Wildguzzi.com
General Category => General Discussion => Topic started by: philwarner on December 08, 2019, 04:47:45 PM
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I switched to larger "Harley Style" grips on my 96 California because the smaller OEM throttle grip put my hand to sleep from having to grip it tightly, but the throttle effort is still quite high, much higher than my Triumph and stiffer than an ex-Guzzy rider thought it should be. the throttle cable seems to be free and the slides snap back with authority when it is released. Does anyone make/sell weaker carb springs for the Dellortos that would lessen the effort?
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There are several different levels of spring stiffness for Dellortos. I have purchased lighter springs from Bevel Heaven, which is my go-to place for carb parts.
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Does anyone make/sell weaker carb springs for the Dellortos that would lessen the effort?
http://www.mgcycle.com/index.php?main_page=product_info&cPath=62&products_id=2110
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I think I got mine from MG Cycle for my 96 Sport. But be warned! Happened to me ONCE. After a couple of miles of wide open riding, 135mph+, when I shut her down the slides didn't drop right away and my speed maintained for a couple of seconds which felt like much more, like 15 seconds. That's why they put those heavy springs in there.
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Not sure where I got the idea originally (I owned a MKII Le Mans in '82/83), but I thought 'Big Twins' with Slide Carbs needed strong return Springs to stop the Slides 'hanging up' if the Throttle was closed at high revs.
Something to do with the high Intake Vacuum?
Might be totally wrong, but it's one of those things you hear somewhere, and it sticks in the memory.
Ha-ha!
Guzzidad must have been typing while I was searching . . .
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http://www.mgcycle.com/index.php?main_page=product_info&cPath=62&products_id=2110
http://guzzino.com/thspphfphm30.html
https://www.dellorto.co.uk/shop/dellorto-motorcycle-carburettors-parts/carburettor-parts/phm-parts/internal-slide-spring-medium/
There are several different levels of spring stiffness for Dellortos. I have purchased lighter springs from Bevel Heaven, which is my go-to place for carb parts.
https://store.bevelheaven.com/Carb-Fuel-Related-etc/Slide-Spring-PHF-M/
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I’m sure there’s a liability reason for the stiff springs. The stockers in my LM V were so stiff they caused my hands to cramp. I’ve never had any trouble with the lighter ones.
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I don't have a photo but I use one of those thin rubber throttle rockers pushed over to rub on my handlebar-end mirrors. It holds the throttle lightly enough to take your hand off and the throttle does not snap back. Yes, kinda like a dead man throttle. But it's so easy to use that I did it to three cycles.
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I think I got mine from MG Cycle for my 96 Sport. But be warned! Happened to me ONCE. After a couple of miles of wide open riding, 135mph+, when I shut her down the slides didn't drop right away and my speed maintained for a couple of seconds which felt like much more, like 15 seconds. That's why they put those heavy springs in there.
Thanks to all for the links to the Dellorto springs. Perhaps the Guzzi guys I've met who thought my throttle was a lot stiffer then theirs had already replaced the heavy springs. I don't anticipate any prolonged 135 MPH rides, but I'll keep in mind the warning. Was your experience with the lightest springs? I am leaning toward the #8550 springs from MG Cycle that say made by Dellorto and are the lightest ones. My Triumph America is carbed and has a lighter throttle and I've not seen any slide sticking with it, but again no 135 MPH sustained rides and perhaps an apples to oranges comparison.
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I also have found the throttle rocker does the job. Simple enough.
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I've not had any sticking with the lighter springs, but like others, no sustained high speeds.
I do have an idea, though. If this really is a problem I think I've got a solution. There are three springs in these carbs - two inside the carb and one outside on the control arm. The small one inside the carb only retains the needle, so it stays. The large one, of course, gets replaced with a lighter one. It's the one outside I'm thinking of.
Replace that one with a shorter one that only comes into play at the last 1/4 travel of the arm, since full throttle is the problem.
My carbs have had those extra arms removed, so they're not needed for normal riding. But I might reinstall them for a little extra 'push' at the top end.
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It's nothing to do with sustained high speeds, or even speed itself.
It could happen in first gear, first pull-away of the day.
Anytime the Throttle is taken to Wide-Open, then shut suddenly (like when that myopic car driver pulls out on you), doesn't matter what gear or what speed you're doing.
It may not ever happen, probably depends a lot on the condition of the Slides and their Bores more than anything.
