Bogging/choking when starting off!

[tonyprue]

Fitted a new Dellorto 30mm PHBH but only rode it a couple of miles to my sons garage where it has been for 2 plus years.(medical reasons)

Got it out recently, new petrol, cleaned carb, fired up, rode home, went to cafe and back next day, 12 miles round trip pretty good, however it bogs/chokes smokes when pulling away under load, needs a lot of revs to get going but goes well when on the move!

It is a Mugello 200, 42mm expansion and carb is set at 50 pilot, AV266 atomizer, 70 choke, 118 main, x2 needle 3rd clip, remote air filter(sweetbreathe type) which I would like to keep but it does seem better without it!

Checked choke and it looks fine, not sticking. Air screw out 2 turns. On stand it starts first/second kick, ticks over, revs up fine but a bit of smoke at low revs!

Would appreciate any advice, not sure if is it rich/lean? I have other jets/atomizers and needles I can use but not sure where to start.

Thanks

Apologies for long post!!

[Norrie Bodge]

X2 needle on 3rd clip with an AV266 is rich
Move clip to 2nd clip (from needle top) & try
May even poss needed to drop it to position 1.5 with a thin washer under clip ?
1 adjustment at a time tho ok
GL

[Rich Oswald]

What slide are you on. If it's a 40 try a 45.

[tonyprue]

Thanks for help will try needle when it stops raining.

Sure it is a 40 slide will have to get 45 if needle does not work

I have a AV268 atomizer, also have X7 needle, 45/55 pilots I can use.

As you say one step at a time will let you know how it goes.

Thanks

[Norrie Bodge]

Thanks for help will try needle when it stops raining.

Sure it is a 40 slide will have to get 45 if needle does not work

I have a AV268 atomizer, also have X7 needle, 45/55 pilots I can use.

As you say one step at a time will let you know how it goes.

Thanks

Av268 & x7 needle on 2nd clip is a good combination

[tonyprue]

Hi again

Choking up is much better now, running AV268, x7 needle 45 pilot(not sure about that though should it be 50) 118 main 40 slide.

Took it out today to the Cafe but still rich, at one traffic light literally had to wait with full throttle till it cleared, then was almost fine but not perfect, then happened once again on way home! Once it was going it pulled quite well through the gears!

Got home took air filter off went round village, no side panel and it was a different bike, pulled like sh*t in every gear, bit of splutter around 1/4 - 1/2 throttle if not giving it the big un! Very impressed!

What do I need to do now to try and get it running with the filter or should I just leave it off and put up with the mess!!!

Thanks for any advice.

[Storkfoot]

Please clarify which Mugello 200 you have. Also, please clarify what exhaust too.

I had a large block Mugello 200 back in 2010. It had no real speed or torque increase on a standard 200. But, they may have changed since or you may be referring to the 198 small block Mugello which, I believe, is a lot more sporty.

I do suspect that your jetting is too rich in the lower and mid range which is why, when you let more air in by taking the filter off, it feels much better. For example, I have the AV268/x7 combination on a TS1 225.

[tonyprue]

Hi

I have owned the bike for 11 years and it came with the kit already on and did not run a filter.

I have had a GP 200 and fitted a Sil 200 to another bike, this would out pull both of those no problem!

I had some work done by someone local a while back and asked for a filter(dynoed at the time, he reckoned 19BHP) but it was never as quick as without, it also had a 30mm Spaco phbm which started playing up so hence the new Dellorto.

It has a 42 mm expansion, needle clip is on second from top(forgot to mention that)

I would just like it to start, be reliable and smooth don't need to do 80mph, I have a Vespa GTS for that.

I could take it and get it set up but at the risk of upsetting the neighbours I would like to do sort it myself.

Any advice would be appreciated it is getting better the more I play with it!

[Storkfoot]

A genuine Breath Sweet filter, which is only one skin, isn’t especially restrictive so should not make the jetting overly rich on its own.

But, if you say it runs better without a filter, that is telling you that the jetting is too rich.

Every engine is different which means it is really difficult for anyone on a forum to give you precise jetting instructions. I shall try and give you an idea though.

I am assuming you have a large block Mugello 200 with a 42mm Clubman exhaust ( I have never heard of an expansion exhaust designated as 42 mm). In which case:

Your main jet looks about okay.

I’d try an AV264/x13 2nd clip with the filter. That is leaning out the mid range jetting. Even if it is not spot on, if it runs better than it is now, it should tell you whether your engine needs leaner jetting ie. if it needs less fuel and more air in the mixture. If that is too lean, I’d try AV266/x7 and try altering the needle clip up and down to see which is best.

The pilot jet - you need to play around with one or two but I’d have thought between 45-50. You can get a good idea of a correct pilot by the engine tick over and revving to 1/8 throttle. The amount of smoke coming out of the exhaust gives you an idea too.

The slide should be okay at 40, especially if the engine likes the change in atomiser and needle to AV264/x13.

Alternatively, do you have anyone in your local area who can stick the scooter on a dyno to analyse the air/fuel ratio throughout the throttle progression? If you do, that is often money well spent as it is stops you spending a small fortune on jets, needles and atomisers that you may never use again.

Good luck.

Ps. It may also be a good idea to clean the filter in petrol or soapy water too, if you haven’t already.

[Storkfoot]

Having said all that, the port timings on some of the old Mugellos have been questioned in the past. I had a Mugello 186 years ago that was a temperamental starter when warm and would bog down with a PM exhaust. I sold it on eventually but, with hindsight, I wish I had checked the port timings.

[Rich Oswald]

Even better than a breathe sweet, I would try a Chiselspeed panel filter. These do not really affect the jetting much at all. I would also try the 50 slide, but just one change at a time. Always do plug chops at each throttle opening to check it doesn't run lean. Alternatively, I would run without a filter at all, if, as you say, it ran much better without but this would mean it's getting more air so closer checks to make sure it's not lean would be necessary.

Rich'

[tonyprue]

Thanks for all the advice, couple errors on my part , had bike 8 years, getting confused with my 150 special and it is a 48mm expansion!

Away for a week so will play some more when I get back. I appreciate it is hard to say what settings would work as engines are all different so was looking for useful suggestions which I have been given thanks! I did give filter a good clean but it was one I got with carb so not had much use. The filter is a air ram which was attached to bellows, very soft rubber though, and fitted round the carb mouth , small part, but I got a bell mouth and had a sweet breathe type fitting which Is what I have been trying.

I do have some one local with a dyno which will be the last resort if I can’t get it right!

Watch this space!

[Nudger]

Did you ever sort this?