Help! Mystery starting problem

[Big Shasta]

Anyone worked on heads- do you use 2 stroke oil on bolts like manual says - and molybnium disulfide grease on cams? Seems like the whole area is bathed in engine oil when run...

I believe the oil on the bolts helps you achieve the proper torque and the MolyB on the cams probably assumes you are doing some sort of break in of new parts. Do you need it in this application? Probably not, you didn't remove the cams right? (or did you have to for head removal?)

Looking at the pictures, with that much of the wear surfaces "unmated" I'd probably use the cam lube, there will always be some slight alignment difference that might cause some new wear on first start up. the cam lube helps lessen that.

 

[smthng]

If the manual says to oil them, do so. Unoiled bolts aren't as tight as oiled bolts at the same torque reading. All their torque specs would be based on oiled bolts, so yours should be too... especially on something as long as a head.

 

[andyak]

Today I broke down the 2002 jetski MR1. The head had a broken exhaust valve in Cylinder 1- head seat damage (slight) and piston damage.

SBT wants an extra $300 for the damage plus the $495 for a head exchange. - s $795 for new head plus shipping.
Piston, rings, bearings - etc.- minimum around $150 - OR I can just keep the parts for a rainy day.

My boat engine is awaiting seal kit then I will see if compression is back - there is no apparent damage.


BOY was it easier to remove the exhaust on an engine that hasn't seen saltwater!!!!

I got all exhaust off (10 collector bolts, and all the manifold bolts) off and easily separated in less than 5 minutes!!! AND NO BROKEN BOLTS!

Not a hint of the white chalky buildup seen in my saltwater boat engine.

So - with this in mind, if you have a freshwater boat - you can probably change out a leaking exhaust collector manifold in the boat just by raising the engine to get the impact wrench under there. (if you didn't know, this was the project that precipitated the removal of the engine that will not start now)

 

[buckbuck]

Any updates?

 

[andyak]

Still awaiting seal kit for non starting boat engine.

Tested the valves for leaks and I have a couple intake valves with imperfect seals- do not think this was/is the starting problem- but it needs addressing. I am going to lap all valves before reassembly.

I am thinking about re ringing the Pistons as well. Would need to get new piston bolts/nuts and 10 stretching non reusable bolts for crankcase assembly and then would be dumb not to do new bearings- then we are talking $350 plus in parts to do that And not sure it needs it...

Still deciding.

 

[MikeyL]

Lordy, Andy, after all of this tedious work you've done, I surely hope this fixes it.
I feel there are likely 100+ of us watching your thread closely, hoping the VERY Best for you ... and this engine.
Take Care, Mikey

 

[andyak]

My backup plan is the jetski engine I am rebuilding concurrently. I have ordered the head swap from SBT. I went to a local machine shop to have them retap the bolt hole in the crank block as I didn't want to risk not being perpendicular when I drilled it. The shop manager looked at my head as well and basically told me to go with the SBT swap.

I ordered everything for the ski engine including new bearings replacement piston/bolts/nuts rings for all 4 - this engine will be like new when done. bores are in great shape.

Hopefully I will have 2 engines running in the boat and 1 spare in the garage when I am done

 

[Glassman]

.....

Hopefully I will have 2 engines running in the boat and 1 spare in the garage when I am done

how fast will the garage go on just one engine ?

 

[andyak]

While I am awaiting tools and parts to do my valve job.
I am giving the block the oil on the piston test. So far it looks good probably Won't separate the case. I will pull oil pan and clean it all out.

 

[andyak]

Well I lapped all the valves cleaned everything up put on a new head gasket bolted everything together torqued it all properly and then tested for compression.

Initially I didn't get good compression and after cutting my hand pretty good on the output shaft I added a little oil to each cylinder and then achieved readings of 180 to 210 for all cylinders

Spent most of the day putting it together and putting it back in the boat got it in there cranked it a bunch without any plugs to prime the oil proceeded to put in the plugs and no joy

Took up my compression tester and the cylinders are down to under 60 again each!! I'm ready to drown this Engine - and put in the other one once I rebuild it.


