Comparison of 2V Models – 1000, 900, 800, 750, 620 and 600

With 2003 bringing the biggest changes to the 2V engine range since, well, the 750 Paso really, I thought I’d do a little report showing some specs and some graphs. Just to give you an idea of where they are heading. And, as appears to be a forming habit in this TPG owned era, interchangeability of parts is slowly becoming a thing of the past.

First up, a comparison table for the models from ’91 onward. No point complicating it with things prior to that. This table is best viewed in conjunction with the reports for the 620, 800 and 1000, which have more detailed dyno graph comparisons.

Notes:

• All dimensions quoted in mm, all valve timing quoted at 1mm lift, without clearance. this.
• * The ’02 900M ie had the 5.9M ECU instead of the 1.5M.
• ** The "900 Carb Small valve" refers to the engines fitted to 900M models from ’97 to ’99. See the "900: Not all created equal" report for more on this

Next, a quick summary of the major physical changes made from old to new. There are also other minor changes made, like oil passages, stuff like that. Not a big enough deal for me to list.

600 to 620

• 750 crank – 61.5mm stroke
• New pistons – shorter compression height, same bore as 600
• 750 size valves
• Camshaft timing and lift revised
• Camshaft design revised – 2 bearings instead of 3, not interchangeable, except 800 (?)
• Head design revised – as per cam changes, LH cam end cap revised
• Same exhaust headers and mufflers fitted on 620Sport as 800 and 1000 models. The 600SS ran a smaller diameter header with a 2 into 1 collector into a single muffler – M models have always used the same 40mm sized headers and mufflers on all 600/750/900.

750 to 800

• New crank – 66mm stroke (same as 916, 996 engines)
• New pistons – shorter compression height, same bore as 750
• 900 size valves
• Camshaft timing and lift revised
• Camshaft design revised – 2 bearings instead of 3, not interchangeable, except 620 (?)
• Head design revised – as per cam changes, LH cam end cap revised
• 6 Speed gearbox fitted – from 400 engines with sprung damper in clutch drive
• Same exhaust headers and mufflers fitted on 800SS/Sport as the old 900 and 1000 models. The 750SS/Sport used a smaller diameter header with the same size stamped x-over, muffler pipes and mufflers as the 900 – M models have always used the same 40mm sized headers and mufflers on all 600/750/900.

900 to 1000

• New cylinders with revised fin design/arrangement
• 94mm bore with new pistons
• New crank – 71.5mm stroke
• New conrods
• Bigger valves
• Camshaft timing and lift revised
• Camshaft design revised – cam runs in machined bore in head without ball bearings, not interchangeable
• Head design revised – twin spark plugs, exhaust port length reduced, header pipe cavity opened for better cooling
• Increased compression ratio
• Alloy clutch basket and plates
• Different exhaust headers to suit cylinder head re-design, diameter unchanged.

That’s about it for the major ones as I have seen/read/been told so far. The increases in capacity are probably just competition based I would think, trying to let old tech air cooled 2V engines keep up with newer water cooled 4V ones (SV650 perhaps?). The 620 and 800 are pretty easily done, and would require just a small change to the crank and piston manufacturing CNC files I’d say. The 1000 is much more of a re-design, much like the Testastretta compared to the Desmoquattro - similar bottom end, new cylinders and heads.

In terms of power making, the use of shorter duration cams with more lift and bigger valves - as started by the 916SPS of ’97 and continued with the 748R, S4 and ST4S – to generate broader torque curves and more peak power is transferred over to the 2V series. As these are the first really serious changes to the 2V engines since the introduction of the 750 Paso in ’87, and combined with the addition of fuel injection from the previous generation 750/900 ie models, the improvements gained are quite apparent. The 620 is far closer to the 750 than the 600, the 800 almost matching the 900. Real steps forward made with simple, very sound changes to the bits that matter.

I have been rather impressed with the on-road performance of all these new engines so far. Even the 620 feels far better than I expected it to, and the 1000 is a fairly serious engine. Whether we can coax enough power from it to approach things like the VTR 1000 engine yet I don’t know. It is still only a 2V engine after all, but the midrange power is very impressive. I’m not sure what the journos were talking about either when they mentioned some roughness in the engine. It’s as smooth as the 800, and quite a bit faster. The way it throws the front wheel up in first gear without trying, even with the standard 15/38 over-gearing, is almost a little worrying.

