Where do I buy new 310cc piston?

[ChvyCruzen]

Where can I get ahold of pistons made for 310cc??

Can I have my sleeve honed and still get away with it overbored by say .002? Enough to do re-hone?

[kiesta00]

I'm sure ESR and CT sell the big bore pistons. Not real sure about your hone question though

[C-LEIGH RACING]

Have you checked with Nac's, they are a Pro-X dealer.

I would get someone to measure the bore first to see how much it is worn. Normal piston to cylinder, new bore is 0.0003 & can go as high as 0.0010 but its dangerous & can end up busting a piston.
If its no more than 0.0005 worn, I wouldnt even worrie about honing it unless its seized or has some bad scars.
Neil

[ChvyCruzen]

Neil - I didn't know Nac's sold the big bore pistons kits. I am confused though, NIKS piston kit states that STD bore is 66mm for 87-89 but Pro-x says STD is 72mm.

What is the difference in 86 style vs 87-89 style piston? I know that the 86 is a short rod - I dont know if my motor is 86 or 87-89. Any way to tell? I've already got the motor torn apart.

Thanks for help guys.

[ChvyCruzen]

I measured my cylinder jug at the top and got 72.8-73.0mm at the bottom it was mostly 72.80mm.

Does this mean I have the 72.5mm piston right now? It is in need of honing, could I get away with honing and new 72.5 piston with rings or bore out to 73mm??

[C-LEIGH RACING]

On a stock cylinder like it came from Honda when bought new, the cylinder bore is 66.00mm, thats on a stock Honda cylinder.
The Pro-X cylinders, or cylinder kits offered, can be bought with a bore size from a 66.00mm up to a 80.00mm.
If you have a LA Sleeve catolog, their listings for the big bore Pro-X cylinders only go as high as a 330cc for the TRX250R, but they do have the 350cc, its just listed for the CR250R dirt bike.
The 80.00mm piston cylinder kit (410cc), is a special build offered by CT Racing only.

Those measurements on your cylinder are going to be a little tricky. The big bore pistons are machined just a little under the finished bore size. Like say a new STD 72.00mm piston, it will measure 71.95mm. The 72.50mm will measure 72.45mm.
If you have a true 72.80mm measurement in the bore at its most worn point you will have 0.035 piston the cylinder clearance on a new 72.50mm piston. 72.80mm bore wont be big enough just to drop a 73.00mm piston in, you will need to get it bored & honed.

Hone fitting a new piston without boring first is a process that if done needs to be a operator thats done it many times before. A cylinder bore will wear egg shaped & you will have areas that are not worn as much as others. Because of that the operator of the hone needs to work the hone in the smallest part of the bore ( short strokes ) & then work the hone to the parts worn more. Another factor, is the condition of the hone stones them self. If the stone has a bow to it, say the stone is worn more in the center than on each end, you cant get a true straight hone job from that stone.
Kinda long but hope you understand.

The pistons,
86 models are shaped different on the intake side from the 87/88/89s. They have an arch cut out at the bottom of the skirt, intake side & the wrist pin hole is machined lower down in the piston because of the shorter con rod used in the 85/86 engines.
The 87/88/89 pistons have a full skirt, front & back look almost the same but has a window cut in on the intake side. The wrist pin hole is machined higher up in the piston because of the longer con rod used in the 87/88/89 engines.
Neil

[ChvyCruzen]

Sorry for repeat postings, its my first time dealing with this kind of stuff.

I looked for part # off the piston and got W845 - which is the 86 style piston. I couldnt get PS, or

Does this neccesarily mean I have 86 bottom end? How can I tell if my bottom end is 86 or 87-89?

Thanks guys!

[ChvyCruzen]

Thanks for your help Neil.

It seems that my piston is 86 style. So that means my jug is also 86 style? Could you possible run a 86 style piston in a 87-89 long rod??

[kiesta00]

ahh here we go again with spacer plate/longrod/shortrod piston configs lol. If you want to run an 86 piston in a longrod motor, you have to use a spacer plate from esr or pro design to make up for the shorter piston pin height (makes the piston 5mm taller). The stroke is the same, just the piston height/cylinder height is moved up about 5mm.

[ChvyCruzen]

Thanks for clearing that up. I know that there was an option of running a spacer plate, just wasn't sure how it applies. I get easily confused sometimes!

So other than the crank and cylinder height, the cases and tranny are the same?? I know 89 has updated clutch and stuff, but I mean in general.

Thanks guys!

[C-LEIGH RACING]

Originally posted by ChvyCruzen
Thanks for clearing that up. I know that there was an option of running a spacer plate, just wasn't sure how it applies. I get easily confused sometimes!

So other than the crank and cylinder height, the cases and tranny are the same?? I know 89 has updated clutch and stuff, but I mean in general.

Thanks guys!

In general yes they are the same, just minor improvments over the production years to the engine & frame, allthough the improvments to the frame I wouldnt call it that. The 89 frame was lighter but cracked alot easier than the old 86 models.
Neil

[iamjasyn]

Originally posted by ChvyCruzen

So other than the crank and cylinder height, the cases and tranny are the same?? I know 89 has updated clutch and stuff, but I mean in general.

Thanks guys!

The gearing for 5th and 6th I believe is different between 86 and 88-89. I'm not sure where the 87 stood - if I were to guess I'd say it's the same as the 86. Usually if you buy aftermarket gears for example, you'll find some fine print about them being for the later model year transmission.