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Better hurry up, mikstr!

Old 08-17-2010, 11:24 AM
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Better hurry up, mikstr!

I had a bit of a mishap, my last time out. The coolant bypass tube decided to separate from the water pump body and dump avery last bit of my coolant out on the track and into the bottom of my lower fairing - good thing I was running Water Wetter. Anyway, my first indication was when I happened to look at my temp gauge and it was at about 210, when it had been running at 180. Two laps before, I had the *** end slide going into turn 3. I thought it was strange, but it seemed ok after that. I decided to pull in and saw the coolant everywhere.

As the engine was cooliing, it made that sharp tink, tink sound. I knew I had overheated it and the heads were moving around on the block. I got the water pump fixed at the track - the guy installed a setscrew through the pump body and pipe and sealed it up with red loctite. He told me it happens pretty often with Honda water pumps.

I ran a couple sessions that afternoon, then had a really good, full day the following day - the best in a long time. But my coolant reservoir was losing water, so I knew I had blown head gaskets and possibly warped my heads - not to mention that the cylinders would be out of round. Great. I got it home and the coolant resorvoir smelled like exhaust, confirming the head gasket problem.

So I tore it down. In the meantime, I found a REALLY good engine, with very low miles that a guy had bought for a kart project that never happened. He sold it to me for $250, because he was tired of having it in the garage. The cylinder walls and everything I have inspected still look new.

When I got the heads off my motor, I found out that the heads didn't warp! The cylinders were about .0025-.003 out of round, which is not too terrible, for a 4" bore. I put new head gaskets in and it will run like a champ. It might burn a bit of oil, where it never did before. At least I'm back up and running. I'm happy about that.

so in the meantime, I've been planning a custom piston design. I measured the installed height of the stock pistons, from the donor engine and the shelf-stock JE pistons in my engine. The JE pistons averaged .020" below the block deck and the stock pistons were .024" below. The head gaskets are .027" thick installed. So the squish clearance is tighter with JE pistons, but I would like to be in the .035-.040" range. I also want to end up with a true 12.5:1 compression ratio. JEs and Wisecos are about 11.3:1.

I found a guy that had some custom CP pistons made, that produce 12.5:1 compression ratio, with stock combustion chambers. They are designed with a higher compression height, for tighter squish and a ~.002-.0025" skirt clearance, in stock bores. I have a set of stock RC51 pistons to measure. I know the specified compression height for the CP pistons. I'm measuring the stock piston height - from the wrist pin center, to the squish face. If the squish sounds right, I'll probably buy a set of those.

Once I know the piston weights, I'll send my spare crank out to be lightened and balanced for the pistons and Carillo rods.

I may have a winter project brewing...
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Old 08-17-2010, 11:43 AM
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Argh... And here I thought I had a headstart on mikstr... Now you gonna go chasing me as well?

I refuse to work on the bike when it's riding season... Unless it's raining... Which it is... So I'm going to the garage... Cya...
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Old 08-17-2010, 12:57 PM
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AS I do not have the proper tools or work area to undertake the rebuild, I will handing the job over to my dealer, who at one time built the race engines for Honda Canada's Superbike effort. Needless to say it will be in good hands.... I will dropping it off in late Fall as I don't want to lose riding time (our season here in Canada being short enough as it is....)
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Old 08-17-2010, 01:06 PM
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I have a hard time riding when it's canoe racing season, which it is. And my bike was broken, so I had to fix it. Planning a track day on the 28th.

Also...

I got my exhaust system mounted up. Took off about 7 lbs, and moved the mass center of the rest down and further fwd. so I had to put it on the scale, for new semi-dry weight numbers (no oil, no coolant, almost no fuel).

drum roll.......

185 lb front
186 lb rear

with fluids, I think I'll actually have a slight forward weight bias. Here ducky ducky...
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Old 08-17-2010, 05:41 PM
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Is this a combined weight of 371 lbs for an rc51? They are calling them 439 lbs dry stock!
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Old 08-19-2010, 08:36 AM
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Yup. That's the dry weight. Pretty amazing. I didn't do anything that special. Light wheels, semi-light exhaust system, light battery, no extra wiring, Sharkskinz.

I just built a good race bike and that's what I ended up with.
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