175TS in UK

[ranton_rambler]

Throttle valve cutaway too big?

Maybe, but only a 40 slide fitted.

[ranton_rambler]

Hi Ian, the figures quoted in Ducati Manual for the 175 TS, 12 - 15 Degrees Static, Extent of auto advance 28 Degrees,
Total advance at 3000 RPM 40 - 43 Degrees.
HTH
Brian

Thanks Brian. If it’s at full advance by 3000 the curve must start just above idle. No tacho on this bike but I think my old analogue meter can be used as one so I’ll do a check when I get chance. Weather looks good at the weekend so might go out on a nice dependable Guzzi instead.

[double diamond]

Ian,
If you have it running, that’s half the battle! If you’re checking ignition timing with a degree wheel, it’s a fairly simple step to check cam timing if you have any question that it’s correct. My experience is that if static ignition timing is close ( the factory manual gives a range of 3 degrees) and you have verified that it’s advancing and has spark, then the problem is elsewhere.
Since you elected to install a PHB carb rather than sticking with the stock instrument, unless the supplier has developed settings for your 175TS, you are now the development engineer! I recently took a VHB carb with unknown jetting, installed it on a Ducati 350 and started it up. Since the pilot circuit settings were close to stock, it would start and idle. I could rev it to about quarter throttle, at which point it would transition to the main circuit and the engine would shut off. I looked up factory jetting, installed all the bits and it ran perfectly. What this tells me is that you need to get close to factory settings. Granted, your PHB is 2mm larger than stock but the VHB in my example was bored 1mm larger, so stock jetting will get you close.
In the tech section of this site under Dellorto carb information, you will find a chart of jetting for most Ducati models. Your 175 TS shows, for instance, an 80 slide cutaway for the stock MB22. You stated you have a 40 cutaway installed. Which suggests to me that you’re way off on cutaway. Your main jet should be close to stock, perhaps a bit larger due to the larger bore of the carb but if you haven't enlarged the port to the bore of the carb, venturi size may have no effect. The chart lists the needle jet as a 260. Seems to me Dellorto marks needle jets with the metric dimension of the I.d. Of the jet (verify before assuming i’m Correct on this), so you need a PHB needle jet marked 260. (2.60mm). As far as the needle, if the I’d number called out in the chart will work in the PHB carb, you could try it. Otherwise, ascertain the taper of the MB22 needle called out in the chart and find a PHB needle that is identical or close. Dellorto published specifications on all the VHB/PHB/PHM tuning parts which you can find on the web. Finding MB22 specs might be challenging but you can always measure the stock needle yourself. This will get you close to standard jetting. What you really need to do is run the bike on a dynamometer with a fuel/air ratio meter in the exhaust but...
Hope this gets you on the right track Ian.
Matt

[ranton_rambler]

Decided to go back to a known state where it previously ran alright- slave tank, no air cleaner, atomiser and needle as-received. Still no good, so decided something else must have changed. Basically, brand-new condenser failed. Hunted round and found the old one - instant transformation! Still seems a bit rich but should be able to sort it now I hope.

[DBDBrian]

Good result Ian, not a bad thing to retrace one's steps.

Brian

[Samurai]

Hi Ian,

As you know I fitted a PHBL22 to my 175TS and had very similar problems to you.

It was complicated by ignition issues, but I too found the stock setting supplied way too rich. After a year of meticulously changing one setting at a time, keeping a record of the results and spending way too much money on needles and jets, I'm still not quite there, but at least have a bike that starts first kick (most of the time), idles perfectly and revs reasonably cleanly through the whole range.

Here's what I'm currently running to give you a starting point: Open carb with trumpet gause filter, 264k atomiser, D31 needle (3rd notch from top), .30 pilot jet, .40 choke jet and .98 main jet.

I don't seem to be able to get it to pull over 1/4 throttle if I drop to the next smallest atomiser I currently have, which is a 260k, or use a weaker needle or notch position in the current 264k. It all seems to be about the needle profile combined with atomiser at this stage and it rapidly gets expensive trying guesstimates!

