Well after porting my motor, and installing an expansion pipe I started looking for another performance upgrade that will increase driveability at the same time. I read another thread about a bike with a custom pipelyne reed kit:
Spy Pics of Team BoXer's full suspension race bike!. When purchasing the reed kit from them you must supply your own carb, the one they use is the Walbro HDA-63:
Lawn Equipment | Lawn and Garden Accessories (quick search: hda-63-1). Their solution is a great design from the pictures i have seen but I can not see spending $120 for their reed kit plus $57 for a carb when the engine kit cost $160. The only way I could see spending this amount is if I was planning on racing the bike. Now to fabricate your own reed kit is a lot of work and those who do not have the fabrication skills should support the small business and purchase their kit but if any of you are like me and enjoy tinkering I decided to fabricate or purchase the parts I couldnt fabricate to create my own kit.
Their kit consists of a reed valve, reed, and manifold. I first sourced the carb and the reed valve.
I decided to go with the same carb used as Pipelyne. The carb is a diaphragm design with adjustable hi and low fuel mixtures and idle circuit. This carb is used on many chainsaws.
The reed valve is basically a check valve for the intake that only allows the flow of air in one direction. Some valve designs integrate a limiting plate that prevents the reeds from opening too far which inturn causes premature reed failure. I located a reed valve with reed, limiting plate and valve body from ebay for $16:
eBay Motors: Geely Moped Parts JL50QT 49cc (50cc) Reed Valve (item 170198754808 end time Oct-29-08 00:59:26 PDT).
After all of the parts arrived I began analyzing the adapter plates required to mate all of these parts together. First to mate the carb to the reed valve, I used a piece of 1.5x.125 flat stock and drilled the bolt holes, and intake hole. next i drilled the holes for the carb to mate up, and welded studs into these holes. I bolted the adapter plate to the reed valve then cut the heads of the bolts enough to allow clearance for the carb to seat flush. I sealed the adapter plate to the reed valve with copper gasket sealant. Next I fabricated a mounting flange for the manifold I was going to create to the reed valve. Next I used flat sheet metal to fabricate a manifold to house the reed valve and provide smooth air flow to the engine. I also fabricated a flange to mate the manifold to the engine. I then welded the two flanges to the manifold. Next fortunately or unfortunately this carb is of diaphragm design which requires a crankcase pulse, so we have to tap into the crankcase. I first seperated the head from the engine and set it off to the side. (This is a perfect opportunity to modify the intake and exhaust ports which I have already done which incredibly smooths out the engine at all rpm.) Next I took some 3/16" ID S.S. tubing and enlarged one end slightly. I drilled a hole the same size as the smaller section of the tubing, into the left side transfer port section of the crankcase (only space I could find to install it with out splitting the case). I used a shop vac to prevent shavings from falling into the crankcase. I tapped the tubing into the hole from inside the crankcase until flush with the larger section of tubing on the inside (I placed JB Weld on the outside of the tubing before I installed it.) I then took a washer and placed it around the outside of the tubing on the outside of the engine and tack welded it in place to prevent the tubing from falling inside the engine. I then closed the engine back up. Then I mated the carb to the manifold and then sealed it all with copper gasket sealant. I then used some rubber fuel line to mate the crankcase pulse port to the carb port. I then followed the instructions for setting up the carb and test fired the engine. Before I ran out of time I got a chance to ride up and down the street a little bit and it accelerates so smooth but need to tune the high mixture more this weekend because the engine bogged down at 16 mph. I also could get the engine to idle very very slow and still have it accelerate away which was amazing. Also this weekend I will need to fabricate a way to mount my performance air filter to the carb. More pictures to come this weekend.
