Looking for a new engine

M

MaximaFan

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Apr 6, 2004
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I am parting my engine out due to a bad crank and am looking for a 780 for my 2000 SRX if anyone has a good stock motor or preferably a 780 motor they want to get rid of let me know. And by the way has anyone else turned a crank and in doing so advanced the timing thus burning down pistons this is what we believe is happening to me.

Thanks,

JT
 
bluehammer said:
Do you mean twisting a crank out of phase? Who's 780 is it? Problems with the same cylinder?
Click to expand...

I dont think he HAS a 780, just looking for one.
 
I believe it is twisted and I am having a buddy bring a Dial Indicator over to check to make sure. It is burning down the middle cylinder, 2 times now so we believe it is predetonating and thus hammering down on trhat middle cylinder. Anyone had this happen before? If this is the case I will be in need of either a new crank which I will weld or a new 780. Any input is appreciated.
JT
 
never seen one do that yet, and I have fixed alot of srx's, had some before with crank run out, but its not gonna advance the ign timing. It shows up with vibration in the bars when running and it will be low on power. What exactly has happened to the sled?, has it been modified? cold air kit? tempa flow? heads cut? bored carbs? need a little more information to help ya out.

As far as the crank goes, if its out, it can simply be brought back into spec and welded, not a super expensive fix, labor intensive from having to tea th engine completely apart.
 
Hey MrViper

Here is what was going on, I had a tempa flow which ended up leaning out the middle cylinder at WOT so it locked up something fierce. We did not think to check the crank so we replaced piston, rings,cylinder and took it out again to test and it pre det on us.The plugs looked way rich since we jetted up so I know it wasn't a lean condition. There are no mods besides the bender can and clutch work which you suggested. We will be testing the crank this weekend so if it is the crank could you tell me who to use to fix it and a possible cost? I am tearing my hair out trying to get my Blue Baby back in action and it keeps throwin me curve balls, but I am not a quitter so sooner than later it will be roarin again! Any input in appreciated and thanks to MR Viper for sharing his knowledgwe with all of us! By the way any idea why it is the middle cylinder that goes everytime?
JT
 
I could be wrong here, but if you seize a piston really hard it could put the crank out of phase on that particular rod throw, thus changing the timing in that cylinder. We did this on a dyno once a few years ago but didn't lose the cylinder. The dyno showed a power loss, thus causing the dyno test to be aborted. Any takers here?
 
ahhh yes, the good old tempa blow.
I would ask this, granted you jetted up the mains with a tempa blow, but where is all the rest of the jetting?, needles,pilots, fuel screws? when did the sled burn down? was it cruising, or wide open throttle?
To move the crank enough to screw it up would be highly unlikely, as the sled has a 3d ign system, not a std sytem where the plug fires all the time as in the 98-99 srx. Youd need to move ALL the crank throws, and it would take both end throws to move the center cylinder this much, very highly doubt it, theres 2 press fits here, the end throws have only 1, these are the guys that move much more easily. If it moved it that much it would idle like a harley davidson. I guess anything is possible with enough force, but have fixed alot of blown up srx's, lots from tempa blows too, never ever seen a center crank throw moved, pto ones, yes.

Another thing comes to mind when its the same cylinder, does it have a air leak?, such as the carb boot?, leaking reed block gasket?
 
I wish you lived in MN Mrviper but I am goint to bring what you wrote previously home to show my buddy who's helping me fix it and we will look at all of the options such as air leak, in carb boot or reed block gasket. I really appreciate all of your guys help!!
JT
 
to check this you need 2 tools, a dial indicator and a degree wheel, your gonna set up the dial indiactor and find true top dead center on pto side, then set your degree wheel pointer to 0 and move it 120 degrees, mark your degree wheel #1, then move to center cylinder, and do the same thing, then on to mag side, should be 120 degrees between cylinders tdc, if its not its out of phase. The last check is with dial indicator on the pto end stub, rotate the engine over and see how much run out it has.
 
I just called my buddy he said he tested for leaks and there wasn't any leaks, but he firmly believes when it locked up at WOT the middle cylinder locked up and twisted that part of the crank so until I check it this wknd it is all speculation, but I will be sure to keep u guys updated so we can store this situation in our heads for future scenarios.
JT
 
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