DF25 Timing Mark 90 deg off on crank

[OBwrecker]

Well fellas, and possibly ladies,

Got an issue I've never ran into, so I figured this is the perfect opportunity to join a forum!! Please bear with me, this may take a minute to explain.
. A few months ago had a customer complain about loss of power in his 1999 DF25 four stroke. Next day he tells me it came to an abrupt stop and wont do anything. Low and behold, it skipped timing and bent every exhaust valve.
. Following the suzuki service manual, I replaced the exhaust valves and related parts, as well as the timing chain and cam sprocket. Unfortunately the tensiontension longer available, but after some testing this one seems to be working fine.
. Now for the fun part. I aligned the timing Mark's as the manual described, but found the top of piston 1 was hitting the exhaust valve again while turning the engine to set the valves on cylinder 2. Also found the tip dead center Mark's on the camshaft were also not aligning when their cylinders were at TDC. Long story short, this entire problem was corrected when I rotated the crank 90 degrees. Everything lined up as it should ( other than the crank mark) I have compression and zero piston to valve interference.
Got the engine back together tonight. She started up and soundedpretty good. Went to start her a second time and she damn near ripped my arm out of socket with the pull cord. I've already determined that the pull cord mechanism is fine and has zero issues. So, any ideas?Resized_20201026_192256.jpeg

[OBwrecker]

And, I'm fully aware that what I just described as moving timing Mark's off 90 degrees sounds like something from spaceballs........but believe me, the engine would not stop interfering with the valves had I left the Mark's aligned. Had it together and apart atleast 5 times......

[briscoe]

Did you ever figure out what happened with 90° off TDC? I was just curious

[noelm007]

The starter cord "pulling back" is a sign of timing being wrong, it fires way too early and stops dead, or even worse, backwards for a second, I suggest you have done something terribly wrong, especially if you have been playing with the timing chain.

[OBwrecker]

I'll be tearing it back down next week. I'll send some photos.

[redlowrey]

Did you first establish why it bent the valves, or are you assuming it was from the loose chain and tensioner, it sounds like it sheered the key on the crank or the locating pin on the cam the first time, If it sheered the key on the flywheel it would only effect ignition timing. If the crank and cam locating keys are fine, you are setting the camshaft timing up wrong.

[OBwrecker]

Fellas,
I apologize that I haven't updated this threat recently. I ended up deciding to advance the timing 2-3 teeth instead of the 90 degrees, which gave me the clearance I needed between the piston and exhaust valves. I know this sounds absolutely ludicrous, but the engine idled on the stand just fine. I then let it sit on said stand for two years.

Redlowrey, Both keys on the crank and flywheel were fine. The locating pin on the camshaft was just fine as well. I'll be honest though, I have no idea what caused this engine to skip timing in the first place. The old timing chain was slightly stretched, but nothing that I believe would have caused this issue. I do know that the timing chain tensioner appears to be hydraulically actuated, perhaps it ran low on oil? Perhaps a combination of low oil pressure and a rock did the trick?

Anyway, long story short, I just put this engine on the back of a 16 foot John Boat last week, hoping it will be much more fuel efficient than my Ol' Smokey's I usually run. Took a spray of ether, but it started up and ran just fine. A few trips back and forth then I got some water in the fuel so it went back on the trailer.

After cleaning all the water out and re-installing the water separator I'm now having some running issues, but I'm going to attribute that to the carbs needing a good cleaning after having some dirty fuel pushed into them. I'll be doing that this week and I'll give you an update soon.


I'm sorry I don't have better photos to share, I've looked and it appears I didn't take any.