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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Mikuni carb size
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<blockquote data-quote="BigEd" data-source="post: 16815" data-attributes="member: 161"><p><strong>Mikuni carb size (28mm jetting)</strong></p><p></p><p><span style="font-family: 'Verdana'"><span style="font-size: 15px">Dear John,</span></span></p><p><span style="font-family: 'Verdana'"><span style="font-size: 15px">When I first built my Rapide I persevered for several thousand miles with a pair of second-hand 1-1/8 Monobloc carbs that stuck open over half throttle. I quite like the Monobloc as a carburettor but after much unsuccessful fettling I decided that enough was enough. I considered the options, new original type 276, reconditioned or new monobloc or new Mikuni. I built the bike to ride so originality is not a prime consideration. (Function over form.) Mikuni's are definitely not original but are nicely made with bodies of a good alloy and chrome plated brass slides so they will last. a pair of VM 28mm Mikuni's also cost less than the other options. Motocarb supplied the carburettors with the following settings:</span></span><span style="font-size: 15px"> * <span style="font-family: 'Verdana'"><span style="color: black">Main Jet 190</span></span></span></p><p><span style="font-size: 15px"> <span style="font-family: 'Verdana'"><span style="color: black">Needle Jet P-6 (182)</span></span></span></p><p><span style="font-size: 15px"> <span style="font-family: 'Verdana'"><span style="color: black">Needle 5FL 14 (I put it in the middle notch.)</span></span></span></p><p><span style="font-size: 15px"> <span style="font-family: 'Verdana'"><span style="color: black">Slide 2.5</span></span></span></p><p><span style="font-size: 15px"> <span style="font-family: 'Verdana'"><span style="color: black">Pilot Jet 30</span></span></span></p><p><span style="font-size: 15px"> <span style="font-family: 'Verdana'"><span style="color: black">Air Jet 2.0</span></span></span></p><p><span style="font-family: 'Verdana'"><span style="font-size: 15px">The Mikuni's are stub fitting so I made up some adaptors and used a suitable size radiator hose and Jubilee clips to secure them. You will also probably have to make up some new throttle cables. I concocted something that worked using a mix of original cables and some </span></span></p><p><span style="font-family: 'Verdana'"><span style="font-size: 15px">pieces of stainless bi-cycle cable from Halfords. There are no chokes as such but there is a start lever that in effect uses a seperate set of passages to supply a rich starting mixture. Engage the start levers, keep the throttle shut and it usually starts first or second kick.</span></span></p><p><span style="font-family: 'Verdana'"><span style="font-size: 15px">The engine immediately had a regular tickover, something I had never quite achieved with the worn Monobloc's. (New monobloc's probably would have achieved the same.)</span></span></p><p><span style="font-family: 'Verdana'"><span style="font-size: 15px">I have experimented with a few settings. I put in 160 main jets, leaned off the pilot screws, lowered the needle and eventually put the needle in the lowest notch. It was perhaps not quite as "drivable" but still OK. On a fairly steady two up run from Hinckley to Malvern I got almost 65 mpg. Note that this is a corrected figure as the odometer is a little generous with the miles when compared to the Garmin GPS I use. It is generally doing 50 - 60 mpg depending on the type of riding I'm doing. The engine has MK1 cams and 7.3:1 pistons. I use the cheapest regular fuel that I can find locally, usually at Morrison's just around the corner.</span></span></p><p><span style="font-family: 'Verdana'"><span style="font-size: 15px">The magneto is one of Tony's new BT-H items, sparking twin plugs with the advance set to around 30 - 32 degrees BTDC. The silencer is one from the spares company and sounds fairly free flowing. I have two spare slides that I may make into 3's to see how they work. </span></span></p></blockquote><p></p>
[QUOTE="BigEd, post: 16815, member: 161"] [B]Mikuni carb size (28mm jetting)[/B] [FONT=Verdana][SIZE=4]Dear John, When I first built my Rapide I persevered for several thousand miles with a pair of second-hand 1-1/8 Monobloc carbs that stuck open over half throttle. I quite like the Monobloc as a carburettor but after much unsuccessful fettling I decided that enough was enough. I considered the options, new original type 276, reconditioned or new monobloc or new Mikuni. I built the bike to ride so originality is not a prime consideration. (Function over form.) Mikuni's are definitely not original but are nicely made with bodies of a good alloy and chrome plated brass slides so they will last. a pair of VM 28mm Mikuni's also cost less than the other options. Motocarb supplied the carburettors with the following settings:[/SIZE][/FONT][SIZE=4] * [FONT=Verdana][COLOR=black]Main Jet 190[/COLOR][/FONT] [FONT=Verdana][COLOR=black]Needle Jet P-6 (182)[/COLOR][/FONT] [FONT=Verdana][COLOR=black]Needle 5FL 14 (I put it in the middle notch.)[/COLOR][/FONT] [FONT=Verdana][COLOR=black]Slide 2.5[/COLOR][/FONT] [FONT=Verdana][COLOR=black]Pilot Jet 30[/COLOR][/FONT] [FONT=Verdana][COLOR=black]Air Jet 2.0[/COLOR][/FONT][/SIZE] [FONT=Verdana][SIZE=4]The Mikuni's are stub fitting so I made up some adaptors and used a suitable size radiator hose and Jubilee clips to secure them. You will also probably have to make up some new throttle cables. I concocted something that worked using a mix of original cables and some pieces of stainless bi-cycle cable from Halfords. There are no chokes as such but there is a start lever that in effect uses a seperate set of passages to supply a rich starting mixture. Engage the start levers, keep the throttle shut and it usually starts first or second kick. The engine immediately had a regular tickover, something I had never quite achieved with the worn Monobloc's. (New monobloc's probably would have achieved the same.) I have experimented with a few settings. I put in 160 main jets, leaned off the pilot screws, lowered the needle and eventually put the needle in the lowest notch. It was perhaps not quite as "drivable" but still OK. On a fairly steady two up run from Hinckley to Malvern I got almost 65 mpg. Note that this is a corrected figure as the odometer is a little generous with the miles when compared to the Garmin GPS I use. It is generally doing 50 - 60 mpg depending on the type of riding I'm doing. The engine has MK1 cams and 7.3:1 pistons. I use the cheapest regular fuel that I can find locally, usually at Morrison's just around the corner. The magneto is one of Tony's new BT-H items, sparking twin plugs with the advance set to around 30 - 32 degrees BTDC. The silencer is one from the spares company and sounds fairly free flowing. I have two spare slides that I may make into 3's to see how they work. [/SIZE][/FONT] [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Mikuni carb size
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