Dyno chart, 11:1 and stage 1 cam

[harold]

I posted some dyno charts in a previous post. To those that didn't see it, I had an 11:1 piston and a HotCams stage 1 cam put in. I already had installed a Mikuni 42 mm HSR. I got this chart today, and it shows torque and Hp, stock (with Mikuni) and with the new parts. I never had it dynoed when the carbs were stock. The cam moves the power band just a little up it seems, so the peak RPM power goes up more than at 5,250. It isn't anywhere near the 50-70 Hp figures I have heard about, but I think they had more work done.
Overall, it is noticeable, but mostly at higher speeds. With the abundant low end torque, a stage 2 cam would probably be a good runner. They require different springs, at the least, and so up the cost another step.

The next step is a lighter front wheel, and maybe better front caliper.

[harold]

Here is a picture of the 11:1 piston. A little different than the stock flat top, and born ready for higher lift cams.

[chisleu]

Now that is pretty!

That is not a lot of clearance to the head! Any pictures of that piston from the side? Wondering how much clearance from the wristpin to the bottom ring.

[Bill Jurgenson]

such pistons are slipper-type, i.w. with very short skirts.

My "blue" motor was quite similar in setup:
some porting,
JE 102 piston
Megacycle 280/2 cam with stock springs
Carillo and lightened crank - but not my lighten freewheel thing which I had not yet started with.
TM42 carb on Bikeworx manifold with big K&N:

my first attempt at a better exhaust system:

I was still using the stock DENSO box, the reason for the sudden drop beyond 7000 with that 7200 limiter.

But most things being quite similar, the gain of over 10hp must be mostly due to the exhaust system, some of course to the cam.
You can see that at 4500 I have about the same hp as Harold at the RPM but his stops there.

The red line is with the Stock L&W muffler. The other with a BOS (for a KAWA 750) with DB eater. The photo shows it with a BSM which, while pretty is not at all good as a can.

the point I want to emphasize is the importance of the exhaust system which too many around here seem to shrug off. Apart for the all important chassis tuning as the very first thing, the exhaust is the next thing to tackle, long before any bigger is better tuning stuff.
10hp difference is not nuttin.

[basser23]

Good point Bill,
I sent a note to Tim Barker a little while ago and he is planning more Skorpion exhausts..I asked him to send me a note when he starts..
I have decided to optimize what I have already before I get into any serious mods..going with Tunebike's kit.k&n's ,a Raptor spacer, Tim's exhaust
will be about it for awhile. Lighter chain and sprockets,Beasley fender,seat,(maybe Forza or RS250 seat) and fairing...maybe GS500/Katana wheels...
FZ1000 shock,tune the front end a bit...depends on $$$
Mine will only have street use on country roads.....

[chisleu]

such pistons are slipper-type, i.w. with very short skirts.

Thanks. I was trying to get an idea from the diagrams/pictures if there was enough room to raise the wrist pin to accommodate a longer rod / de-stroke. It seems that I could do ~8500rpms with no destroke at all, so maybe a crank would be overkill anyway. Just stuff I like to noodle around as my job often affords me time to think about things unrelated to the task at hand. I have a MS2 here setup for hall or ignition input that I could use provided I can find a ~45psi fuel pump with a low enough draw to run on the stock electrical system. I'm betting there are low LPH pumps with motorcycle friendly current draws out there, but I've not started looking. This would be a project to build while waiting on engine internals to arrive provided the engine goes and I decide to stay ICE instead of electric. Boy am I off-topic. Nevermind! As you were.

[Bill Jurgenson]

for a starter, Tim Barker offers (ed?) a 5mm longer conrod which also utilizes the the 3mm smaller wristpin from the XT550 and is thus lighter. With the appropriate spacer under the cylinder you can adjust for this as well as for pistons with other compression heights. This is normal engine building practice.
Problem with the Skorpion (can't say for a Baggi) is the engine mount at the top. For 1 or 2mm no problem really; the holes in the frame can be elongated that much.
Maybe not for the faint of heart, I removed the cross tube entirely - check my blog - with no repercussions to date.
With that gone, there is nothing in the way and - even better - you can work on the motor topend and cylinder without yanking or even tilting it.
I use a "wrong" flat top piston and adjust with a 1.5mm base gasket.
a future plan of mine would have Tim's conrod in a crank with 10mm less stroke, leaving engine height pretty much the same.
My SZR, the bike I normally ride does not have the problem since the top mount is bolted in and can be modified to suit.

[harold]

I rode the bike for the first time in a couple of weeks, and the pilot was still acting a bit lean. So now I am running a 96 needle-the richest, a 147.5 main, and changed to a 30 pilot from a 27.5. It helped, and I am sure I can get it perfect now with just a little more adjustment of the air screw. My old drag strip section of road for the first time has seen an improvement. I was getting 60 Mph, and today I hit 67. My roll on spot now goes from 60 to 90 in somewhere around 200 yards.
The bike is nothing but fun now. Hitting it in 2nd pretty much at any lower RPM puts the wheel in the air until you run out of revs. Stock when I bought it, you couldn't get the wheel off the ground in 1st, unless of course you dumped the clutch.
I think I will keep it.

[edfmaniac]

Good to hear. We are doing pretty much the same engine mods and I will be completely satisfied with 2nd gear power wheelies. What gearing are you running?

I just found out that the Aprilia dealership in central Texas has a state of the art dyno facility so I will be posting my results when I do my work in a few more months.

[harold]

I changed from the stock 45 tooth to a 47. It was a hassle without enlarging the chain, and made no noticable difference.