240 is awfully high, but it may just be that your guage reads high. My compression on my ESR310 motor with a race dome was around 175, but your guage on my motor may read at 220.

 

I had trouble when I got my R and fried pistons/rings and eventually seized the bottom-end.
Had good plug checks, jetting, etc.
Found out it had an air leak in a very common place. The "dry side" crank seal leaked and caused a lean condition and fried things. Take off your shifter, pull the left case off. If you see even a hint of oil in the case half, it's leaking air at the crank seal.
The seal only costs about $15 and once I had a new one in my motor ran 7 seasons without any trouble at all.
Oh yeah, it had a Weisco piston also.

One other thing to check; piston to sidewall clearance. With a Weisco you need at least .0045 clearance for the piston to be able to expand.

Final thing; I run 50:1 Amsoil 2000 and it's never been a problem. If you're really running 240lbs compression you need to be running at least 108 octane.

 

ok, I will check the crank case for sure. Also when I ran that compression test, it was using an automotive type tester which I think might measure a different way (not sure, I will check).

Ok I took the jug off last night and things do not look good at all. The rings are siezed to the piston on both the intake side and the exhaust side, and there is also some major scuffing on the inside of the cylinder walls. I think its going to need to be punched out again. Someone mentioned that it would need at least .045'' clearance, well the Weisco box reads .030''

The bike has the following mods

86 Motor punched out to a 265 with a decking job to bump the compression up.
Full FMF Gold pipe (Fatty) with silencer
PWK 39mm carb running 180/45
Boysen reed cage with dual stage reeds (also some reed block spacer thing)
K&N filter with outerwears and no air box lid
Weisco Hot rod and crank
Billet exhaust flange

Lots of other goodies but nothing motor related, this bike is using all OEM ignition components.

Lets say for example my compression is WAY too high and I ran 93 in this bike, correct me if I am wrong but 93 would have caused the motor to run much hotter then it should be considering the compression ratio?

When I put this bike back together before It failed again, I noticed that the cylinder cap gasket DID NOT want to go on very easly at all so I had to force it on there. This was a cosmetic brand gasket with the little tab pointing towards the exhaust side. Think there could have been a possible air leak on the cap?

Here are some pics, hopefully the link will work

Pics of motor

 

The photo link did not work for me. If you are using an octane that is too low for the amount of compression you are running you will have detonation which can cause a meltdown. You definitely need to run a race fuel if your 240 PSI is accurate, I would recommend a 110 octane. Once the motor is back together definitely have a leakdown test ran on it. While you are putting it back together replace any seals that you suspect may need replacing. Your main jet size sounds like it's in the right area, especially since it's not a big bore. For instance, I'm at 750 feet above sea level and on my ESR 310 PV motor with a 38MM Airstryker and no air box lid I'm running a 200 main with a 52 pilot.

 

Ok, Leak check sounds like a good idea. I think I might take the motor to a shop to have this done because I have no idea how to do it. I also noticed that there was some oil in the bottom of the crank case, this should be here right? I will try and get these links working ASAP

Thanks,
Brad

 

If you are talking the center cases, yes, there should be oil in there. No oil means you weren't getting any to it or that you weren't putting any in your mix.

If you are considering replacing the "dry side" crank seal, please! Get a proper puller for the flywheel. If you don't want to get one, take it to a shop and have them do it. I don't have one and I'm sorta lazy so I take mine to a shop and have it done and parts/labor come to about $50.

I was once told to replace this seal every time a top-end is done. I know people that don't and get away with it, but my motors last a looonnngggg time without problems so what the hell? Spend a little more now and save later.

The description of your motor really indicates a lean condition most likely caused by a leak somewhere.

I also recommend using Honda gaskets as I have had trouble with Cometic in the past. The head gasket will go on easily but will only go on easily one way.

 

Yeah, This is really starting to sound like a air leak somewhere. If the jetting was off, it was richer then leaner so an air leak would be my guess on that. As far as the clearances go, the Weisco piston box said right on it .0030 which I understand is not enough. What gets me is that this builder is extremely reputable in the 2-stroke 2 wheeler business so I figured why not have him do the TRX jug along with my 99 CR250. Has anyone out there ever heard of, or dealt with Eric Gorr from Forward motion racing?

Thanks,
Brad

 

I can't seem to get these pics to work but if anyone would like to take a look please feel free and email me at bchitwood73@hotmail.com and I will send them to your email addy.

Thanks,
Brad

 

bchitwood73, My family has used Eric for many many yrs. He definately does know his stuff. He was actually one of the head engine builders for factory Honda(again dirtbikes) in the 80's. I know for a fact he is great with 2 stroke dirtbikes. I don't know about his experience with quads, but I don't believe you can get much more simple than the 1980's cylinder design on the 250r's. Give him a call and explain your problems/conditions and I'm sure he'll be able to help you out. He is really a top notch fella and REALLY nice to talk to. He has sat down and talked to us before about questions/problems we've had in the past and always takes the time to answer them. For my two cent, I agree with everyone else it sounds like you have an air leak.

 

Yep, I do believe that 240 on pump gas would cause problems. It could have built too much heat and seized from that instead of actually detonating itself to death. That would be apparent from the piston crown and by the plug. The color of the plug was a little lean sounding to me. Are you running a standard head gasket?