Hi all,
I have a 501 engined 3 1/2 which I was lucky enough to buy already built, it has PHBH26BS carbs on it, the info. on the Dutch clubs site tells me it should have 28mm carbs.
I am wondering if this is wrong for this engine or if the site has it wrong?
Is there likely to be a real world gain from changing them, and has anyone got any not in use, that they would be prepared to sell.
Any info. greatly appreciated.
Pete
501 carbs
Re: 501 carbs
Well if it really is a 501 (a Camel derived 501 looks just like a 500) then it would have had 28mm carbs (or even 30mm 'pumper' carbs for the USA).
You might gain something at full throttle and high rpm with the bigger carbs, but if you don't use high rpm and full throttle much, then what's the point?
Spend the money on a dyno session to get the carbs you have jetted as well as they can be.
You might gain something at full throttle and high rpm with the bigger carbs, but if you don't use high rpm and full throttle much, then what's the point?
Spend the money on a dyno session to get the carbs you have jetted as well as they can be.
Paul Compton
http://www.morini-mania.co.uk
http://www.youtube.com/user/EVguru
http://www.morini-mania.co.uk
http://www.youtube.com/user/EVguru
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'It must be a .....'
- Posts: 369
- Joined: 12 Sep 2010 12:25
Re: 501 carbs
Hi, if it has a 501 motor it will run much better with the original 28mm carbs, even low down it will respond much better and cleaner.
The 501 carburation is generally much better than the 26mm carb 500.
The 501 carburation is generally much better than the 26mm carb 500.
Re: 501 carbs
Thanks Paul,
Yes, it is a late 501 so I've been told although I have no real idea of it's origins. I would imagine the carbs were what the builder had, as the ole in the ead is near to 30mm.
It tends to get run flat out at Cadwell and sometimes mallory, also I've done a few BEMSEE "parades" at Brands so she does get hammered a fair bit.
I recently had it on a dyno and she revs straight through very well with a very flat torque curve, the only problem is that she is only putting out about 29 bhp at the rear wheel which is loads down on what I thought she should be doing.
A lot of this is probably due to the very quiet, very restrictive silencers, not sure whether to think of getting a new system made, if I did, 2 into 1 or 2 into 2 ? or whether to simply drill some holes in the end of my ones.
Hence my wondering about sourcing the correct size carbs, and what the improvement might be. She has also always been a pig to start despite NLM's attentions, I'm even starting to wonder if I might have 2 stroke carbs but am not sure what the diference is with Dellorto's.
Yes, it is a late 501 so I've been told although I have no real idea of it's origins. I would imagine the carbs were what the builder had, as the ole in the ead is near to 30mm.
It tends to get run flat out at Cadwell and sometimes mallory, also I've done a few BEMSEE "parades" at Brands so she does get hammered a fair bit.
I recently had it on a dyno and she revs straight through very well with a very flat torque curve, the only problem is that she is only putting out about 29 bhp at the rear wheel which is loads down on what I thought she should be doing.
A lot of this is probably due to the very quiet, very restrictive silencers, not sure whether to think of getting a new system made, if I did, 2 into 1 or 2 into 2 ? or whether to simply drill some holes in the end of my ones.
Hence my wondering about sourcing the correct size carbs, and what the improvement might be. She has also always been a pig to start despite NLM's attentions, I'm even starting to wonder if I might have 2 stroke carbs but am not sure what the diference is with Dellorto's.
Re: 501 carbs
My 501-engined 3 1/2 has 28mm Dellortos and was a beautifully responsive and torquey first-kick starter until I had a slight off which put everything out of synch; the carbs have now been cleaned and probably just need rebalancing.
"I'll have a V please, Bob."
Re: 501 carbs
Hi Mark,
I understand you have Paul Miles old bike, it would be interesting to get together one day, probably next year now! and compare them.
Mine is a first kick starter sometimes, others it's a twelth kick starter.
I just though I should clear up any confusion, Moggie and Pedro are both me, the result of using someone elses computor and search engine, and having brain fade over my details.
My comment about two stroke carbs results from me looking on ebay for PHBH carbs and noticing that most are for the racing scooter boys, they seem most readily available.
I heard about your off and hope all is back to normal now.
Regards
Pete
I understand you have Paul Miles old bike, it would be interesting to get together one day, probably next year now! and compare them.
Mine is a first kick starter sometimes, others it's a twelth kick starter.
I just though I should clear up any confusion, Moggie and Pedro are both me, the result of using someone elses computor and search engine, and having brain fade over my details.
My comment about two stroke carbs results from me looking on ebay for PHBH carbs and noticing that most are for the racing scooter boys, they seem most readily available.
I heard about your off and hope all is back to normal now.
Regards
Pete
Re: 501 carbs
Hi Pete, yes it's Paul's Moreini, and it really was a grin-inducing beast (and will be again!) It would be good to meet and discuss machines; I'm in Stevenage, so if you're around, or feel like a ride out, do let me know. I'm now riding again after a year's break, and it's wonderful to be on two wheels again!
Regards, Mark.
Regards, Mark.
"I'll have a V please, Bob."
Re: 501 carbs
Is there a consensus on best carb settings for a 501 engine with a standard 500 (roadster) airbox? I assume the jetting for an ex camel 501 engine with standard L cam is going to be rather different when fitted to an early 500 chassis with the standard 478 airbox. Other's experience might save me a lot of trial and error!
