Valve to piston clearance: 2H7 head with 3H5 piston

[motoman]

I had an epiphany yesterday while I was digging up and repairing a few leaking lawn sprinklers in the front yard.

Toro six inch stainless steel lawn sprinkler springs work perfectly for valve checking springs and will make setting up the valve train a lot easier for me!



XS1100_Valve_Check_Springs_Toro_Lawn_Sprinkler by Scott_Ci, on Flickr

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Motor valves and sprinklers...............next you'll be configuring water injection.

[3Phase]

Motor valves and sprinklers...............next you'll be configuring water injection.

Water injection, yeah, right... Oh! Oh! Four mist emitters, a small Hudson sprayer with a windshield washer pump and a couple of tees and I can....

I just finished lapping the valves on the '79F head. Now I just have to clean it up without getting valve grinding compound and carbon bits everywhere it's not supposed to go.

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[Rettic]

79 Head, 81 Pistons

I actually ended up doing this exact thing in September, well without all of the calculating and clearance checking and all that, put the head and cams on, any binding? Nope, fire it up!

I needed a good set of jugs,and found a cheap set of 81's on ebay with pistons. The engine re-builder suggested using the higher dome pistons, and said they would clear, and would give me a little boost. Needless to say, almost 3k miles later, I am very happy with it. Not sure about the power increase, butt dyno is happy.

Helped on mileage a little. went from 32mpg tops to 36mpg consistent. No carb/air filter/exhaust changes were made, just the taller pistons.

[3Phase]

Right on, Rettic! Thanks!

I was getting 35 or 36 MPG before I dove 'head first' <smirk> into this latest project so maybe it'll stay somewhere close to the old numbers and I won't have to fool around too much tuning it.

From what I've measured on my engine I'll be keeping the valves at the loose end of the clearance range. The Intake valve is a little close to the piston for me to be entirely happy with it because I don't know for an absolute written-in-stone fact how close it'll get to the piston at high RPM during extreme heat under a heavy load. Basically, I don't want to wind up walking out of the middle of the Mojave or trying to push-ride an XS275.


(Meanwhile back in the jungle!) The head is clean and soaking overnight in its last bath in mineral spirits.

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[Orange4]

Does anyone know what the compression ratios are for these different scenarios of base gasket in/out, piston swap etc? Even a guide to calculate using measurements which are XS specific would be great.

[3Phase]

Found some of the pictures

REPOST pictures for 2H7 head with 3H5 pistons:

The old Yamaha head gasket was used for both tests and it's ~1.25mm on the gasket and the fire rings.

The new (green) D&K base gasket from Cruzin' Image was ~ 0.5mm before it was installed. It's glued to the engine block now so I can't measure it without removing it and possibly wrecking the gasket but I'll try to think of something.

The new, unused, D&K head gasket from Cruzin' Image is ~1.3mm on the gasket and 1.6mm on the fire rings. It's asbestos-free, doesn't have any graphite on it at all and it doesn't seem as well made as the Yamaha head gasket. I may have to order a head gasket from Yamaha if the D&K gasket isn't up to snuff.


The cylinder to engine case base gasket was installed for this second test and some fresh clay was put on the piston.


The Intake and Exhaust valve clearance adjustment shims were reset for this second valve to piston clearance check. The Exhaust was only at 8mm and the Intake was only 1mm. The 'old' Intake shim was a 260 and the 'new' shim is a 250. I think the too large Intake shim was the one I gleeped and swapped for Columbo's last valve adjustment and I forgot to check it before I did the clearance test yesterday. Oops....

The Exhaust is now set to 10mm clearance but the Intake is only set to 5mm because I didn't have a smaller shim for the test.


Intake 1.9mm clearance
Exhaust 3.3mm clearance

The Intake valve would probably gain at least another half to a full millimeter of piston clearance if a smaller shim was available to set its clearance to 8mm instead of 5mm.



I'm beat and this thing fought me for most of the day!

Most of the time was lost because the cam timing dots refused to line up correctly. The valves had to be re-shimmed before I could do the test and I couldn't rotate the engine/cams to make sure the shims were seated without messing up the clay so I had to pull the cams back out.

I flat out lost two shims while setting the valves and I still don't know where they are besides, "In the garage!" I need a beer!

[3Phase]

Photobucket crashed --&gt; re-repost

REPOSTED repost pictures for 2H7 head with 3H5 pistons:

The old Yamaha head gasket was used for both tests and it's ~1.25mm on the gasket and the fire rings.

The new (green) D&K base gasket from Cruzin' Image was ~ 0.5mm before it was installed. It's glued to the engine block now so I can't measure it without removing it and possibly wrecking the gasket but I'll try to think of something.

The new, unused, D&K head gasket from Cruzin' Image is ~1.3mm on the gasket and 1.6mm on the fire rings. It's asbestos-free, doesn't have any graphite on it at all and it doesn't seem as well made as the Yamaha head gasket. I may have to order a head gasket from Yamaha if the D&K gasket isn't up to snuff.


The cylinder to engine case base gasket was installed for this second test and some fresh clay was put on the piston.


The Intake and Exhaust valve clearance adjustment shims were reset for this second valve to piston clearance check. The Exhaust was only at 8mm and the Intake was only 1mm. The 'old' Intake shim was a 260 and the 'new' shim is a 250. I think the too large Intake shim was the one I gleeped and swapped for Columbo's last valve adjustment and I forgot to check it before I did the clearance test yesterday. Oops....

The Exhaust is now set to 10mm clearance but the Intake is only set to 5mm because I didn't have a smaller shim for the test.


Intake 1.9mm clearance
Exhaust 3.3mm clearance

The Intake valve would probably gain at least another half to a full millimeter of piston clearance if a smaller shim was available to set its clearance to 8mm instead of 5mm.



I'm beat and this thing fought me for most of the day!

Most of the time was lost because the cam timing dots refused to line up correctly. The valves had to be re-shimmed before I could do the test and I couldn't rotate the engine/cams to make sure the shims were seated without messing up the clay so I had to pull the cams back out.

I flat out lost two shims while setting the valves and I still don't know where they are besides, "In the garage!" I need a beer!

[MaximPhil]

Hi Scott,
After that beer Just a theoretical question: Your check would have been on a cold engine. Would the connecting rod not stretch some in a hot high revving engine ?

Phil

[3Phase]

I checked everything cold. I don't have an engine lab to check parts when they're hot and I can't do it the hard way either because I'd get shot if I got caught putting parts in the oven to see how much they expand.

Sure, as the engine RPMs and temperatures go up, the parts all expand and the connecting rods will stretch like rubber bands with weights on one end.

I don't have an oil cooler hooked up and I do most of my riding loaded for bear at sustained high speeds in warm and hot climates so I decided not to use the 3H5 pistons with the 2H7 head. I bought a set of 2H7 pistons and jugs from Andreas so Columbo will be a '78E at heart.