2001 Virage 700 Engine Vibration

[Bluedmax]

Hi all. I have a 2001 Polaris Virage with the 700 2 stroke engine. My original engine melted one of the pistons last year after 20 years of riding, so i ordered a new long block from SBT and installed over the winter. It runs good, but vibrates a bit more than my original engine. My original engine did have some vibration just off idle but would go away as you rev through it. This new engine vibrates around the same rpm, but shakes a little worse and I have to rev a bit higher before it smooths out. I thought maybe the new engine had a balance issue, but now I'm thinking it might be an engine alignment issue? I installed the new motor with the same shims and tried to line up the wear marks on the mounting brackets in the same location, but it could be a slightly different position than original. I've seen where alignment is critical in other models, but is it critical for my model? The splined shaft end that goes into the engine coupler is machined with a slight curve, which I've heard is supposed to allow for some misalignment and easier install. Or if it's the engine, I'll obviously want to get it exchanged before the warranty runs out. I also noticed the reman engine didn't come with the "L" bracket that installs across the top of the cylinder heads. Not sure if this would affect anything, but I still have it and plan to install on the new engine and re-torque the head bolts back to spec. Anyone have experience with this? Thanks in advance.

[casey67]

Never experienced that issue, but never installed a SBT engine.

Try loosening the mount nuts and wiggle the engine a bit. Possible one of the mounts could be bound up.
With nuts tight, does the engine move when trying to move it? A broken mount could transfer more vibration.

Absolutely reinstall the head brace. It mounts to the head cover bolts.

The bevel on shaft is for easier install.
Not sure they could really screw up crankshaft balance. But rebuilt engines do get overbored, meaning the pistons are slightly larger. Do the usual fuel mixture checks, aricher running engine will be smoother, wouldnt hurt after 20 years.

[Bluedmax]

Thanks for the reply.

I'll try loosening the mount nuts again to see if anything frees up. Otherwise the engine mounting is very tight with no play and I specifically checked the condition of all the mounts before installing. They were all in good condition.

I was definitely planning to install the head brace. SBC had very good detailed instructions for the new engine install, but failed to include that step. I called their tech line to inform them and now have the proper torque specs for the head cover bolts so I can get that done.

What are the usual fuel mixture checks? Do you mean like checking spark plug color? I pulled the carb a few years back to clean and check everything. I installed a stock kit and reinstalled. It's run good since. If a re-jet or modification is needed because of the overbored engine, I could use some direction as to how much of a jet change is needed.

[casey67]

Checking Fuel mixture by looking at piston wash.

[Bluedmax]

How much run time do you think is needed to have an accurate wash reading? I'm not quite half way through the engine break-in procedure with about 2 total hours on it and attached are pics of what the 2 pistons and cylinders look like so far. If the carbon outline that is developing is any indication of what is to come, it would appear I'm looking good or maybe a bit on the rich side (which I'm ok with)?

[casey67]

Hard for me to tell, pictures in that environment are difficult.

having 4 fingernail sized clean spots is best.

All black is too lean.
The larger the clean spots the richer it is .

[Bluedmax]

I'll get some hours on it and check it again maybe in a few weeks.

[Bluedmax]

Back again after several weeks of riding. So I have now fixed the vibration, but have developed another problem. I fixed the vibration by re-shimming the engine to be straight with the pump shaft. This was a complete shade tree fix, no special alignment tools used. I used a level on the pump shaft and adjusted the trailer jack till the shaft was perfectly horizontal. I then transferred the level to lay flat across the top of the cylinder heads. I noticed 2 things... first, the engine was not level. Second, the shaft didn't line up perfectly into the coupler. I shimmed the engine until it was perfectly level, then adjusted the entire engine height so the shaft slid straight into the coupler. Before tightening the motor mounts, I spun the started to "center" the engine with the shaft. The vibration is now dramatically reduced, as good as or better than stock (prior to my engine swap).

The new problem I am having is with the exhaust bolts. I didn't have 5 hours of riding when I noticed the exhaust bolts had all come loose and some fell out, which allowed water to be pumped into the hull. Thinking maybe I had messed up and not tightened them properly, I pulled the manifold completely out, cleaned all the gasket material off, ordered new exhaust gaskets and reinstalled using blue Loctite. Now I don't think I have another 2 hours of riding and I just noticed 2 bolts came loose again and another 2 bolts have snapped completely off. One snapped at the head (should be doable) and I fear the other snapped flush at the cylinder. I've yet to pull everything back apart, but a quick search on Green Hulk landed me this string... http://greenhulk.net/showthre...+exhaust+bolts. Sounds like the exact same thing I'm experiencing. My first check once I get everything apart is obviously going to be with a straight edge across both the cylinder surfaces, also the exhaust manifold surface. I would hope my new "long block" engine from SBT would have been cleaned properly of old gaskets, assembled correctly, and cylinders aligned and torqued properly. But knowing my luck they're not. I guess I'll know once I get a straight edge across them. One of my biggest concerns and questions is... do you think I've damaged the engine at all from the water that's been leaking from the coolant passage around the exhaust port? It only leaks while running, so I'm hoping the exhaust pressure would have continually pushed the water out, not into the engine. Also any additional thoughts of what to check for or procedures to follow would be appreciated. So much for a trouble free summer of riding

[casey67]

The loctite on exhaust bolts is a must. Having the manifold in place before tightening the cylinder nuts is helpfull, checking both surfaces will verify if it was needed.

