Help!help!help

[riderssb250x]

hey guys i have a 250r i beleive its an 87.. well i started a projet oou of it and it came time to do the topend its got a wiseco 67.5 mm piston in it(526M06750) AND WHEN I LOOKED AROUND FOR A PISTON KIT IM BEING TOLD ITS A PISTON FROM AN 86!? well i dont know what to do if my bike is an 86 or an 87 or if pistons are interchangebl=( cause an 87 wiseco doesent make 67.5mm pistons can someone help pleasee

[trx250rider]

what is the vin# on your engine and the one on your frame?

[trx250rider]

for the engine all vins will start with TB06E if its a trx
1986: 1000014-1021097
1987:8000015-8008442
1988:8100014-8109454
1989:8200001-subsequent

say for instance your vin is TB06E-8001432 then you would have a 87 engine...hope this helps

[86 Quad R]

does the cylinder have a spacer plate under it?

[Honda 250r 001]

pistons interchange but sometimes you need to run a spacer plate. if you run the 86 piston with a 87 rod you need a spacer plate. so there should be a spacer plate under that cylinder, if not you have a 86 rod in that 87 motor.

[matt250r21]

Check the rod, if it is OEM Honda it will have HA2 stamped on it 87-89 TRX250R long rod or KZ4 86 TRX250R and 85-86 ATC250R short rod. As mentioned above check to see if there is a 4.5mm spacer plate under the cylinder.

[riderssb250x]

i gotta ncheck the engine numbers tomorow i nknow for sure its a trx engine, but i dont recall seeing a spacer what does it look like? i have the cylinder off and i dont think theyer was a spacer there and ill check on the rod also!

[mdickerson319]

Not to steal thread, but the i have a rod that has KA4 and a 3 on it. Any clue to what rod this is?

[Honda 250r 001]

no i dont know. possibly a hotorods or somethin. does your piston have a full skirt or a cut away skirt? on the intake side?

[Langbolt]

As for RODS:

'86 IS "KA4 7" = 125.5mm

'87 is "HA2 2" =130.5mm

Who said Wiseco doesn't make a 67.50mm Piston for the '87-89 TRX ? (i tried to upload the PDF but was an invalid format)

Go to WISECO.com and you'll see.

Part#562MO6750 = '87-89

Part#526MO6750 = '85-86

Have a look in the INTAKE port. If you see Two vertical bridges it is an '87-89 cylinder. If it's wide open (OLD CR250 style) then it's an '86


:devil:

[riderssb250x]

well i took a look at the rod and it says ka4 8??? i dont know what this is and the person who says that the 67.5mm is not for the 87 was my local dealer but im seeing online that i can buy a wiseco kit thats 67.5 mm for an 87 so im confused is the dealer just wrong and i can run that size piston or am i nrunning the rod from an 87 and the piston>?

i am not running a spacer there is none there and also i checked the numbers and someone took the tag off!!! ahhh someone please helop me figure this mess outt!!!

im pretty sure i can just get the piston for an 87 becasue on moto-man.com it says that that size is availabl;e for an 87... HELP

[riderssb250x]

ALSO ... im pretty sure my piston had a full skirt..

[Honda 250r 001]

i have a feeling you are running the long rod set up. with no spacer and a full skirt on the piston. do u need a replacement piston? size 67.50 just like the one you mentioned? I have one if you need it.

[Langbolt]

riderssb250x

You're running an '86 rod so you MUST run the '86 Piston.

The difference is the '86 rod is 5mm shorter as well as the Piston's pin height is raised 5mm.

If you put an '87 piston on a '86 rod the piston will be 5mm below deck height (top of the cylinder)

What the other guy's are saying IF you had an '87 rod you could run the '87 Piston.....but you require a 5mm spacer plate if you run the '86 piston.

This setup ('87 rod & '86 piston with spacer plate) was used for motors that wanted MORE case volume (better midrange)

Did you confirm the Cylinder year yet ?

Hope this helps

:devil:

[riderssb250x]

havent confirmed the cylinder year yet i will tomo, so im definetly runing an 86 rod your saying? by thje numbers i gave you? so i should just get an 86 67.5 mm piston to do a topend right? the 87 will not work? please help

whats the advanteges and disadvanteges of this setup anyone runnin it???

[Langbolt]

Yes! You're definitely running an '86 rod. (might even be an '85)

So you must use the '86 Piston.

You CAN NOT use the '87 style piston.....when you install it your piston won't come to the top of the cylinder.....it'll be 5mm below.

Have you had your cylinder bored and honed to accept the 67.50mm bore ? Just curious.....

:devil:

[riderssb250x]

well im not sure, the bike was runing when i got it and it screamed and i ripped all down most iof its at the powdercoaters and oi decided to throw a fresh topend in it so its all new for the spring and thats when i came along the problem i beilive its bored for that piston so im goint to get a topend kit in 67.5 mm for an 86 250r?

how do i hone the cylinder do i nreed to do this if im puting a new topend in? do you know the main steps to doing it if you could please help me outt! thanks man ur awesome

[Langbolt]

First thing I would do is take your cylinder to a reputable machine shop (one that bores & hones bike engines) and have them measure it.

They'll use a bore gauge and see if your cylinder is out of round and look to see if there are any scores in the cylinder.

They may just hone it and you'll be good to go!

You could hone it yourself.....but if they have a good sunnen hone you'll get the best job possible......A ball hone is just good for a cleanup when you change rings every race.

Besides they only charge like $10 to hone (buying one will run ya $40)

It's best to find out the size also so you don't put it all back together to have a failure because of excessive clearance (piston slap)

Remember to clean everything before re-assembly.....and make sure you're using a clean work area too!