So, some graphs. First up is all std. 1000DS is mauve, 900 ie is red, 900 carb is blue, 800 is green, 750 ie is purple, 750 carb is yellow, 620 is pink, 600M is aqua. The models used can also vary things a touch. The 900 carb is an SS, whereas the 900M tends not to have the big midrange dip (due to mufflers). The 600 shown is a 600M, which has the same style and size exhaust as the 900SS & M, whereas the 600SS has a small diameter 2-1. First graph is power, second torque.

Next, slip on mufflers added. For the carb models, fuel changes are not usually required to get the best dyno power. For the injected models, this can often make a difference. 800 especially (see the 800 report). So, where applicable, runs will be shown with appropriate ECU changes/upgrades/richening. Just for the sake of the example. The runs share the same colours as the previous pair of graphs – 1000DS is mauve, 900 ie is red, 900 carb is blue, 800 is green, 750 ie is purple, 750 carb is yellow, 620 is pink, 600M is aqua. I’ve added a 600SS, with its smaller diameter 2-1, shown in orange. The 750 ie is a 750SS ie with a DP air filter kit (with the open lid). This is the only 750 ie w/slip on mufflers run I have with RPM reference, so will have to do. It makes about 2 Hp more from about 5,000 RPM onward compared to the std air filter/airbox lid.

The main difference in engine characteristic between the carbed and injected engines is shown clearly with the above torque graph. The carbed engines – 900 in particular (blue) - with the long inlet manifolds make their peak torque a bit lower, and then fall away much faster. For a given capacity they make more torque at lower RPM, but don’t hold it. This is why the injected models make more power. They make more torque at high RPM. The mathematical formula for Power is Torque x RPM, so more torque at a given RPM, or the same torque at higher RPM, means more power. The 900 carb curve, with noticeably more torque up to 6,000 RPM, shows why these engines feel so good on a windy road. Just not so flash on the straights.

Keep in mind the 750 ie has the air filter kit and the same holds true for the 750. Although, on the road, I’d say there is much less difference between them (I’ve been doing a bit of riding on a 750SS ie recently) and the ie bike’s better top end is noticeable. What effect, if any, the smaller exhaust header pipes have I’m not sure. I have read of people fitting 900 sized headers to 750SS carb models and losing power all thru the rev range as a result, but it doesn’t seem to upset the 750M carb model, which uses the 40mm header size of the 900. Been meaning to do a test on it, but haven’t got there yet. The 600SS, compared to the 600M, is down from about 4,000 RPM up. But it is also a 2-1, not a full 2-1-2 small diameter system.

The 600 is much less affected by the long manifolds. Although its torque peak is under 6,000 RPM, a good 1,500 RPM lower than the 620, the curve doesn’t fall away like it does on the 750 or 900 (especially) and it makes more power per cc than the carbed 750 or 900. The differences are not huge, but still measurable – the table below shows the calculated Hp/litre and ft-lb/litre (torque) from the above "slip on muffler" graphs.

The 620 and 800 are very good in both the power and torque per litre departments – again confirming the benefits of the new head sizing and cams. Both the 600 (M, as compared to the SS) and 900 carb models do pretty well in the torque per litre, but the poor 750 (in either form) is behind the 8 ball from the start. It’s just wrong, unfortunately.

The 900 ie is lacking in Hp/litre compared to the 800 and 620, but it too could do with some bigger valves. To some extent, it suffers (although much less) from the same incomplete development as the 750. When the 900 was fitted with injection, the only other tuning change was to longer duration cams with more exhaust lift. This may have been a compromise caused by the existing design - they would have been better off fitting larger valves at that point, although fitting larger valves (of enough increase) to 900 heads is not possible without re-angling the valves, as a 1mm increase on both inlet and exhaust valve diameter in a 900 generates valve to valve clearance problems (interference, actually) on overlap with any cams pretty much, without sinking the valves below the std seat heights. The 1000 heads have re-angled valves, the only way to get the sizes required into the head design. Not that this helps the 1000 make the power/litre the 620 and 800 do - it pretty much compares with the 900 ie on power, and is a bit better on torque/litre.

So the 900 ie is something of a compromise in my opinion, whereas the 900 carb worked very well as it was, for what it was. It was never going to be a powerful engine with the long manifolds and the std 9:1 ish compression ratio, but it made good low/mid range power and is a very nice road engine. And 900 carb cams are capable of making over 90 Hp from 900cc with good ports under them and short manifolds feeding them.

Really, the changes made to the 620, 800 and 1000 could have easily been made to the old 600, 750 and 900 with similar results in outright number terms. It’s not the capacity that makes the power as such (some people seem to misinterpret this capacity and power relationship), but the use of appropriate valve sizing and cam timing. As stated previously, the fact the capacities have changed would have more to do with marketing advantages (the old "bigger, better" claim) than anything else I’d think.

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