GP150 lockdown project

[Storkfoot]

I put the shiney stand on for the time being.

Then moved on to the headset. I tried to fit the gear change (expensive one from a well known Italian make). That didn’t go well. The handle part is out of plane with the housing part so when you twist it, one side grinds in to the handlebar. That will be going back.

I then moved on to the throttle side to encounter this:



At this point, I laughed and packed up for the day

[Toddy]

I put the shiney stand on for the time being.

Then moved on to the headset. I tried to fit the gear change (expensive one from a well known Italian make). That didn’t go well. The handle part is out of plane with the housing part so when you twist it, one side grinds in to the handlebar. That will be going back.

I then moved on to the throttle side to encounter this:



At this point, I laughed and packed up for the day

No national winners then

[Fast n Furious]

Aye....gonna need some longer handlebar grips there matey.

[Storkfoot]

I’d forgotten the National was on to be honest but, then again, I never pick the winner

The dremel was called in to action to allow me to fit the grip. Job done and on to the next part that needs to be battered into submission to enable it to be fitted

[Storkfoot]

The way the breath sweet filter compresses against the panel is far from ideal.

I have run this engine on 3 previous scooters but they have had either standard tanks or a twin tank conversion. The large PHBH and Breath Sweet filter has not been an issue on these scooters but it is now with a toolbox and the larger tank with full length cutout.

[Toddy]

Will it fit better horizontally Paul?

[Storkfoot]

Will it fit better horizontally Paul?

I hadn’t thought to try, mate. It’ll definitely stop the compression of the foam part but it just looks wrong and points the filter towards all the muck coming off the back wheel.

But, thanks for the idea. I shall consider it

[Warkton Tornado No.1]

You could keep the elbow but manufacture a bespoke foam filter.

Sheet foam is available & can be shaped to fit the space available.

My thinking would be two undersize oval ends, one with hole to suit the elbow. The wraparound 'cylinder portion is then hot glued to the ends. if you think of how an oval silencer is made, the principle is the same.

if you wanted, there could even be a spout connection to the air scoop hole (50 mm bore) with a foam baffle piece internally so that a mix of some fresh, filtered air would mix in with the under panel 'stagnant' filtered air.

I have found that good filter foam barely affects the carburation but that the connection elbow volume is quite critical. Even a 40 mm bore elbow with no filtration fitted will choke the Dell'Orto you have. Well, it does on my engines PH's do not have a built in, well though out overflow/anti-flood as some carbs do. Another reason that PWK's are a revelation

Dell'Orto PH range are very prone to hot start issues as in the kind of flooding you can barely see. The fuel expands in the carb & richens up enough to cause problems on attempting to restart. You may need to add an overflow to the bellows. An old bicycle gutted inner tube valve suffices, as low as can be fitted, with a piece of plastic/rubber pipe stuffed with a bit of wire wool @ the exit to avoid dirty air getting sucked in. The pipe can even be routed through the flywheel cover clip (if one is fitted as with early GP's)

I hope that helps

[Covboy]

My breath sweet on a 25 mm dellorto fits fine horizontally, no issues

[dickie]

I run a breathe sweet vertically on a 175 with 28mm phbh. The foam and the elbow both get squeezed with the panel on. It's on an LI series 3.

We tried it on Mick Abbey's dyno with panel on and off and couldn't see a difference at all; just the difference you see between dyno runs.

I certainly wouldn't rush to say "it makes no difference", just because it didn't in my case. Especially as mine is a low power 13bhp motor and consequently not exactly gulping air. But it certainly came as a surprise to me.

[Storkfoot]

Thanks, all.

I am in no rush to get rid of the Breath Sweet filter as it is one of the best bits of kit I have ever bought for a Lambretta. From memory, this engine dynoed better with the filter than open mouthed.

My GT inlet manifold is downdraught which is not helping. There’s a good 3cms between the carb and the cowling. Also, the thickness of the PHBH is 90mm whereas a TM24, say, is 75mm.

This picture shows the space for the filter. It is only 5cms wide between the toolbox and the tank whereas the mouth of the elbow is 6cms, ignoring the red ring at the base of the filter itself which is wider still.



Food for thought

[Rich Oswald]

Will it fit better horizontally Paul?

That's exactly what I was going to say and they don't seem to get any dirtier that way. Also the advantage of using it horizontal is you don't get the chugging on start up due to spit back.

[Storkfoot]

Setting up the reverse pull drum brake



Another option to try filter wise. It’s a sock type Ram Air.

[Storkfoot]

You could keep the elbow but manufacture a bespoke foam filter.

