Where did you get this info? I've yet to see an after-market performance pipe manufacturer claim an rpm operating range and have always wondered why not? Of course, I have only bought one pipe new.... just always wondered why they don't publish it in adds.
I'm not doubting you just sayin'.
LeoVince have them on theit site. I get them from Sip for other pipes, they're under the description.
2010 Gilera Runner SP50
If it ain't broke you obviously haven't tuned it enough
I marked the cylinder where the exhaust port roof would need to be for 190 degrees. 190 is actually center of the huge mark. I know that's not precise, but I can always check the porting with the degree wheel when it's close.
I started working with the exhaust port, but I didn't go all the way to where I needed it to be. I'm gonna wait till I get my other bits, then I have room to smooth it out without going over the duration I want. I widened the port just slightly. Never measured. Maybe 1-2mm total.
I checked out the skirt by the boost port as well and decided to grind it out a bit.
Pulled the cases apart again and checked this cylinder against what I had matched to the old cylinder (for anyone that wasn't watchin' the Venus build, I tried it on there and ended up determining it's too worn). The boost and transfers will need a little matching.
I brought the boost port toward the cylinder. You should see the difference in the left and right side in this pic.
Last Edit: Aug 14, 2017 13:59:32 GMT -5 by 90GTVert
It's probably a bad choice, but I decided to go a little (maybe a lot) more radical on port timing. I kinda wanna see what a 103cc does over 10,000RPM... aside from grenading. My initial figures/goals were 190 exhaust duration and 133 transfer duration. Wellll... I kicked it up a notch. The finished durations are 196 exhaust and 136 transfer. The exhasut duration should be good for 10,500-11,000RPM. The transfer duration is intended for 12,000-13,000RPM accodriding to Bell's stats, but I have liked the additional transfer duration in the Venus. The longer durations are said to reduce the narrow, "pipey", powerband. I know the Venus will chug along happily at 4,000RPM or pull to about 9,000RPM with it's transfer durations intended for 10,000-11,000RPM according to Bell's book. Hopefully I haven't just made a big mistake, but time will tell.
Here's the exhaust port in it's finished form. Chord width was increased to just a hair over 34mm.
I filed the piston's crown to get the 3 degrees of transfer duration that I needed, and to get the final 2 degrees of exhaust duration without enlarging the port farther. Then I gave teh piston a little smoother finish.
I still have a little bit of work left to finish the case to cylinder match up and I need to finish the header. Then I should be done with port work.
Last Edit: Aug 14, 2017 14:00:50 GMT -5 by 90GTVert
I hope not. It's got a healthy chamfer and I tried to keep the port shape mild. I figured the port shape might also help me if the duration is a bit much since it's not going to flow quite as much as a flatter roof would.
The long trans duration will help. I thought i had mentioned that? I did this to shaka,s jug and it runs very strong with a worn piston. Its at around 135-140 trans and 180-190ex, cant remember now? I did file some off the ex side of the piston to get the timing higher.
All in all, that lil 70 LOVED it, and i was impressed with the results! Wrecked it right into my sons electric scooter and my workbench on a wheelie it ran so good lol. Thats a whole other story tho lol.Hits hard about 8-8,500 and lightswitches to 10,500-11,000 and pulls lika mofo! Im sure your Bigblock will like you for this and will will love what it does for you!