It only takes a little bit of dirt to wreck a 2-stroke

:devil:

[riderssb250x]

alright thanks i think ill take it to my local shop and have a hone done, is it definately neccary to hone it even if the cylinder looks in good shape?

also should i be using 86 or 87 gaskets!?

i was plaining on only throwin rings nin but now that its all apart mine as weell go the whole 9 and throw a fresh topend in it get a nice hone and be ready to go for the spring?

[Langbolt]

Most definitely! You can't install fresh rings in an un-honed cylinder.

The hatch pattern from the hone breaks in the rings to seal the cylinder. It holds the oil to polish the rings.

If you didn't hone it they would just overheat and seize!

Unless your just replacing the rings every race.....it's best to replace the piston too in your case.

For gaskets.....they're all the same from '86-89

here's a tip:

If you're running the stock head and want to increase the Compression without machining the head order the CR250 head gasket (it's cheaper too!)

Part# 12254-KZ3-000

:devil:

[riderssb250x]

i dont have to mod anything for the cr250 headgasket to fit? what years woirk? also how does it affect the compression?? im really intrested in doing this!!

and a regulaar hone should be under 20 dollars right?

[Langbolt]

'86 to '91 will work....I gave you the '91 part number

It'll raise your compression about 15psi.....and you don't have to modify anything.

yeah....depending on the shop....$20 should be right.



:devil:

[riderssb250x]

saweeeeet=) thanks for the help man ill deff keep you posted im gona take that cylinder saturday to get a hone its in really good shaoe so i should be able to get away with a hone and a topend for the season

and im gona grab one of those headgaskets off ebat cheap real quick thanks dude

[Langbolt]

Ebay ?

Go down to your local HONDA dealer!

It's only $16.00

Using E-bay and you'll have to pay shipping.....and WAIT.

:devil:

[riderssb250x]

hey langbolt I got another question you know bhow you said the 86 rod is 5mm shorter ? is that afecting my 72mm stroke woukld it mean I have a shorter stroke?

is there advantages to to running the 86 rod and piston?

[Langbolt]

Yes! The '86 rod is shorter by 5mm....the stroke stays the same at 72mm

The Stroke is determined by how far the lower crank pin is offest from the crankshaft's center.

The Piston goes Up & Down 72mm all TRX250r's

Rod length only affects dwell angle. Long rods for torque - Short for quick rev.

Same as Strokers......Short for rev...long for torque.

If you use the '86 rod & '86 piston.....you'll build a motor that will be a real screamer.

:devil:

[All250R]

The shorter rod will also exaggerate port timing a little. I believe all of the Honda CR's have a short rod installed. That rod was shared between the two bikes that year and is why the 86 rod's have the CR model designator stamped onto them (KA4). The longer rod in addition to lingering at the top and bottom of the stroke longer is rhumored also to increase bore life by moving the piston pin up in the piston 5mm.

The bridged intake opening is the same concept. The stock TRX's were designed for modest power and reliability. An open intake flows better than the bridged 87-89. It's true that the 86 cylinder is like the older CR cylinder. In fact it's very similar or the same cylinder that Honda installed on the 85CR250. If the cylinders are different, the difference would be found mostly in port/timing design. However, the open intake port is consistent across almost all CR years, not just the older models.

86 setups can be made very fast. The transfers I think are better in the 88-89 TRX and later model CR cylinders, but again the key word is "made" very fast.

Lastly for my 2cents worth is that crank could be very old. Honda quit making them several years ago. At some point you want to check to make sure its still healthy. You can rebuild the crank with an aftermarket rod kit, but you can't buy the whole assembly new anymore. Long rods are nice way to drop in an all new OEM quality crank, but like langbolt was indicating, short rods have their worthwhile merits - Honda thinks so too looks like; plus you don't have to run a base plate to keep an 86/CR piston.

[riderssb250x]

thanks for all the info guys im going to keep the 86 rod and piston setup and get a new topend and cr 250 head gasket. im taking my cylinder to get a hone at my local dealer tomorow or this week and the im ordering a topend gasket kit a cr 250 head gasket some new boyseen reeds and a wiseco top end kit and i should be good to go1 my crank and rod bearings seem to be healythy i checked them out


STILL GOTTA DETERMINE IF ITS AN 86 OR 87 CYLINDER WILL DO TOMO AND POST! Vtahnks guys keep the info coming=)

[All250R]

Originally posted by riderssb250x
thanks for all the info guys im going to keep the 86 rod and piston setup and get a new topend and cr 250 head gasket. im taking my cylinder to get a hone at my local dealer tomorow or this week and the im ordering a topend gasket kit a cr 250 head gasket some new boyseen reeds and a wiseco top end kit and i should be good to go1 my crank and rod bearings seem to be healythy i checked them out


STILL GOTTA DETERMINE IF ITS AN 86 OR 87 CYLINDER WILL DO TOMO AND POST! Vtahnks guys keep the info coming=)

You should take langbolt's advice and get the cylinder measured. The most expensive part of a top end are the parts. Buying a new piston and gaskets and putting them into an out of spec bore doesn't make sense.

[riderssb250x]

the dealer is going to hone and measure it after the hone is done

[riderssb250x]

I checked out the cylinder andon the intake side its seems to look like there is only one big port it doesent look like 2 ports so im guesing its and 86 langbolt?

[Langbolt]

Yes! You have an '86 Cylinder

:devil:

[riderssb250x]

LANGBOLT! THE 250r IS AN 86!

after all this trouble i fonaly confiremed it the odds of the concting rod piston cylinder and then i cam to fond out when trying to remove the a arm buishings that they are unremovable so its an 86 im glad to have confirmed this!