Honda finally stepped up to challenge the 250cc street bike market with the CBR250R, released back in 2011. Sales were brisk for the $3995 (non-ABS) machines, as new riders flocked to grab up something light and easy to handle. The Honda was a single cylinder machine (76x55mm) with DOHC and 4 valve cylinder head. Outfitted with fuel injection and a close-ratio, six-speed transmission, rider reviews were mostly positive except for the lack of horsepower (just under 24hp) in comparison to the prevailing 250 Ninja machines which had been on the market for over 20 years. Weighing in at around 350 lbs, with 17” wheels/tires, the bikes were nimble and incredibly economical (in the range of 60-80mpg).
Kawasaki countered with a new 296cc Ninja 300, which made some 34 horsepower and weighed little more than the Honda. Now behind a good 10 horsepower, Honda stepped up by enlarging the 250 engine to 286cc with a fresh 76x63mm engine upgrade. That added another 3-4 horsepower to virtually the same chassis as the 250 models, giving a top speed right at 100mph. Gas mileage was now rated at 71mpg. Those who were so taken with the 250s stepped up to grab the CBR300R editions, which had risen about $400 over the old 250cc pricing.
As soon as Honda announced the enlarged model, all Hell broke loose as Yamaha stepped in with a new 321cc parallel twin, then KTM stepped up with a flyweight version of their 390cc Enduro machine in full street bike configuration with horsepower ratings up into the mid-high 30s.
As with everything known in the universe now, there are CBR300R blogs/forums where owners can share their joys and woes of these mini-sport machines, which are manufactured in Indonesia. More than a few entries noted, that like the 250s, these new 300R models tended to use oil faster than expected, causing some oil starvation failures when the level got too low. The engines only hold 1.9L (around 2 quarts), so those reporting oil consumption of a quart per 1,000 miles got themselves in trouble when the failed to check the little oil level window on a regular basis.
Bill has had some fascination about these little machines but had not thrown a leg over any of them except at a dealer’s showroom floor. As can be imagined, when the CBR300R models were released, any leftover CBR250R machines sat unappreciated for weeks and months at a time on the dealer’s floors. Use machine prices have plummeted into the $2000-2500 range, even with very low miles accumulated. A recent Craigslist posting showed up recently with details showing as “2015 CBR300R needs new engine.” A quick call to the seller revealed that he was the 2nd owner and was using the bike for commuting about 50 miles a day. He had changed the oil and filter 2,000 miles previously and just rode the bike daily without checking the level. His commute came to an abrupt halt when the engine “slowed down” on the freeway at about 70mph and failed to restart for more than a few seconds.
The bike was taken to a nearby Honda dealer who noted a distinct lack of oil then estimated a $800 charge to remove the engine and determine the damage (price was not a repair cost). Apparently they started the engine with some added oil so it was up to the mark, but it did the same routine… start for about 10 seconds, then stalled, start for 5 seconds, then stalled, then did not turn over at all. So, it went up for sale as-is and subsequently was transported to Casa De Honda for teardown and determination of the extent of damages. Running an engine out of oil can do massive damage to most small motorcycle engines. Generally the piston is the “fuse” when the oil runs low and sticks/seizes to the cylinder bore. In chats with friends who work at Honda dealers, one had come in with a seized piston and the piston and cylinder were covered by warranty. Unfortunately, the 1 year warranty had expired in early Sept. so it isn’t looking like any help from Honda is forthcoming.
Once all the bodywork was peeled off (very time-consuming with lots of fasteners involved), the engine was finally dropped out the bottom of the chassis. Actually, it didn’t want to come straight down and the final solution was to lay the bike over on some pads and wiggle the engine out horizontally.
Once the engine was up on the bench, disassembly began in earnest. The top cam cover was removed and initially the view of the camshafts and roller rocker arms showed a little heating, but nothing that was alarming. Removing the camshaft bearing holders freed up the camshafts (after the camchain tensioner was pulled off the back of the cylinder). So far so good…. Loosening the four head nuts and two long 6mm bolts allowed the cylinder head to come off for a look at the piston crown and bore. Thankfully, there was no apparent damage to the piston/rings and cylinder bore either.
Apparent from the beginning were piles of brass filings, specks and shavings in the drained oil, the oil filter and the oil screen, as well as the lower 2” of the crankcase and outer covers. It looked like an explosion of brass inside the cases, raining particles everywhere. Once the cylinder was pulled off the crankcases, the problem became very apparent; the connecting rod’s two thrust washers were now just one and some shreds of the second one with the connecting rod moving very reluctantly on the crankpin. Interestingly enough, the engine has a high pressure oil pump which feeds two automotive style plain bearings pressed into each side of the crankcase halves (vertically split cases). The connecting rod is a one-piece unit with roller bearings and thrust washers all pressed together in one assembly. One might expect that the main bearings would have taken a hit along with the rod bearing, but that was not the case. The only failed part was the crankshaft/rod assembly.
Checking on-line pricing, it was amazing to see that the retail price of a CBR300R crankshaft was just $250, with some dealers offering them for $50 off. Fortunately, a local dealer who is a long-time friend of Bill has offered a substantial discount in the parts department. The price came down to nearly $175 and all the associated parts totaled less than $350. With a $1200 purchase price, plus a new tire installed on the back, the CBR300R with a rebuilt engine will cost less than $2000 ready to drive. Obviously, there are a lot of work hours and some financial investment involved in the process, but perhaps a fully rideable machine will be ready for Bill’s first test drive before Halloween (or at least before Thanksgiving) if all goes according to plan.
When you look at the overall specifications, the CBR300R isn’t too different from the 1961-67 CB77 Super Hawk machines, apart from the huge tires, liquid-cooling, fuel injection and 6-speed transmission. The horsepower and weights are nearly a match and both machines will touch about 100mph. The two DLS brakes on the CB77 aren’t a match for the disc brakes on the 2015 machine, but the comparison is an interesting thing to ponder, isn’t it?