ST1100 jetting from factory?

[mtnpat]

Question for everyone.....

....in my experience all of my Japanese motorcycles have come from the factory with the carbs jetted more on the lean side to meet some EPA regulations. All have benefited (more power) from bigger jets and more fuel.

Is the 96 ST1100 the same way?

The reason I ask, is that my bike seems to have noticeably more power in colder weather (40 degrees verses 60 or above). In my thinking, colder air means a denser charge or "more air". If the ST came from the factory already too lean the additional air would make it run worse not better.

Are STs the oddball and come from the factory more rich than lean? Is that why people are adding low-restriction air filters like the K&N?

Thanks

-mtnpat

 

[Brant]

Correct, cooler air is denser, having more O2 for same volume. That's why all us gear heads back in the day set our muscle cars up pulling in outside air instead of 'under the hood' air. A 'lean burn' on motorcycles was set up that way from factory since 1980 across the board. Doubt very seriously the K&N use is attributed to rich jetting. Its reusability contributes to it use on our scoots, as long as the outer foam is removed and tossed....permanently. Most any bike that utilizes vacuum diaphram carbs also need NO re-jetting for altitude, etc.(check my location, and everthing I ride is UP from there, to 12,000ft.) Vacuum loss with altitude allows slide/metering rod to NOT be lifted as far. Hope that helps, as other than that, haven't a clue what your getting at, unless your entertaining the idea of re-jetting the ST, which would be a mistake, IMHO.

 

[mtnpat]

I have good friends in Grand Junction (Whitewater actually)! I visit every chance I get . Love the Grand Mesa, etc, etc.

Nope, no plans to rejet, just wondering if from the factory STs are setup too lean, too rich......or just right?

-mtnpat

 

[saaz]

It depends what year ST11 you have, and which region it is from. Many US models have leaner pilot jets and main jets, so replacing with the sizes used in other markets/years might help power. Also quite a few in the US raise the jet needle with a thin washer to improve midrange performance. When I had my 1996 Australian mode on a dyno 100,000kms ago it was actually running rich from mid range up. I put in a carb kit and the fuel economy went back to what it had been, but no noticeable power difference.

 

[Brant]

I have good friends in Grand Junction (Whitewater actually)! I visit every chance I get . Love the Grand Mesa, etc, etc.

Nope, no plans to rejet, just wondering if from the factory STs are setup too lean, too rich......or just right?

-mtnpat

Guessin' my 92' is 'just right' with a tad of plug color and 50-52mpg@80mph on the slab all day long. But my preferance is to get out of the valley off the slab and ride scenic mountain two-lane roads at a bit slower pace, which pulls mileage down to the 46-48mpg range depending on the ups and downs.

 

[afrymoyer]

ST's are tuned lean from the factory. Adding a K&N filter makes it worse. Best to use the OEM Honda filter with factory jetting. If you want the best tune for your ST, then change out the jets and set to the earlier model Canadian spec's. This is by far, the best tune for the ST1100. They run like an animal in the mid-range and pull HARD down low with these spec's. Pulls like a V-4 was meant to......

 

[ST1100Y]

Adding a K&N filter makes it worse. Best to use the OEM Honda filter with factory jetting.

+1... tried the K&N once and suffered snow white(!!) spark plug electrodes within ~400km Threw that thang out as quickly as I could (and this with the EC spec #128 main/# 40 idle jetting). Just keep it well maintained (carb isolators, tubes etc...) and properly synced... that engine is a torque monster, and whatever you'd try to 'tweak' on it will only compromise its excellent abilities and performance.

 

[mtnpat]

ST's are tuned lean from the factory. Adding a K&N filter makes it worse. Best to use the OEM Honda filter with factory jetting. If you want the best tune for your ST, then change out the jets and set to the earlier model Canadian spec's. This is by far, the best tune for the ST1100. They run like an animal in the mid-range and pull HARD down low with these spec's. Pulls like a V-4 was meant to......

Don't tempt me

 

[Brant]

+1... tried the K&N once and suffered snow white(!!) spark plug electrodes within ~400km Threw that thang out as quickly as I could (and this with the EC spec #128 main/# 40 idle jetting). Just keep it well maintained (carb isolators, tubes etc...) and properly synced... that engine is a torque monster, and whatever you'd try to 'tweak' on it will only compromise its excellent abilities and performance.

+1.......still run the K&N filter that was on it when purchased 8yrs. ago., but bike generally runs 5,000ft elev. here locally all the way up to 12,500ft., with the occassionally LD ride that covers lower elevations. The off-set of the two keeps the cyl. burn happy with everthing else factory stock.