I'm wondering if this could happen if the oil pump is jammed not working - as I got compression when oil was added to cylinders... any ideas?

 

[Big Shasta]

Classis worn rings. If your failing compression but it passes when you oil the cylinders, it's re-ring time.

I would be concerned with putting in new rings without new honing of the cylinder walls. You would never get the rings to seat, you need that roughness of new honing....but then also, aren't these cylinders nykasil (sp) coated? Can they be honed?

I wish you would have put an inside mic in the bore when you had the chance to see if you have significant cylinder wall wear.

 

[andyak]

I would concur except for the fact that it ran perfect before I removed it and replaced an exhaust gasket, then put back and it has not run since.

 

[Big Shasta]

I hear you, it's very strange. But the compression test and then again with oil in the cylinders can't really lie. If it was anything other than rings, it wouldn't change.

 

[andyak]

What if the oil pump is jammed up with sludge and not putting out- would that not have the same affect? There has to be something that is not working from a removal to a reinstall that would explain loss of pressure across all cylinders when the week before it was removed it started right up easily and ran strong at 9700 rpm evenly matched with the other engine on the lake.

I thought it was the head gasket- so I replaced it and did a complete valve lapping as well for good measure ( 20 valves takes a while!!) .
I left the lower case alone as I thought it had to be fine.

I also pulled the oil pan and cleaned out - all looked good not much sludge.
- but I didn't disassemble or test the oil pump as I had no gaskets or rebuild kit.

Any thoughts or ideas?

 

[CrankyGypsy]

THIS IS AGGRAVATING ME!!!

What if the oil pump is jammed up with sludge and not putting out- would that not have the same affect?

nah, you can run engines without oil and/or oil pressure.

 

[andyak]

Ok. I still am at a loss as to how all the rings could from good to bad in a simple pull and reinstall.

It just doesn't seem possible!

I hate unsolved mechanical mysteries!



I have the crankcase from my spare engine being de glossed replated and bead blasted at the machine shop right now. So I will have that and a new head from sbt ( although my newly lapped oem head may be better ) I have new rings, rod bolts and nuts, and head bolts, and new bearings coming. So I will have enough parts to rebuild one of these engines!

 

[subysti]

I'm thinking you may have cracked the head or the block when removing it causing the loss of compression. More likely the head. At least warped it somehow. When its out of the boat and you tested it ok it may have just been sitting right Ben when bolted back in to the boat its torquing on it somehow to open the crack or warp. Just a thought.

 

[CrankyGypsy]

@andyak i wasn't exactly on board with a timing issue being the culprit, but what did you do about the lower chain sprocket? seems improbable that it skipped, but did you check to see that it was correct in relation to the cam sprockets? and if so, how did you do that? - because it doesn't mention it in the manual, from what i saw.

 

[andyak]

I was very careful with timing check on reinstall of head. Initially I was off by 1 tooth but I corrected right away. When you put in the chain tensioner it changes things just a little. I used a rod in cylinder 1 to tell exactly where tdc was and then got cams to line up exactly.

My final in boat test will be to add a little 2 cycle oil to each cylinder and check compression again to rule out some things.

 

[rkluck]

This is odd but if you add oil to the cylinder and compression goes up you are basically making a better seal briefly. This would imply rings (as stated above). A warped head would still reflect low compression even with the oil added. The oil pump is not putting oil in the cylinder so that can't impact the compression (I don't know for sure but guessing this is a 4 cycle). But as you stated, I am confused as to why this just started. Is there any chance debris got put into the cylinders and damaged the seals or something similar to that when you were replacing the exhaust gasket? I doubt it but just throwing a thought out. My disclaimer is "I am just a shade tree mechanic and not an expert as many people here are".