Topic: Carb jetting???

[biokiller]

Hello All-

I have a 71 Cb450. Stock motor, K&N filters no airbox, and straight open pipes. I have 130 main jets now, any idea what I should be going up to??

Also what do i set the floats at???

Thanks for the help.
Tom

[Soos]

Elevation would be nice to know, and are they stocker carbs?





l8r

[tbpmusic]

Floats are 20mm.

Why do people always just assume the first thing to do is start fooling with the carbs??

How do your plugs look with the current jetting??
Are they lean??
Don't mess with it until you've gathered some basic diagnostic data.
450's have very tolerant carbs, don't just start changing stuff.

[crazypj]

Its going to be rich mid range without airbox. drop needle as low as possible and do some tests.
I've had some success by fitting a spring between frame/carbs to hold rear of carbs at stock height (they droop without airbox and run even richer)
PJ

[tbpmusic]

Needles on 450 carbs are not adjustable.

[biokiller]

I'm in Chicago so very little elevation. Stock card, just rebuilt. i have just set the float height, seem alittle better now.
I wasn't looking to change the jet, I was looking for advice if it need it from others experiences. I had one side that was running very cold, and the plug would foul out from carbon. So we where thinking it was running rich.
now that i adjusted the floats, seem allot better!

Thanks for the input.

Tom

[tbpmusic]

Tom -

Please don't get defensive - in your first post you specifically asked for jetting advice,

Again, you have to judge the jetting from the appearance of the plugs.
I had a couple of 450's when I moved to the Chicago area from Denver, didn't have to touch the jetting at all.
With my latest 450, I went to foam filters and much less restrictive mufflers, and I'm still running the original 130 jets.
They're very forgiving carbs.
And there are other things going on besides jetting - get a good compression reading first. If you don't have a gauge, maybe borrow one, or even get a shop to do it for a couple of bucks - even auto shops can do it for you. Honda draws the "line in the sand" at 164 pounds on a 450.

It's just a matter of gathering the basic diagnostic info before you start to change things up.

Use this method and get a plug "reading" - then go here and interpret what you see - http://www.4secondsflat.com/plug_chart.html
Put in clean plugs, then take off and get on it hard for a few miles. Chop the engine, pull off the road and yank the plugs out - compare them to the chart.

Bad rings or valves (detectable by low compression) can cause blackened spark plugs, too.
timing that's not spot on can also cause "dirty" looking plugs.

[biokiller]

Excellent help. just need it to warm up some more so I can get it out to check the plugs.

Thanks for all the input.

Tom