atc+trx=?

[iceman atc]

In an issue of dirt wheels I read that the trx 250R motors were set up for more power compared to the atc due to the extra front wheel and frame weight .I was wondering what exactly the difference was due to the fact I baught an 85 atcR with an 87 or 88 trx motor. All I know is its a hand full!:wondering

[tecat-z]

Small year to year changes.
87 up long rod motors
88-89 trx 5-6 gear ratios were lowered.
Some people prefer certain year cylinders over others.
89 roller actuator
These are generally considered the "biggest"

[Yamada]

Doesn't the TRX had a thciker head gasket to lower the compression. I think I read somewhere that the TRX had overheating issue, so Honda decided to lower the compression to help keep the engine cool.

[iceman atc]

thanks 4 responding Im not sure what year my jug is all I know is its black and the rest of the motor is gun metal gray.

[Blown 331]

Doesn't the TRX had a thciker head gasket to lower the compression. I think I read somewhere that the TRX had overheating issue, so Honda decided to lower the compression to help keep the engine cool.

The CR has the thinnest head gasket, ATC in the middle, TRX is the thickest. I usually just take the gasket, grind the rivets holding the layers together then just run one thin layer.

[iceman atc]

I think i heard some thing like tha about the head gaskets but Im not sure.

[Tri-Z Pilot]

The thicker gastket is due to the later trx's having a longer stroke isnt it?

Hey tec-z, what do you mean by roller actuator? That has to do with the clutch mech. right?

[iceman atc]

Yeah Thicker gasket for longer stroke that makes sense.

[1upfront]

No it has the same stroke, but a longer rod and it takes more than a thicker head gasket to make up for that, longrods had a taller cylinder too.

[cr480r]

No it has the same stroke, but a longer rod and it takes more than a thicker head gasket to make up for that, longrods had a taller cylinder too.

the long rods have a shorter piston..

[Tri-Z Pilot]

if you have the same stroke goin on, whats the sense of havin a longer rod? is it just so there was less work/parts needed when adding a stroked crank? perhaps its just a little late and im just confusing myself?:lol:

[300rman]

if you have the same stroke goin on, whats the sense of havin a longer rod? is it just so there was less work/parts needed when adding a stroked crank? perhaps its just a little late and im just confusing myself?:lol:

longer rod= less extreme rod angles, thus resulting is less wear on pistons, wrist pins, and bearings. It makes the engine last longer.

[Tri-Z Pilot]

the long rods have a shorter piston..

i see, that helps a me understand a little better. what exactly was the idea behind such a change? less piston mass for a little more rev?

[cr480r]

i see, that helps a me understand a little better. what exactly was the idea behind such a change? less piston mass for a little more rev?

the short piston is just to allow the longer rod.. the longer rod improves the rod/stroke ratio..

[Tri-Z Pilot]

so i guess it was basically done more as a reliability update than for performance reasons. is that the point your trying to get across 480?

[DixiePlowboy]

Doesn't the longer rod exert more leverage on the crankshaft, and therefore improve torque? I could very well be mistaken, but I've assumed for two decades that that was the reason Honda changed rods.

[Yamahondaman]

Correct .. same stroke.. just piston pin location for the longer rod for the 4-wheelers .. and YES ... that set up is NASTY in the ATC's !

[edog]

longer rod= less extreme rod angles, thus resulting is less wear on pistons, wrist pins, and bearings. It makes the engine last longer.

Good info!!!
Didn't know that.

[Blown 331]

I was under the assumption that all the cylinders were the same. And that TRX and ATC motors were identical in 86? Not true?

[Yamahondaman]

Same in "86" .. Diff from 87-89 , because the 86 TRX was a Turd they did the Rod and Cyl. Change to compensate the extra torqe that was needed from the added wieght... the clutch cover area is abit diff also

[Blown 331]

Same in "86" .. Diff from 87-89 , because the 86 TRX was a Turd they did the Rod and Cyl. Change to compensate the extra torqe that was needed from the added wieght... the clutch cover area is abit diff also

Thats what I thought. Just seeing people say ATC vs TRX motor is the reason I asked that question. So saying ATC vs TRX motor is not correct. It should actually be phrased 85/86 motor vs 87/88/89 motor.

[Yamahondaman]

Well i say 85-89 'ATC-TRX" 250-R..
i like the "87" Cyl. the BEST !! :naughty:
the Transfers are abit Diff.

[iceman atc]

Its crazy how different these are, but Ill testify the trx motor in the atc is WICKED!

[bigpimpin]

so the trx motor is a upgrade to the atc motor?

[oscarmayer]

actualyl having a long rod and a piston pin heightened allows for a longer "dwell" time and thus tricks the motor into thinking it's bigger than it is. in lamens terms it means more power due to more time to compress everything and hold it compressed for a better burn,

longer rods have a more EXTREME angle onthe piston and pin not less. thus causing more stress. I would not be supprised to fing the long rod's piston to be a bit thicker and heavier so it can handle the more extreme loads the longer rod will asert ont he side skerts. I know in honda drag racing for card (simular stuff as the smller motors as far as basic designs go) we love putting in a longer rod and moving the piston wrist pin up we can then chop the piston bottom skirt up some and this allowing for a much lighter piston that's thicker at the pin journals than the stocker of the same bore. the logner rod design was probelby good for another 4-5 hp on the small motors in a 2.0l 4-banger it gives you abotu 45-50 hp increase when done correctly.

rememebr the longer the rod the less stable it is at higher rpm. street bikes can run 14k-16k rpms because they run a shorter stroke than a car. the shoter the stroke the less pressre ont he sides and less stress on the rod so you can really zing that puppy. on one of the drak motors we "de-srtoked" it and had custom piston made to move the pin ont he pistons down to allow the piston tot ake up the extra slack. the results were amazing. 13k rpm on a 4cyclinder street class drag car.

anyway, i'm babbling so i'll shut up.
i hope this helps some.