twinsted crank, or oddly failed MSD enhancer?

[Mouthfulloflake]

so once again wife was riding my ski, it was running well.
she said it lost power, sounded funny and then died, she was unable to restart it.

she swam it in.

I couldnt get it to start, replaced coil ( the old had the wires cut back nearly too short I happened to have a good one with me)

no dice.

it turns over fine, shows 155 psi in each hole ( same as the last few years), BUT
it sounds odd when it turns over, like the ignition is out of time, sometimes it nearly stops from turning over, I think from the sparkplug ignition too late into the compression stroke.

so im thinking the flywheel must have sheared the key.

I remove the flywheel, key was good, look at stator plate, its tight, and its right where I had put it years ago.

so button the front end back up, think that maybe its a broken reed, so I yank the carb and intake.

stock metal reeds still look perfect.

with the plugs laying out on the head and cranking it over, its a good consistant fat blue spark at the plugs, the msd is firing with every engine rotation.

so Im guessing that the msd is either gone haywire and the timing cirve has freaked out, or the crank is twisted and the con rods are no longer 180 degrees apart?

has anyone ever seen a msd enhancer exhibit these symptoms ?

or has anyone had a crank twist on a very mild 701 engine?

thanks for any help, I plan to swap CDI next, and if that doesnt fix it , Ill yank that engine out.

 

[Matt_E]

I don't know how common a twisted crank is on 2-cylinder cranks.
It's pretty easy to check, though - just just calipers and/or a TDC dial indicator.

 

[Big Kahuna]

you can get to wooden dowels same length, stick them down in the plug holes, rotate the the pistons and mark the dowels. Basically looking to see that they are equally moving up and down on 180 degrees from each other.

 

[Mouthfulloflake]

yeah I was going over in my head how I could check the crank without pulling the engine apart.

I think though if its NOT the CDI, then the engine must come apart anyway, I cant see what else it could be.

I even tried a spoon full of fresh premix down the carb, thinking I had some water in the fuel tank.

same thing.

thanks guys!

 

[chriselmore_1]

want to sell the old coil with the too short wires?

 

[Matt_E]

Even that's too complicated if you think about it. Just find TDC in one, then make sure the other one is at BDC.

you can get to wooden dowels same length, stick them down in the plug holes, rotate the the pistons and mark the dowels. Basically looking to see that they are equally moving up and down on 180 degrees from each other.

 

[Mouthfulloflake]

Chriselmore_1, I tried to send you a PM, your box is full

Matt_E,
I was thinking remove the head, and use the depth function of a vernier caliper to max out the depth reading on one cylinder, and then measure any difference in height between the other cylinder and the deck?

the more I think about it though, I cant imagine it would be so far out and not run at all, it must be a very obvious difference, or im chasing a ghost.

do you have ANY other ideas what might be wrong?

 

[Matt_E]

No need to take the head off. Find tdc through the spark plug hole. Then use dial or vernier calipers through the other spark plug hole to verify that one is at bdc (rotate crank slightly in either direction to see that it is indeed bottomed out.)

 

[B0000M]

how are your magnets on the flywheel? none at all broken??

 

[Mouthfulloflake]

the magnets looked fine, all intact.

if you put the sparkplugs into the plug boots, and lay them on top of the engine, and hit the green button, it turns over, and they spark nice blue fat, with what appears to be a normal 'rythym'

Ill see if I can get a video of the sound and that.

 

[Idok]

did you check the rear seal? is your bendix sticking and slamming against the flywheel?



how is the crank just going to "twist" under normal operating conditions...that doesnt make any sense

 

[the WaTeRhAwK]

a buddy subbed his ski a few weeks ago, ingested water and twisted the hell out of his crank. brought it back and it shook like crazy and ran like a hog.

 

[Matt_E]

Seen it happen to an 1100 crank just recently. The crank was otherwise perfect, no signs of abuse. It happens.

 

[Idok]

it doesnt "just happen" there has to be a reason



never heard about this happening to a yamaha twin....







now, a polaris triple...maybe..

 

[Matt_E]

The yamaha triple I got in my garage looks perfect - but it's twisted. I'll post pics later. Maybe it wasn't pinned 100% right - but then again, it's the original 97 crank. In fact, the entire motor looked perfect. Maybe someone can tell me what caused it, because I sure as hell can't figure it out.

 

[showmepro1200]

What did the "sounded funny", sound like??

Keep us posted what you find too

 

[Matt_E]

Every time I've had odd sounds during cranking, something major was wrong with the engine. A main bearing may have locked up.

 

[Mouthfulloflake]

I am unsure how a bad crank bearing would prevent the ski from starting and running?

My wife doesnt have good throttle dicispline, she likely held it pinned, came out of the water, and then back in.. shock loading the pump.. total guess there, I wasnt watching.

it doesnt sound like its grinding, or anything like that, it simply sounds like the plugs are firing at the wrong time.

I have time this afternoon to mess with it, so video coming soon hopefully.

150+ psi both holes
flywheel key wasnt sheared ( I replaced it anyway)
stator plate was tight, all coils intact.
Bendix appears to operate normally, not rusty, smooth operation.
flywheel magnets intact
fresh coil ( jss wires) old msd enhancer
spark test with plugs out, fat blue spark, consistant as long as the engine is spinning over.

the odd sound, as if it it spins over a few times, then becomes harder to turn.
with the plugs out, it will spin over just fine, and not make the odd sound.

thanks for the help and ideas guys!

 

[the WaTeRhAwK]

maybe the starter is toast. :dunno:

 

[Idok]

i had a 550 with a bad crank bearing that woudl spin like mad with the plugs out, but not hardly at all with them in....


had a similar failure locally not too long ago....bad main rod bearing and the motor woudnt spin over