85 ATC 250r cyl vs 88 TRX 250r cyl

[whiteman350x]

I have both the 85 and 88 cly's. I have heard the the 88 is a better choice than the 85. The piston for the 88 is listed for a "bridged intake". What diff does the bridged intake make? In short which one should I use on my 85 250r resto?

[KASEY]

the bridge in the intake takes all the strain off the lower piston skirt,so no worries about breakage,,, as far as performance i don't think in stock form you will notice much difference between them,,,

[Lots_Of_Nothing]

well with the 85 cylinder you use the short rod, and with the 88 you use the long rod....alot of the trx250R racers switch there crank and cylinder to 85/86 for the shorter rod because it revs faster..

[KASEY]

THE cylinders are the same!!!!! you can use it on a long or short rod motor,,,,,,, its the piston that makes the different

bore and stroke are the same,,,,,, the longer rod used a lower deck height piston the short rod a higher deck height

wiseco 526 is a short rod piston
wiseco 562 is a long rod piston

[Lots_Of_Nothing]

OOooookkk, kasey, will you please stop saving the world!.......ahaha yes, im just saying, alot of the racer guys (like team LRD) use the shorter rods because it revs faster.

[KASEY]

YEAH WHATEVER,,, the short and long rod motors have the same stroke ,,so it can;t rev faster,,, the piston travels exactly the same distance,,,,,, so explain how it would rev faster! the long rod is 4mm longer and the pin location in the piston is 4mm higher so the deck height is the same,,,,

[Lots_Of_Nothing]

well im just saying, i talked to a LRD guy on the phone for quite awhile (Mike), because we started off talkin about a pipe for my R, then we talked about other stuff, and he was telling me about this....i will find out...

[200x Basket]

you could use eith but both those guys are right, the port timing on the 88 is differnet so you have to use the combos correctly or get the spacer. if using a short piston/cylinder on a long rod. i suggest getting the 85 ported and forget it.

[Tri-Z Pilot]

Why would it be called a long rod, if it is the same length? The longer the stroke, the more top end power you are going to get. A shorter rod will make the bike rev faster and give you better acceleration. Have you ever noticed how a built up american v8 has that top end power, that revs out strong, as opposed to a import car which typically has a lot shorter stroke, which makes them revv really fast, but they top out pretty quick.

[whiteman350x]

O. k. So since I bought an 88 pistion I need a long rod crank. I have a crank that I got off ebay. Do not know the year. The rod has HA2 3 on it. Is this enough info to tell if it is long or short? If not what is the length of the long rod or the short one for that matter, so I can measure it and see what I have?

[KASEY]

tri-z pilot ,,, the bore and stroke are the same ,,, the cranks are the same too ,,,its just the lenght of the rod that is different and that is compensated for in the pin location in the piston which is higher than a short rod piston ...your getting stroke mixed up with rod lenght,,, the lenght of the rod has nothing to do with stroke

all TRX's and atc 250r's 85 and newer have the same bore and stroke

[ChrisD]

I run a 88-89 long rod with an 86 piston and 5mm spacer plate. The long rod is supposed to make the engine "breath" better.

The truth...not much difference between the two setups. If you have a short rod then leave it alone. My 85 ATC is just as powerful.

ONE IMPORTANT DIFFERENCE. The 88-89 is supposed to have a better port design, but you can bore out the 85-87 motors more. I'm up to .120 over on my 85 motor. I think that you can only go to .80 over on the 88-89 motors.

[Tri-Z Pilot]

OK, I understand now Kasey.

[whiteman350x]

Great info guys!! Now help me figure out which rod I have. What is the length of both so I can measure it and see?