Rough running

[norbert]

Hi Ian,
have already found them her in Germany as well with the help of the number you mentioned. I´m going to try them

norbert

[fastharry]

Have you tried doing a plug chop after holding the bike at the required revs to make it splutter for as long as is safely possible on an open road, it will give you an indication of wether it is running rich or lean, The needle position can effect it around half throttle, and possibly going down on the main jet may help at higher throttle openings, especially if its rich, worth a try as it costs nothing, i have been jetting down on my race engine because of todays fuels.

[Lewes96]

Hi, must admit I haven’t tried the plug chop. I have some 112 jets now which I will try next to see what that shows, but if that fails I will do the plug test. Lots of good feedback though dand plenty of things to try out.

[72degrees]

Hi, if your filters are the source of the problem? have a look at Polini 90 degree filters with covers as an alternative to the standard air box/filters and tuck up under the tank in still air, out of the weather etc and avoid some of the problems with K&N, Ramair etc filters especially in the wet.

<Googles>

Hmm, they look worth a try. I shall report back after a trial on the 2C/375 and if they work well may also put some on the Forgotten Error - although that might raise 'period parts' eligibility issues

Well I've never known a change of air filter make so much difference. On first pulling away for my usual test route it felt great - possibly liking the more overall correct inlet length, then I found it really didn't want to pull above 1/4 throttle under heavy load, but revving well on a small throttle opening downhill. So some re-jetting or needle height adjustment is needed. It was a bit like the Forgotten Error when I first got that going by swapping engines, so a quick experiment will be to swap in the main jets (125 rather than 130) from the PHBH28s on that (that run with S&Bs). Though going on what was said about S&Bs being restrictive that may be the opposite of what's required - it will soon be obvious! If, instead, it needs even bigger mains I'm looking forward to getting it WFO I should have a look at the plugs first I suppose. If all else fails I'll try a 'chop'.

[simonnorthroad]

Having just bought a Morini 350 with S&Bs facing fore and aft I got a pair of carb to airbox rubbers from Start Gomma, and, at less than £20 each, a pair of foam Ramair filters for a Honda Superdream *shudders* fit snuggly over the ends up under the tank. From a distance it ALMOST looks standard. Yet to run the bike up or check the jetting however. P.O. went from 112 mains to 125s which im guessing will be very rich

[72degrees]

I'm now down to 121 mains on the 375/L5/PHBH28 with Pollini elbows/filters. Going in the right direction but still reluctant to get on a really wide throttle. I'm hoping for the odd day of better weather again soon to continue the quest. On checking, I remembered that I also had to go to a very lean needle (X1) height to get it running nicely on the S&Bs can't remember what atomisers though - must check.

[72degrees]

I'm now down to 121 mains on the 375/L5/PHBH28 with Pollini elbows/filters. Going in the right direction but still reluctant to get on a really wide throttle. I'm hoping for the odd day of better weather again soon to continue the quest. On checking, I remembered that I also had to go to a very lean needle (X1) height to get it running nicely on the S&Bs can't remember what atomisers though - must check.

Down to 117s now and at least able to persuade it get WFO. It has a massive rich flat spot at half throttle and 5000-6000 (not uncommon) but will rev good and high in a low gear and < half throttle.

Not worth fiddling more with now until the winter project is complete, but I can see me trying to find a cheap dyno place nearby next spring.

I'm now going to have to check the needle position again. Perhaps they are on the bottom groove rather than top - I know they are at the extreme one way or another (a senior moment). If top, then it's different needle and or atomiser time, and that could get expensive The Forgotten Error will keep S&Bs!

[72degrees]

Nope. Needles already on leanest notch. Dellorto only have one 260T atomiser in stock, so on their advice I'm trying X8 needles. All useful development work with a view to next season I suppose, if we have a few more days with dry roads soon.

[norbert]

Had a bad surprise yesterday when I intented to fix the Polini Filters 203.0098. I did not read carefully enough before I ordered them. They are 90°, what is fine, but they are for 46mm connection The Dellorto 28 (as well as the 26, if I´m not too wrong) are 42 mm.
How did you mange to fix these Polini filters? I only can find them for 37mm or 46mm connection

['It must be a .....']

Hi Norbert, sorry about the initial surprise.

Like you I could only find the filters in 37/46 mm diameters? and yes the flanges on the 26/28mm PHBH carbs are 42mm (width is 8.4mm) with a 43.4mm lip.
You can simply tighten up the clamps or as I did fit a 2mm thick rubber spacer on the flange behind the lip, alternatively you could use four O rings on each carb?

Not a massive problem yet I appreciate your initial disappointment.

Good luck with the filters and let us know how you get on.
Have fun, Ian

[72degrees]

Mine seem to stay in place OK on my PHBH28s if the clip is done up really tight.

[Steve Brown]

I used a strip of foam rubber round each carb as well. The 'O' ring idea would be a good one too. I also used a cable tie through each of the plastic covers to act as a support as the original airbox connectors would have done.

[72degrees]

Mine already had cable ties looped under the carb intakes to take the strain when using S&Bs. I've been surprised how much leaner it needs to be jetted with the Pollinis (than with S&BS).

[pedro]

Presumably if you are having to lean the mixture off compared to S&B's then the Pollini's are more restrictive, is that not defeating the object of going to pod filters in the first place?
Or to put it another way, are the Pollini's such a good idea?

[Steve Brown]

My 500W engine seems fine on them. I think Pete's is a stage or three higher tuned. I seem to remember the instruction sheet with them saying they could be used with out the plastic outer shell, maybe that would be more suitable for a bike that spends a lot of time A Tutto Gas. Mine is a trail bike and I'm not a fast trail rider