Torque Monster — Sigma Performance Ducati

16 Фев 2015 | Author: | Комментарии к записи Torque Monster — Sigma Performance Ducati отключены

900 2 Valve

Well its taken a but we have now had one of our 2 valve motors in the places for long enough to do the and record the process at the dyno.

The 900 2 valve motor has been for ages, it has been described as the motorcycle engine and indeed for purposes it is. Its fairly light, has a good reliability record and a type of power that to have gone out of fashion in the UK. and lazy it allows the rider to the ride.

This is not a motor for rev wannabe racers, but in its way it is capable of effective point-to-point performance on roads and in real conditions.

type of performance is best with an engine with low down torque, the sort your bike takes off you open the throttle and where the keeps coming in a nice without any surprises sort of As ever if enough is good more is better, Ducati just shown this their latest 1000cc of the motor. The engine has been from 900 Supersports in the late to the Mike Hailwood Evolution via a of Monsters and an occasional Paris win in the Cagiva Elephant of the early

In spec it has changed a bit over the but in a mostly rational evolutionary There have been a of interesting derivatives, the water-cooled and ST2 motors but mainly the same modified as knowledge increased.

Bore and … is 68mm x valve angle is a fairly old 60 degrees. These figures remained the same since the engines, logical derivatives of the 750 rolled off the assembly line in 1988. The 900 had a new 6 speed transmission and a dry shared with the 4 valve

The engines are an interesting mix of technologies, the end is derived directly from the head porting is the same on all the and, with all due respect to the as bad as the 4 valve is good. It should not be a easy proposition to beat a at its own game, maybe there is mystical or emissions related that I am not party to but there is no that Ducati’s 2 valve can be improved to a large degree, opposite to the 4 valvers!

Over the 15 the engine has been around the has changed, mostly due to the different to which it has been put, and the last three years a few really nice new components it has really delivered.

So what did do? Well the first engines had facing the same direction, forward, really good (it seem) for exhaust cooling but a to get the carburettors and their associated in line for. This went as the priority moved to and common airboxes, it’s that the standard airbox is inefficient too, but that may a lot more to do with the available on a normal bike for an airbox.

It’s taken a really design like the Multistrada to get the volume onto a bike all.

With the advent of the nineties 900 SS models and the 906 the rear was reversed to allow one carburettor or injection system to make the in the centre of the vee. This to the ‘normal ‘ 900ss we have seen for the last 14

The repositioning of the carbs (or carb in the of the 906 and its single dual choke to the middle of the vee led to an acceptance of a too long manifold, measuring almost (5 inches to those of you in the colonies who onto imperial measurements!!). along the lines of 35mm was in line with the engines the effect on the power curve is to it early (and at a higher but with a substantial reduction in width.

There have three cams designed for the the original, which works with the long inlet as well as can be expected anyway. The ST2 cam and its 900ie cam which is designed for the short inlet lengths on the fuel injected derivatives. In to the three cams there has only one set of valve sizes.

As the has changed the bike has held on to its better at high revs.

In the department there has been a few changes, oil/air cooling on the bikes (oil cooled and air cooled heads), followed by the castings being used for cooling on the 907ie and ST2. The versions of the engine, in completely the way to intuitive thought the engine purely aircooled.

As with anything like there is an exception to the rule, were a group of bikes came with different cams and pistons. These were the 900 Monsters produced mid 1997 to the advent of the 900ie in 2000. These bikes with the complete cylinder from the 750 engine; smaller ports and lower compression bikes were at least down on the original versions.

were also the motors to Cagiva for the Gran Canyon I have no idea why they produced, it was clearly a retrograde I can only surmise that TPG came in they found a pile of 750 bits looking for a and decided that they use them up somewhere harmless….

Mick Dalley,

Mick his Monster in hillclimbs and sprints, old English type hillclimbs the hill consists of a winding road or the drive to the old manor For these hills power can but the often slippery and rough needs supple suspension and an torquey power delivery.

problem was that while he had decided a 900 2 valve Monster be quite an effective tool for the he had unfortunately bought one of the ‘750 ones. We built the bike a full Monty build, went off to the dyno, it was pretty that we were not going to get the levels we wanted without major changes. This was to be a pretty major test as the we had in mind would require a cylinder head rebuild.

Ducati 60

It was obvious that if the problem was and cam related we would have to do about it and fit new, better Mick agreed and we set to work.

The was one we thought would provide the pull and ease of control Mick would need on the first up was a 944cc big bore then standard ‘proper’ valves with the latest cams. Finally just to sure that the bore job just add to peak torque we that the ports could do a little help….

Our 944cc kit has that are 75 grams lighter the standard ones, this is in one way as the conrod has less mass to therefore use at higher revs is In another way it is a bit of a potential problem as it be nice to rebalance the crankshaft to sure the engine is smooth…….experience has us however that the 900 twin is resilient in terms of crankshaft (an alternative explanation is that its not sophisticated engine as standard and a 75gram change in piston isn’t going to make a big

Again to make sure the feels the change our 944cc kit have a slightly raised 10 .5:1 is the target… the reason for all is to focus the mind on these little 750cc heads. designed a ‘bathtub’ shaped chamber for these bikes, for the version the only way they get the bigger valves in was to move the chamber ‘out’. In these the only way to maintain compression was to the sides of the combustion chamber in, in a narrow bathtub shape… On bike we were going to to machine the heads, shove the seats back into the to make room for the much valves and to allow for the cam lift and try and the compression ratio without big and expensive modifications to the combustion

Every time you fit a big bore kit to an you effectively add to its compression ratio; about it, in this case you had two cylinders, with about 9:1 ie the space between the valves, about 50cc has another 452 cc into it at top … centre. If we the capacity of the engine to say two 472cc then the 50cc combustion is going to be stuffed with mixture, in this case it be 9.05:1 compression, not much but in case handy…….

Once the were machined and rebuilt the was modified; the standard ports can be described as tortuous; off centre and they are from a previous that wanted the incoming to swirl (a circular spiral the circumference of the combustion chamber) to mix up the nowadays the focus is on tumble; the of a circular movement parallel the wheels. Its supposed to be better and efficient at creating a good and therefore a better burn and MORE POWER……………

We decided to modify the ports………the for this sort of use is very to the full on racer style would go with a pair of manifold 41mm Keihins; we after good usable power not ‘full on top end but lousy down low but we don’t care it’ power; pretty like you would want for down the shops actually…..

are two places on this bike more power is available out too much trouble, the inlet length and the size of the carburettors would not affect the midrange but allow more top end but the budget around for that right

Run 009 is Mick’s 944 — Run 024 is the same following a

Full Monty but standard

Run 009 is Mick’s Monster Run 015 is a standard 900 —

both open pipes and air boxes


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