787 rotary valve shaft question

[nycdon73]

Good Arterton everyone! I have a question on a rotex 787 motor. I noticed that when I turn the crankshaft counter clockwise and hold the rotery valve, the rotery shaft skips and clicks, and I can keep the valve from turning. It is solid when I turn the crank clockwise. Is this a normal condition? If it is normal, I realize must set the timing back to 147 degrees.


Thank you all for you replies!

 

[racerxxx]

It should not skip in either direction.

 

[nycdon73]

Thank you for your reply. So I quess the gear is bad as the person who rebuilt it set the timing wrong and it backfired.
And broke the starter shaft right off. Do you think the shaft gear Sheard, or is it possible the crank head went bad?

 

[nycdon73]

Sorry. Meant the crank gear went bad.

 

[racerxxx]

Ouch, can you find any brass in the oil from the rotary valve lines?

 

[racerxxx]

I have never see a crank gear slide on a 787 crank, on a smaller 720 engine, yes.

 

[nycdon73]

I'm not sure. We took the motor out. The oil lines were bocked off as it was running premix.

 

[nycdon73]

Ok so the crank gear can't slide. So what function does the spring accomplish on the valve shaft?

 

[racerxxx]

I don't "think" the great can slide, I never "saw" one that did.

So, the lines were blocked off, did you have oil in there? Is there oil in there now?

 

[nycdon73]

How do I check if there is oil?

 

[racerxxx]

Did you guys put plugs in it or is there rubber lines coming off the fittings?

Could you post a pic?

 

[snikwad003]

[MENTION=79189]nycdon73[/MENTION], racerxxx is talking about a different set of oil lines seprate from the oil injection. They feed oil to the cavity that the brass gear is in, does this ski still have the oil tank or a small oil bottle connected to the fittings on the crankcase?

 

[nycdon73]

[MENTION=79189]nycdon73[/MENTION], racerxxx is talking about a different set of oil lines seprate from the oil injection. They feed oil to the cavity that the brass gear is in, does this ski still have the oil tank or a small oil bottle connected to the fittings on the crankcase?

No. The lines are not connected to the oil tank at all.

 

[nycdon73]

The two lines come together at a t fitting and the single end of the t is blocked off.

 

[snikwad003]

There oil in those lines?

 

[racerxxx]

There oil in those lines?

It sounds like there are no lines at all going to the rv.

I want to see pics. I'm thinking I'm going to see pipe plugs in the engine where there is supposed to be the lines. It's just an assumption.

 

[racerxxx]

Nevermind some how i missed a post.

 

[nycdon73]

There is one line on each side of the engine the are connected to a t fitting that is blocked off. After fixing the shaft should I re connect them to the oil tank for better lubrication?

 

[nycdon73]

Thank you for your reply. I see now that the two crankcase lubrication lines should go over the mag cover and be filled with oil if not using the tank. Question, can I remove only the bottom crank case cover to clean out the gear broken pierces and replace the shaft?

 

[racerxxx]

You need to remove the flywheel and mag housing to at least be able to get to split the cases? Personally I would tear the whole thing down to get a good inspection on everything.

 

[nycdon73]

Thank you. Much appreciated!

 

[nycdon73]

I have torn down the engine and and replaced the rotary shaft. Now I see there is no mark at all on this SBT crank gear to align the counter balance shaft. I have been looking very closely. Nothing. can you tell me how to align the counter balance shaft to crank on a Rotex 787?

 

[mikidymac]

There are no marks to align. Throw the rotary shaft in any way you like. The timing is done by the teeth on the rotary valve itself. Also it is eccentric and flipping it over will change it about a degree. Follow the manual and make sure you have the correct degree valve for your engine. You can print the degree wheel page from the manual and use that to set the timing.

Also the typical reason for the broken starter is that it is a cheap aftermarket one. The only ones using are OEM.

 

[nycdon73]

There are no marks to align. Throw the rotary shaft in any way you like. The timing is done by the teeth on the rotary valve itself. Also it is eccentric and flipping it over will change it about a degree. Follow the manual and make sure you have the correct degree valve for your engine. You can print the degree wheel page from the manual and use that to set the timing.

Also the typical reason for the broken starter is that it is a cheap aftermarket one. The only ones using are OEM.

Thank you for your reply. The question is! How do I realign the counter balance shaft to crank. No mark on crank gear. Sorry for confusion

 

[ace422]

maybe call SBT and confirm, I believe setting the crank and cb with the balancing weights opposite each other will get you aligned.