Second seize, need advice

[2strokespirit]

Hi Guys...

I am stumped....

I have a 1999 CR500, still on original tires since new....

The bike seized and I bought it from the original owners like that.... They have replaced piston and rings and seized it after about 1 hour of riding....

I opened it up and I could not understand why it seized, the bridge was relieved, there was no signs of detonation, the piston crown has no marks at all, just a few seize marks on the sides on the piston and in the cylinder.... The exhaust bridge are relieved, so that has been ruled out.... The crankcase has more then enough oil in it and the gas was mixed....

Ok, so I went ahead and bought a brand new barrel, piston and rings (oem), gaskets, seals, cdi, coil and water pump shaft and impeller for the motor....

I assembled the motor, did a leak down test and all came out well...

I have build a lot of motors so its not my first one, I also ported this baby running a 190 exh 128 transfer....
I run a PC pipe and silencer.... Still have the PJ carb...

Si I started it and it fired up on the 4th kick.... Warmed her up and went for a cruse... Came back and checked for leaks and stuff... All seemed well...

Did a few heat cycles and after that took her for a long drive, she ran flawless....

SO when I cam back I just pushed her a little harder.... She ran awesome with TONS of power.... Then all of a sudden, she locked up for a split second.... I pulled the clutch, and stopped.... I then pushed the kickstarter and there was enough compression, I thought I might have made a mistake and nothing happened... Started her up and she started first kick.... I ride her back home with no problems, and still tons of power....

I also did a few plug chops, and she feels a little rich.... 178 main, needle on 4th clip, 55 pilot.... 1000ft above....
Attached is the plug on a flat speed ride, brand new plug, I know how to do this, as said not the first time.....

BUt I need more advice as I am stumped and have no more options.... I want to assemble the motor with new piston and rings after rebore, but want to avoid this to happen again....

I opened the motor and find that the piston did hot seize with 4 very light marks, yet the rings did not melt into the piston, is so small, but it happened....

Please guys any advice are so welcome.....

One more thing, what did bother me is the bike idles for about a minute perfectly and then slowly loose rpms and dies, I thought this to be an airleak, but yet again, the leak down test passed!! If it was an airleak, there would have been signs of piston melting etc... This looks like a seize due to a lack of oil, which I can rule out, running a fully synthetic Castrol oil with a 32:1 mix.....

[AlisoBob]

My only advise:

1. Run Maxima '927

2. Open up the piston to wall .0015

3. If you run Wiseco pistons, throw them away

4. Run Maxima '927

5. Check the condition of the radiators very carefully. At full song, the CR500 generates allot of heat. Rads that work fine at 1/2 throttle or lower may not be up to full throttle bursts. Some guy soak them in this stuff, and are amazed by what falls out....



Post some photos of the damaged parts.

[2strokespirit]

Its stock oem piston, on new barrel... The clearance was to big from the factory at 0.14mm, the service limit is 0.1 if I remember correct...

I am also starting to think the radiators are blocked... I did use spanjaard radiator "cleaner" and removed lots of junk from it before assembled the motor...

We cannot get castor oil here... This is my second CR and the first one never had a issue with Castrol oil.... The previous owner ran Bellray....

I might think this is a radiator problem.....

[Kuma]

How is your exhaust gasket?
is there any chance your seals were installed reversed?
seems like 32:1 should be plenty of oil, I run 50:1 golden spectrol with no issues.
just throughing out some ideas, could the crank be bent a little, might do a static leak down fine but while running the seal may not be able to keep up.
you should be able to check the stator side by pulling the cover and while at idle shoot some WD40 and see if you notice any change in rpm, shouldn't effect the electrics?
where are you at that you can't get castor oil? are they afraid someone is going to make ricin?

[2strokespirit]

The oil I use is more then good enough, trust me.... I am used to 2-strokes ans use these in all banshees etc... I like running a rich mixture, just me, but I do jet for it... The exhaust keeps dry even at 32:1 on this oil..

The crank has been check on a dial gauge upon rebuild... I am starting to blame the radiators, but I never see it pushing out liquid....

Seals are installed correct... If the motor ran that lean, one should have seen it on the sparkplug and on the piston crown... On close inspection on the plug, there is no lean condition or ali specs whatsoever.... I suspect a cooling issue, but I can't imagine the radiators will have issue....

I really appreciate your help....

Jip, no castor!

Exhaust gasket is new....! Thanks

[2strokeforever]

Its stock oem piston, on new barrel

theres some funny stuff coming out of the honda factory.....
send it to roosty and then ride the crap out of it

[coley13]

what the hell did you do to your spark plug ?

[2strokespirit]

what the hell did you do to your spark plug ?

A proper plug chop

[AlisoBob]

A proper slap chop

[britincali]

Do you warm it up?

[100hp honda]

'99 with original tires and light piston seize so you bought new jug ? bore job is $65 new jug is $350 aint it.

[NightBiker07]

I had a similar issue with my 300r three wheeler. ran fine all day long, except on top. when it was WFO for ANY length of time, it would sieze. cool down, and start right back up again. dicked with the jetting for EVER, and one more jet size up, it blubbered, one down it siezed.....never did figure it out.

i thought a clearance problem, but i checked it, and all was well. And ive run the same oil in my KX80 and my CR250. both have had the S*&T run out of them, never had an oil related problem.



idk about wiseco being junk. I have one in my CR250, no problems yet, or with the one in there before.
Cast pistons seem to be a bit more forgiving on the bore though. but its an age old argument, just make sure whatever you run is set up properly.

It'll be interesting watching this issue get resolved.

[cmotodad]

May seem silly but did the bike sit for any legnth of time? If so, is the carb all clean with no particles floating around. The idle changing might be heat related.

[2strokespirit]

@100hp honda, I bought the bike seized, the exhaust bridge cracked, thats why I replaced the jug.... I did not want to remove the bridge on the other jug....

Mine seized with very light marks.... Everything is new on this motor, I have stripped it down to the ground on rebuild and the carb as well.... I know 2-strokes well, I have spoked to miller racing engines also, we had a good chat and the guy knows his stuff.... I do 2-stroke building as a second job in south africa, I am not new to 2-strokes.... The reason i asked it here is because there is more experience CR500 builders then most other places and thought I might learn something on the 500s.... Yes the bike get warm very well before every ride.... This is about the 16th CR motor I have done.... Thats Why I am out of options...

I am thinking that the radiators might be blocked, anyone tried those oversize Chinese radiators on ebay? We run them with great feedback on the Banshees..... But the CR vibrates and I am not sure will they last, I just like the idea of more coolant and better cooling....

I will keep you guys updated and thanks for the feedback and help....

My companies name is BVH Racing Developments, you can google it...

I will send out the radiators for cleaning this week....

We run Wiseco in all motors we build, except this one had an oem piston in it.... Let don't go there.... I love Wossner, but hard to get in our Country..

[2strokeforever]

anyone tried those oversize Chinese radiators on ebay?

got some for my af, just need to finish modifing the right one to fit, look well built

[2strokespirit]

anyone tried those oversize Chinese radiators on ebay?

got some for my af, just need to finish modifing the right one to fit, look well built

Nice, please keep me updated!!