Are all pipe bolts and rear support bracket in place ? ( the 2 cylinder pipe should have a large bolt, like 1/2 way down)

At some point Polaris ditched the gaskets and went with silicone. IIRC they again used gaskets in production.
I think it may have been more because of the gaskets. They also really stressed having cylinders properly aligned.


LOL....Is there even such a thing as "trouble free" anything water sport. There is a saying about "the best day in a boaters life" and its not the day you bought it.

[Myself]

I would hope my new "long block" engine from SBT would have been cleaned properly of old gaskets, assembled correctly, and cylinders aligned and torqued properly.

UUummmmm, ya......I wouldn't bank on that at ALL!! They have absolutely HORRIBLE assembly practices. Gasket surfaces that look like they were cleaned with a belt sander, one cylinder shorter than the others, massive amounts of sealant to help seal up the mess, etc.

[Bluedmax]

I would think loctite is a must also, but there was none on the factory bolts when I took them off. That's why I didn't use it on my initial install. Now I think I'm going to regret using it trying to get the broken bolts out!

All the pipe bolts and rear support bracket are in place. There's 1 or 2 large bolts towards the front, then 2 side by side that fasten an ear to a motor mount bracket on the left rear motor mount.

The original engine had exhaust gaskets, which is why I used new gaskets on reassembly. My dad bought the ski new and to my knowledge, the manifold had never been removed. Definitely no sign of silicone.

Yeah I know there's no such thing! Just wishful thinking. I also have a 1978 Hallett jet boat, so between the two, the tool box is normally handy.

I'll get everything pulled and start with a straight edge.

Do you think there would be any water damage to the engine from the leak? Anything specific to look for?

[Bluedmax]

So you've had bad experiences with them? I tried finding some engine shops that would do the work, even asked the question originally on Greenhulk. Couldn't find anything, so opted for SBT. Other than this exhaust thing, the engine seems to run good and have the same power as stock. I purchased the engine on 9/29 and do have a 1 year warranty, so I still have a little time yet.

[Myself]

I build all my own at my shop. I DID however pull an SBT engine for a replacement for a customer last year. It was a 951 Di that was vibrating so bad it was loosening exhaust bolts within 10 minutes. These have a balance shaft and I'm certain it was out of time. Anyway, they sent a replacement which wouldn't fire up.......no air pressure out of the onboard air compressor......which is PART of the rebuild. I got the OK from their warranty dept to take the compressor head off instead of R&R another engine. Found valve disc had never been replaced. I had a good used one on hand and it's been running fine ever since. If a critical part like that is missed, do you really think they are checking clearances, chasing bolt holes, wire wheeling all the bolt threads, etc?????? NOPE!

[casey67]

If the engine was started on the trailer after exhaust was leaking, I don't think there is any damage. Most of it is pressure in exhaust-that would keep water out. And any water after shut off should be pushed out with the trailer start.
Typically leaks at the exhaust gaskets cause temp issues, before hard to diag running issues, then external leaks.

Rust is biggest issue with water inside engine. With a well lubed crankshaft, the oil displaces the water- IF there was any small amount.

Yeah, with machine work, you are paying for attention/time spent. The more repeat work you do (volume with very common engine parts/more profitable repairs) the more a company makes.
As you noticed finding anyone to deal with "Orphaned" brands is difficult.
I commend SBT for even trying,while even at a low cost. They really are the best available.

[Bluedmax]

Casey 67 - We're lucky enough to have a dock on a river and keep the ski in the water for summer. So it's been in the water until today when I finally had a chance to pull it out. I fired it briefly on the trailer, but it HAS been in the water this whole time. Hopefully there's enough lubrication throughout the engine to keep rust away, but after you read below, it may not matter anyway.

I got the manifold / pipe assembly pulled tonight. There's a total of 6 bolts that hold the manifold on the cylinders, there's 3 bolts per cylinder, each set of 3 bolts has 1 long bolt and 2 shorter bolts. It was interesting to find that all 4 short bolts were snapped off and the 2 long bolts were intact. I would have thought the 2 long bolts would have had "more leverage" on them and snapped before the short ones, but that's besides the point and it is what it is.

So upon inspection with a straight edge, the surface of the actual pipe/manifold seems to be straight and flat (as I expected). The cylinders however are not perfectly aligned across each other. With a straight edge across the mating surface of both cylinders I was able to "rock" the straight edge back and forth across the two. I grabbed a feeler gauge to measure the gap and there appears to be about a 0.013 difference. Not a lot, but definitely doesn't sound good to me. I'm thinking it should be perfectly aligned and flat 0.000 or close to it right? Then of course I have 3 broken bolts that were sheared down into their threaded holes (one of the broken bolts had the shoulder exposed and I could back it out by hand).

So the big question is... is a difference of 0.013" between the cylinder mating surfaces "out of tolerance" and be cause for my issues?