cylinder boring

[chamberlain31c]

how much can safely be bored from a stock 87 cylinder with out sleeving it? if im correct 68.25 will make a 265 write? or what will?and are 87's long rod motors? or just 88 &89 thanks

[Langbolt]

Wiseco lists piston for the '87-89 cylinders up to 68.0mm

And the sleeve is pretty thin when you're there!

bore * bore * stroke * .7854 / 1000 = displacement

68 * 68 * 72 * .7854 / 1000 = 261.48cc

square root (265cc * 1000 / .7854 / 72 ) = 68.455mm

A 265 is based on an '86

'87-'89 are (130.5mm) Long rod motors - HA2 stamped on beam

'86 are (125.5mm) Short rod - HB9 stamped on beam

[zedicus00]

87"s are long rods but they had the taller geared tranny like the 86. stick a spacer plate under the jug and run an 86 year piston and you will be fine. basically the jugs are all the same from 85 to 89. the diference is n the piston and rods. the spacer plate allows for 85 -86 pistons to be used on the 87-89 rod.

[Langbolt]

I have to disagee,

The '86 tranny 5th & 6th had one extra tooth on their gears, 87-89 didn't.

It's just the '86 that had the taller gearing.

Also the Jugs are different:

'86 resembled the older CR port layout.....big mouth opening.

'87-89 had three vertical window ports.

I don't recommend running an '86 piston on an '87-89 jug....grab a '86 jug. Very cheap on E-bay!

So the Long rod (HA2) with '86 piston (68.5mm) & 5mm spacer plate along with the '86 jug and you've got your 265cc that you're after.

:devil:

[All250R]

HA2 is the ATC designator
HB9 is the TRX designator

The short rod has the CR designator of KA4 I believe because Honda runs installs a short rod on the CR - it's definitely not HB9 though.

The 87 rod should say HA2 since it was produced also for the 87 ATC250R which didn't make sales in the US. By the way HA2 parts for the TRX are ATC carry-overs.

I believe the 88-89 long rods are all HB9 stamped.

[1promodfan]

Where is Neil at???? We need some help here!!! Does anyone know where Corinth church is?.....(inside joke)

[Langbolt]

ALL250R.....you're correct....my apologies.

I went and opened my "Box O Rods" lol

'86 IS "KA4 7"

'87 is "HA2 2"

'88 & 89 is .......? I've never seen an HB9......not too many of them here in Canada in my area.

Thanks

[C-LEIGH RACING]

Originally posted by 1promodfan
Where is Neil at???? We need some help here!!! Does anyone know where Corinth church is?.....(inside joke)

:D :D :D These guys dont want me to post how far you can bore a stock TRX cylinder or the many different pistons from other brands can be used in one.
Now do you :D .

:eek: what, 71.95mm, no way.
Neil

[1promodfan]

Originally posted by C-LEIGH RACING
:D :D :D These guys dont want me to post how far you can bore a stock TRX cylinder or the many different pistons from other brands can be used in one.
Now do you :D .

:eek: what, 71.95mm, no way.
Neil

Neil, I don't know if these guys are ready for that yz 250 piston stuff!!:eek2:

[C-LEIGH RACING]

Originally posted by chamberlain31c
how much can safely be bored from a stock 87 cylinder with out sleeving it? if im correct 68.25 will make a 265 write? or what will?and are 87's long rod motors? or just 88 &89 thanks


68.25mm would be a 263.40cc
68.50mm, 265.34cc
Neil

[250R_SV]

I have a quadracer piston 70.00 in my cylinder in my R. nice torque. You might ask why a suzuki piston?? The one I had to ride got damaged and I had the spare cylinder and a friend had the piston, and we had an event in a couple of days so we did the experiment and worked, Im still riding with it. Although sometimes its hard to start but what the heck, maybe some adjustment is needed. I live in El Salvador so I couldnt buy the piston because there is no dealer here, I buy everything in the states.