250R motor ... What year???

[stever250r]

I had a friend give me a 250R bottom end for my project quad but he wasnt sure what year it was. I plan on tearing it down, replacing main bearings and crank and then putting a ESR PV top end on it.

I know the 86-87 were short rod.. 88-89 were long rod...

Is there any other way to tell what year bottom end I have???

If it currently has a short rod 86-87,,, would it be better to just replace the crank assy with a 88-89 long rod?

Can someone tell me what would be my best setup with the ESR 310 PV and some way that I can tell what year bottom end I have??


Steve

[honda350r]

What color is the bottom end ? The long rods are 87-89

[stever250r]

bottom end is a metallic silver or gray.

[velocityatv]

This chart is very useful. Look at the bottom of the chart and you'll find a section for serial #'s (if it still has the plate on it )

http://www.macdizzy.com/trx_specs.htm

[stever250r]

The serial number on the engine is... TBO6E_2502482...


I see the numbers at the bottom of the chart but my number does not fall in sequence anywhere???

Am i looking at the chart wrong??

[honda350r]

Originally posted by stever250r
bottom end is a metallic silver or gray.

Ok ,then it is a 86 or 87

Does the rod say ha4 or ha2?

[stever250r]

Rod says.... KA4.... or a really messed up HA4

[honda350r]

That is a 1986 short rod engine ..

[stever250r]

Thanks guys....


Now my question is this..... How should I go about building it????


Should I leave it a short Rod engine? This would eliminate the need for a spacer plate to run the 86 style piston in the ESR 310 PV cylinder ... correct???

I saw the pictures of the bikes you have built 350R.. they look nice....

Give me some advice... I hate to not use the bottom end .. since it was a freebie...

[honda350r]

I would build it as a short rod motor.. Put a non PV 310 on it and go have fun!

I like the 7 porting a trx 5 pipe and 38 carb for trail riding and dunning !

That makes a super fun ride !


If you want to drag race I would go with the 11 port and 40.5 carb with the 11 pipe

No spacer on the short rod

[stever250r]

Gonna be using it for MX.

Ok...will build it as a short rod motor with a ESR 310...ported for MX....


How much power will I be losing by not having the advantage of the longer stroke that an 87-89 engine has? Is it even noticable?
Also what is the major difference in gearing between the two engines?

Sorry to keep asking so many questions.. but its really helping me out.

Thanks

[1988R]

Originally posted by stever250r


How much power will I be losing by not having the advantage of the longer stroke that an 87-89 engine has? Is it even noticable?
Also what is the major difference in gearing between the two engines?



Thanks

There is no difference in the stroke between the years because the wrist pin location is higher up on the piston (more toward the top)for the 87-89 models to compensate for the longer rod. The 85-86 models the wrist pin is more toward the bottom for the shorter rod. On the big bore kits the the pin location is that of the 85-86 years which is why you need a spacer plate to use it with the 87-89 year rods. It would be the same if you had a long rod and used an 86 piston you would also need a plate for that setup

[stever250r]

Thanks.. I knew that at one time but for some reason it had totally slipped my mind.

Thanks,

[Rich250RRacer]

Originally posted by stever250r
The serial number on the engine is... TBO6E_2502482...


I see the numbers at the bottom of the chart but my number does not fall in sequence anywhere???

Am i looking at the chart wrong??

That is an ATC motor. All ATC motor numbers begin with the number 2. TRX motor numbers begin with a 1.

[honda350r]

Originally posted by Rich250RRacer
That is an ATC motor. All ATC motor numbers begin with the number 2. TRX motor numbers begin with a 1.

That may be true,but there is no differance in the engines!! All 86 parts are the same !

[Rich250RRacer]

Originally posted by honda350r
That may be true,but there is no differance in the engines!! All 86 parts are the same !

That's true, everything interchanges. The only difference between 86 ATC motors and TRX motors was the head gasket. There are more differences in an 85 motor, but the parts will still interchange.

[stever250r]

Whew,

You guys had me worried for a second.

So I dont have anything to worry about or be concerned with correct?

Just build it as if it were a TRX engine?

Steve

[honda350r]

Yep !!

[Nate Dogg #76]

I'm going to set the record straight on the differences between the 1986 ATC and TRX engines. The compression ratio was lower on the TRX and the clutch friction plates had double the oil groove jolts. The head gasket was also thicker as mentioned before. Other than this they are the same.

[beerock]

good luck finding a short rod. they dotn make them anymore form honda oem anyhow.

If i were you id buy a long rod and make a spacer plate motor.

long rod crank, 86 piston and spacer plate....

make sure the long rod is a OEM HONDA crank, not a hot rod wiseBLOW

[smorris]

Originally posted by beerock
good luck finding a short rod. they dotn make them anymore form honda oem anyhow.

If i were you id buy a long rod and make a spacer plate motor.

long rod crank, 86 piston and spacer plate....

make sure the long rod is a OEM HONDA crank, not a hot rod wiseBLOW
What he said!!