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Discussion Starter · #1 ·
So here's my sob story. Riding at COTA this last Saturday, in the second session my CBR600RR starting blowing a little oil from a hairline crack in the clutch cover. (Crack was caused by getting t-boned while racing in NOLA the prior weekend.)


So I switched to my CBR250R. Second session out on the little blade, going down the long back straight, shifting up into 5th, there is a large "clunk" and then grinding. I pull off and get picked up by the sag wagon. Putting the bike in the trailer I notice my belly pan is about 1" deep in oil. Taking it off the trailer, I notice that there is a 3" hole in the front of the crankcase - I can easily see into the internal workings of the piston and shifting stuff. Doesn't look good. Pieces of metal all mixed in with the oil in the belly pan.


I'm going to take the motor out and let a mechanic look at it to see the Takagawa big bore kit parts are salvageable. If not, I then need to decide whether to put in a stock engine (about $5-600 on ebay) and sell it (which would require some title work, as I never transferred title and just rode it on the track), or part it out.


In which case I need to decide on what the next ultralight track bike will be. Maybe a KTM390; Ninja 300? I love the cornering of the CBR250R, but any 250 is now underpowered and can't compete in the class.


The good news is I was able to fix my CBR600RR that night and ride all day on Sunday.
 

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Holy crap. That's nuts.

I wonder if the big bore kit proved too much over time for the lower internals? Maybe since you'll have it apart, you can do the 300r crank/piston/balance shaft swap with the big bore kit. I'm sure the internals on the bottom end of the 300r is a little beefier, but who knows.
 
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Hole is an understatement...

Maybe if doing all the title paperwork is too much, you could try selling it as a track bike first?
 

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Go down the Yamaha shop and fix it with a new R3 mate :)


You wont regret it.




PS, are you running the Jet tuning 11,800 revlimiter?
 

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Discussion Starter · #8 ·
Go down the Yamaha shop and fix it with a new R3 mate :)


You wont regret it.




PS, are you running the Jet tuning 11,800 revlimiter?

I hear ya! Are there many racing mods for R3's yet?


I was running the Jettuning 11,800 rev limiter. That could have contributed (although I don't think I was much over redline, if at all). The overbore kit could have contributed also. I'll know more once I have time to remove the engine and take it to the shop to diagnose what can be saved.
 

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Discussion Starter · #9 ·
... you can do the 300r crank/piston/balance shaft swap with the big bore kit.


Do you have a reference as to what this is, what's needed, etc.?


Thanks!
 

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Do you have a reference as to what this is, what's needed, etc.?


Thanks!
Some people have decided to do it, but never posted a how-to or materials list. Based on the design of the engine, all that physically changed was the piston/connecting rod, crankshaft, and balance shaft. Other than the ECU fueling changes, which I'm assuming can be done with the 250's ECU with a fuel controller. But if the 300r ECU plugs up directly to our wiring harness, it might be the best swap. There may be some changes in ignition timing that were implemented.
 

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Actually, I kind of update my previous statement. Seems someone on ADV riders forum has done it on the CRF250L, which as we know uses the same engine. Seems the crank/balancer is a complete drop-in swap.

The CRF250L Owners thread - Page 707 - ADVrider

But, it seems there are some case strengthenings that happened as well on the engineering side that we can't implement; how extensive they are remains to be illucidated. In addition, and I have no idea because I don't own one (Shisoshin, where are you!!! :laugh:), that the O2 sensor was removed from the head. The cams are also different and the flywheel.

CRF250 desplacement mods> CBR300? - Page 2 - CRF250 L/M - ThumperTalk

Again, I suppose I can only confirm the crank and balancer is a drop-in swap, but whatever else was changed has yet to be confirmed by a full-fledged swap.
 

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I am betting wrist pin pulled out of piston or pin failed...just think of the forces involved when that piston is doing 11500 rpms, that pin and piston pin bosses have to stop that piston from traveling upwards and yank it down 11500 times a minute or 190 times a second
 

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I am 100% positive it was the wrist pin. Same thing happened to mine. I didnt blow a hole in the case, but it did a lot of internal damage. I would look into the Duke 390, More HP lots of aftermarket parts available still light weight and flick able. Rode friend of mines a few months back, plenty of power for the track. Take one for a test ride you will love it.
 
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Duke 390 = Goodbye comfort and build quality. :p
 

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Discussion Starter · #15 ·
I would look into the Duke 390, More HP lots of aftermarket parts available still light weight and flick able.


Do you mean the KTM RC390? I've been looking into it. (I beat one on my CBR250 in my last race, but with equal riders it would have blown me away. 3 other did blow me away.)


I've never heard of a Ducati 390. Am I missing something cool?
 

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If you don't like blown engines, stay well away from KToooooooMs.
 

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Do you mean the KTM RC390? I've been looking into it. (I beat one on my CBR250 in my last race, but with equal riders it would have blown me away. 3 other did blow me away.)


I've never heard of a Ducati 390. Am I missing something cool?
Yes the KTM (DUKE) RC390. They race them here in Philippines all the time on the track. They blow my 250 off the track. If I was a big racer I would jump on the 390, I just ride for the fun of it, and to improve my street riding
 

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There are some differences between the 2015 KTM 390 duke and the 2015 KTM RC 390. RC stands for race competition, so it has lower bars, stiffer suspension, and more bodywork.
.

The 390 Duke is similar the CB300f, less fairings, 5" (125 mm) higher handlebars.
 

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Actually, I kind of update my previous statement. Seems someone on ADV riders forum has done it on the CRF250L, which as we know uses the same engine. Seems the crank/balancer is a complete drop-in swap.

The CRF250L Owners thread - Page 707 - ADVrider

But, it seems there are some case strengthenings that happened as well on the engineering side that we can't implement; how extensive they are remains to be illucidated. In addition, and I have no idea because I don't own one (Shisoshin, where are you!!! :laugh:), that the O2 sensor was removed from the head. The cams are also different and the flywheel.

CRF250 desplacement mods> CBR300? - Page 2 - CRF250 L/M - ThumperTalk

Again, I suppose I can only confirm the crank and balancer is a drop-in swap, but whatever else was changed has yet to be confirmed by a full-fledged swap.
As soon as I heard that Honda was coming out with the new 300 and it was going to be an eight millimeter longer stroke first thing I thought of was stroker kit and big bore kit put together. :eek:

It's something I'd like to do one day.
 
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