Fuel starvation then high revs.

[Warkton Tornado No.1]

Seems a little odd that the filter was empty when it had been standing for a week or so, but it was full when parked up?

Somehow, I don’t think the carburettor or reeds are responsible for clogging filters up & you are kidding yourself if you think you can ‘work around’ an issue proven to be there, unless I’ve misinterpreted previous comments...

Good Luck, though

[Watfordwhite]

Wack this has never happened before on tick over, only at med- high revs?
So back in the garage this morning,
FUEL FILTER TAKEN OFF. Due to public pressure.
Carb re striped and re cleaned. Looked perfect to me!

So what we have is
225 Rapido
28mm PHBH
MBD Short reed
MBD clubman
Pilot 55
Atomiser AV256 or could be 266
Red top float needle looks like x9 on it. But to be honest it could be anything!!!!!
Main 158
Choke 70
Air screw 2.5 turns out
Ram air filter

Rebuilt still will not start at all.

[Watfordwhite]

Warkton,
I think you may has miss read or I have not put it down properly. When the scoot was parked up last week the in line filter was full.
The tap turned off. Engine off.
On returning to the scoot this weekend, the filter was empty. Why, when the scooter had not moved? Where would this fuel go, as the engine was not running so it should not consume any fuel? Hence why I think it may be a float problem. If the float is stuck open. Even with the engine not running, gravity would keep on filling the bowl? Until the fuel in the pipe reached its own level. That's my only conclusion.
So if the float is sticking open it may stick closed while running?

[Warkton Tornado No.1]

Warkton,
I think you may has miss read or I have not put it down properly. When the scoot was parked up last week the in line filter was full.
The tap turned off. Engine off.
On returning to the scoot this weekend, the filter was empty. Why, when the scooter had not moved? Where would this fuel go, as the engine was not running so it should not consume any fuel? Hence why I think it may be a float problem. If the float is stuck open. Even with the engine not running, gravity would keep on filling the bowl? Until the fuel in the pipe reached its own level. That's my only conclusion.
So if the float is sticking open it may stick closed while running?

What is your meaning of ‘filter full?’

Reading through the whole thread again, I now presume yours to be ‘filter full of clean fuel’ rather than mine ‘filter full of cr@p’

BTW. The atomiser had better be AV266, not AV256. Main jet 156 sounds huge. Neither of which will have caused the problems you’ve encountered, but perhaps a magnifying glass should be a cheap addition to your tool set. I have one to hand when jetting.

That aside, & the fact that the bike fails to start @ all, ignition would now be my first suspicion. You should check for a spark...

Sorry if that all (& this, following!) sounds patronising, but @ least, previously, it was running, though I note you didn’t respond to the possibility that the tank cap was unobstructed. If you have a healthy spark, I would also advise removing the air filter temporarily until you get the thing running.

Try & keep an open mind because I’m sure we’re all rooting for you....

[St George]

Hi Martin. The main jet sounds as big as a drain pipe, but thats another issue. Sounds like float issues-flooding. Carbs are easy to work on just read up on basic principles.. It all goes tits up when we alter the carbs for tuning. That is why the carb section is so large on the forum. Keep at it mate, she can't fight you forever.

[hullygully]

what size is your float jet? needs to be 280/300 max

[Watfordwhite]

Warkton,
Yes the filter was full of clean fuel. Before this had no issue starting. It always started on first kick, very occasionally 2nd.
Good spark ATM. Good compression. Checked the tank cap and blew that out today as well. Also changed it for my GP which runs well.
Mate, no problem, I'm a novice when it comes to carbs. But machanicaly sorted. C&G me .
This has really baffled me, as it makes no logical sense. The only thing left is the carb. That has been deeply cleaned today and it still is not even interested in starting now. I have a 28PHBH on the GP so may swap it over to see what happens.
So to recap.
Tank clean
Tank cap good and swapped
New FF tap
New fuel line
New fuel
New reed to carb rubber (old one split)
No in line
Jets cleaned and checked
Carb cleaned
Used to start and run really well, until about 20 minuets in and mid to high range in 4th. Then fuel starvation followed by high revs when clutch pulled in then died. 5 minuets it would re start 1st kick until the next 20 minuets.
However this has got worse, now died on tick over after 10 minuets and will not re start.
Fuel flow good.
I still think it's something to do with the float?

[Watfordwhite]

Rechecked the photos of the jets. The atomiser is defo AV 256. The 5 is different from the 6 next to it. That is to say the 6 looks like a 6 the five looks like a flat topped 6.
The float has 90101 gr11 then what looks like a small 3 above the 11

What would a 256 atomiser do? Does it even exist? I can upload the photos of the jets and float if it helps?
What effect would a large main jet have? Looking at the photos again the main jet could be 150. It must be my age. Going to get a magnifying glass tomorrow. The plug (before this) was always a med - dark brown colour. After cutting out last week it was black.
The bike was always very carbie sounding. I did wonder if a 28mm was to big? Saying that I am not a high revs type of guy... Hence the Rapido and not a RB.