As long as you're aware it could happen, and can hit the Kill-Switch easily . . .
There were some Flat-Slide Carbs available years ago for big Guzzis (and other similar Engines), maybe still are, the Slides ran on Small Roller Bearings.
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Go with mediums - Light are too light, slides won't shut when revs are up high. Put many details on how to get lighter throttle on another thread on this topic...https://wildguzzi.com/forum/index.php?topic=93549.0
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don't forget that carbs with real pumpers (not vhbs) have a slide ramp operated pumper lever. you will feel a real increase in effort when the lever hits the ramp at 1/2 throttle. only way to lessen, remove lever and disable pumper
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40-mm carbs are much more prone to sticking with light springs than smaller carbs due to the greater slide area exposed to vacuum. I’ve installed much lighter springs on three sets of 36 mm carbs, ridden with them for maybe 130,000 miles total and never had a problem. The throttle pull is similar to modern bike when fitted.
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I got use to not having a throttle return spring on my older bikes because we took them off our police bikes. We had to have a free right hand on demand due to using the radio and other emergency equipment. Best cruise control available also.
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I put softer springs from MG cycle in my LeMans. Never had a problem with the slides hanging despite them being WFO a lot. Can't say they helped hand pain much though. I would try the Throttle Rockers first. Springs may help if you only ride for an hour or two but all day touring, not so much.
Pete
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If you do all the steps (medium springs and very clean, slick lubed grip and grip housing and cables routed well) your PHF 36s will be easy to operate without destroying your wrist. No modifications necessary.
Check your accel pumps by pressing them with a finger when your carb tops are off to install springs. You'll see how fun they are for your engine. ;)
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don't forget that carbs with real pumpers (not vhbs) have a slide ramp operated pumper lever. you will feel a real increase in effort when the lever hits the ramp at 1/2 throttle. only way to lessen, remove lever and disable pumper
Oh, and I forgot, if you have bell cranks on your carbs (nothing to do with the pump by the way), swap them out for flat tops. The bell cranks, make like a quick throttle decreasing throttle travel and increasing throttle effort. See Archimedes.
Along the same line, we should have a database of throttle barrel diameters. The larger the barrel, the softer (but further) it would turn. I suspect that the 2C throttle is softer than the monopoly piece throttles.
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I think I got mine from MG Cycle for my 96 Sport. But be warned! Happened to me ONCE. After a couple of miles of wide open riding, 135mph+, when I shut her down the slides didn't drop right away and my speed maintained for a couple of seconds which felt like much more, like 15 seconds. That's why they put those heavy springs in there.
That's a product of the Sport 1100 pressurized airbox, but without a return cable that sort of thing can happen to any Guzzi with Dellortos.
That used to happen on my Sport 1100 sometimes, when it still had the Dellortos. Problem was solved with FCR41 carbs.
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I installed the light springs from MG cycle in my PHM 40's- they are the lever style, and for insurance I trimmed back the return springs on the levers so they only activate at half throttle and up. Cruising effort is light, WOT is higher but still considerably lighter than stock which was ridiculous.
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Oh, and I forgot, if you have bell cranks on your carbs (nothing to do with the pump by the way), swap them out for flat tops. The bell cranks, make like a quick throttle decreasing throttle travel and increasing throttle effort. See Archimedes.
Along the same line, we should have a database of throttle barrel diameters. The larger the barrel, the softer (but further) it would turn. I suspect that the 2C throttle is softer than the monopoly piece throttles.
Normal way of saying this is degrees/ mm travel
2c throttle 120 deg/ 40. mm
Domino QA. 90/40mm
Me, I like slow action on road but never in my life, road or track have dellortos stuck, used the lightest springs with flat tops since 85 at least, even with QA throttle and 41.5 Malossi bored carbs.Same springs as ducati 900ss same 40mm carbs, funny how ducati owners never have this debate.
There is NO reason to suffer heavy throttle, blisters from 78-85 healed now but not forgotten
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Update: I received the lighter springs from MG Cycle and the ones I replaced were apparently the medium weight springs judging from their .0465 wire diameter. The twist at the throttle is much easier now and although the throttle does not quite return by itself, I don't think that will be a problem as the slides close nicely with a slight return rotation. It may even return by itself once the engine is vibrating the bars. (I am still working on the tank mounting and cleaning up a few things). I anticipate a much nicer ride when I get done.