PHBL 25 pilot jet advice please

[Pompeydave]

No sorry, my dad’s in hospital so I’m kind of prioritising other things at the moment.

[Pompeydave]

Bike being dyno’d tomorrow. Will report back with results.

[Cgt75b]

Let’s hope you’re dad’s ok the scooter can wait.

[Pompeydave]

Hi all, bike dyno run done on Saturday by Paul Jolliffe in Pompey.

The 25PHBL has the following spec:

Atomiser: AQ 266
Choke: 60
Main: 95
Pilot: 53
Needle: D22 on the top clip

It was also found to have a 30 slide, which was the cause of the low down slow running issue and over richness.

Tom Palmer was there and he thankfully supplied a spare 40 slide. Paul found that the choke cable was slightly tight and wasn’t always seating properly when turned off. The solution is to fit an elbow and slightly longer cable.

Also, he’s recommended that the jetting is about right with the main being slightly on the rich side of perfect for safer motorway running. He’s also suggested that I change the timing from 16BTDC to 19, and if it’s still is a big boggy low down, to try a 45 slide and then an AQ265 atomiser. Key point being to try one thing at a time.


Anyway, it instantly rides way cleaner low down with the 40 slide. Choke elbow and longer cable ordered and the timing change is up next. I’ll report back with progress.

[Storkfoot]

Did the dyno operator give you a printout of the air fuel ratio throughout the throttle range?

[Pompeydave]

No, I’ll see if I can get a printout from him. Think each run is saved.

[Adam_Winstone]

Hi all, bike dyno run done on Saturday by Paul Jolliffe in Pompey.

The 25PHBL has the following spec:

Atomiser: AQ 266
Choke: 60
Main: 95
Pilot: 53
Needle: D22 on the top clip

It was also found to have a 30 slide, which was the cause of the low down slow running issue and over richness.

Tom Palmer was there and he thankfully supplied a spare 40 slide. Paul found that the choke cable was slightly tight and wasn’t always seating properly when turned off. The solution is to fit an elbow and slightly longer cable.

Also, he’s recommended that the jetting is about right with the main being slightly on the rich side of perfect for safer motorway running. He’s also suggested that I change the timing from 16BTDC to 19, and if it’s still is a big boggy low down, to try a 45 slide and then an AQ265 atomiser. Key point being to try one thing at a time.


Anyway, it instantly rides way cleaner low down with the 40 slide. Choke elbow and longer cable ordered and the timing change is up next. I’ll report back with progress.

Well, that 30 slide will certainly be the cause of richness low down! My own PHBL has progressed from 40 to 45, then onto 50 but with a richer atomiser.

NB: 19 degrees may be absolutely right for you bike's specifics, especially if low compression. However, do keep an eye on plug colour and ear out for any pinking as the last time a respected engine builder corrected a pal's very reliable Euro trekker's 16 to 19 when it went in to have seals replaced for the season ahead. After using it for local small road testing, he set off for Avignon and made it as far as Newbury (from Oxford)!!! Recovery, strip and new piston, with timing reset to the previously marked 16 degrees and his bike then ran to Avignon without issue, coving approx. 450 miles in a single day. Not bad for an iron 175 with a 22mm carb

[Warkton Tornado No.1]

As the consequence of more information being revealed as it goes along, I’m just ‘observing’ this Post as, to my mind, the carburettor settings have seemed all over the place.

I’ve yet to get my head around a main jet of 95 & wonder if that is a somewhat worn item

[Pompeydave]

No it’s a new carb bought in 2021. Is a 95 main too small then do you think? It’s done about 4000 miles in that time.

Re the timing it IS uber reliable at 16 BTDC, but it feels a bit short on power for quite a torquey kit that the Allstyles one is.

I was quoted only 11BHP by Johnny Gilbert when he dyno’d it on the Island two years ago. Feel it should make a bit more than that- maybe the 40 slide will help, maybe 19 BTDC will help further. I’ll try it at 19 and it’s being run on Paul Jolliffe’s dyno again next Saturday and he’ll give me a printout this time. I’ll update with findings.

Thanks for all the comments and advice chaps, it’s much appreciated.

[Pompeydave]

Hi all. Anyone know what to do next when trying to upload a photo of the dyno run I’m getting a message saying:

‘Sorry, the board attachment quota has been reached’.

[Toddy]

Hi all. Anyone know what to do next when trying to upload a photo of the dyno run I’m getting a message saying:

‘Sorry, the board attachment quota has been reached’.

You need to use a photo hosting sight like this

https://postimages.org/

[Storkfoot]

Hi all. Anyone know what to do next when trying to upload a photo of the dyno run I’m getting a message saying:

‘Sorry, the board attachment quota has been reached’.

You need to use a photo hosting sight like this

https://postimages.org/

When uploaded, click on “hot link for forums” and then click on the box at the right. That’ll give you the link to cut and then “paste” into this forum.

[Pompeydave]

cdn images

Hi all, here’s yesterday’s dyno run. The revs are doubled and the HP figure is 7BHP over actual due to a software glitch apparently so it’s making only about 10bhp currently. Thoughts?

[Storkfoot]

The Air Fuel ratio seems okay. It’s on the rich side of the line but not so far out that it should be the cause of poor running.

[Pompeydave]

Yep, the 30 slide seems to have been what caused it. This run was with the 40 fitted.

[Pompeydave]

I’ll try it again on the dyno once I’ve advanced the timing from 16 to 19 BTDC.