The bike is still too rich judging by the black plug, but it's not wet now and apart from a very slight hesitation around 1/4 throttle, it pulls strong and clean.

I'm fact my son was following me at the weekend on his GSXR750 with a digital speedometer and said it got up to 74mph on a downhill sloping dual carriageway!

As one of the other guys suggested, once I've put a few more miles on it, I'm going for a Dyno session, as you could spend a fortune and take forever getting it spot on otherwise.

One thing I would say, that I read on this forum and has since proved correct, is that if your ignition or spark are in any way dodgy, that will do you no favours whatsoever. As soon as I fitted the Electrex World system it started and ran pretty well, even though it was painfully rich.

Hope this helps a bit and good luck, it seems to be as much an art as a science getting the fuelling right!

[ranton_rambler]

I did go back and read your thread to see what I could glean, although I have a 24mm carb with an air cleaner and popular wisdom seems to be that these carbs are sensitive to air inlet conditions.
At the moment it seems happy with a 35 pilot jet. Started 3rd kick from cold with “choke” then 1st kick when warm, stable idle and crisp response to the throttle. Not registered yet so don’t want to ride too far, but a few runs up the lane shows that it won’t take more than half throttle...

[Samurai]

Hi Ian,

Yeah, mine will run idle Ok on a .35 pilot jet too, but at 1/2 throttle you'll be well into the needle jet range, so should concentrate your efforts here. Unfortunately this also is the hardest one to figure out, as there are so many permutations! Ask me how I know . . .

What size needle jet and needle are you using? Mine came with the standard 268k jet and a D27 needle. What colour is the plug? What happens if you raise or lower the needle a notch, better or worst? If it runs better without the air filter you are obviously way too rich like I was.

At this stage I found iit was really helpful to keep a detailed list of the settings and results. Only change one thing at a time or you'll be chasing your tail! Once you've found an improvement by changing a setting in one direction e.g. weaker/richer you need to figure out if you can move forward by just altering the needle position or whether you need to change the needle within the same jet or then change the jet size up or down.

If you change the jet size, I found you are often into having to find the correct needle that will now produce the same or better result in that new jet and so on . . .

Make sure you clean the plug thoroughly between settings and have a supply of new ones for when you start getting in the right ball park. It can all take a considerable amount of time, but you do get really quick at changing carb settings

[ranton_rambler]

Friday afternoon I tried swapping atomisers, from 268 to 266 then 264, but with little effect. Maybe slightly better but hard to be sure. Going back to it on Saturday, it was reluctant to start from cold with the 264, so went back to 266. This afternoon it started first kick, so I’m happy with that. Ventured a bit further to get onto a more open bit of road and found it would pull through the mid-range with a bit of care but ran out of steam towards full throttle. Lifting the needle one notch improved the mid-range but ran out of time. One more notch to try before I start looking at needle profiles and main jets.

[Samurai]

Hi Ian, that's good news you're making progress!

I wouldn't bother about the main jet a the moment as that will only come into effect at pretty much full throttle.

You need to be EITHER changing needles OR atomisers, as they are both basically affecting fuel flow. Personally, if you've had issues running smaller jets than 266k, then I'd concentrate on finding the best needle for that jet. If you run out of notch positions before finding the right setting, then choose another needle size, profile and/or taper. If you still can't find the correct setting on that atomiser once you've run out of needle options, THEN adjust the jet size and start again . . .

Download the very helpful D'ellorto tuning manual from their website and it will explain how, why and what you should be changing.

I forgot to mention in my last post that I'd also fitted the lighter 6.5g floats and this cut down the over-fuelling somewhat as well.

I'll find you the link to a source of 3rd party D'ellorto replica needle sets, for a fraction of the price of genuine. This makes it MUCH more economic to experiment.

Keep persevering!