For those who have done it, had it done, or know someone that did it...what cost might I expect from replacing my F3 pistons with new and reboring the cylinders. Any recommended aftermarket pistons that use stock crank? I'm just weighing options given the shop suggested I replace my piston rings while my 20K miles engine is apart...and one of my carbon coated pistonsseems more oval than circular (hope my eyes areplaying tricks).

Thanks in advance.

 

Not sure on the cost, as my bike had it when I bought it, but I have a Wiseco 637cc 13:1compression kit installed. You have to run premium with this kit, but it certainly runs strong for a 10 year old motor. Power wise I haven't dyno'd it, but I talked to another guy who did and he said he put down over 115at the wheel with full exhaust, intake and jetting on his bike. That sounds a little high to me, but I would say if your lookin for a little more power then go for theWiseco kit. I'm unsure of my jetting, but I have a full exhasut at the moment, and it's got plenty of power. I plan to swap in a K&N and rejet it, maybe a dyno tune this summer once I get some extra cash.

I think the kit is $400-$500 for parts, plus a few hundred in labor to install. So if your not looking to drop a ton into your motor then replacing the rings would be your best bet.

 

20k isn't much on that motor. Why is it apart...? Do you have the bad tranny in the General Tech forum..? I think your shop is trying to talk you into something.

First, they should have a bore guage they can measure if its "hour-glassed" bad enough to even need a bore. This is aside from a visual inspection for galling/scratches/gouges etc.

Second, if the piston grooves and skirt diameterare in spec and the ring end gaps are in spec (I'd bet a paycheck they are with only 20,000 miles) there is no need to replace them. Skirts will always have some scratches on them, but deep gouges are bad.

I'm serious about "only 20K"...I torn down an F3 motor with 53K....I found virtually NOTHING needed replacement...though many things were to the"looser" end of spec...nothing was to the wear limit. abadfish had 78K on his F3. These are 100,000 miles motors....especially in routine street use.

Now, if things are "bad" or you want a power upgrade...read on.

Machining is two different steps..... like a .5mm oversize OEM pistonsmany shopswill just hone to size...maybe $20-30 a hole.

If you go larger like a 1mm overbore OEM or 2mm aftermarket, its a Bore and hone, which costsmore.... $40-60 per hole depending on where you are.....the CBR has the cylinder integral to the case, and the machinists hate that and charge accordingly.

OEM cast pistons...$60 a hole

Wiseco Kit is $450 give or take.

JE Pistons are another good choice....I think they have a 618 kit.

Head Gasket $50

With the integral block/case design, you have to remove the rods to remove the pistons. I am not sure off hand if the rod bolts are torque to yield type or not...if so, they should be replaced and the nuts....probably another $40-60

Labor...you already have the engine apart at a shop by the sounds of it. This extra bit of labor is probably 4 hours....pull the head, remove rods and pistons, reasemble

Good luck........

 

Thanks for the info.

This is myfirst bike, but I'm probably the 3rd owner on this F3, I bought the bike looking a bit rough, then it was extra rough after I recovered it from being stolen....I assume that these have been a hard 20k. I am one of the people with a F3 that was jumping out of 2nd. I'm a motorcycle novice that hoped the problem was just shift linkage related...then was hoping it was just a shift fork...then was hoping I could just replace 2nd gear....now everything is apart in my buddies garage.The weather is getting nice...now i just want to ride.

Anyway, do those piston kits use stock crank and connecting rods?

 

Yes...stock bottom end. Aftermarket pistons will come with wrist pins and clips.

But, if the torque specs for the rod bolts are a torque number plus degree's, that means they are torque to yeild type and need to be replaced. I got a manual at home and can check later.

20K hard miles....its still on the street, and these things are tough....it might see hard loading 5% of its life in street use. You can run these things 4000 miles on the track where its WOT 80% of the time, put in fresh rings and do it again.

For comparison, I bought a used zx7 from a serviceman. He'd been stationed in Germany and did lots of hardcore moutnain riding, highspeed autobahn stuff...all of it...his tires looked like they came off the race track. I bought it will 41K. At 48,000 milesI cracked it open as I was doing an 800 kit...NOTHING needed to be replaced. I still did rod bearings for the heck of it.

If you are worried about it, I'd do this. I would pull one piston (you cantakeit out the top, but clean up the top edge of thecylinder first)....look at the rod bearings (you can plastigage them if you want, but visual tells a lot)...if you don't see copper, and only small spots of shinny, they are generally good). Thenmeasure the ring groove width, piston skirt and ring end gap per the manual.

Then go from there.....doesn't sound like you are looking to dump a lot of money in this thing. F2/3 motors are cheap too...