PHF accelerator jet angle?

rdvowles

rdvowles

New member
Location
Port Erin, Isle of Man
Anyone know if there's a set position for the accelerator jet to be angled at. I currently have them firing straight up but wonder if they should be firing down the carb into the inlet?
Cheers, Rob
 
The jet has a flat corresponding with a flat in its locating bore, should slide in easily and is then correctly positioned.

piet
 
When they are correctly located the fuel stream will squirt directly into the carb throat toward the engine.
 
sfcpiet said:
The jet has a flat corresponding with a flat in its locating bore, should slide in easily and is then correctly positioned.

piet
Click to expand...
sound about right ......accel pumps on Dells are soo over rated
 
I guess the left hand carb must have had the accelerator jet jammed in in the past as I had to lever it out with a plastic lever (toothbrush handle) and it will fit in at any angle but does fit less tightly if lined up properly. Also explains why I was having trouble calibrating it. I think the jet was pointing down after I first rebuilt it and the fuel would just ooze out of it. Now fitted correctly, it fires a jet of fuel through the carb into the inlet, much easier to catch & calibrate. The other two carbs were ok and the jets only fit when lined up correctly.

I've attached a picture of my hi-tech set-up for calibrating the accelerator jets  ;)  The carb mounting plate screwed to a length of 3"x2" timber and mounted in a B&D Workmate at about the right angle. I just mounted one carb at a time on the same end, connected to one of those small plastic fuel containers suspended from the rafters. then adjusted until 20 operations of the throttle gave 4cc of fuel.

Thanks,
Rob.
 

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That's the first time I've heard of anyone actually going to the trouble of measuring the accelerator pump delivery volume.
I use a simpler, but slightly less accurate method. I just have a look down the carb throat, and if it squirts, that's good enough.  :D
 
Dellortoman said:
That's the first time I've heard of anyone actually going to the trouble of measuring the accelerator pump delivery volume.
I use a simpler, but slightly less accurate method. I just have a look down the carb throat, and if it squirts, that's good enough.  :D
Click to expand...

RTFM Cam. :D

Different fuel volumes required for different applications, according to Dellorto/Laverda at least.  Most bikes can do very well without the troublesome things, but sometimes they are actually beneficial.

Calibrating pump volume is part of a proper overhaul of these carbs.

piet
 
Yeah, I know it's a bit lazy not to calibrate it.  But there's an on-going debate about whether you need accel pumps at all. So it seems these old softly tuned Laverda tractor engines will do OK with anything from zero to full pump flow. It's unlikely that a pump will deliver too much fuel (unless someone has fiddled with it) so if it has a healthy squirt and the engine runs OK, I'll leave it alone. I'd be a lot fussier if it was feeding a more highly strung engine like the V6, or if there was a massive flat spot in engine performance.
 
Accelerator squirt is so important on FCR carbs used on all dirtbikes before fuel injection. If it's not set well it can overwhelmed the engine causing a huge bog and even stalling or no punch from lack of juice down low. But thats on bikes running HUGE carbs. My 250 has a 37mm carb and 450s ran 41mm. That's like Ducatis running 40mm Dels,not easy to get them to pull right through the range.So that's probably why it's not so critical on Laverda with 32mm carbs.
 
Dellortoman said:
That's the first time I've heard of anyone actually going to the trouble of measuring the accelerator pump delivery volume.
I use a simpler, but slightly less accurate method. I just have a look down the carb throat, and if it squirts, that's good enough.  :D
Click to expand...

I'm with Cam. If I see mine a squirtin', they're workin'. I just had the carbs off and checked the float levels and pump action. My bike goes well. I don't think I would benefit much from calibrating 20 pumps to whatever.

My two Bobs worth.
 
Took mine off the Jota..no difference. Keith put them back in..so thats how it runs currently.Always wondered how it can be good to squirt neat fuel  in when blipping on a downchange...cant believe they all stay in sych either..is it possible to be definive about their effect  by some kind of test?
 
There objective is to allow big fist fulls of throttle to cause the bike to immediately accelerate.That full throttle effect is hard to do with the std 2 turns of your hand Laverda gadget.If your bike does this without the squirt, then you don't need them.I have told this one a few times here. I had a Husky 350 4 stroke that came with a Delordo. It had a horrible jerky throttle action that made it hard to ride in slow difficult terrain. I put this down to the extra friction of the pump gadget so I pulled the bit off that actives the squirt on the carb. That worked great,nice and smooth action but I then couldn't pull power wheel stands to get over logs and rocks.It just wouldn't instantly jump with a big fist full. I refitted the accelerator pump gadget to the slide and the instant power was back.They have a purpose.Maybe you dont jump logs on your Laverda so disable them and see
 
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