The Zilla rebuild saga continues... I have the motor ready to set in the frame today. But as usual another question has come up.
The ports and cases have been ported & polished (by whom I don't know but the guy in OKC that assembled this beast for me said it was some of the best looking work he'd seen on a zilla motor). The airbox lid has been drilled, and an FMF Fatty pipe is hangin in the frame. So I was looking everything over for one last final check and I noticed machining marks in the carb throat. Got the micrometer out and it measures 39.5 mm. Pulled the main jet, it's 350. That's the stock jet size...... Anyone have experience with this type of setup?
How about it Harry McDermott, you guys still bore these carbs? What is a good starting place on the jetting?
I haven't looked at the needle or pilot yet.
I am going to run 927 @ 32 to 1 unless someone has a better plan. And the altitude here is 927 ft...

 

I'm curious My service manual says the zilla came with a mikuni carb. all years. Mine has a keihin? The guy I bought from raced it and has extensive mods. What carb do you have? Premix I use 927 at 32:01 like you, I have very good results, but 927 I have been told breaks down in cold weather so in the winter I use golden spectre.

 

Chapy - I have the Mikuni carb (38mm stock). The only Zilla I know of that might have had a Keihin stock was possibly the 87 models???
Can you tell any diference in the way the beast runs when you switch to the Golden Spectro?

Denny

 

Nope, 87's have the Mikuni 38mm flat-slide, too.........I like Klotz Techni-plate, or whatever its called..........

 

Hello,
I just put a 38mm Zilla carb on my LT250 and I am not sure if choke is up or down. I only put it on a couple days ago and the handle is in the "up" position, and it idles good and runs strong down the alley. The choke mechanism is different than the 34mm mikunis in that the lever is swapped to the other side and an extra pivot point is added.
IF you can help, that would be great. Seems to me that the Up position of the zilla carb is the same as the down position of the quadracer carb

 

Slacker1bob,

The choke is off when it's in the up position. Also I found a LT500 Engine 4 sale on Ebay

http://cgi.ebay.com/ebaymotors/ws/eb...mp;r=0&t=0




OutCast
LT500RJ

 

Thats what I thought.
Thanks

 

[img]i/expressions/face-icon-small-cool.gif[/img] If your quad is cleaning out good with a #350 jet then try going smaller maybe a #340 jet,mine had the mikuni 38mm flat and the main in it was a #300 main jet.Try calling F.T.Z. racing or look them up at FTZracing.com cuz the old stock carbs are out dated and they have the best carbs on the market,I bought a 41mm smoothbore of these guy's and that carb came all set up,the only thing I had to adjust was the air/fuel screw I know you may not be in the market to buy a new carb,so try leaning it out a little at a time............... .................................................. ........ 87 Zilla full drag porting,.080 over,head shaved.005,F.T.Z. drag pipe,P.V.L.ignition,44mm Lectron carb,N.O.S........Bad *** machine low 13.00's in the quarter without N.O.S.@ 90 mph.

 

When I lived in Amarillo, TX (Which should be 'close' to the same elevation as you) I ran a 430 Main in my stock 38mm flat slide Mikuni.
Mods to the machine are different, so it's hard to give you a starting place.

The biggest thing is... start off rich!
Worst thing that can happen on a rich motor is fouling the plug...
Too lean = oops!

See what I'm gettin' at?

Each bike is different with different mods.. just be patient, and you'll get it dialed in.
there is a vast amount of jetting info on the web.. try searching Sudco or mikuni pages..

Even though the carb is outdated (Along with the rest of our 12 y/o quads) The stocker is still a good 'all around' carb... Some prefer the Keihn, I don't particularly care for them...

Just my $.02