Airhead shorter piston longer rod experiences?

The pushrod tubes (obviously) are shortened too and have to be bent a little to make them line up.
They don't leak, but I use a bit of silicone on them just to be sure.

The real problem is that the pushrods are not perfectly in line with the cam followers ( lifters) and they are prone to a bit of flexing.

Displacement remaining constant, more torque through greater angularity via longer stroke OR shorter RLR is much more than "just theory".

I think you are missing the point that longer RLR's do not have across the board increased torque over shorter RLR's. Shorter RLR's create more torque through greater mechanical advantage until the RPM's get high enough that a shorter RLR's piston gets itself out of the way before the flame front has a chance to push on it. Longer RLR's have less mechanical advantage over shorter RLR's any way you look at it. You are spot on about where the piston is per degree of crank movement but at lower RPM that aspect is no advantage since the slower speed of the engine is enough to get the piston to hang around for the flame front to push on it. That combined with more leverage through angularity means that short RLR's have the torque advantage just off idle.

It is my understanding the regular 100 power kit, not the 1070, is dimensionally and materially the same as or pretty dam close to OEM, since it uses the same size cylinder size, same nycasil, and a 9.5 piston which is the same as an R100RS piston of the same year. Only the pistons are lighter. Still have three rings, so to keep the same rod and increase compression, the gudgeon to crown has to be slightly bigger, and that should keep the ring lands big. To reduce the piston weight by 110 grams and have a big gudgeon to crown, more stuff must have come off the waist?
So running the same 87 or 89octane really shouldnt be a problem. I realize teh 8.2's can run irish cream, but the 9.5's arent into the 90octanes to run right, I do believe.

This is my fervent hope and dream, anyway.

Richie Moores website has some useful information, including dyno charts, show results from various engine mods including long rods and short skirt pistons.

I believe Richie has a 103BHP airhead engine

Link here http://www.moorespeed.co.uk/technical

now that was an interesting read! Thanks, Rob. I need to figure out a way to make a few thousand dollars of expendable cash.

Long rod, what?

Long Con rod with a shorter piston. Send Richie an email and ask him about it.

Richie Posted this on UKGSer :-

the long rod kit has more torque and more power . the standard 100gs has about 47ft/lb at the wheel and about 51 bhp . the long rod kit gives 57ft/lb and 64bhp on standard heads it is all a lot more efficiant due to side thrust and rod angle. i normally just use these for racing because it gives you a higher base level to start tuning but the cost is high.

Imho the rod-length is most of academic interest.
You might (or not) gain 4-5% power between 3000-7000 RPM but the cost is high.

When it comes to reliability of big-bore kits it's worth to remember that there are different solutions on the market. I run a big-bore kit myself and I'm not worried at all.

Academic interests??? I have SEEN it work! As have MANY others!

I do think some even advocates of longer RLR's mistakenly focus longer RLR gains on rod angularity. Some famous tuners I think rightly think the gains mostly have to do with TDC piston dwell and flame front speed.

Different solutions to big bore kits?? The one solution they need and no one has done is moving the cylinder studs out to make more room. They ALL have the same issues as long as the studs are where they are. Of course, moving the studs out would require completely re-casting the heads AND cylinders.

Did I get it right - this guy believes in a more than 20% gain in torque/performance just by increasing rod length?

Kind regards
Sven

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Yes it works, and if you check out Farmers link you can see some dyno-graphs. They are in the range I described. Be sure to read the right graphs...<o></o>
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So multiple Paris Dakar on a single set with cylinders or 200.000 km doesn't count?

I didn't read his charts. I have seen the results myself with a dyno.

Who is trying to WIN Paris Dakar on wrung out cylinders and pistons? Over and over again? Was the class wide open or 1000cc?

Just about anything will work. How well is the question. Big bore kits do work but I expect my rings to seat better and my gaskets to not leak oil. I am just going on what I have seen myself. No googling.

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Raymon Loizeaux, he started in at least 18 Paris Dakar rallyes so I guess he knew what he was doing. I never said he tried to win.<o></o>
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It isn't that difficult. After all I've managed it.<o></o>
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One thing I find strange is that you say you have a lot of experience with big-bore kits but not modifying clutches. Is there a trick here? I got clutch-problems with my lightly modified Siebenrock 1000ccm-kit. <o></o>
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I don't have that much experience with high mileage big bore kits but the ones that I have experience with had big issues. Looking at the almost non-existent gasket surface sealing area and the distorted cylinders explained the trouble to me.

When I was working for Chris at San Jose BMW with the very late Wrecking Ball in road race trim, it had basically a stock K75 clutch in it and Chris told me that in hindsight the mod needn't had been done. I am willing to bet that that bike was making WAY more power than your setup.

More than likely you have a warped cover plate and pressure plate. I have quite a bit of experience with the late model clutches handling quite a bit more power than stock with NO problems other than the ones they SOMETIMES have anyway. NO clutch is perfect that I know of.

What about the class rules? Who said he was running the same top end year after year?

the Seibenrock kit is 1070cc and has a modified camshaft, so it's not just rod length that gives the power.

thx!

A longer rod is not going to do a damn thing by itself.I believe most of you are thinking that it increases CCs which it doesn't. That would be a longer stroke which means a shorter rod is needed so the piston doesn't hit the head or the wristpin moved closer to the crown as mentioned.In some cases a plate between the jug and cases will alleviate the problem but also requires redegreeing the cams for optimal results.

I'm not thinking that. Richie says his rods are 15mm longer and he makes the shorter piston to counter that. The gains come though higher compression pistons and more efficient thrust angles.

The guys having work done by him seem really pleased with the results and he seems like a genuine open guy.

the clutch problems started for me at about 60ftlb at the wheel and about 75bhp you could open the throttle in 4th or 5th at about 70mph and just smoke the clutch. my 980cc sidecar race engines have about 100bhp at the wheel thats over 110 at the crank and the standard clutch with a heavy spring has no hope. the longer rod with moore dwell at tdc helps the power with the high top piston. i have spent more than a month on the dyno trying many things and long rods work on this engine.

I have seen stock clutches hold up behind engines that turn about the same numbers. Then again, I have seen stock hp smoke many a clutch as well. I bit more spring pressure might help at some point but remember that all the later model bikes with way more power stock have about the same exact clutch. K12's for instance.

Rob, most in the know including Yunick attribute most longer RLR's gains to the increased piston dwell at TDC and NOT more efficient thrust angles. Yes, longer RLR's do have a slight advantage in not trying to cock the piston quite as much but they have a distinct disadvantage as far as thrust angles at the rod/crank are concerned. Dr. Curve explains it pretty well.