Ducati.ms - The Ultimate Ducati Forum banner

New to ST2 RPM and Fuel/range queststions.

3598 Views 9 Replies 8 Participants Last post by  tahoest2
I have posted before as I have just bought a 98 ST2 with about 19,500 on it. When I first bought it I had some odd electrical issues, which seem to have been fixed. It appears that the wires leading to the battery had gotten hot/corroded over time and the connection wasn't solid. So, I 'think' this issue is behind me. 200 miles since having it fixed and all seems well.

Now, a few questions.

1. I didn't fill my tank to the rim, but fairly full. First tank of gas I got 100 miles. Saddle bags attached but empty and I weigh 170lbs. It was a mix of highway and normal riding(I live in Tahoe so not 'city' miles). This seems EXTREMELY low to me.

2. The bike runs rough between 3,700 and 3,900 rpms. If you are riding in say 30-40mph traffic and keep the throttle steady within that range the bike almost starts to lurch. The moment you are above or under this rpm range there isn't an issue. Curios what might cause this?

Any input on my fuel consumption and rough rpm range is appreciate.
1 - 10 of 10 Posts
I go about 150 between fill ups depending on speed and throttle input. With stock gearing I got 45 mpg on long 2 lane trips (3000 plus miles) and with the 45 tooth in the back I now get 43 mpg. I can't find it right now but somewhere there on the Internets is an article that explains that there is a math error in the chip that causes surging around 3,700 and 3,900 rpm. I'm sure others who are more knowledgeable will soon chime in.
I'll toss in my 2 cents here.

100 miles on a tank seems very low. If i fill the tank to the rim, i can expect ~200 miles until i hit reserve. This would be mid 40s to about 50mpg.

The stumbling at ~4k rpm is a common problem to everything I have ever ridden with the marelli 1.6 computer (both my ST2 and a cagiva gran canyon) You can fiddle with the mixture, the better idea is to just get an aftermarket chip.

Another hugely helpful thing is to check the condition of the internal fuel tank hoses and the fuel filter. If the hoses are deteriorating, they filter may be clogging with rubber bits. This will cause both rough running and poor mileage.
Check your air filter too. When I first got my ST2 a mouse or something left a bunch of nut shells on top of the filter causing rough running and poor gas mileage.
A friend's 1998 ST2 had some crappy running between 3500 and 4000rpm. That turned out to be a bad TPS. (Throttle Position Sensor)

In general, I think you need to go down a gear, and get up OVER 4000 rpm for average riding. Especially in the higher gears. Mine didn't like 4000rpm in 5th or 6th gears. you can see the gauges start to flutter about when adding throttle. 4500 to 5K was much better. gotta be careful, though 'cuz that gives to about 80mph with 15/42 sprockets!

This "tank" of gas... how many GALLONS did it take to refill it? If you stop right when the fuel light comes on, it typically takes about 4 gallons to refill. LOOK AT YOUR MANUAL (or grab one on-line at Ducati.com--the MY2000 is very similar to 1998).

The manual says 5.4 gallons. Guess what? I just put 5.39 gallons in me ST4S the other day. I'd say it was pretty dry at that point. What I usually do is when the light comes on, usually somewhere between 140 or 170 miles (depending on city/hwy driving). I ADD 40 miles in my head, to get me closer to a 5 gallon refill...

My ST2 was getting around 40mpg typically, or about 52mpg on a trip. This was with the DP chip, open airbox lid, and DP exhaust. And I always used regular grade gas--never had any ping/knock problems--engine was never apart in the 52,000 miles of ownership.
See less See more
The 3800-4000 rpm stumble has been discussed many times on this forum, and appears to be as ECU issue (as stated above). You can make it less noticeable, but generally you can't get it to go away.

This "tank" of gas... how many GALLONS did it take to refill it?
Yes, that is the key question. I've heard of the yellow "reserve" light coming on far too early. Mine comes on after I've gone through about 3.0 gallons of gas, which is usually around 140-160 miles. Typically, I'm getting 42-47 mpg with slip-ons, eprom, airbox mod, and a 14/41 (or 14/42) gear ratio. The lowest I ever got was 38 mpg, and that was with all the above mods, riding two-up, and some pretty spirited mountain twsty road riding.
My ST2 also gets over 200mi per tank. The reserve light comes on at about 150 miles .... really early. When you said you got 100 mi per tank, were you estimating based on the low fuel light? (or did you actually measure the fuel used? I think the St2 tank is about 5 USgal.)
As for the stumbling .... you need an after market chip (FIM), make sure the bike is in good tune, and I would consider drilling the airbox. Mine responded really well to more open mufflers too. (FBF Forzas)
My 2 cents.
Thanks for all the feedback on rpm's and gas. I have searched the RPM 'issue' and I guess it is what it is. My bike has a new/aftermarket chip already. Not sure what brand however. But, from everything I've read, having a flat spot between about 3750 and 3950 is 'normal'. These machines are clearly not meant to run around town between 20-40mph.

Easy fix, ride at 4k or above-or less than 3,500 if possible.

As for my gas situation. I'm seeing much better mileage on my following tanks. Not sure what the deal was with the first tank. The low light went on at about 90 miles. The bike is new to me so I'm not certain how many miles to expect when it's flashing. From what I'm reading, I think I could count on 30 for sure, if not more like 50-60.

My last tank I did seem to get more in the 40mpg range. Still a mystery on my first tank but I'm glad about getting more. Kind of hard to tour with only a 100 mile range. 150-200 makes sense.

Thanks again for the info.
The 3800 RPM stumple is a computer problem, and no chip will entirely eliminate it, though perhaps lessen it. FIM had a good writeup on why this occurs, and why it can't be eliminated.

I typical get the low fuel light at 200km of normal riding, and maybe 270 km on the rare occasions that I do highway riding. At that point, the tank will take 15 liter to fill (4 US gal), so I have 6 liters of reserve. The tank holds 22 liters filled to the brim, of which 21-21.5 are usable (if you run out of gas, you can piss in your tank to get at the last 1/2 liter). I measured this when I drained the tank to replace the internal lines.

Just thought I'd update. I just ran 50 miles and only burned through about 1 gallon of gas. So I seem to be well on my way to getting 150-200 miles per tank. Not sure why my first tank burned so quickly.
1 - 10 of 10 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.