CAM swap for 1st Generation

[northwind]

Yup, again the baseline isn't very useful there. Look how different the fuel curves are for the 2 dynos, changing the cams didn't do that.

Originally Posted by yorkie_chris

...but has anyone got any proof the other way? Those dyno runs were 2 years apart for example. And it was only making 63 beforehand.

Well, if you look at the other, unrelated dyno report that was referenced, it shows a base-line horse power of 66.2HP which seems to be strickingly consistent to the 63HP shown in the second dyno report. See http://www.jhsracing.co.uk/archive/9..._std_w_key.htm

Therefore, if we assume the two dyno reports that have been referenced are not fabricated--and I have no reason to believe they are--they are easily reconcilled together with the conclusion that the cam swap is what caused the +-8 HP gain and NOT the exhaust system change.

BUT, I am keeping an open mind, does anyone have a before and after cam swap dyno report that shows something differant?

[northwind]

They're certainly not fabricated, but that doesn't mean they're useful. I've got a dyno chart of my bike making 64bhp at the rear wheel because of the terrible Renegade airkit, which would flatter my other mods if I was to use it as a baseline, for instance.

Like I say, my own comparisons went south but if I was to make an educated guess as to how much of my 79-and-a-bit bhp was from cams, how much was from fuelling, and how much was other stuff, I'd say the honours are probably more or less shared, with a big synergy (ie, both might be adding 10bhp together but neither would add 5bhp by themselves). I've rejetted since then which ought to push me through 80, but is that last half a horse from rejetting, or did the rejetting just remove an inefficiency and allow the rest of the engine to work better? Once you get into this sort of thing, it's very hard to give positive figures, which is one reason I'm so skeptical when people say "Part X gave me Y bhp"

Example... Fit a 700cc kit into a standard SV, it'll still be strangled by the exhaust, filter and cams, you'll get a few bhp. Fit a 700cc kit into my bike and because the other inefficiencies are all gone, you'll probably get more bhp. Until it snaps its crank. So which is "right?" How many bhp does the 700cc kit add? There's no one right answer.

[northwind]

Oh, this might anger Mr Holland again- it's a while since I've done that- but nobody who doesn't sell the ignition advancer has ever duplicated that result. Personally I would bet an entire scottish pound that the initial run there is weak- atmospheric conditions or operator error, perhaps, or any one of a dozen other reasons. The low-end boost of the advancer is real, but I don't believe that the high end is. I certainly didn't get it. If you bump that curve so that the peaks overlay, you see the difference in shape- which is still useful and shows the benefit of the advancer, but the rest can IMO be attributed to inaccurate comparison.

Northwind, I agree with your second to last post above. That a collection of modifications can create a synergy that collectively does good things but that the items, individually, may have limited value. So I am looking for how to maximize the synergy with the cam swap. Presumably, with a higher performance cam comes a need for more air and fuel to maximize the benefit and without that added air and fuel, the result may be disappointing. I have snorkeled to give it more air but I suspect there is a need to give it more fuel with some carb tweaking. I am hoping to find someone that has done this modification and can give some starting point changes to make to the carb.

[yorkie_chris]

Desnorkelled filter will make it run incredibly lean alone. Full system and a rejet is usually a good start...

[northwind]

I'm not very good with the desnorkelled filter, but as YC says if you've desnorkelled it all the way the bike'll be lean as anything. I did some compares with my Race RS and it's not quite as open but not drastically less, so with a full system it's time for the big jets. Something like a 170 DJ main would probably have done me.

[Richie]

Mines was kicking out 88 horses...

if you look closely you can see the SV in the background...


okay, Coat, taxi for 1...

Originally Posted by northwind

...but as YC says if you've desnorkelled it all the way the bike'll be lean as anything. ....

Is using tank risers necessary to get the benefical effects of snorkling?

[northwind]

Ah, here I don't really know- I use spacers, Factory Pro recommend them, as do lots of people but others say they do nothing. There's no way I'm paying £20 for a dyno run to test this when the spacers themselves cost me practically nothing, so I use them But whether they make any difference, I really don't know. Clearing off the sound dampening foam under the tank, and making sure that the airbox and carbs are fully seated to maximise the gap, does the same thing and is free (no reason not to do both!)