uh oh!wtf happened?

B

Budget_Blaster

New Member
Dec 25, 2009
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So im out on my blaster a few mins ago and it was running great as usual and all of a sudden it died so i pulled over and tried to restart when i found that the engine wouldnt turn over.so after a few mins i got it to turn over and it started i immediately took it back home pulled the plug and it looked fine so i did a compression test and only got 135psi which is a major drop from what it was.

So i put a new plug in went out and ran it again and it ran just fine again.wtf would make it do that?am i on borrowed time since it apparently momentarily seized?i looked in through the plug hole and it looks normal idk wtf is going on but 135psi sounds low for a 240bbk with 4hrs on it doesnt it?

Any ideas im stumped.
 
Budget_Blaster said:
So im out on my blaster a few mins ago and it was running great as usual and all of a sudden it died so i pulled over and tried to restart when i found that the engine wouldnt turn over.so after a few mins i got it to turn over and it started i immediately took it back home pulled the plug and it looked fine so i did a compression test and only got 135psi which is a major drop from what it was.

So i put a new plug in went out and ran it again and it ran just fine again.wtf would make it do that?am i on borrowed time since it apparently momentarily seized?i looked in through the plug hole and it looks normal idk wtf is going on but 135psi sounds low for a 240bbk with 4hrs on it doesnt it?

Any ideas im stumped.
Click to expand...

Slight low, yeah, what compression were you at after build?
Sound like a ring issue, NO DOUBT.

Were they fitted correctly? In at the ring gap location locked?
I would not push it, pull the head and check rings, first, for sure.

Report back ASAP...
 
Budget_Blaster said:
So im out on my blaster a few mins ago and it was running great as usual and all of a sudden it died so i pulled over and tried to restart when i found that the engine wouldnt turn over.so after a few mins i got it to turn over and it started i immediately took it back home pulled the plug and it looked fine so i did a compression test and only got 135psi which is a major drop from what it was.

So i put a new plug in went out and ran it again and it ran just fine again.wtf would make it do that?am i on borrowed time since it apparently momentarily seized?i looked in through the plug hole and it looks normal idk wtf is going on but 135psi sounds low for a 240bbk with 4hrs on it doesnt it?

Any ideas im stumped.
Click to expand...

A 280 main strikes me as a little low for a 240 kit. Could of just been a fouled plug though.
 
No injection premix at 32:1,not hydrolocked since i smoked a cig and let it cool and it then moved by hand and then fired up on the second kick,and yea im thinking it hit seized.

Theres actually a 340 main in it.but i dont understand wtf it hot seized ive been riding this with no issues why all of a sudden in a 70 degree day with 30+ mph winds out here coming off the fields would it hot seize i dont get it i know theres no leaks.plug chops say its correct.

The odd thing is my kdx with a new top end just cooked the rings 15 mins prior to this m not having a good day!
 
Running it too lean on both bikes and getting on it too much(patience). I'm not too familiar with 2 strokes yet, BUT you ALWAYS run an engine rich, when breaking them in...... Helps prevent blowing your stuff up.

Been a while for me, but last engine I "broke in" was my Harley. Did 500-600 miles 1st year. Halfway thru 2nd year, it was running like crap. Forgot I had a 31 jet in my S&S.... now running with a 28......... BUT I didn't blow it up.

NEVER look for performance while "break in", just get some miles. I imagine with a 2 stroke, you need to cool OFTEN. Clean the plug, and use fresh mixed gas(dont fill the tank). 2 bikes going down, puts it on your end, or bad gas/oil/build.......Just my opinion.....
 
Believe it or not I had a similar problem with my cr250 I was running it on a fresh top end that was just broken in and doing a few hot laps then it sputtered then just cut off,I didn't take the risk so I took it home and when I took the jug off every thing perfect not one scratch any were,then I took off the clutch cover and fount a nut came loose and with it came a washer lol,so I guess it got stuck in there ne'er the crank gear and the clutch basket gear and got wedged in there witch caused me to have to get a new clutch basket,something as simple as an improper torqued nut can cause all of that headache,now I'm not saying that's your problem but never over look anything bud.
 
4 hrs into it wth numerous heat cycles and cool downs i dont see how it wasnt broke in?

Both bikes indicated on the plugs even when they blew they were pig rich!the plugs werent white or charred they both had oil residue on them and both are unchanged from the last time they were ridden.the kdx has even been to bad lands a few weeks ago on the same jetting/build as it sits rght now and did have one issue.

I dont get it the signs point to correct tunes on both bikes according to the current plugs and previous plug chops.i have a degree in automotive and have buiot countless quads,bikes,engines and even have taught engine performance at the local college im not a novice i dont claim to know it all but im not an impatient novice which is why this dont make sense i was maybe a 1/4-1/2 throttle when it quit.
 
Im open to suggestions.and just so i know 135psi is too low for a bbk correct?

If the bore checks out can i rering it and start the break in again or should i replace the vitos piston?
Hw durable are the pistons from vitos its a cast piston standard vitos bbk.what are the chances i caught it in time?


I let it cool down swapped in a new plug and went from 1.5 turns out on tdhe a/f screw to 2.5 and rode it and rode like normal.idk im stumped.
 
my bbk was 183psi after rebuild and same after break in, your not going to know what happend with out taking it apart, is your airfilter clean, and oiled?
 
when I worked at my uncles honda shop I've never herd of this kind of problem before,you are rite it's very weird to just cut off and lock up,did you have to break it lose to get it to crank over or did it just crank over after it cooled down,also if the piston is not scortched or scratched it's most likely a good piston and if you do tear it down if I were you I would definitely replace the rings ya know,but if you do get new rings make sure to hone it again,as far as pistons go I always run forged pistons that have a high silicone content for good lubrication like wiseco,all vitos forged pistons are made by wiseco so you should be good.
 
Its a vitos cast piston and yea i had to break it loose to get it to fire.

So yea im stumped and about to tear it down and find out the damage ill let you guys know what happened.
 
if you went from 1.5 out on the airscrew to 2.0 out on the airscrew you leaned it out, you probably need more pilot jet, and running the low RPM lean is what hot seized it
 
M curious if your running the advanced timing still. If so this will cause some excessive heat without higher octane however I would say either you pw clearance or ring caps are a little tight. I would re ring and hone along with a double check on clearances. Hopefully piston isn't to scared up. Keep us posted!
 
brandoz28 said:
if you went from 1.5 out on the airscrew to 2.0 out on the airscrew you leaned it out, you probably need more pilot jet, and running the low RPM lean is what hot seized it
Click to expand...

the whole time i was reading this thread i was wondering if he only changed the needle and main on a stock carb and left the pilot alone.
 
airleak...blown head gasket both will cause slow heat buildup...i dont thinks its jetting, your not gonna fry an engine with the pilot being slightly off
 
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