Lean issue?

[WMarshy]

Hey guys,

Well, I embarked on a mission to clean and paint my header today, went and got some 60 grit sand paper and flat balck header paint. Once I got the header off I took a glance at my valve stems and noticed they have a LARGE amount of white deposit on them. Looks like its running way lean. I will take pics of the valve stems tomorrow and also pull the plugs to see whats going on. I just installed a K&N filter in place of the stock, do I need to jump up a jet size you think running a Jardine and K&N filter? Seems to run fine and smooth, maybe even a little better between 3k-4k rpm now with the K&N...

[dbeardslee]

I'm not sure valve stem deposits are a good indication of running rich or lean. I think you'll be better off making adjustments based on plug color. As far as the jetting is concerned, how is it jetted now? Based on the jetting recommendations you should be running 142.5 mains with the stock 42.5 pilots.

I would be somewhat concerned about the stem deposits - if they get too crudded up it can cause them to stick. When I first got mine there was a lot of crud on the stems. I pulled the head, cleaned the crud, lapped the valves, and reshimmed. It made a HUGE difference in how it ran - way smoother. As the valves are the business end of the pump that pulls the gas through the carbs, it will have an affect there too in terms of your mixture adjustments and how well you can balance them. JAT

[Larrym]

Mismatch between plugs and valve color???

I believe that that the exhaust valve deposits/color shouldn't be that far off what you would find inside the cylinder and on the spark plugs. I mean the valves are the first place downstream the gases go.

This is one of the reasons why I generally don't recommend changing spark plug "heat ranges" to hotter/colder as a fix to a lean/rich condition as seen at the plugs. The "range change" at the plug can make the plugs appear to be the right color but what is happening in the rest of the cylinder stays the same.

I'd suggest confirming the "white/lean" condition by examining the plugs as dbeardslee stated. Then making the proper jet change sizes based on what you've already got and the tech tips chart as a guide.

As far as removing the deposits, that's a grey area (Pun intended!). I saw light tan deposits on my exhaust valves when I took off my headers as well. My choice was to not use any mechanical means like scraping (gouging/scratching, etc.). I sprayed the valves with a good penetrant (softening/dissolving agent??)after rotating the motor by hand to fully extend each valve in turn.

Don't know if that really had any positive effect as I just bolted the exhaust back on afterwards. Haven't stuck my face/eyes in there since doing that so I can't confirm any benefits.

Bike did smoke a lot afterwards on the initial start-up. Cleared up by the time I drove down the road though.

I've not yet decided to pour some "chemical" into the gas tank as an attempt to "clean my valve stems." Still on the fence as far as seeing all those products as snake oil or the real McCoy.

HTH.

[dbeardslee]

The first head I did I tried chemicals to remove the deposits - with the valves removed. I started with a 24 hour soak in carb cleaner, then went to paint stripper, and the deposits just laughed. Finally got the deposits off with elbow grease and a dull, relatively soft metal scraper. Total time invested was a couple days. The next one I did I took the valves and put them in a drill press, spun them, and used an old hacksaw blade (held with the teeth facing backwards) with very light pressure as per TRBig's recommendation. Took about 30 seconds per valve. I kind of doubt whether there's a chemical out there that will really clean thirty year old deposits - at least not one you'd want around your motor.

[Larrym]

PT Barnum.

Thanks dbeardslee,

I kinda figured I was "spitting directly into the wind" on that one.

Plus one more on the side of snake oil.

It's really beginning to tick me off when the part stores keep showing those displays of a "gunked" valve right next to the "shiny" one. Especially when I'm standing right there next to it about to swipe my credit card.

[dbeardslee]

It's really beginning to tick me off when the part stores keep showing those displays of a "gunked" valve right next to the "shiny" one.

That's right up there with the little Lucas Oil gear machine you see on the counter in a lot of autoparts stores - the ones with the two sets of gears sealed in plastic. One set is supposedly lubed with Lucas products, and the other is lubed with bad old regular oil. When you turn the little hand cranks the Lucas gears are much easier to turn. I'm convinced that one's fixed, although if I ever have a little plastic box with little plastic gears and hand cranks, Lucas is definitely the stuff I'm going to lube it with .

[Larrym]

Leakproof seals??

I totally can't resist that one. I not only spin it a few times to watch it but I keep on cranking it until the counter person is finished with the person ahead of me.

My plan isn't to break it or anything. Just to hopefully wear the darned thing out or make it leak or something.

Then they'd have to toss it in the garbage and it'd be out of my sight.

Been 6 years now but I'm very patient.

[WMarshy]

update...

Sorry no pics of the valve stem, I ran out of time. I sanded and wire brushed my entire Jardine header yesterday and into the night then decided to wait untill I had daylight today to shoot some paint. Its a really big task to do by hand. Had to redo sanding today because it rained last night and I left the pipe out! So, I had to rush around just to be able to get to work in time.

What I found:
Valves 1-3 are nice and brown but only #4 stem is white. All of them have about the same amount of crud on them... I will pull plugs tomorrow and see how they are running. I dont know the last time the valves were shimed let alone lapped. I know it smokes a little on start up untill its warm, Im thinking valve seal are in its future. In that case, I will be pulling the head cleaning the stems, lapping, new seals, and adjust lashing.

Currently I have stock jetting 137.5 mains with 42.5 pilot. By increasing the mains to 142.5 it richens the main circuit, ~3000 rpm and up, and by increasing the pilot it richens idle to ~3000 rpm correct? Can I but just the jets alone from a yamaha dealer still? Thanks

[Larrym]

Whitey ain't Righty.

Brown/tan be the best. Rather than re-jet any circuit (Main or idle) across all four carbs, I'd look into how come #4 isn't playing along like the rest of the gang. When I got my bike the main jet was broken and part of it laying at the bottom of the float bowl.

You've got three that apparently are working well so anything different in carb #4 should stand out like a sore thumb. Restriction? Blockages? or just an adjustment likely.

Be glad that you found it when you did. One cylinder being wonky is something that doesn't always get noticed cause the other three seem to provide enough power. (Just ask anyone with the Yamaha 750 triple.)

Sorry to hear about needing to re-sand the pipes. That's not only the hardest part to do but it takes so much time..... Fun??? Not-so-much.

[dbeardslee]

By increasing the mains to 142.5 it richens the main circuit, ~3000 rpm and up, and by increasing the pilot it richens idle to ~3000 rpm correct?

Actually, the mains will affect the entire range. Pilots will too, but not to the extent that the mains will. If you bump the mains, you're going to see a change on the low end too. On the evolution of my jetting, when I first got Betsy she had a 4/1 and a free flowing air filter (sound familiar?). I had it jetted at 142.5 with that setup and the plugs were happy. Colortune also confirmed that jetting. Then I drilled the airbox, and had to bump them to 145 and went to 45 pilots. Got rid of the airbox and went to pods and had to go to 147.5's. Each time I made a change, it affected the mixture, and each time it was a minor PITA to get the carbs dialed back in. It was worth the effort though as your not going to get the full benefit from the mods unless you set the carbs up right.

[WMarshy]

What I'd really like to do is a valve adjustment to make sure they are all in spec, then balance the carbs after I bump 2 main jets to 142.5... How much more work is changing valve seals, do you have to pull the head to drop the valves? If so, that turns a weekend job into a full week job. Sounds like a good winter project to me.

[dbeardslee]

Gotta take the head off to do the valve seals - I'm sure they'll wait until winter. Setting the clearances is a good idea.