First -- the return of Jiggles. Now this lunatic re-emerges!

[corksil]

Was feeling inspired today so I dropped the engine off the frame of the 250r that has been parked for 9 months. At 30k miles the bike had been getting harder and harder to start and after a final failed attempt to get her going with starting fluid, she was garaged.

Until today.

After tearing down the engine and inspecting things it looks as if the part list will be as follows.

Ninja 300 crank
2mm overbore (2*64mm weisco pistons and rings)
Gaskets and seals

Once completed, this will re-birth the tired 250 as a 315cc.

Already on the bike are a long list of mods including carb work, area-p full exhaust, pod filter, race cams, and a few other shenanigans which will compliment the new 300 stroker crank and overbore pistons.

If anyone knows where I can get a 300 crank in usable condition, or has some 64mm pistons laying around.. PM me or reply in this thread. If I can't find a 300 crank for significantly less than retail -- it will be omitted from the list of parts in the rebuild. Splitting the cases and installing a 300 crank is no small project.

Now you guys are supposed to shower me with adulation and adore my return. Truth be told -- most of you folks probably don't remember me. Well... he's at it again.

[Suki2003]

You crazy. But it's the good kind of crazy. Go for it man!

[Racer x]

Welcome back.
Good luck with the build.

[allanoue]

[MrAtom]

I thought you rode your bike into a volcano or something, dude.

[Snake]

Good luck bud.

[corksil]

Engine came off pretty easily. Should've simply removed it when I had to do my last valve lash adjustment.

Head came off along with cylinder in a few minutes.

Measuring piston and checking clearances.

Still within spec. Starting to wonder how much I want to put into this project. If I need new rings, it's 37/piston * 2 for OEM. That's the cost of one aftermaket piston with rings, which would net me overbore gains in addition to compression ratio increase from 11.6 to 12.5. Need to see how much I'm looking at for a 2mm overbore job.

Valves and retainers came out easily after I fabricated a valve-spring compressor out of spare fork-spring preload conduit left over from the last bike build I did.

Stay tuned. And in all seriousness --- where the hell am I going to get a usable 300 crank? I did a blanket search of every single state in the US this morning and didn't find a single ninja 300 being sold for parts. 467 for a new OEM 300 crank isn't in the budget... Help me out guys.

[CrazyCanuckGoat]

I'm in the same boat as you. Was/am planning a 315 build over the winter (JE pistons though and a 300 head). I may have to forgo the crank for now if I can't find a cheap donor.

One thing I noticed you didn't mention in your posts, from what I've read, we would also need the conrods and balance shaft from the 300....not just the crank.

Cheapest motor I've found to get to me in Canda was close to $2000 shipping included. That's alot of bucks just to strip it down.

If you happen to find that pot of gold, let me know lol.

[corksil]

Yeah I ultimately scrapped the project and ended up buying a different bike and investing the time to a greater benefit and a different result.

Once I tore everything down and measured it all to be still on the tight end of the spec sheet -- it wasn't cost effective to scrap the usable parts and re-build the engine with different parts and more variables to deal with.

The 300 cranks haven't come down far enough in price to make things financially viable. Eventually they will, and I'll go ahead with the project as planned but for now -- it wouldn't have been smart to scrap my barely-broken-in parts to exchange for different stuff from a 300. Even at 31k miles, everything inside the 250 engine was minty fresh and the tolerances were tight.

For thirty bucks I settled on a unit with increased ignition timing advance. Once I can dial in a little more timing and get a little more familiar with the tuning characteristics of this particular engine I might feel comfortable buying expensive 300 parts. It's a constant and never ending search for the cheapest HP gains.

Then again, once something breaks it's always smartest to replace it with an upgraded part -- assuming that the cause of failure is clearly identified and that the mistake is learned from in such a way that it won't cause the new replacement part to fail in the same way. If I float a valve due to higher rev limit, crack the pistons due to detonation I wasn't hearing, or spin a main bearing -- I might be looking for 300 parts again soon. The bottom end on these bikes seems very durable and used 250 cylinders are cheap. I haven't found any stiffer valve springs on the market which leads me to believe that it's not a typical point of failure on these engines.

Anyways, good luck with the project and make a thread for the build and post pictures.

[JohnnyBravo]

Welcome back