'Blueprinting' a Jetex Carb

[turbovan]

I agree with muppet most of the objections against the jetex carbs are just snobbery, there is nothing fundamentally wrong with them. There are two main problems, strip the carb removing the float valve and fuel filter cover, get a 2.2mm drill and carefully push it shank end first up the float valve hole to the area behind the filter, you will find in most cases there is an obstruction as the fuel comes from behind the filter and down to the float valve, very carefully drill the needlevalve hole right up to the top and you will remove the restriction to flow at the top of the hole. Clean the body well after doing this. For big CC motors you can drill the needle valve seat and hole to 2.3mm or even 2.4mm. The next problem is on tuned motors the atomiser is approx 1.7mm hole size (2) and a 5899-1 (1.5mm) richest is required, the number of people siezing motors whilst high speed cruising on the original number 2 .......... also... the jets may say one number, but when you measure them accurately they are almost always bigger, for example a 128 main is 1.3 mm hole size, a 130. the airflow is no different to a 22 Dellorto and a 24mm version is avalible and plenty of people have reamed them to 25 or 26mm. If you want to throw them in the bin, throw them my way first!

[Doom Patrol]

That's interesting stuff. I do have a Jetex carb I use as a spare. I'm going to give that a go I think. What would you class as larger CC? I'm thinking 185.

[rosscla]

....there is nothing fundamentally wrong with them....

Then goes on to give us ten lines of explanation of what's fundamentally wrong with them.....

The drillings
The float valve
The atomiser
The jets

So that must mean the slide and spring are good...

[joeswoonara]

....there is nothing fundamentally wrong with them....

Then goes on to give us ten lines of explanation of what's fundamentally wrong with them.....

The drillings
The float valve
The atomiser
The jets

So that must mean the slide and spring are good...

[soosh]

I'm thinking Triggers broom.

[Muttley McLadd]

ok whatever,everyone to there own, i'll stick with the jetex till it goes wrong then try a PHBH but i expect that will make a bigger splash.

PHBH wont go wrong. Do it properly and it'll be fine.

[Doom Patrol]

Let's not go off on a Jetex V PHBL because they are altogether different. The Jetex isn't perfect by any means. The Jets are iffy and apparently the needle can be obstructed. The fact remains that a lot of them do work and with slight tweaks they can work even better. What's not to like? I know I'd take the usability of the Dell'orto design over a more complex PHBL when it comes to faffing around in the garage.

[dennis]

I think the answer is in the titlle, isn't that what turbovan is doing when he works on a jetex, you try bolting any ph,mikuni carb on a lambretta and you have to set it up, friend of mine has got a tub full needles and jets for ph carbs which he has had to buy try to set up ph carbs, he has now gone back to a sh22 delorto bored to 26mm and still uses a jetex on his other scoot, yes jetex arn't the best but once set up do the job.

[Doom Patrol]

Points and Jetex carbs. The way forward.

You've got to wonder though. With the variability of modern fuels if the precise settings on a PHBL carb don't make them more susceptible to going off track? Maybe the broad broom approach of a traditional carburettor is safer in this day and age? Just saying....

[Muttley McLadd]

You've got to wonder though. With the variability of modern fuels if the precise settings on a PHBL carb don't make them more susceptible to going off track? Maybe the broad broom approach of a traditional carburettor is safer in this day and age? Just saying....

A PHBH is pretty traditional, and not exactly cutting edge.

I'd be more concerned about a 'modern' exhaust gasket falling to bits and fu cking up my engine than a bit of crap fuel.

Who uses a 22mil carb these days anyway? Tortoises?