Rotax 787 RFI Rebuild - Part 1

Welcome to part 1 of the Rotax 787 RFI Rebuild. In this first episode of this series i install the new crankshaft, install the rotary valve shaft, time the balance shaft, and join the cases.
For more awesome 2 Stroke videos check out my Rotax 951 Rebuild Series!
• Rotax 951 Rebuild
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[@andrewcalk878]

Hey , isn’t there an o-ring that goes on the pto end of crankshaft before the main seal?

[@DeWoodysShop]

Yes there is sorry did not film it or mention it specifically.

[@JOSERGMMXX]

having that issue right now air leak by pto area cause didnt put that o- ring i guess

[@andrewcalk878]

@@JOSERGMMXX oh yeah dude..same with another big channel “todaywewrench” both of them forgot a critical part..useless

[@freelectron2029]

everyone wants to go make a video "showing you how to do it" but doesnt know what they are doing themselves then doesnt take responsibility for spreading false info. really annoying.

[@andrewcalk878]

@@freelectron2029 really frustrating

[@jasonmoore9252]

Great job except you forgot a some MAJOR steps in the rebuild. Mostly those crank seals around the rotary valve should be sealed in the case with Loctite 518 or else they will leak at some point. Do not try silicone or other sealants, it has to be anaerobic semi-flex sealant, Permatex makes the same exact stuff as Loctite. Also many of the case and cylinder-head bolts require Loctite 518 on their threads NOT Loctite 243 (248 in your vid). The use of 518 on the case bolts & cylinder-head bolts are clearly stated in the repair manual, the use on the crank seals for rotary valve is not in the book and less known but anyone that does lots of these things knows to use it on them. Also if those seals are leaking and the rest of the engine is fine I don't waste customers $$ by doing a complete rebuild or even replacing those seals. Just open the case up, clean the seals and groove the seals fit in thecase then add the Loctite 518 between the seals & case. Figured I would pass on the information to agreat tech to help a brother out. It's no fun getting one of these back after a couple seasons after a rebuild to have the seals leaking again.

[@ansissvars3523]

Good video. But why you do not whant to show deetails. Like balanser shaft, timing point have 2 teath diapason.

[@ansissvars3523]

Or precision in ther is not so important?

[@flyingkevo]

how much did it cost you to rebuild it yourself?

[@grast5150]

Question, Should you not use 515 or 525 gasket maker on the crank shaft seals?

[@DeWoodysShop]

Rotax does not call for it, There should be no need for that on good modern case that fit and seal correctly. There is gasket maker on the edges but if you mean putting it all the way around the seal no.

[@genetemplet7022]

I agree 100%. I was told nothing was needed on the inner lip seals when I did my first engine. Now I have a "shut off" valve on the rotary valve feed line because it leaks internally. LOL Second engine I tried moto seal on the inner lip seals but didn't like it as it set up too fast. I use 518 as it is anerobic and won't get hard till oxygen is removed. I will not assemble an engine without something on those inner lip seals. I also use a very light coat of sealant on the outer edges of all the lip seals and end caps but not Motor Seal. :D

[@jasonmoore9252]

​@@genetemplet7022 YES you have to use the anaerobic sealer on those seals, it's not in the manual but anyone that knows these things should know to use a Loctite 518 or equivalent on them. Also the same anaerobic sealer is supposed to be used on the threads of the case bolts & the 8 cylinder-head bolts.

[@kyletaylor6935]

When you were putting the sealant on the case halves, what was the little bolt you were using on the tube to help squeeze the sealant out? That looks very cleaver and convenient

[@DeWoodysShop]

Its like a hollow little tube winder thing. It came with the yamabond in the package. It is really useful for sure.

[@martinkx250f]

I see you bolted the cylinders to the upper half of the case pretty quickly before flipping it up! Is it a mandatory step or is it also possible to first close the crankcase and then assemble the cylinders? Thanks

[@DeWoodysShop]

Its not, I mentioned it was just sitting on it for somewhere for the rods to go while I assembled it.

[@ripptydevibes2581]

I installed a brand new SBT 787 carb engine, on my oil deleted jet jon boat. Unfortunately when I filled my oil loop (rotary valve bath) there must have been an airlock bubble. Luckily in the first 3 minutes of light throttle on the water, I saw that the oil loop ran dry on one side, not the other. Immediately halted the mission and came back t the shop and ended up putting in again as much oil as originally. So, the valve bath was HALF full of oil on a brief run. Do you know the internal design of these blocks well enough, was half full enough oil for the crank to sling around and keep everything wet? Or do you think we need to pull and inspect anytihng? My full time mechanic career tells me everything should still be fine but these seadoos are not yet fully understood in my mind!

[@DeWoodysShop]

It should be fine if you are talking about the internal bevel drive inside the block. Normally the oil is "pumped" through there, I think its the bevel gear itself moving the oil through there. But its all ball bearings and just a gear so long as a reasonable amount of oil was already in it i would not be worried. The disk itself is the sensitive thing in the system that can quickly get ruined. But if you are a running pre-mix should not be an issue for you.

[@saracondon7115]

I bought a 3D with the same problem, were you able to buy the complete crank assembly ready to install?

[@DeWoodysShop]

Yes just bought a rebuilt crank from sbt I believe. Has all the bearing and seals on.

[@jasongrenon9129]

Any tips on getting the motor out of the 3D? About to embark on this journey at the end of the season

[@DeWoodysShop]

Its really not bad as far as skis go. I think I took the pipe and throttle bodies off if I remembered right

[@bradleycarroll5038]

where do you recommend to order parts from ? thanks great vids

[@DeWoodysShop]

Partzilla.com or my local deal since they price match and give me a discount.

[@rashpaldhaliwal1713]

You have 787 Or you can rebuild for me Where are you Your video is really good

[@DeWoodysShop]

Only the one in the 3D. I am in north east Texas.

[@JOSERGMMXX]

i purchase a crankshaft from ebay brand wsm looks like the one you install gold color center seal in the center , cause old cranksfhaft are red color anyways is been 3 times already replacing the rotary valve shaft cause keep damage the brass gear ,only last 5 min running and goes bad so i decide to split motor again and check diameter of both middle gear crankshaft and are not the same old crankshaft is little bit not much but is bigger of the wsm brand do you think this may be the issue of keep the damaged the brass gear maybe is not completly grabing the tooth of the brass gear

[@jasonmoore9252]

When the seals are leaking I don't even waste my customers $$ with new seals or a crank, all that is needed is to clean the seals for the rotary valve and install with Loctite 518 (anaerobic semi-flex sealant). Even if I do a rebuild that requires a new crank/seals I always set those seals for the rotary valve with Loctite 518, that is if you don't want them to ever leak again.

[@jeanpaulrodriguez3367]

What type of oil are you using in the red tank

[@DeWoodysShop]

Its two stroke oil. I think pre-mix Yamaha "yamalube"

[@papadonjetski9535]

Who did you purchase the crankshaft from?

[@DeWoodysShop]

Its a WSM rebuild kit.

[@shannonwilliams601]

The sky made a huge mistake I have been building two-stroke jet skis for over 20 years he did not put any sealer between the two case halves it's very important and you also put it around the edge of the main seals otherwise you will have a pressure leak eventually these engines are so old you're not dealing with totally flat surfaces anymore this is a big No-No

[@DeWoodysShop]

If you refer to this video between 6:50 and 8:40, I spend almost two minuets putting case sealant on and talking about it.🧐

[@genetemplet7022]

Yup, ALWAYS put something on the outside of the lip seals. No leaks.

[@tg5509]

He did. Thanks for the video man!