250R block on 300 ? Will it fit ?

[Mohawk]

Hi Guys, for those that have torn down both motors, would a 250R cylinder block fit in the 300 engine ?

I know the coolant inlet is a different shape on the rear of the block, but the question is whether I could use a 250R block bored out to 64mm or possibly 66mm in a 300 engine rebuild ?!

Thanks

[Mohawk]

Bump, someone must know, I’m sure ��

[gantt]

After reading some old threads comparing the 250 and 300 engines I’d say they won’t swap.

[Mohawk]

Originally Posted by gantt

After reading some old threads comparing the 250 and 300 engines I’d say they won’t swap.

Thanks Gantt, I've read through some big bore & comparison posts, but most of the pics have been consumed by PhotoBucket etc, so no longer available. It looks to me like it might fit. Just won't one of the guys that has done the tear downs to confrm.

[gantt]

Originally Posted by Mohawk

Thanks Gantt, I've read through some big bore & comparison posts, but most of the pics have been consumed by PhotoBucket etc, so no longer available. It looks to me like it might fit. Just won't one of the guys that has done the tear downs to confrm.

you might try sending a PM to the guys that was involved in the old threads. sometimes people will get an email notification when they receive a PM at a forum. its a long shot though.... have you tried searching the 300 forums??

[bruce71198]

Yes it should work. I have the cylinders from both sitting in front of me but no crank case to test it on. However you could not put a 300 cylinder block on 250 crank cases. The problem you may have is finding 4mm over pistons with the right size wrist pin.

[Mohawk]

Originally Posted by bruce71198

Yes it should work. I have the cylinders from both sitting in front of me but no crank case to test it on. However you could not put a 300 cylinder block on 250 crank cases. The problem you may have is finding 4mm over pistons with the right size wrist pin.

Thanks Bruce, I thought the 250 & 300 shared the same size wrist pin !

Are they different ?

I found a Wiseco pdf for the Versys 300 listing 12.5-1 pistons in 62/64 & 66mm diameters.

[Mohawk]

So I just checked again, Wiseco part # 40219M06600 is a 66mm piston for EX300 (will fit Versy-X 300, same engine) replace 6600 with either 6400 or 6200 for 64 & 62mm versions, all have 16mm wrist pin, as do the 250's I believe.

So 62mm would up compression from stock 10.6:1 to 12.5:1, the others are adjusted to keep cmpresssion at 12.5:1 regardless of bore, less material above the top ring.

JE list a full set of pistons for the 250, so would need the inlet pockets opened a little for the larger intake valve, but that is all I think. The stock JE 62mm high comp piston is 134g, the 66mm FSR slipper piston is 137g, say minus 1g for opening the valve cutout a little, so say 136g, which is not bad.
I need to confirm the stock 300 piston weight ! Wiseco unfortunately don't publish there piston weights, but I have seen mention in someones 282cc big bore of them being 152g, which is crazy.

Any info on 300 piston weights is appreciated. Franken Big Bore on the way

[bruce71198]

I'm a little foggy on my Ninjas engine builds as I havent messed with one in a while. The wrist pins may vary well be the same size. I was running ZX6 pistons and rods and I think those wrist pins are smaller. You'll need to run 300 big bore pistons due to the pin bore to deck height eith the shorter 300 rods.

[DannoXYZ]

Compression-height is different between 250 and 300 pistons. That's distance between centre of pin and top of piston.

In either case, if you're going overbore, you'll want to sleeve either type of cylinder. Bruce has some great build threads with using ZX6 pistons, rods and sleeves. There's absolutely nothing that will go into 300's alloy cylinders. Until you Nikasil* coat it or install sleeves. Types of rings used will also depend upon type of cylinder-wall, either Nikasil or iron sleeves.

* Nikasil is patented process by Mahle. So called something else in U.S. Check out U.S. Chrome for one supplier that can do that plating process, called something else...

There are hypereutetic alloys used for blocks by Porsche, BMW and Mercedes (alusil) that has high percentage of silicon. At end of boring and honing process, an additional etching/lapping step is used to remove aluminium from cylinder walls, leaving hard silicon crystals. These are extremely durable bores, easily lasting 200k-miles with practically zero wear. Iron-coated pistons are used in these bores. I'm not sure if 300's cylinders is made of this material or if pistons have some special coating. Certainly rings are different than what's needed for iron bores.

[bruce71198]

I'm not saying its the right thing to do but I run the low tension rings designed for the nicasil in the iron bores

[Triple Jim]

Originally Posted by DannoXYZ

At end of boring and honing process, an additional etching/lapping step is used to remove aluminium from cylinder walls, leaving hard silicon crystals. These are extremely durable bores, easily lasting 200k-miles with practically zero wear. Iron-coated pistons are used in these bores.

Exactly what the Chevy Vega used, and it worked very well. Unless you overheated the engine badly, that is.

[DannoXYZ]

Originally Posted by Triple Jim

Exactly what the Chevy Vega used, and it worked very well. Unless you overheated the engine badly, that is.

Yeah, good ole Reynolds 390! I think German blocks used material from different foundry, KB perhaps. Overheating badly any engine would not end well!

