2 questions: float height and oil blow by

[tab1324]

I have two questions or actually lines of questions...

1) What does the float height in your carb affect? Does in enrich the circuit? Does it just allow more gas for WOT? I was cruising the other day and when getting on WOT it felt a bit like the power was lacking. Maybe this is more of a jetting issue as I have put on pods and not changed jets yet. Plugs look on the lean side and to me it feels like it's not getting enough gas. Planning to change the jets tomorrow but should I also adjust float height for the WOT response? It's an 82 XJ and the floats are at about 25 mm.

2) When I installed the pod filters I bought a fuel filter to install as a breather for the oil line. I zip tied it up near the battery and upon removing the seat I see that the battery has a light spray of oil on top of it. This is after only about 80-100 miles of riding. Is this blow by a concern or does this seem normal? Maybe it's the filter I'm using which has (2) barbed ends - one is clamped into the hose and the other is open.

Thanks,

Tom B.

[Ken Talbot]

Float height controls the level of fuel in the float bowls, and this has an effect on the fuel flow through the main jets. Tsunami used to run heavy to the rich side, and consistently got about 30mpg compared to the 40 mpg that SWMBO's 'H got. Without changing any jets, I lowered the floats by 2mm, and my mileage picked up to the same 40mpg. No more black plugs, and Tsunami will still pull strong all the way to redline.

With the stock breather set-up, that 'blow-by' goes into the airbox and gets sucked in and burned - no misting of oil where you don't want it. This won't hurt anything more than aesthetics. Heck, if yu get enough oil mist coming out of the filter, you'll start marking your spot every time you park, sort of like some well-known American-made big twins are rumored to do from time to time, not to mention any names.

[skids]

Ken, Tsunami is a model H, right? What did you set the floats at for the perfect setting?

Originally posted by Ken Talbot
Float height controls the level of fuel in the float bowls, and this has an effect on the fuel flow through the main jets. Tsunami used to run heavy to the rich side, and consistently got about 30mpg compared to the 40 mpg that SWMBO's 'H got. Without changing any jets, I lowered the floats by 2mm, and my mileage picked up to the same 40mpg. No more black plugs, and Tsunami will still pull strong all the way to redline.

[Ken Talbot]

Yes, Sid, Tsunami is an 'H. I don't recall for sure, but I believe it is up around 26.5mm

[tab1324]

getting dialed in

Ken,

I took a look at my floats tonight and they're about 21 mm from the carb flange (not the recess where the gasket sits but the top edge). I don't know the specs for the 82 XJ but to me it's acting like it doesn't have enough gas at WOT. It still may be jetting but I know that megathread where Mike Hart was trying to figure jets out really never seemed to sort it out. Last I heard he was playing with float heights. I adjusted tonight so they're about 20 mm. which should raise the gas level when the carbs are upright correct? I still have the original 112.5 mains in but I'm thinking they might be drilled out because I was going to drill them for 120 size but the drill bit went through without removing metal.

To get dialed in, should I take care of jetting first and stay away from float heights or should I try to kill two birds with one stone? I guess it's more like killing one bird with two stones isn't it..

Anyway, I'm trying to find the specs for float height on the XJ so I can see if I'm on the lean or rich side. Seems to me that 20 mm should be really rich but like I said, the bike is acting lean at WOT.

Tom B.

[Ken Talbot]

In your first post, you say the plugs look lean, but maybe that's something to look at a bit more critically before you start messing around with too many things. Check a few threads describing the 'chop' technique and see if you can get some repeatable results at various engine speeds, loads, etc. Then some of the more knowledgeable XSives might be able to zoom right in on the solution.

[tab1324]

adjustments

Well, I ended up checking my floats and setting them to about 20 mm above the raised gasket flange (high point on the carb when upside down). I did this so that I'd have enough fuel for the WOT. Then due to the pod filters I added, I opened up the jets from 112.5 to 128 (closest drill bit I could find in a reasonable size). In the mega thread, Mike Hart had gone all the way up to 142.5 mains and just then noticed it was running rich. I thought I'd be safe and start somewhere in between.

Wow, the accelleration has improved. Pulls hard all the way up to 8500 (that's as far as I went). Still a slight boggy below 3500 rpm but nothing worth complaining about. I might try to sort this out to get smooth low end transitions but where would I start for that? Is that a pilot adjustment or just idle mixture maybe... Idle shouldn't affect anything else though really should it. I didn't do a real 'chop' test but I looked at the plugs when I got home after running pretty hard and they looked a bit better than 112.5 mains but still slightly lean. Don't know how much more I wanna go up though because normally I ride much more sedately.

Any comments on the low end transition area? I know I'm supposed to rev this thing but I do like to run around 3500-4000 when cruising.

Tom B.

[thumperjsa]

I have heard people caution about drilling the jets. Fuel does not seem to flow through them as correctly. You can by the jets pretty cheap from mikesxs.