Questions about running lean

Let's start with some background: I got my '82 Maxin 750 in late fall of last year and have not ridden it much. Last week, I finished a valve adjustment, put in a new air filter, and a fuel filter. I sync'd the carbs, and then ran into some problems with the colortune. When I started the motor with the colortune in #1, the vacuum hose popped off #1 or #2. I decided to call it a day and went for a ride. Mostly highway.

When I got back, the motor was hot, and I think it was too hot. There is still some Seafoam mixed in the tank, and I have 10W40 in but it was only 7* C here. My friend's bike that is also air cooled was hot, but you could touch the fins. Mine was much hotter.

Today I pulled the plugs and all four of them are white. Obviously I am running lean and am lucky that I didn't have a really bad day yesterday. After looking at the fuel filter installation, I am wondering if that could be the cause. I have one of the 90* filters, and am wondering if there is enough flow, or if this could cause a lean condition. The filter isn't always full, so I am thinking that the filter needs to be lowered a bit to improve the flow of fuel. Could this cause the lean mixture? I thought I would ask before making a lot of changes to the mixture screws.

Thanks for your insight,

 

If you have a poor fuel supply the bike will perform badly, but it won't run lean, if your pilot screws are at 2 1/2 turns out, bring them out 1/4 turn.

 

Thanks, Wizard. I'm wondering if this is a petcock problem. I went out to check on the fuel filter "line". I propped up the seat end of the tank a couple of inches and then for the heck of it, I turned the valve to prime. Now, my thinking was that there should be a good flow of fuel (the tank is almost full), but there was barely a trickle. Could this be the problem?

The bike seemed to run well while syncing the carbs and while on the ride, so maybe I have lean idle mixtures and a malfunctioning petcock?

I'm getting a headache...

 

Take 2 Advil & go sit in the dark. 8)

 

yup bad petcock seals and diaphram .... do the entire petcock kit not just the two or three o-rings. most places sell it for about $20 - $25 5 min to install .... also while you have it apart clean every passage front top and bottom i found that the PO of my bike put tank liner in with the petcock installed rendering the same problem. dont throw away your tank side fuel screen if you can clean it and re-install it .. i havnt found anybody who has them. You might ping CHACAL on that though.

i have had those headaches before - - Front Fork Suspension Dampener Nut (it reminded me of brain teaser problem)

 

Well, I was already in the dark, Wizard, but took two Advil and sat a spell. Then I went back out to the garage. Took the tank off and ran the petcock in prime with no hoses. Ran good.

Started over with the colortune, and did not connect the carbtune at this point. I think I got them all set and did not pop off any vacuum caps. I adjusted the carbs until they were orange and then in a bit. I figured it would be better to be a little on the rich side than the lean side. I was surprised by how many turns out it took. Perhaps this bike wasn't adjusted for a long time; perhaps never since it left the factory.

Then I synced the carbs again and cleaned up. Also lowered the filter and there seems to be more fuel in it.

My fingers are crossed...

 

Lazy petcock, I'll bet. It's not uncommon for them to develop a trait where they are umm.. less than responsive to vacuum, or erratically responsive. If it runs fine on PRI (mine does) it's rebuild or replace time. Chacal carries both rebuild kits and "stock" replacements (although the style has changed a bit from the old days.)

Unfortunately chacal doesn't carry round tuits.