My Cagiva MITO Is Basically a MITO SP 94/95 Without the Limitat
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Marzo 2005 Rev.3 TUNING THE MITO My Cagiva MITO is basically a old MITO SP 93 without the limitations given for the Italian 125 sport pro championship. This article contains a listing of possible changes in what regards the Cagiva MITO engine. As a choice there is also an article from MOTOTECNICA (12/95) on the setup of the MITO standard engine. The changes made on the engine of my MITO, that could also be applied to a standard engine, and other, are here underlined: • compression ratio and squish: In dependence of your fuel quality use 14-15:1 compression ratio (first MITO had 11.8:1 ; last MITO '93 had 15:1) and for the squish diagram 0.80mm (first MITO 1.2 ; last MITO 0.8mm). If you want better acceleration use conic squish: 0.75mm external – 0.85mm internal. • ignition timing: I suggest 1.60mm to 1.70mm piston stroke (first MITO 1.0mm- 14.30°, last MITO 1.8mm, MITO Racing 1.55mm-18°) Lower values are associated to a better final velocity, higher values to a better acceleration. If you race, you could also modify the ignition timing curve (as on the Mito SP) bringing it to zero after the max power region, to earn a few revs. Attention: this operation is exclusively for racing bikes, because the motor heats very much and you may experience breakdown. • exhaust: I use the MITO SP '95 exhaust with the original silencer MITO EV. I suggest for the Mito 2 ->’93 and Mito ev owners to hand-make an exhaust based on the one of the MITO 2 '93 or MITO EV and ABSOLUTELY use original silencers MITO 2 '93 or MITO EV. You can purchase the entire exhaust and silencer from JollyMoto (for your specific Mito version) but they produce less performance. In Italy you can find many craftsman who build very good exhausts (my preference is for Figaroli), but they are probably difficult to find out of the country. If you use in extreme conditions the bike (for example competition) you should insulate with some thermal insulator the final part of the expansion chamber. Attention: if you change only the silencer, an inferior internal diameter gets more revs, a greater internal diameter gets better acceleration. A wrong silencer can decrease performance! • carburettor and carburation: I use CIM by Dell'Orto VHSA Venturi diameter: 32 mm High speed Jet: 167 (10°C) , 165 (20°C) , 163 (25°) Starter Jet: 48 Throttle Piston: 55 Metering pin: U19 Metering pin position: 1nd Main Nozzle: ET262 You must adapt the suction coupling between the carburettor and the blade valve. Do not take away the airbox but use sponge with more open cells. The exact carburation is very important to have good performances and to ensure engine reliability and lasting. A helping can be the picture in the Cagiva workshop manual. For this last operation some experience is needed. With the changes made until now, you could be using (probably) the same carburation for the Dell'Orto 32. It is recommended to start with a higher mainjet, verifying the carburetion, and then eventually decreasing it. The less experts, during summer, on the original engine can simply reduce the high speed jet by 2-3 points. The last MITO EV uses a MIKUNI 35. Using big carburators, the carburation is very sensitive to climatic condition (temperature, pressure); bad carburation involves sensible decrease in performance and higher fuel consumption. Eventually use elliptic carburators that assure a more gradual response to throttle aperture. I judge that the standard single sheet carbon fiber blade valve is too stiff and prefer the fiber glass blade valve. Indicativally a stiff blade valve warrants more revs, a less stiff blade valve gets better acceleration. • heads: They have a different shape depending on the pistons, therefore the ones of the Mito '92 and newer have a different combustion chamber. Even the compression ratio changes. Measure the compression ratio and verify squish and, if necessary, model the head. To obtain more revs over the max power peak you must round off (only a little) the corner between squish area and combustion chamber. The following is a schematic of a two ring piston head (Mototecnica 12/95): Figura 1 - Two ring piston head The following drawing represents the head for of the single ring pistons designed by a friend of mine for my Mito (thanx Pier!). I use it on my motorcycle for everyday use, with 100 octane W-Power gasoline, which can usually be found at Italian Shell gas stations. The compression ratio is 14,9:1, and guarantees a good acceleration. Figura 2 - Single ring piston head, only for competition • cylinder: I use a SP '93 cylinder. The SP cylinders are the best ones. As an alternative it is possible to use the '93 cylinder or more recent ones and eventually prepare them. The '93 cylinders have the exhaust outlet diamenter of 35mm, those before 33mm!! Take care of the connection between the cylinder and the carter and of the gasket between these two elements. The Polini 165 kit has not as high performance as the SP cylinder, although it can be prepared. Unfortunately the kits pistons are of poor quality. • piston: I use the single ring piston '93 (Vertex or the good and expensive Mahle) that is a little bit more performing, but the ring lasts less time in respect with the two rings of the first series piston. The two ring pistons have a different profile and weigth more, but the rings and pistons must be changed after 15000 Km. Cagiva says that the best mating clearance is 0.045-0.055mm (wear limit 0.080mm). • sparkplug: Recommended: NGK B95EGV (or BR10 EGV). • primary drive and clutch: The Mito SP, Racing and Mito ev use primary transmission with straight sprockets. This has better rendering and is compatible with all old engines. If you have the possibility, use it! I normally use aftermarket clutch and the reinforced springs used on Mito SP. Many of the operations listed require experience and special tools! To lighten the Mito you can use the Marchesini wheels of the Mito SP (1 kg rotational mass to 4 kg suspended mass). Fairing in fibre glass or carbon fibre and screwings in ergal and titanium (expensive). I have seen some Mitos travelling with Marchesini and Marvic magnesium wheels adapted for it. Another operation can be the substitution of the original brake tube (although fairly good) with one covered by kevlar. Use the original Cagiva (manufactured by Brembo), Brembo or Ferodo Racing (mixture 459) brake pad. Use high quality chain and keep it greased. In the rich carburated and badly utilized engines, inconvenients may occur in the exhaust valve, so there's the need of cleaning it periodically. In the first MITO change the exhaust valve with the one of the 2nd series. When you change the piston, verify that the clearance between exhaust valve and piston is 0.70mm!! In the 1st series MITO the electronic circuitry begins to open the exhaust valve at about 7250 rpm while the others at 8000 rpm. I use Motul 600 oil, and Agip oil recommended by Cagiva for the clutch. A note: please do not mail me questions on how to measure compression ratio, squish… etc. If you do not know how to make these measurements it is best that you don’t try the modifications. These modifications generally don’t reduce the reliability of the engine, if well done, but I assume no responsibility on the effects that may arise from the modifications. Figura 3 - Una vecchia foto della mia Mito TEST Since many have asked how much is the true horsepower of the Mito, I have decided to add the measures made on my bike at the test bench. When these tests were taken (somewhere in 2002/2003) the motor was at the end of it’s life span and needed complete review. Some test conditions: • motor base with about 38.000Km; • Standard 73037 cylinder with about 20.000Km; • Vertex one-ring piston with about 8.000Km; • Standard chain • The test took place after three winter months of non-use: no adjustments to carburation or other, just started up and drove to the test bench. There was a series of three tests with 5th gear; power was measured at the wheel (32,0HP – 31,8HP – 32,2HP). Figura 4 - Graphics of test numer two. http://www.mitoclub.com/ Article updated for the Cagiva Mito 125 Club by {mRk}. This article may be electronically distributed only with NO CHANGE in its current state!.