Sheet foam is available & can be shaped to fit the space available.

My thinking would be two undersize oval ends, one with hole to suit the elbow. The wraparound 'cylinder portion is then hot glued to the ends. if you think of how an oval silencer is made, the principle is the same.

if you wanted, there could even be a spout connection to the air scoop hole (50 mm bore) with a foam baffle piece internally so that a mix of some fresh, filtered air would mix in with the under panel 'stagnant' filtered air.

I have found that good filter foam barely affects the carburation but that the connection elbow volume is quite critical. Even a 40 mm bore elbow with no filtration fitted will choke the Dell'Orto you have. Well, it does on my engines PH's do not have a built in, well though out overflow/anti-flood as some carbs do. Another reason that PWK's are a revelation

Dell'Orto PH range are very prone to hot start issues as in the kind of flooding you can barely see. The fuel expands in the carb & richens up enough to cause problems on attempting to restart. You may need to add an overflow to the bellows. An old bicycle gutted inner tube valve suffices, as low as can be fitted, with a piece of plastic/rubber pipe stuffed with a bit of wire wool @ the exit to avoid dirty air getting sucked in. The pipe can even be routed through the flywheel cover clip (if one is fitted as with early GP's)

I hope that helps

I’d be interested if you could send me links for the foam and glue you use please

[Warkton Tornado No.1]

Sorry for the delay, but this is the kind of stuff I've used:

https://www.ebay.co.uk/itm/15mm-Air-Fil ... SwRYJgd1vn

Somewhere on this Forum I posted some pictures, but as I seem to be so vocal(!) they'll take some finding.

If you do want images, I will find some.

[dickie]

Setting up the reverse pull drum brake

I've done 2 reverse pull drums. Both were very effective and I still run one now. The first one I did used a gp cam and while it stopped well, it came on so suddenly that I was scared to touch the lever! So I put it back to standard.

I'm not certain that it was the different cam that caused this, but it's all i can think of.

Just a tip in case you find the same issue.

[Storkfoot]

I've done 2 reverse pull drums. Both were very effective and I still run one now. The first one I did used a gp cam and while it stopped well, it came on so suddenly that I was scared to touch the lever! So I put it back to standard.

I'm not certain that it was the different cam that caused this, but it's all i can think of.

Just a tip in case you find the same issue.

Cheers. I too ran one on another scooter fitted with this engine. I have spent some time fettling the shoes to try and ensure they both engage at the same time. I shall consider what you say about the GP cam if it is fierce

[Storkfoot]

Sorry for the delay, but this is the kind of stuff I've used:

https://www.ebay.co.uk/itm/15mm-Air-Fil ... SwRYJgd1vn

Somewhere on this Forum I posted some pictures, but as I seem to be so vocal(!) they'll take some finding.

If you do want images, I will find some.

Thanks. I have ordered some and I know someone with a hot glue gun. Worth a go anyway

I found this which is not what you refer to but is interesting anyway.

viewtopic.php?f=7&t=7385&p=63476&hilit=Filter#p63476

[Warkton Tornado No.1]

I've done 2 reverse pull drums. Both were very effective and I still run one now. The first one I did used a gp cam and while it stopped well, it came on so suddenly that I was scared to touch the lever! So I put it back to standard.

I'm not certain that it was the different cam that caused this, but it's all i can think of.

Just a tip in case you find the same issue.

Cheers. I too ran one on another scooter fitted with this engine. I have spent some time fettling the shoes to try and ensure they both engage at the same time. I shall consider what you say about the GP cam if it is fierce

i ran a TV175 S2 drum brake whilst saving for a hydraulic inboard disc on track. Very effective but you must be cautious in the wet. I tapered the ends of each shoe & used only OEM with the GP cam.

I think the longer clutch arm fits the same splines for more feel.

Having had a cable pear shaped nipple come off, I remind everybody that 'we' could probably all benefit from a trustworthy Bowden cable & think a 3 mm inner could be accommodated for even further improvement. Any thoughts? i am aware of the barrel nipples that do away with the OEM fitting in the lever, but they are not as good even as a clutch cable IMHO & experience

[Storkfoot]

The cable I have fitted is the one sold for the disc brake. The diameter of the cable is 2mm with the outer 7.5mm. To be honest, neither the inner or outer appear as substantial as they last time I built a reverse pull drum three or four years ago. The petrol hose is being used to firm up the cable.

I am no expert but a thicker cable with a pre formed “u” bend at the hub end would make life easier. This would mean soldering or forming your own barrel attachment at the headset end though.