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Need some advice of rebuild or drop in SBT for a 2008 RXP-X

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cegpcola

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I recently purchased a 2008 RXP-X with an engine noise for a deal that I couldn't turn down. I have checked the Supercharger which is in good shape, pulled the valve cover and no broken rockers, and pulled the pump to make sure the noise was in the engine as expected it still was. I figured it to be a rod knock from the little that I had heard it, but wanted to try a few things to make sure. So now I am at the point were I need to make up my mind if I want to rebuild or buy an SBT drop in. I think the damage is limited, as there no shavings in the oil. I am more than likely looking at a new rod, new crank, new rod and main bearings as well as stretch bolts and gaskets. The ski only has 39 hours on it, and when I pulled the rocker cover it was super clean. I am an automotive mechanic and have no problems doing the work, but I am just wondering if it would be worth it to rebuild over the slightly higher cost for an SBT drop in. Any thoughts or suggestions would be welcome.

Also, or these engines prone to rod bearing failure, and should I look at ARP Rod bolts and a hone for the rods based on the ARP bolt's added clamping force?

Just want a stock ski but fix any issues that might cause a future failure while I am at it.

Kurtis
 
Hope you're ready to spend some big bucks. Only good thing about your situation is that the engine still is a good core. SBT has had a hit or miss reputation. If personally look elsewhere.
 
That is the kind of answer I was looking for......I know how SBT is with their Yamaha 2 stroke stuff, but wasn't sure on their 4 stroke Rotax motors. Cost isn't going to be too high for me since I will be doing the rebuild. Anyone else that wants to advise on their experience with either rebuilding one or buying a drop in from SBT it would be helpful.
 
Even with you doing the build you're looking at around 3k in motor, gaskets, bolts and miscellaneous items. It adds up quick.
 
With some rough research on parts cost, so far my estimate is around $1500-$1600 in parts and then my time. It will also depend on what everything else looks like when I open up the engine. My high end that I expect is around $2000. Even at $3K, I am well to the good as far as value in the ski goes anyways.
 
As long as when it's all said and done you can sell the ski (if you chose to of course) and break even, you're good to go.
 
Nothing to worry about. I bought my 00 RX not running for a price that if I decide to light it on fire and sell the trailer I'll get enough money to cover my initial investment, cost of gas to light it on fire, and beer I drank while it burned. Deals like that you can't pass up. You're way ahead already. Running a ski like yours depending on condition and hrs in my are will go for 6700-7000 with trailer.
 
Yeah, I figured I couldn't go wrong on the deal. don't get me wrong, I am going to try and keep the repairs cheap but right, but overall I have plenty of room in the value.
 
They are not prone to bearing or rod failure, but it does happen. I see one or two per year. I did one that sounds similar to yours that only had a slight knock. It turned out to be a rod bearing but was caught early. The crank and piston were fine, new rod and bearing and it was good to go and have winterized it twice since.

If yours is only 39 hours, I would expect you to be able to reuse almost everything. I would not go the SBT route on a nearly new OEM motor that just needs fixed. I don't think the cost will be over $1k but it depends on the damage once tore down. Make sure to check everything that it is within spec tolerances, replace all gaskets, all stretch bolts(including the flywheel kit), torque to sequence, have your head checked by a qualified machine shop for bent valves and seat condition.
 
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Thanks. Good info, and pretty much what I am expecting to see once torn down. I have a great machinist that we use at the shop. So no need for ARP Rod bolts since this is not a common failure? I will for sure install the ARP Flywheel bolts since they are only $25 and will hold up a lot better then the stockers from what I have seen and read.
 
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Here are pics of what I found when I opened it up. Rod bearing on front cylinder feels to have spun, but didn't crack it open because the very front main bearing spun and hammered the block. Block will not be useable. It is a shame, only 39 hours on the ski and everything else in the engine looks brand new and super clean.

So where to from here. SBT said that the damage would add another $200 to my cost based on the pictures I sent, but I am afraid it might be even more. Can't find a good used block that I could build from, or I would buy a new rod, maybe new pistons and rings if a bore was needed, new bearings and gaskets.

Thoughts?
 
Do you have a pic of the Vent hole you are speaking of? Not completely familiar with the Variations of the Rotax blocks.
 
All the 4tec blocks are the same except for a couple of minor things. There is an extra screw boss on the newer ones and the vent hole below.

4tec block vent hole.jpg
 
Another couple of questions came to mind while looking at options to keep cost down. 1) Is there any differences in the Cranks in the 4-Tec engines? 2) Is there any other differences in the Blocks in the 4-Tec engines?

I am thinking about buying a used complete engine from a different model and using the Crank and Block. This would save me some money in the long run to be able to use the crank instead of having to buy a new crank after the bearing damage in mine. I would make sure that there are no issues with rod knock/bearing failure prior to purchase, but I have found a full engine from a 185 Wake that runs right around the same price as that Block above. Any thoughts?

edit: Another thought I had was maybe looking into using ARP main stud kit and having the block align honed. Just not sure that there will be enough surface removed to make it work. I could check with my machine shop on that option.
 
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1)Yes, cranks changed mid year 2006 when the TOPS system changed. Actually, just the timing chain pin location changed for the different position of the coil pickup.
2)Only the 2 differences I pointed out above.

If you can get a complete running engine 185hp for $600, you better buy it, or give me the info so I can. :thumbsup:
Depends on the year of the 185hp engine for the differences, 07 or newer would be better or you won't be able to use the crank.

You should have a machine shop look at your crank and block. There are oversized main bearings available and all your machine shop will have to do is fit to size(standard practice in the automotive world). Cranks can also be repaired for a reasonable cost if the damage isn't too bad. Machine shops can also often repair the journals of the Al block as well.
 
So, the 185 was a bust. I have found another option, it is a rebuilt 2006 215 long block. The builder says that it should be fine since the head and block are matched, and they would include the correct crank trigger for the timing difference. They are asking $2500 for it right now, and this isn't looking like a bad option, however the main drawback I have is that the valves weren't replaced, just cleaned and checked and new Valve stem seals installed. The engine supposedly had 112 hours on it when it was rebuilt. Any thoughts on doing this and then continue to look for a block to rebuild my original 255 Rotax and just have a spare laying around ready to go.
 
The old valves will need replaced, not worth the risk especially when you're going to push them hard with the bigger fuel injectors and x sc and higher rpms than the 185hp has ever seen. They drop at 100 hours all the time so yours would be tick...tick...tick...sooner or later! Why can't you use your head?

Why not just buy a block and build it? It should only take a week.
 
I can buy a block and build it, but just don't have the personal time to devote to it at the moment. With a drop in, it wouldn't take much more than an evening after work to get it running. What I was looking at is dropping this in and still building my engine when I have a little more time to devote to it in a few months. I would prefer to build what I have. It sucks that the machine shops around here do not have the equipment to fix the damage to the block
 
understand the lack of time but it only takes a few hours to build a motor, so maybe a few eves after work. it's simple to box up the block and send it to someone to fix. the damage doesn't look that bad. call ppg and see what they think. unless you find an x motor to drop in, I wouldn't do it.
 
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