
Max. Power: 60.6 rwhp (74.2 shp) at 6,831 RPM
Average fuel consumption: 41.8 mpg (5.63 litres/100km)

2nd Modification
- Removal of the Snorkel
- Replacement of the original by a K&N Air Filter
- Change of carburettor needles and main Jets to 116 (RF Dynojet kit RF-5105)
Results:
Max. Torque: 50.9Lb.ft / 69.0Nm (81.15 Nm) at 3,562 RPM
Max. Power: 58.9 rwhp (72.2 shp) at 6,986 RPM
Average fuel consumption: 38.1 mpg (6.18 litres/100km)

3rd Modification
- Air Box Restrictor Plate removed
- Jenk's Bolts HJR 01 Velocity Stack - Rubber
Results:
Max. Torque: 52.6Lb.ft / 71.3Nm (83.85 Nm) at 5,769 RPM
Max. Power: 61.3 rwhp (75.10 shp) at 7,295 RPM
Average fuel consumption: 40.0 mpg (5.88 litres/100km)

Below the comparison between dyno runs.

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Joao M. Vidal
- 2005 Triumph Thunderbird Sport
- 2006 Triumph Bonneville T100
- 2008 Triumph Sprint ST

thrux351

check float levels

steviek

My bike also runs richer on the right than the left, though judging by the performance, not enough to worry a lot about. I don't get any feeling from the engine that it's running very rich anywhere in the rev range and it doesn't sound like you were feeling anything amiss before the dyno run.

My plan was basically to get each carb at its best lean idle by ear, balance them, and after thrux351's timely reminder, I'll check my float levels as well I'll then clean the plugs, swap 'em over, and run her for a while before checking them again. I just got rid of the stock paper filter for a Uni and I don't know what effect, if any, this will have on the imbalance. None, probably, but we'll see.

If the plugs still show the right side running rich, I'll take out the NH baffles I have in my togas. They don't make a lot of difference to the air flow, but they're a variable as they are wrapped in loft insulation and so one might be having more of an effect than the other. Other than this, I'll leave it until winter and overhaul the carbs while the bike is off the road. I've probably sinned enough this year that I should do that as a pennance anyway

After that? Dunno - check the coils, plug leads etc etc. It'll keep me busy when the roads are icy

Hope you figure out what's causing your issue.

__________________
In a world that becomes more ordered, regulated and monitored every year, choosing to roar down the road on an impractical, dangerous, and downright glorious piece of machinery is as free as most of us will ever get. Thank God for the motorcycle!

mikeinva

somethings not right in your carbs check float levels .one slide maybe opening quicker then the other might play with shims.( hope you didnt mess up by drilling slides) the red line is close to right the rich dip you see maybe slides opening to quick.You dont want 12.5 to 1 mix you want it to stay between 13 and 14 to 1 thats where the hp is.Another thing that 1.19 corection factor is kinda high if i did the math right thats48.56 raw hp. look at the air presure numbers 25.42 if it was that low iwouldnt want to be there lol.

SCbonneville

I would definitely have the carbs balanced before changing anything inside. If there is still a large difference, I'd double check that there isn't a bit of trash in the "leaner" carb's jets...

If every thing looks good... then I'd go look at adjusting the carb setting... You have to look at the rpm range that the carb leans out to know what adjustments to make.

Pilot jets control from 15% to 40% throttle
Shims/needles from 30% to 75%
Main jets from 50% to WOT

These are guides... do a goggle search on tuning Keihin CVK carbs for a more detailed explanation...