Mikuni carb for Whizzer NE5

datz510 · #1 04-17-2009, 02:05 PM

I've got a 2008 Whizzer that I picked up from Lennyharp. I swapped him my Rotten Orange build for it. Anyway, This whizzer has some issues off idle that I need to sort out. It has very little power until it hits about 3k rpm and then it takes off. The bike has a nasty stutter when rolling on the throttle like it misfires and wants to die, but then picks up with a little more throttle.. once past that and past 3krpm it pulls hard.

I was thinking about trying a Mikuni carb on it in place of the stock Keihin(sp?). The stock carb is dialed in as close as it can be, but there is still something wrong with it. Its possible it may just be a bad carb.

Anway, for those of you that have gone to a Mikuni carb on your Whizzers, what size would you recommend for this engine? I found some that look like they'll bolt right up, but have a few different sizes to choose from.

This bike has Quenton's upgraded headwork done and once its up above 3k rpm, it pulls hard and seems to run OK. Getting from idle up to 3k rpm that is the problem.

datz510 · #2 04-17-2009, 02:07 PM

Also, if you guys have any other ideas, I'd like to hear them.

datz510 · #3 04-18-2009, 03:30 AM

I played witht he stock carb a bit tonight and got it pretty close. I found the C clip on the needle was on the top position, basically starving the engine for fuel until the throttle opens up wide.

Runs MUCH better now.. I'm taking it down to the Death Race in Tucson tommorrow, so will see how she runs down there.

datz510 · #4 04-19-2009, 07:11 PM

went through the whole bike today checking things out. I played with the cam timing, checked ignition, and then checked the valve adjustment.

Turns out that the intake valve lash was very loose and was set at .020-.025"!!!! The intake valve was barely opening! I adjusted both the intake and exhaust valves and set them to .006" and .008" respectively and the bike runs SO much better now.

I tinkered with the carb a bit more, sealed up the intake manifold and found that it was missing a gasket. So, I made a gasket and got the intake air tight.

The carb is very close, but still not right. I can't get a consistant idle, but running down the road, the bike is at 90% tuned now. Its pretty darn close. It actually has reasonable power at the low end now.

I'll be ordering up a nice Mikuni 26mm carb to get it dialed in 100%. The carb that is on there belongs in the garbage..

**Dave31** · #5 04-19-2009, 08:11 PM

Cool datz, I am glad you are getting ti figured out, that is one beautiful Whizzer .

datz510 · #6 04-20-2009, 12:29 AM

Thanks!! Its a fun bike!

I ended up going with a Dell'Orto 24mm PHBL carb, as I found that it will fit better than the Mikuni, plus its got a dedicated idle circuit w/ separate idle jet.

The Mikuni 26mm VM carbs all had too large of a manifold mount to make it work cleanly. This 24mm should be enough carb for this engine.

Also, tonight I put the baffle back in the exhaust.. and guess what? My low end came back. The engine likes the back pressure for low end torque!

lennyharp · #7 04-20-2009, 02:39 AM

I guess I was right that this beast just needed a better master to make it cooperate. That was a great day yesterday even if all our bikes quit for various reasons. You grinned all day and never even ran one lap. The whizzer would win now but not yesterday. That yellow is wicked good looking.!!!

datz510 · #8 04-20-2009, 03:44 AM

Tonight I went through a bit of my tax return and ordered up a bunch of goodies for myself and the whizzer, including a vintage look Brooks B67 seat, leather tool bag, vintage parcel rack.

Also put in an order with Whizzer and picked up new gaskets, a mirror, a spare exhaust baffle, belt cover, replacement battery, and a few other things.

Then got some very nice Jeantet leather aviator goggles to ride with:

I think I'm gonna need to start a build-a-Whizzer thread.