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swtuggle
- Posts: 47
- Joined: 24 Oct 2011 02:36
- Location: Steilacoom, WA, USA
- Location: Steilacoom, Washington, USA
Re: 501 carbs
PHBH28BS: 50 chokes, 50 slides, 53 pilots, 132 mains, X6 needles on top groove, 268T atomizers.
This is an otherwise-stock Excalibur 507 with deflowered Excalibur/Camel/Dart type airbox with moderately baffled exhaust. Running a much-improved 39 tooth versus original 45 tooth sprocket. Don't know how a 500 airbox flows in comparison.
Characteristics: Tickover around 1200 rpm; pulls well from 2500 on up; very good transition/progression circuit at 1/8 to 1/4 throttle; no bog, lag or stumble when throttle is opened, either slightly or whacked open.
I believe it was Morizzi who said his 500 Sei wouldn't run with the jets I listed, but it has taken these sizes to eliminate the stuttering I was experiencing at specific rpm/throttle positions.
This is an otherwise-stock Excalibur 507 with deflowered Excalibur/Camel/Dart type airbox with moderately baffled exhaust. Running a much-improved 39 tooth versus original 45 tooth sprocket. Don't know how a 500 airbox flows in comparison.
Characteristics: Tickover around 1200 rpm; pulls well from 2500 on up; very good transition/progression circuit at 1/8 to 1/4 throttle; no bog, lag or stumble when throttle is opened, either slightly or whacked open.
I believe it was Morizzi who said his 500 Sei wouldn't run with the jets I listed, but it has taken these sizes to eliminate the stuttering I was experiencing at specific rpm/throttle positions.
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moriniboy23
- Posts: 33
- Joined: 30 Mar 2009 17:52
Re: 501 carbs
53 pilots?! Blimey. Im still playing with the jetting on my 501 engined 350 but it starts without choke and runs lumpy on 42s! Im just about to try some 40s. The standard pilots were 38s in the Excalibers in Europe...
Re: 501 carbs
So difficult to advise on defiitive jetting on any bike let alone one that is no longer standard fitted with OEM carbs.
I agree with Paul (guru) above that sorting the 26mm carbs would be a better prospect as long as you aren´t a WOT or WFO type. Riding style and road type has a lot to do with it. A race bike and road bike have different needs and even 2 nearly identical bikes can be jetted differently due to internal wear and ignition differences.
There is more than one way to skin a cat too. If you look at the jetting swtuggle suggests then his X6 needle is just a tad leaner than the X1 at lower openings. Use X1 and you would most probably want a smaller idle jet. A 268 atomiser seems also quite large so a slightly smaller one and the needle raised should give similar results.
The trick is to get an even spread of fuel delivery through the circuits and through the opening range. The Dellorto tuning guide is good but simplistic. All circuits are working at all times but they have areas where they are more influential than others due to proportioning.
Once you have it close then riding style comes in due to revs. RPM is directly linked to piston speed and this is directly linked to air velocity through the venturi. (Bernoullis Principle) At the same throttle opening in different gears the mixture will change. The higher the gearing the leaner the mixture. This is a fine adjustment and not for initial set up though so swtuggles recommendation on his Excalibur won´t have true relevance for a track day bike.
53 idles sound high too but he is using 50 slides. It will be interesting to know how many turns he has out on his mixture screws. If in good condition that can be an indicator. I have 43 slides in my 500. I modified them myself and one cylinder prefers a different main to the other. 130F/127R. Mine isn´t a 501 engine and it has 26 PHBH´s. 28´s have a 15% greater choke area but the 501 only has a 6% greater displacement thus only 6% more air trying to get through a door that is 15% bigger so venturi velocity is lower thus slightly larger jetting is needed to compensate. Remember that the area of a circle is a squared function and that the smaller the circle area then proportionally the greater the contact with the sides so boundary effect plays a small resistance part too.
Hope this helps and doesn´t confuse.
Rod
I agree with Paul (guru) above that sorting the 26mm carbs would be a better prospect as long as you aren´t a WOT or WFO type. Riding style and road type has a lot to do with it. A race bike and road bike have different needs and even 2 nearly identical bikes can be jetted differently due to internal wear and ignition differences.
There is more than one way to skin a cat too. If you look at the jetting swtuggle suggests then his X6 needle is just a tad leaner than the X1 at lower openings. Use X1 and you would most probably want a smaller idle jet. A 268 atomiser seems also quite large so a slightly smaller one and the needle raised should give similar results.
The trick is to get an even spread of fuel delivery through the circuits and through the opening range. The Dellorto tuning guide is good but simplistic. All circuits are working at all times but they have areas where they are more influential than others due to proportioning.
Once you have it close then riding style comes in due to revs. RPM is directly linked to piston speed and this is directly linked to air velocity through the venturi. (Bernoullis Principle) At the same throttle opening in different gears the mixture will change. The higher the gearing the leaner the mixture. This is a fine adjustment and not for initial set up though so swtuggles recommendation on his Excalibur won´t have true relevance for a track day bike.
53 idles sound high too but he is using 50 slides. It will be interesting to know how many turns he has out on his mixture screws. If in good condition that can be an indicator. I have 43 slides in my 500. I modified them myself and one cylinder prefers a different main to the other. 130F/127R. Mine isn´t a 501 engine and it has 26 PHBH´s. 28´s have a 15% greater choke area but the 501 only has a 6% greater displacement thus only 6% more air trying to get through a door that is 15% bigger so venturi velocity is lower thus slightly larger jetting is needed to compensate. Remember that the area of a circle is a squared function and that the smaller the circle area then proportionally the greater the contact with the sides so boundary effect plays a small resistance part too.
Hope this helps and doesn´t confuse.
Rod