XS11 back from the brink.

[TopCatGr58]

Hey Orange,

Look at this recent thread, Steve's posted some good info regarding the problems with mix/matching early/late model cams and engines!!

http://www.xs11.com/forum/showthread...869#post429869

Other's have commented about the concern and need to peform a valve piston clearance measurement before actually firing it up to ensure that you have enough to prevent them from meeting each other after the engine components heat up and expand and such!

You have the early model 79 engine and igntion/timing to go with the early cams, but I think you're saying you have slightly later model 80 pistons/head/valves. With the properly matched ignition/timing for the early cam, you may get a boost in being able to let in more air/fuel mixture due the larger valves??

T.C.

[Orange4]

OK,

Here's what I got:

80 heads and pistons, early 79 cams, .048 copper head gasket, no barrel base gasket.

I set up the cams and put home made piano wire helper springs on the valves so I could push the valves down easily to measure. This was a good dry run for final assembly. I used the depth gauge end of a caliper to measure so I might pick up a dial gauge to really nail down the numbers. I'm confident they are very close though.

#1 cylinder Exhaust
20deg BTDC: .175
15deg BTDC: .13
10deg BTDC: .15
0deg TDC: .15

I'm surmising that since the later cams have more lift there are deeper piston pockets

Intake
0deg TDC: .135
10deg ATDC: .130
20deg ATDC: .155

So, even with no base gasket there's scads of room there. I think .1 is recommended for exhaust and .08 for intake if I'm not mistaken.

Now, I'm contemplating shaving the head a bit but they want $75 for it at my local engine shop. HMMM.

[DGXSER]

I did not go back through the post so, sorry if this repeat. I highly recommend you find all the post by Dan Hodges. He is a long time member here who has tried about everything and documented all his efforts to increase HP from these beast. Seems he was not recommending shaving the head IIRC.

[Orange4]

Yeah I have read most of his good reasons and they are valve timing, valve to piston clearance and reduction of tapered squish zone. Since I have measured V-P and it's fine, I am not concerned about a small amount of timing change and am only contemplating a shave of .015 or so to clean up the surface. The squish zone should be good too. I have to calculate comp ratio now though.

Good to have all you guys encouraging due diligence. My dry run of cam install was instructive and it was good to have the pictorial handy.

Now I'm thinking about polishing the valve faces, not because I'm expecting any noticeable gains but because I love the way it looks and I like to polish stuff.

[crazy steve]

If you're using a matched set of '80 pistons/head, you'll have no issues with valve/piston clearances with the early cams as the intake lift is the same for all years and the early exhaust lift is less by .020".

Cutting the head is a bad idea, as that will retard your cam timing when you move the centerline of the cams and the crankshaft closer together, although you're aware of this. Big problem here is there is no truly accurate cam timing numbers as Yamaha never released them, what info you can find is 'as measured' by individuals.

The ignition needs to 'match' the cams also; to understand the differences, look here: http://www.xs11.com/forum/showthread.php?t=37189

One of the 'good/bad' things about these motors is Yamaha did an excellent job of 'optimizing' each combination (within the emission requirements they also had to meet), but it left a very narrow 'tuning window' if looking for additional power; get outside that window and you'll suffer power loss and/or drivability issues.

I'm not trying to rain on your parade, just trying to point out how hard it is to go outside the 'window' and get better-than-stock results. If you haven't read Dan Hodges posts on this, you should; Dan spent more money on dyno time than most of us have in our entire bikes. Even the 'big bore' kits with the increase in displacement and a compression jump have produced little real-world power over stock. The handful of owners who have managed to get big numbers generally did so by painstakingly 'super-tuning' their combination but needed constant fiddling to maintain that power.

I'd hate to see you expend a lot of time and money and end up being disappointed...

[MPittma100]

Piston to Valve Clearance

The best way to check actual piston to valve clearance is to use modeling clay on the valve depressions in the pistons while manually turning the engine over.

You do have to pull the head back off to see what the clearance is, but no more accurate measurement exists. After doing this you can do what ever to the cylinder head surface.

There are some draw backs of modifying the compression ratio - mainly the fact that the stock cams are only going to flow so much air and the likely scenario of not having enough camshaft to justify the modifications is pretty high.

It could benefit us to contact a camshaft manufacturer to see what the possibilities are of making some performance cams for these engines.

Mike

[crazy steve]

...It could benefit us to contact a camshaft manufacturer to see what the possibilities are of making some performance cams for these engines.

There is still somebody out there that grinds cams for these, although I don't recall who off the top of my head. But they're not new cams, they're regrinds on welded stock cores. New blanks are unobtainium....

Not cheap either, as the last time I looked a set was over $400 exchange, and I don't think that included the springs.

Another issue is a cam/bucket valve train is difficult to gain lift. Because you lack the multiplication of rocker arms or roller surfaces, 'fast' ramp designs are tough to get without gaining duration (and killing low-end power) and/or sacrificing valve train longevity. That's why 3, 4, and even 5 valve heads showed up; if you can't open the valve more or make it bigger, several smaller valves with more area is the answer.

[Orange4]

These guys list one for the excess:

http://www.webcamshafts.com/

No prices.

Stock 78 intake cams for comparison:
Lift .346 Duration 241°@.050

High performance street cam for stock engines. Price Per Set (2).
Lift.365/.365 Duration 286°/286° Duration@.050 245°/245° Grind #118

Strong mid and upper end performance for street / strip. Requires High Compression Piston, and Performance Valve Spring
Kit. Price Per Set (2).
.395/.395 284°/284° 256°/256° Grind #110

Excellent upper end performance for racing engines. Requires Performance Valve Spring Kit, Shim Under Followers, and
High Compression Piston. Price Per Set (2).
.435/.435 288°/288° 260°/260° Grind #125

Valve Springs Only
VS-Y11
Dual performance valve springs. OK up to 0.440” valve lift. Stock retainers OK

Very expensive fun, I expect.

[crazy steve]

Yep, those are the guys.... prices have gone up; $513 a set exchange + $63 for the springs.

And unfortunately, welded cams aren't known for their reliability or longevity...

[Orange4]

Spokes!

I know this isn't true xs11 but I do love me some spokes! Just picked this up yesterday. Next job will be my GL1000 rear wheel conversion. Nice thing about this mod is it's so easily reversible.

[Schming]

Looks good, does the caliper clear the wires ?

[Orange4]

It's from an XS650 and apparently it is a bolt on conversion. I have not mounted the calipers though, I think the 650 had the same calipers.

[jetmechmarty]

The XS650 wheel requires no modification other than adding a brake rotor to the left side if it isn't there already.

[ViperRon]

If you are looking for performance out of the bike you are definatly limited on mechanical design and apparently not worried about how long it stays together. You may want to focus your energy toward Nitros and mixed race fuels. Out of the pump gas today is not what it was years ago so even if you get the compression up the fuel is not. Nitros will give a definate gain in power but engine life will deminish quickly if you do not get the ratios right.

[Orange4]

Some progress...

Slapped on the pipes I just got from Andreas (along with a bunch of other good parts) to replace the 4 into one Jardines with road rash that the bike came with. They fit nice and tight. I really like long pipes. I'm going to fab up some custom mounts so it's all solid. The stock ones are functional but a bit beat up. Happy customer.