Ps. The breath sweet has been off all day. So no air filter. But was fitted when cut out.

I do appreciate all of you help and advise on this.
Baffled of Watford.

[Warkton Tornado No.1]

The process of elimination continues!

Is your ignition electronic or points? (Condensers fail on points whilst still indicating a healthy spark)

AV atomisers range from 260 to 300 (according to Eurocarb)

An over-sized main jet shouldn’t be responsible for failure to start.

Is the needle assembled correctly with regard to the slide & needle plate? You wouldn’t be the first....

Personally, I wouldn’t consider 28 mm “too big” on what is a tuned cylinder (Rapido) though opinion varies.

It would definitely be worth swapping carbs if they are the same mounting & trying both machines.

[Watfordwhite]

Electronic ignition
Must be AV266 ( still looks like a 5 )
I'm not sure. Is there any brake down picture showing this set up correctly?
Will do the carb swap over next weekend. The GP is a 175 stage 4 so I expect the jetting to be different. But if it starts we know it's a carb problem. Either the float or a blockage somewhere In the carb.
People talk about the needle clip set on 1,2 or 3. What does this mean and what does it do? There seemed to be very little movement up and down on the float needle. Although I'm not sure how much there should be?

[Warkton Tornado No.1]

Dell'Orto PHBH.JPG

Needle Clip positions may be anything from leanest [Top (1)] to richest [Bottom (4)]

Dell'Orto PHBH X Needle.JPG

[Watfordwhite]

Thanks walton, do you have a link to this page so I can see what number is what please mate?

[St George]

Hi Martin. I might have some spare needles and jets in my black hole of a garage. If I have them still let me know what size etc. I can pop them in post FOC

[Warkton Tornado No.1]

Thanks walton, do you have a link to this page so I can see what number is what please mate?

Hi Wilford.

Is this what you mean:

http://www.dellorto.co.uk/shop/dellorto ... edle-phbh/

Then click on:

View X-W Needle charts

[Wack]

If as you say the fuel line was empty then the fuel must have gone into the carb and possibly the cylinder in which case the whole top end and possibly the exhaust could be full, seen it before and no amount of kicking over will get it running until the fuel is cleared out. When you try to start it with a dry plug is it wet when you remove it?

[mickey c]

I'm reading this thread with interest as my scoot rides ok & then revs it's nuts off in a very scary way!

I'm none the wiser but would agree with Wack's suggestion - I've found loads of petrol in exhausts a few times and no way would the engine run until I found this & emptied them!

[Watfordwhite]

Sorry Warkton, bloody Apple auto correct...

Interesting comments about the fuel in the exhaust. I will check. But still don't understand how the fuel would drain into the carb unless the float was sticking open. And if it sticks open, it may stick closed. That I think is my problem, and would explain the issues.

Thanks for the offer StGeorge. Kind of you. But I won't be changing the jets until I understand fully the implications of doing so. Once I can get it running again ( when it did run, it was great) it will go to be dynoed and let a professional do it properly.

Getting my C&G in mechanics at a time when fuel injection was just coming on to most cars, we were never taught about carbs. So my knowledge is limited.

Again, thank you all for your help and comments. Together we can fix it...

[Warkton Tornado No.1]

Yet another suggestion (or three), if your float is to blame...

Could be punctured, though unlikely. If it is & you obtain a replacement, current thinking is lighter the better (8 grammes, if memory serves) for a two stroke.

If it is sticking between the posts, the posts can be filed down to allow clearance.

Pin could be bent.

More bed time reading for you (copy & paste):

dellorto_motorcycle_carburetor_tuning_guide.pdf

[MickYork]

if the tap was switched off then a sticking float (flooding) wouldn't really be an issue if left overnight........imo.

if you tried to kick it off with the petrol switched off this may help.

alternatively........check the stator as this is a common part that fails and can give some unsual symptons when breaking down.

[grandpa]

Hi Watfordwhite,
If you have compression and a spark you can generally start a scoot for a few seconds by pouring a small amount of fuel on the mouthpiece (venturi) and kicking her over .Alternatively pour a small amout of fuel down plug hole replace plug and it will run for a few seconds.I am not familiar with a PHPB but if it is like a PHBH there is a small hole in the float bowl that leads into a channel that feeds fuel to a moulded well that enables the starter jet to receive fuel.If this is blocked it wont start as I recently found out
Have a look at this:
viewtopic.php?f=6&t=8117&p=70168&hilit=jet+200+wont+start#p70168
and this:
http://www.rotaxjetting.com/PDFs/Docume ... Manual.pdf
This included float height adjustments
Good Luck
Grandpa

" I don't need a Lambretta as I have a bus pass"