top end questions

[norcalduner]

my brother has a 250r motor (no case serial number) with 88-89 cases and an oem/stock cylinder WITH a spacer plate that needs a new top end due to a seizure.

question#1
does he need an 86 style piston due to the spacer plate?

question#2
can or have any of you seized a motor by forgetting to put oil/premix in the fuel? did it seize right away or take some time?

thanks in advance for any input. this is my bros first r and we are still sorting out why the motor seized although he seems pretty certain that he forgot the oil.

[Honda 250r 001]

check the fuel and seee if its clear like normal or darker like mixed. unlixed will cause quick seizure. yes you need a 86 style piston. but you could get a 87-89 piston and screw that spacer.

[norcalduner]

we use sunoco 110 which is colored purple unmixed so he couldn't tell if he poured some oil in or not .....

[matt250r21]

Dependes on the thickness of the spacer plate and if the cylinder was decked. If it is a stock cylinder with a 4.5mm spacer plate and 87-89 long rod crank then you need a 86 style piston.

[All250R]

If the engine has a long rod crank (87-89 stock engines) AND the new bore is over 68.00mm, typically you will need a spacer plate and 86 style piston. If either of those conditions are not met, you don't NEED the spacer plate or 86 piston.

You can put a little of the gasoline on a clean smooth surface, like glass and let it evaporate. If the oil you use is not left on the glass, then you will want to consider a crank rebuild and crank bearings as well as the top end.

[Aceman]

Originally posted by norcalduner
he seems pretty certain that he forgot the oil.

I worried about that too. So I started dumping the Klotz into the bottom of my natural colored cans first, then adding fuel. Pretty easy to see red oil in a white can, so I can be sure no mistakes are made.

[C-LEIGH RACING]

Ok
Now lets throw a stick in the spokes.
There are 3 different thickness of spacer plates used,,,, which one do you have under the cylinder.
Neil

[norcalduner]

Originally posted by C-LEIGH RACING
Ok
Now lets throw a stick in the spokes.
There are 3 different thickness of spacer plates used,,,, which one do you have under the cylinder.
Neil

I measured the plate to be at approx. 4.80 mm. Here is a pic of the piston Neil. Its all damaged exactly at the exhaust port area only.

[norcalduner]

question #3
since we got about 25 gallons of racegas that we doubt, have any of you put any "pre-mixed fuel" in your truck's fuel tank so as not to go to waste ?

[05LSR250R]

Throwing a small amount of pre-mix in your vehicle wont hurt. I've thrown a couple old gallons in there before. Just make sure your not on empty when you do it! The trucks a Toyota Tacoma 6 cyl.

[05LSR250R]

In other words dont fill it up with pre-mix. Should be able to get away with 5 gals per 20 gals.

[Qracer]

If it is leaded race fuel it will ruin the O2 sensors.

[Honda 250r 001]

im guessin your fuel was mixed. have you ever jetted before? i think you might be a bit lean. the rest of the piston looks great to me except the exhaust part. and if it woulda not premixed it woulda got real hot and it woulda melted the piston a more or parts woulda fallen off it. and the rings look like theres something left. as i said above. what were ur jets.

[norcalduner]

Here are the specifics:
1. motor is 275cc, carb is 38 a/s, pipe is trx5
2. main jet @ 185
3. pilot jet @ 60
4. needle clip @ middle position
5. air screws turned out 1 1/2 turns
6. compression checked at sea level is 200 psi
7. riding elevation @ 3000 ft (high desert)
8. ambient temp @ 60 F

[C-LEIGH RACING]

Looking at the piston pic, by the cutaway on the front edge of the skirt, it almost looks like a YZ250 piston, but the 4.80mm plate dont match up if it is.
Using the YZ piston, you would need a 2.5mm plate. The ol 85/86 model TRX250R piston, you would need a 3mm.
Take a piece of scotch brite or sandpaper & clean the piston top a little & see what numbers are on it.
It might be a TriZ 250 piston, I've see those used it the TRX engines before.
If its a YZ piston & a Wiseco brand, should have 560MO or W560P something on top.


Oh,
that putting the race gas in your truck, you got to be carefull if its an older model truck. It does something to the gas hoses on the insides & next thing you know your sitting beside the road & the engines not getting any gas.
Been there done that.
It will do the same thing on the lawn mower as well. Had to clean out the carb, bunch of little black specks all in the bowl I guess from the gas hose comming apart on the inside.

I can tell you this about a Ford, the computer will set itself for the higher octain & run good but then when you go to the pump & get reg 87, the computer wont come back down, will need to hook up & re-set the computer.
Of course though, thats the price of having a Ford in the first place.
CHEV RO LAY, bigger, better & 6 inch longer.
Neil

[All250R]

Originally posted by norcalduner
Here are the specifics:
1. motor is 275cc, carb is 38 a/s, pipe is trx5
2. main jet @ 185
3. pilot jet @ 60
4. needle clip @ middle position
5. air screws turned out 1 1/2 turns
6. compression checked at sea level is 200 psi
7. riding elevation @ 3000 ft (high desert)
8. ambient temp @ 60 F

Did you perform some test to see if oil was in the fuel or not? Knowing that would be an important and easy thing to help you be confident you're not wasting your money before you go riding again on a new top end - you don't want to seize the new one too.

p.s. - These jetting numbers look pretty safe, however there several things that can lead to engine failure that you'd want to verify -> check the oil content in the fuel first.

[norcalduner]

I performed some "experiments" and did prove there WAS oil in the fuel. So now we are lost on the diagnosis and cause of this seizure.

[C-LEIGH RACING]

I can tell you this much by reading the pic of that piston.
#1
been seized more than once.
#2
been hot, hot enough to bake the oil in place on the sides of the piston. May have been high engine temps, but probably more than likely from blow by from stuck rings after the first seizure.
#3
unless you have washed the top of the piston with something making it ashy looking, or its been hot enough to burn the carbon turning it ashy. Head gasket leaking & coolant being blown in will make a piston top look like that as well.
Neil

[norcalduner]

It is a pro-x piston as marked on the inside with the markings HM25084. I also noticed the missing 3 vertical holes on the side of the piston facing the exhaust port below the seizure marks.

My bro mentioned it hesitated at mid throttle before hitting the powerband. I noticed it would pop once or two during idle a few times.