Originally Posted by Mohawk

So I just checked again, Wiseco part # 40219M06600 is a 66mm piston for EX300 (will fit Versy-X 300, same engine) replace 6600 with either 6400 or 6200 for 64 & 62mm versions, all have 16mm wrist pin, as do the 250's I believe.

So 62mm would up compression from stock 10.6:1 to 12.5:1, the others are adjusted to keep cmpresssion at 12.5:1 regardless of bore, less material above the top ring.

JE list a full set of pistons for the 250, so would need the inlet pockets opened a little for the larger intake valve, but that is all I think. The stock JE 62mm high comp piston is 134g, the 66mm FSR slipper piston is 137g, say minus 1g for opening the valve cutout a little, so say 136g, which is not bad.
I need to confirm the stock 300 piston weight ! Wiseco unfortunately don't publish there piston weights, but I have seen mention in someones 282cc big bore of them being 152g, which is crazy.

Any info on 300 piston weights is appreciated. Franken Big Bore on the way

You'll want to use 300 pistons in your build due to extra stroke (and compression-height difference). Using 250 pistons with 300 crank would result in way too much compression. Factory 300 pistons are pretty much flat-top and 12.5:1 don't protrude into combustion chamber anywhere nearly as much as 12.5:1 250 pistons. Again, due to longer stroke and ratio of displacement to CC volume.

Be sure your Wiseco pistons aren't early model with this flaw cuong-nutz discovered. https://www.ninjette.org/forums/showthread.php?t=163044

[Mohawk]

So IIRC the 300 12.5:1 piston is designed to work in the 300 cylinder head. So no issues there regardless of bore, they are ALL made to end with 12.5:1 compression.

Besides I’m happy modifying & polishing piston crowns, if used from another bike, like ZX6R etc.

Re the stroke, unless the 250 & 300 blocks are different heights, the stroke is irrelevant.
It is my understanding that the 250 & 300 use basically the same crank, as they are interchangeable between crankcases. The 300 uses a 4mm further offset crank pin, giving 8mm more stroke, but a shorter connecting rod to maintain the same TDC piston stop height.

I have it from the manufacturers of a couple of aftermarket systems, that any ring that runs in a Nikasil or other plated bore will run fine in an iron bore, but NOT the other way round.

So if the 250 cylinder will fit in the 300 engine between cylinder head & crankcase, it is a simpler job to get that bored to the required diameter than getting a 300 cylinder bored & coated again, never mind the loss of material around the 300’s open deck cylinders.

So my aim here is to get 66mm bore for 335cc with much better torque, I’m not to worried about extra power as my application is a Versys-X 300

I just dug out the data for my 282cc pistons, which are modified ZX6R 66mm ones & compared them to stock 250R ones that arrived with the block.
66mm complete = 180g
62mm complete = 167g
Complete means with rings, circlips & wrist pin. The 66mm has a 1mm lower deck height & 2mm lower dome with a smooth squish area, no steps like the 250’s. the aim there was to keep the compression reasonable.

Anyone have the weight of a complete 300 piston to hand ?

Unfortunately the 250R has the top water seal O-ring cut into the liner where as on the older Pregen it was machined into the cylinder block. So for 66mm I need to resleeve the block, or an alternative would be to sleeve the 300 cylinders. Options I need to look into.

More when I get round to it. Time is an issue for me, as I’m working away from home at the moment

As always YMMV

[DannoXYZ]

Originally Posted by Mohawk

Re the stroke, unless the 250 & 300 blocks are different heights, the stroke is irrelevant.
It is my understanding that the 250 & 300 use basically the same crank, as they are interchangeable between crankcases. The 300 uses a 4mm further offset crank pin, giving 8mm more stroke, but a shorter connecting rod to maintain the same TDC piston stop height.

Uh, no, do maths and you'll see difference. Longer stroke on 300 gives larger displacement volume. This volume will then be compressed into roughly same CC in head. Therefore, same 250 pistons will give higher compression on 300 engine.

Just because Wiseco designed 250 & 300 to yield same 12.5:1 compression does not mean pistons are same. Dome on 300 12.5:1 piston is much, much flatter and lower than 250 12.5:1 piston. About 5-7cc less dome on 300 piston from rough look of it. There's absolutely not enough material in 250 piston top (3.5-4mm) to remove enough to reduce compression of 250 piston inside 300 engine.

Plug in numbers on this calculator and see for yourself: http://www.diamondracing.net/tools/

Eagle Rods has even better calculator, but appears they've moved it or taken offline.

[Mohawk]

I don’t believe I said anything about using 250 pistons in 300 !
The Wiseco 300 pistons are correct for THAT application. No need for calculators etc.

Thanks for your input.

[DannoXYZ]

You're most welcome!

For installing ZX6 sleeves into either pre-gen or new-gen 250 cylinder-blocks, you'll want to bore out blocks for interference fit with sleeves and completely remove O-ring grooves. Then use some anaerobic sealant when pressing sleeves into block.

I prefer to have sleeve flanges be about 0,05mm above deck for extra clamping from head.