The Yellow Jacket build thread

**fairracing31** · #21 (**permalink**) 05-04-2009, 12:49 PM

Thanks for the diagram datz, I am sure that will be helpful to others.

Quenton Guenther · #22 (**permalink**) 05-04-2009, 08:30 PM

Hi Datz,
Make sure the spark plug [if C7E] has an extra washer, because the exhaust valve can hit the tip on certain versions of the head. The most common failure is the ignition sensor. As long as the green wire from the coil is ground and the green wire from the CDI is not grounded the ignition should be ready to fire. Never assume the spark plug is good, as many have spent hours looking for a problem and it was the plug. A good sub for the plug is an Autolite #4303.

When I designed the vent system the PVC valve needs to be level to work best. The PVC valve is gravity contolled.

Have fun,
Quenton

datz510 · #23 (**permalink**) 05-05-2009, 12:35 AM

Quenton, that info was great! I found a couple problems that I've corrected.

This NE5 has your machined head on it (used to be Lennyharp's bike), so it is set up for the shorter plug. I pulled the plug out and found that the insulator was cracked and dangling against the electrode. I think that was my fault when I regapped the plug. At least I found it. I found an NGK at the autoparts store that cross referenced with it, so that went back in the bike.

Next up, I was looking around at the connections at the coil. Found the female spade plugs on the wires at the coil were VERY loose on the coil spade terminals. So, I pulled those off and slightly crimped them with pliers so that they fit snugly.

Next up, when I pulled the replacement plug, I found that the plug was soaked with fuel. So, I pulled the carb out and I think I just may have found the source of the main problem.. I pulled apart the float bowl and found that the soldered brass floats were half full of fuel. This flooded the bowl and thus flooded the engine.

So, I guess i get to build the custom manifold and install the new dellorto carb sooner than I had thought.

So, Quenton, what length intake runner would you recommend for this engine? I am thinking a 3-4" runner from the port on the head to the carb would give me a bit more low end torque. (at least thats how it works on 4 stroke automobiles)

The carb is a 24mm Dellorto PHBL. Intake runner material is 25mm ID. The manifold to head port flange will be portmatched to transition as smooth as possible. I could also use the aluminum intake block as a smoother and longer transition between the 25mm intake and the smaller head port.

datz510 · #24 (**permalink**) 05-07-2009, 05:39 PM

Ordered up a jet set for the Dellorto carb last night so I can get it installed and dialed in.

Can't wait to ride this thing now that its going to finally run right.

Quenton Guenther · #25 (**permalink**) 05-09-2009, 10:37 AM

Hi Datz510,

The actual length should be 1/2" to 9/16" long for best all around performance.
You are on the right track by tapering the intake manifold to fit the carburetor on one end and the intake port on the other.
Have fun,
Quenton
Get YOUR EZmotorbike TODAY!

datz510 · #26 (**permalink**) 05-11-2009, 06:47 PM

Thanks for the info! I'll see how short I can get it, but I'm going to have to work around the constraints of the cantilever frame with respect to the throttle cable.

I picked up a 90 degree bend for the throttle cable for use with this carb, so it should make the throttle run a little cleaner.

jbcruisin · #27 (**permalink**) 05-11-2009, 07:24 PM

Great looking bike & interesting reading.
Jay

datz510 · #28 (**permalink**) 05-17-2009, 01:48 AM

Made some rather drastic changes to the Yellow Jacket today.

I restored and fitted an original 1950's schwinn springer frontend on it. I also fabricated the parts for the new intake manifold. Just need to go over to Lenny's to see if he can braze it up for me.

Here are photos from today:

Here are the fork peices after sandblasting and painting:

I welded a nut onto the inner side of the left front fork arm for the drum brake mount

Spring with new bumper bushing fitted:

Original AS hardware.. this stuff is rare:

datz510 · #29 (**permalink**) 05-17-2009, 01:49 AM

Original front fender.. I'll be swapping this out for one made for a springer eventually:

Front wheel:

datz510 · #30 (**permalink**) 05-17-2009, 01:50 AM

Here she is all put together (except for the frontmost fender braces):

You can see the fender deformed a bit when I had to bend it to fit it between the springer arms, so I'll find an original 50s Schwinn front fender for it. I think a Black Phantom frontend would be sweet!

The brake mount worked really well:

Detail of the spring: