My R is once again down, imagine that. It is getting oil, not 2-stroke oil into the top end again, I have had that problem before, and it was a blown case gasket, but I dont think thats it this time. Last time it happened, it died and fouled a plug, this time it just started smoking real real bad.
Anyway, I am not going to ask about that, as I ahve decided just to have someone go through my motor and fix it all.

What I would like to know is...will the TCS shocks and the a-arms I have for the R fit a 400ex? I have +2+1 a-arms and TCS SCS shocks up front. I have a TCS rear shock as well. I am pretty sure the fronts fit, but not sure on the rear.
Also, how hard is it to convert the 400ex to take R plastic? Will a shorter R shift lever fit the 400 as well?
I am about to get tired of working on this damn 2-stroke but I just love it. I dont know if I want to sell it, especially for a 400ex, but I dont want to give up my suspension especially as its top notch and work awesome for me.
Just wondering as I ponder what to do.
Thanks Guys

 

I know that the 250R A-Arms, and 400EX A-Arms will fit on a 300EX, so if they both would fit, I would assume that the R's A-Arms will fit. I know to put them on a 300, you have to get a specail kit, but I think that you shouldn't have to on this swap. I dunno bout the rear. The plastic will bolt up pretty close, just drill new holes where need be!

 

I was once in the same boat as you. I blew my R up twice in a matter of 2 hours riding time. I considered going to a thumper, but then I took it to a shop (TMM) and had them go through everything to see what was wrong. turns out it was bad crank bearings and I needed a bore. After they fixed it I havent had a problem since. Just send your motor somewhere, have them work it over, and I doubt you'll have anymore problems as long as you take care of it (until time for a rebuild anyway).

 

I am having a guy do it all for me, the whole bottom end. However, I am gonna be away at college starting wed. and I just dont know if i will have enough time to work on a damn 2 stroke. I dont really want a thumper but ya gots to do what ya gots to do. And right now, I gots ta get the R running again!

But, I was just curious as to whether they would fit. I have htought about keepin the R and then swapping my other stuff to a 400 and seeing if I liked it enough to keep it. If not, then I could get rid of it, if so, then get rid of the R with the 400ex suspension on it!

 

you think youve got it bad! my R has went trhought 3 pistons and i have like prolly 2hrs riding on it! i baught it and it supposedly had new crank brngs and seals! it lost compression after like 2hrs o riding! so i put a new pro-X in it! that lasted 5 min realisticly! that sucks! thne i found out it was a bad lower rod bearing so i got a new crank, crank brngs, crank seals, new weisco piston bored, new head (because the last piston destroyed the old one) and all new gaskets! i was so happy that i ran i went riding to my camp! about half way there i noticed it was gettin warm, so i took it easy! then about a 1/8 mile from there it seized up!!!! i ws soooo pissed! i had about 1 hr on this one! i looked at the cylinder and it was smoking! i just happened to look in the radiator and saw the it was bone dry! it somehow got hott enought to boil all the antifreeze out! then it got so hot that it seized! now im here waiting for another .080 weisco to come it should be here on thursday! so if you think you got it bad top that!

 

Hell, I sure cant top that!
I just gotta ask, are you sure you put anti-freeze in there? I have never had my R boil a bit of it out, let alone the whole radiator full! Thats freakin HOT!
Mine has been running really hot here lately, and I am afraid I hurt my piston or rings, but I didnt lose compression, it still has some?
I am not sure what the hell my problem is!

But I have had to take the motor out of the chassis 5 times in the last 2 weeks!

 

Please dont take this wrong .butt it sounds like you guy's shouldent be doing your own motor work ...bite the bullet and send it in ...you will save alot of money in the long run ...Ive found that extreme attention to detail in motor building is the key to succses! my 2 cent's

 

If you read a bit more carefully, I said that I am sending my motor in to be totally redone by a guy who builds motors for a living as well as races dirtbikes. Shift also said he had his sent in and redone by a professional as well.
So, we arent doing our own engine work.
Race motors sometimes just dont last very long. I have friends who race sprint cars and spend 4 grand to rebuild their motors, sometimes they last 12 races, sometimes 2 laps. When you get to dealing with high compression and trying to get every bit of performance out of a motor, sometimes thing just dont hold, especially with a 15 year old one!

 

If a little more time is spent while the motor is torn down, you save a lot more time and money in the long run. If you seize a piston and just put a new one in, I can almost guarantee you are going to seize another one. There is a reason that the first one seized. With the top end off, check the play on the rod. If it is out of tolerance, tear the bottom end down.

If the top end went because of bad lower end bearings then you must have had an air leak at the cranks seals from the crank movement. You can check for air leaks this way:

Plug the exhaust spigot or remove it and bolt a flat flat on.
Get a pvc adapter from a hardware store that fit into you intake boot and has pipe threads in it.
Put a tee in the adapter with an air fitting and a guage.
With a hand pump, pump 6lbs of air into the motor.
It should hold that pressure for 6 minutes.

The first time I ever did a pressure test, I found a huge air leak. The motor would not have lasted one ride.

Forward Motion Racing has a piston failure guide that can help to determine the cause of a top end failure.

As for the compression loss, that is a judgement call. I lost a clip off my carb needle. This caused an extreme lean condition for a short period of time. After replacing the clip, I checked the compression and it was down from 170 to 160 psi. I pulled the top end to be safe. The oil had gotten coked from the heat and stuck the top ring. A can of Easy Off oven cleaner and a new base gasket later, I was on my way. I figure that if I had not cleaned off the coked oil, the blowby past the top ring would have eaten away at the piston and eventually caused a seizure.

 

it was at a ratio of more water than antifreeze and i was breaking it in and i was in a long wooded section so i couldnt get much air flowing over it and i was trying not to foul a plug and the water (with a hint of antifreeze the last time i listen to my genius frineds) kinda bouled out! then she seized! it never seized the first two times it just wasnt very powerful the first one so i tore it down and then i took the crank to my builder and he said it shouldnt cause a problem so i put a new piston in it and rode it again and the crank gave out and destroyed the piston! then the last time was due to the lack of cooling so dont tell me i dont know what im doing it was just some bad luck (with the crank) and i shouldnt listen to my frineds always trust your gut!