Overbore question

[turbocamino]

 Hello,  Can my stock 1200 cylinders be bored for 1250 pistons...or do i need to sleeve it and clearance the cases? thanks.

[aviationfred]

From what I have seen with the overbore kits for the FJ. Up to the 1219 pistons you don't need sleeves. The 1250 and larger piston kits require sleeves and modification of the lower case.

My 2 cents added.... for any overbore, even the 1195 kit, I would invest in the RPM oil cooler for more oil cooling capability.

Fred

[racerrad8]

Hello,  Can my stock 1200 cylinders be bored for 1250 pistons...or do i need to sleeve it and clearance the cases? thanks.

No, you cannot use anything bigger that 1219 on the stock sleeves & cylinder block. The 1250 cylinder block has siamese cylinders and allows for the larger 1250+ sleeve.

The 1200 block are not and have a gap for air flow and when trying to fit the 1250 + sleeves there is not enough cast material for the sleeve.

So, you need to start with a 1250 block for the 1250+ pistons.

Yes, the cases have to be clearanced for the large sleeves.

Randy- RPM

[aviationfred]

Sorry about not getting all the information regarding the overbore sizing. I did know the 1250 needed sleeving, but I didn't know the 1250 cylinder block has siamese cylinders, and a stock 1200 cylinder block will not work.

Thank you Randy for catching my omission.

Fred

[turbocamino]

  Thanks guys for the reply's. Sounds like an expensive endeavor...that said...if i came across an XJR1250 block for 500.00 it sounds like i may be ahead of things?... was told its an aluminum bore with a chrome bore coating?...not at all familiar with that. Would this be a desirable starting point.

[Pat Conlon]

If you are planning on sleeving the block I would be less worried.

If you think you will get away with installing your 1250 pistons (79mm) in the existing niksil plated bores, I would not buy the block until you thoroughly checked it out.
The racers have found that the plated bores in the 1250 block oval out under the extreme stress of racing. This is not really a problem with street bikes, in fact there are a few advantages of the plated bore cylinders, they shed heat better, they have less surface friction, to name two...however, like other plated bores, when they are done...they are done. If the bores are not oval, you could send them out to be replated but many folks just press in new sleeves

I would just plan on new sleeves and be done with it.

....and as long as you are planning new sleeves, why stop at 79mm pistons? Randy @ RPM has some very tastey 82mm pistons. With the modern short skirt design and using narrow pins, these bad boys weigh in the same as your oem pistons..


Go ahead...you know that you want to....

[RichBaker]

Go ahead...you know that you want to....

  God Damn! God damn the pusher man.   

[fj11.5]

Those are just dam NAUGHTY 

[turbocamino]

Thanks Pat...for the nudge...Thats alot of piston to be throwing around.  The 1250 block was said to be from a 17K stocker.  Also trying to figure how well rings seat with a chrome cylinder ? ...and as to cost...sleeves,installing them and then the bore job. any idea of that cost?   

[ribbert]

RPM has some very tastey 82mm pistons. With the modern short skirt design and using narrow pins, these bad boys weigh in the same as your oem pistons..

The 1219 pistons weigh a wopping 40g less (each) than standard.

[Pat Conlon]

Thanks Pat...for the nudge...Thats alot of piston to be throwing around.  The 1250 block was said to be from a 17K stocker.  Also trying to figure how well rings seat with a chrome cylinder ? ...and as to cost...sleeves,installing them and then the bore job. any idea of that cost?   

Call around. Check eBay. You can get a ovaled 1250 block fairly cheap...... I would guess a salvaged 1250 block with new sleeves, bored and finished honed for around $600-800. Remember you also need to have your engine case relieved to fit the 1250 block. You still need pistons, pins, and rings...you still need some 1250 rods...and with all the expected added torque, you should consider back cutting your tranny gears.
Might as well install some larger exhaust/intake valves....

See where I'm going with this?

I would expect to have *at least* $3k in engine parts/machine work before it is all said and done...realistically more like $4-5k.

[racerrad8]

The 1250 block was said to be from a 17K stocker.

Where did you find a 1250 block in the US, or did you get it from Europe?

Randy - RPM

[aviationfred]

The 1250 block was said to be from a 17K stocker.

Where did you find a 1250 block in the US, or did you get it from Europe?

Randy - RPM

Here is a 1250 cylinder block, Andrews Motorsports in North Carolina.

http://www.ebay.com/itm/Legends-Race-Car-600-INEX-Yamaha-FJ-FJ1100-FJ1200-XJR1250-Cylinder-Block-/180490850307?pt=Motorcycles_Parts_Accessories&hash=item2a0617d003&vxp=mtr#ht_767wt_1161


Fred

[racerrad8]

Here is a 1250 cylinder block, Andrews Motorsports in North Carolina.
Fred

Yep, I now there is access to new ones in the US, I have sold plenty of them for the race car crowd. I personally do not stock them as they are a very expensive item to sit on the shelf.

I can supply just as much and more as Andrews does and usually at better pricing.

That is a lot of money to buy a cylinder to bore out and sleeve for the 82mm pistons.

My question possibly wasn't worded correctly...

...The 1250 block was said to be from a 17K stocker.    

Where did you find a 1250 block with 17K in the US, or did you get it from Europe?

Randy - RPM

[racerrad8]

was told its an aluminum bore with a chrome bore coating?...not at all familiar with that. Would this be a desirable starting point.

That is correct, the sleeves in the 1250/1300 cylinder block are a thin wall nikasil material sleeve. They are not a locally serviceable sleeve and once they are over-size, out of round or tapered you must have them bored out to fit the oversize steel sleeves. You can either just bore them out for replacement 1250 sleeves and resize back to the stock 1250 pistons or you need to overbore the cylinder to fit the larger OD sleeves for the big bore stuff...

Randy - RPM