is one of my rods bent?

[OCD Solutions]

I stand corrected, it would still happen at the same time, just in a different place.

 

[Schmidty721]

Just wanted to make sure I wasn't over looking something when processing that. That tends to happen haha

 

[OCD Solutions]

Nope, good catch.

With that little detail change then it also changes the symptoms of backfires due to a bent rod setting it out of time. If the bent rod is not the culprit then possibly the crank could have come out of alignment causing the misfiring?.?.?

Or, who knows, maybe he has a bent rod, and a bad MSD. Stranger things have happened and while most guys are looking for a single smoking gun, more times than not, there quite often ends up being more than one.

 

[waxhead]

if it was bent it is plausible the flywheel is also not running true. If it was out of true then it will run closer to a pickup on one side and advance the timing. But it really looks like a hydrolock. Can you post a pic of the bore wear please

 

[jetpilot36]

here you can see the crosshatch from last bore that is relatively untouched. so the smooth sections are where the piston was exerting excessive force because of the bent rod. you can clearly see the uneven wear.

 

[jetpilot36]

does anyone have a crank for sale?

 

[waxhead]

And that answer your question as to if it was bent before or after you turned it upsdie down on the bench.
You didnt cause the issue

 

[kawipilot]

I agree with waxhead. It is most likely you got water in there and hydro locked it. When that happens, the piston stops abruptly and the crank will try to keep spinning, and twist out of index, and/or bend the rod like that. If the crank is welded, the damage can be worse. When cylinder one is at top dead center, cylinder two is no longer at bottom dead center. You should check it with a degree wheel. They are just pressed together. so it probably the rear rod that is bent? Then when the rear cylinder locked, the front half of the crank kept going, and since the timing magnet on the flywheel is timed/fixed to the front cylinder, when it fires the rear cylinder, the timing is too advanced (b/c the rear piston is not where it should be) and it backfires. If it happened on the front cylinder, it would just retard the rear cylinder timing, and you would have just lost some power. Of course you could have just sheared a flywheel key AND bent a rod. Spend some time diagnosing, and don't be a parts changer.

 

[jetpilot36]

I agree with waxhead. It is most likely you got water in there and hydro locked it. When that happens, the piston stops abruptly and the crank will try to keep spinning, and twist out of index, and/or bend the rod like that. If the crank is welded, the damage can be worse. When cylinder one is at top dead center, cylinder two is no longer at bottom dead center. You should check it with a degree wheel. They are just pressed together. so it probably the rear rod that is bent? Then when the rear cylinder locked, the front half of the crank kept going, and since the timing magnet on the flywheel is timed/fixed to the front cylinder, when it fires the rear cylinder, the timing is too advanced (b/c the rear piston is not where it should be) and it backfires. If it happened on the front cylinder, it would just retard the rear cylinder timing, and you would have just lost some power. Of course you could have just sheared a flywheel key AND bent a rod. Spend some time diagnosing, and don't be a parts changer.

yes. It was the rear cylinder. that explains the back fire. but the backfire was intermittent. when I go back together with it all, I'm going to install my digital MSD TL. That with the new crank should get me back on the water. I'm just very curious as to why it was backfiring and only revving on the trailer. put it in the water and it wouldn't rev. I came to the conclusion that the MSD analog was bad. bad brain or bad coil. im wondering if the analog is still good and it was just a bent rod giving me problems this whole time.

 

[Little_Franny]

load can change or amplify base engine concerns, no different from haviing a dead coil on one cyl on a v8, will idle ok and rev up fine in nuetral, drop it in gear and add load and all the sudden its way worse.

 

[Dartman]

old msd analog tl's are for the trash bin, go with newer digital

 

[Sasquachcrap]

^^^ don't trash it.( although they are trash.) I'm having issues with mine and need another one to test. Mine tests good on the bench but it won't run in the ski. Pm me if we can work something out? The main reason I want to keep the 4270 is because of the enclosure I just built for it. The newer one won't fit it.

 

[mr.fixitman760]

That rod was definitely bent before you took it apart, if you look close you can see its discolored to more of a blue color, it takes a combo of heat and pressure to do that

 

[jetpilot36]

You can also tell by the wear pattern in the cylinder. Must have happened last season when my oring on the head went bad and I wasnt getting proper cooling. My pissers were sputtering and engine must have got hot. But after I fixed the oring, I did get quite a few more good rides out of it. Makes me think I had two problems.
1. A bent rod
2. Msd going out.

 

[mr.fixitman760]

You can also tell by the wear pattern in the cylinder. Must have happened last season when my oring on the head went bad and I wasnt getting proper cooling. My pissers were sputtering and engine must have got hot. But after I fixed the oring, I did get quite a few more good rides out of it. Makes me think I had two problems.
1. A bent rod
2. Msd going out.

I would say the overheating caused it, but usually if its that bad the rings stick too.