Project 49

[90GTVert]

I tried out the MRP pipe today. I'll get info up on that a bit later. I'm gonna post another update, sorta out of order. This one requires no video editing, so I have time to do it right now.


I should have the parts and materials I need here now to get rid of the old rear lighting setup now. You may recall that the LED tail/brake light died on me again, and it's just been a 194 bulb in the old housing since. The turn signals have plastic studs on them and they're supposed to mount with a nut on that. One of those has been broken for a long time and held on with double sided tape and a wire tire. The other broke off when I removed it today. I think they get brittle from gas spilling on them on fillups.




The lip on the gas tank and the position of the bracket makes it a pain to fit anything. This is the old setup, but the new trailer light, with a right angle pigtail, would hit unless it's spaced out too. No easy bolt-on, or at least not that would make me happy with it.




I sat and stared at this for a few minutes...




Then I decided to chop off everything after the frame tubes. I cleaned up all the traces of the bracket later.




I had some, I think, 3/4" ID (just over 1" OD) steel pipe around. I ran a 1" drill through the frame. It was already 1" ID, but had imperfections in it. Then I ground down the end of some of the steel pipe so it would fit inside snug with a slight taper and hammered it in. I'll weld it later, but I can pick the scooter up with it just being hammered in.




I was using my big electric drill with lots of torque, because it's the only one that holds the 1" bit. First I thought I was gonna break my wrist when it caught. Then I got a good grip on it and it spun the whole scooter over into the floor and busted off the mirror. Luckily it didn't spin at my car instead.


I figure about a 4ft extension will give me tons of clearance and it'll be almost like an early warning system with it stuck that far out the back. I'll just have to find out if I need to use a triangular orange and red reflective sign, like when they haul logs and long loads, to be legal. Not sure.

[2strokd]

:rofl: :lol:

[oldgeek]

:stars: Fall off yer scooter did ya?

[90GTVert]

The MRP exhaust needed a bit more help to get moving, but it's not nearly as hard to tune now with the CVT setup I'm using and the extra torque from the big bore. I used 1,000RPM clutch springs to help a bit, in addition to going to 5g sliders. Leaning out the needle made it hit a little faster, but I got spark knock at part throttle, especially when rolling off, so I went back to where it was.

The MRP ran the hardest of the pipes this time around. It's the only one that revved more than with the ported 49cc. The rest were revving just a little lower on the 68cc. CHTs were the hottest of the group on a cooler day. I'm thinking perhaps the small stinger lets the MRP run hot enough with the 70cc that it does better than the rest.

I still don't like the noise, but it was nice to have 45MPH as about the minimum cruise speed. It's a little more sluggish off the line, but still the fastest accelerating. With some fine tuning, I think this one would really show the others up at this stage.

[90GTVert]

Here's what I left out of the last update. ;D


I only extended each side a few inches. I notched a piece of square tubing and stuck it in place to form a nice flat end piece. Gotta get it all welded up still and do some grinding to keep the end flat. It looks a little off because the stock frame comes out at two different angles. I did my best to get the end bit square with the frame, and I think it's just the pic and diff angles of the original frame that make it look off.




I'm thinking I'll make a plate with the lights that bolts on instead of welding it on. Mostly because it could make any future changes to the lights a lot easier.

[190mech]

The old MRP pipe is starting to shine!Isnt the muffler core on the ZX very small?I seem to remember it was around 15mm ID..

[90GTVert]

20mm I believe. I can't tell a difference in anything but sound if I swap them back and forth.

[2strokd]

Good update!

I recently installed a Leo ZX on the same BBK. It came with an MRP silencer and i must say, it is much louder than i remember a ZX lol. Must be more, or bigger holes in the silencer!?!

Love the tailight section fab work! You just answered my wheelie bar worries!

[90GTVert]

Here's the finished tail piece. I made light panel from 1/8" steel. I thought perhaps the thinner stuff that was stock probably flexed and may have amplified vibrations. Each tube had a washer and nut welded in so I can bolt it on, then the center just goes all the way through with a nut on the back of the cross bar. All have rubber washers.




Tons of clearance. Now I kinda want a bigger gas tank.




The 56 LED truck/trailer light is VERY bright.

[190mech]

Man!You gotta wear shades to look at that tail light!! :thumb:

[90GTVert]

For the next step in the project, I wanted to set the big bore up something like the 49cc was after porting. I started off by marking the exhaust port on the piston, so hopefully I wouldn't make the same mistake I did on the first 49cc piston. Plenty of room left here.




My goal was to get 185/125 durations like the 49cc ported. I used the thickest base gasket I had and that bumped durations up from 184/120 to 185/122. That took care of the exhaust duration. I widened the exhaust port to 70% chord width, again sticking to how the 49cc was done.






I smoothed out the port and chamfered it, but those were the only other changes to the exhaust.




I also rounded out the edges around the boost port and transfer areas on the cylinder skirt. I rounded out areas of the cylinder skirt as well and filed the crown to reach 125 transfer duration.






I finished off by shaving down the head enough to keep 7:1 corrected compression ratio... and fumbled the cylinder onto the glass in the process. :doh:




This is about as similar as I can get to the 49cc cylinder that worked well. If anything changes, I think it may be largely thanks to upping transfer duration. All I've done so far is start it and tune the idle.

[teddy554]

Can you tell me the purpose for the glass.

[190mech]

What is the Exhaust port chord width?65-70% is a good number..

[90GTVert]

70% (33mm) John.

The glass is supposed to keep it true Teddy. I've had good luck with this method...
49ccscoot.proboards.com/index.cgi?board=hints&action=display&thread=941

[190mech]

Sorry,I missed that in the write up!! :beatup: