To install such a kit, you must pull the top end. Acquire cylinders with flat decks. Press the sleeves out of them. Bore the aluminum to accept a larger sleeves. Bore and hone these to accept the larger pistons. Enlarge the spigot hole to accommodate the larger sleeves. Ride only short distances and very gingerly to avoid heat-related problems. For a 108mm piston, a sleeve OD of about 112mm would be required. A deck flange with an OD of 116mm would be called for, with a depth of at least 2mm. There's room. One would only need to remove material from the cases down about 20mm.

What would it cost? Reckon a hundred fifty dollars for cylinder cores. Another hundred fifty per sleeve. Sleeve into cylinder, a hundred fifty per. Modify cases. See alternate means on bigtwins.org. Another hundred. The piston kit: $1400 - this is with reflon skirs and ceramic crows. Total: $2150 - tentative. Maybe more, maybe less. Modified gaskets.

As the machine work and engineering are about the same, other sizes would cost similarly.

For this bore size - and realistically for any size that requires enlarging the spigots - it would be a very good idea to run plated bores and at least a single oil cooler. So - core cylinders: $150; "sleeves" $300; machine work to install sleeves and plate bores $300 + $550; piston kits $1500; case machine work: $300; modified gaskets plus rest of kits $200; modify oil filter cover $100 including lines; $100 minimum for the actual radiator and mounting. That's $3400 not including any freight or wrench work. Enjoy.

Early inspection shows us that 108mm might represent too big of a bore, and 89mm too long of a stroke. The spindle that the cam gear/sprocket rotates on appears to be lubricated by oil scraped off the cylinder walls by the rings on the down stroke. A very large and/or long sleeve would close off the bore that houses this piece. It appears that a hole would need to be bored through the side of the lower sleeve and champfered to oil this critical part. This is not a unique idea. It would necessarily make each cylinder either a front or rear - unless a superfluous hole were put on the other side as well. And because the pistons pull partway out of the bottom of the sleeve at BDC, needed longer sleeves for strokers would come closer to slimmed down flyweights and this oil hole would be essential.

It appears that the low pressure transmission oil feed comes quite close to the pivot bore. A narrow, carefullly-executed drilling may do the trick. This disturbs me on a couple of counts: I have to trust people who's ability and attention to detail I cannot assess. And I need to develop some rather involved instructions. More as this develops. And a hold on this bore and this stroke.

I assembled a crank with rods and pistons to a case today to see what would work. A 106mm bore would work with an 84mm stroke. Maybe. I sent my design thoughts to Falicon to see if they thought that they would work. I run it backward and forward in my head and turn the crank to check clearances. The only machine work necessary would be the reaming of the case spigots to acompany the larger sleeves. The sleeves would need to come lower down and closer to the flyweights. Stock the pistons pull half way out of the sleeves at BDC. This causes piston slap and scoring on the thrust faces. We want to reduce and possibly eliminate this. At BDC the skirts would barely clear the flyweights. One of the front rod nuts comes very close to the back of the windage tray. Some filing may be necessary. Then again, we may get around this with the rod style we utilize. I am dithering between aluminum and a style where the bolts thread directly into the cap. No nuts.

How about 108mm bore by 89mm stroke? Sleeves large enough to guide these pistons would need to come very close together. Especially with a longer stroke. The flyweights will need to be reduced in diameter. Tungsten (or other heavy metal) plugs will be needed to restore balance. The windage tray will need to be dressed with a rotary grinder. Very carefully as a major oil passage moves from one case half to the other in the bottom.

Stroker kits will only be offered in 106mm by 84mm; balanced and complete. If I decide that it is possible, the same will be true of the 108mm by 89mm kits.

For some further analysis, see here.

Last Modified:   Saturday, 09th March, 2024, 10:23am PST