Normal engine noise?

[kwiktsi]

OK, bear with me here. I just got done rebuilding my 787 RFI using SBT pistons and crank. To me, it sounds louder at idle than I expected. It's certainly mechanical and almost a ratcheting/rattling sound, I guess. Don't hear it as I increase the RPM, but don't know if it is just being covered up by other sounds by that point or not. It's not super loud, if I stand back, I don't hear it. With my head over the engine, I do. With the seat on, it's not audible at all. I have a fair amount of experience with snowmobiles, not PWC and snowmobiles are rattle traps between the clutches ratting, pipe sounds, etc. so I just never got an ear for how a "normal" 800 2 stroke idle sounds. Thanks.

 

[ocod]

post a vid but more than likely its the pump rattle which is normal.

 

[griz400]

make sure u put both rubber bumpers on each end of the driveshaft http://www.shopsbt.com/sea-1999-dgtxrfi/45-101A-06.html

 

[kwiktsi]

Should have clarified- not pump. I had it running prior to installing the pump and it was doing it. I can try to video it, but I only have my phone and it will probably sound like crap. Let me see if I can get a good sound clip.

 

[gforney]

check the RAVE valves to make sure they are not touching on the new parts?

 

[kwiktsi]

check the RAVE valves to make sure they are not touching on the new parts?

They were filed for clearance on assembly. I don't know how quiet these motors are supposed to be, if this is a bearing noise, I'm gonna be PISSED!!

 

[SabrToothSqrl]

How old are the bearings?1996? 16 years? Saltwater?

I, personally just pay for a rebuild and 1-2 year no fault. Then you know your good to go.

 

[kwiktsi]

How old are the bearings?1996? 16 years? Saltwater?

I, personally just pay for a rebuild and 1-2 year no fault. Then you know your good to go.

New SBT crank, pistons and wrist pin bearings. I just got the motor back together, the crank was cleaned and lubed with 2 stroke prior to assembly and the wrist pin bearings were lubed with assembly lube.

 

[kwiktsi]

OK, just checked SBT's site and apparently their cranks have a 1 year no fault warranty as well. That puts my mind at ease, I'm really not in the mood to take this thing all apart again right now, so I'll just run it and see if it gets any worse.

 

[racerxxx]

Did you replace the bearings on the counter balance shaft? I know it's too late now but when I assemble the bottom end I'll lay the crank and CB in the bottom case and rotate the crank around as fast as I can and listen, then I'll remove the CB and do it again. Then I'll fully assemble the bottom end and I grab the rods and turn it over as fast as I can, and listen again. At this point the bearings will have the full torqued pressure on them which CAN change the way the rotating assembly sounds, but it should sound close to what it sounded like just pressed in the bottom half. I know when I was just doing the 787 for my XP I put the crank into the bottom end and put the CB in BEFORE I changed the bearings on it and while the bearings felt good they sounded LOUD. Once I put the new bearings on, it was real quiet.

The other thing I'll question on the CB is you have to be VERY careful on the placement of it, the rear counter weight with the gear CAN rub the case in the back if you don't position it correctly. There is a section in the manual that clearly states this. I always use the MAG cover and gasket to help locate the shaft. Meaning there is a fine line of where to lay it so your not cramming the front CB bearing into the MAG cover since this bearing is proud of the case. This tolerance can be quite close, I use a rubber mallet to help "distance" the gear from the case by tapping the shaft in either direction, with the MAG housing on the case. I don't have the top 1/2 of the case on yet so I can see how close it is. You might also want to check the oil in the CB cavity. You can drain it and check it. If you have aluminum shavings in it, I'd say your in for a tear down 'cause I hate to see you pooch a new crank.

Also is everything torqued on the front of the crank? Flywheel nut, Mag to Flywheel?

 

[kwiktsi]

Did you replace the bearings on the counter balance shaft? I know it's too late now but when I assemble the bottom end I'll lay the crank and CB in the bottom case and rotate the crank around as fast as I can and listen, then I'll remove the CB and do it again. Then I'll fully assemble the bottom end and I grab the rods and turn it over as fast as I can, and listen again. At this point the bearings will have the full torqued pressure on them which CAN change the way the rotating assembly sounds, but it should sound close to what it sounded like just pressed in the bottom half. I know when I was just doing the 787 for my XP I put the crank into the bottom end and put the CB in BEFORE I changed the bearings on it and while the bearings felt good they sounded LOUD. Once I put the new bearings on, it was real quiet.

The other thing I'll question on the CB is you have to be VERY careful on the placement of it, the rear counter weight with the gear CAN rub the case in the back if you don't position it correctly. There is a section in the manual that clearly states this. I always use the MAG cover and gasket to help locate the shaft. Meaning there is a fine line of where to lay it so your not cramming the front CB bearing into the MAG cover since this bearing is proud of the case. This tolerance can be quite close, I use a rubber mallet to help "distance" the gear from the case by tapping the shaft in either direction, with the MAG housing on the case. I don't have the top 1/2 of the case on yet so I can see how close it is. You might also want to check the oil in the CB cavity. You can drain it and check it. If you have aluminum shavings in it, I'd say your in for a tear down 'cause I hate to see you pooch a new crank.

Also is everything torqued on the front of the crank? Flywheel nut, Mag to Flywheel?

Thanks for the info. I didn't even think to try your method, I just felt all the bearings, they felt good so I dropped the crank in and spun it some more and all seemed fine.

I didn't see the info in the book about the CB shaft, but I looked closely at it when installing it anyway to make sure it cleared everything and recall thinking that if it weren't for the gasket, I didn't know if the end would clear the MAG cover. The front CB bearing was silky smooth, so that stayed, the rear was rusted to hell so that got changed out. I think this is in the rods though now that I checked it out a bit more. It has the speed/rhythm of rod bearings and if I slightly rock the PTO back and forth, it has a pretty good click to it (more than I would say is normal but not nearly as much as wiped out wrist pin bearings if this makes sense).

Yup, everything is torqued. Like I said, it isn't super loud and is still quieter than before the rebuild, but I am still being paranoid since it is all new and if it isn't normal, I'd like to know! I have one year to see if it gets any worse .

 

[racerxxx]

I looked closely at it when installing it anyway to make sure it cleared everything and recall thinking that if it weren't for the gasket, I didn't know if the end would clear the MAG cover.

Yeah that bearing is way close, makes you triple guess yourself. I could waste an hour just checking and rechecking, this is the foundation for the rest of the mill so you gotta start out dead nuts on. To be honest you should only have a small bit of dwell on the rods at TDC and BDC where the stroke switches from push to pull and pull to push but no where else in the rotation, so if your getting that mid stroke I might be concerned. I really want it to be OK for you, you did an awesome job on the install and clean up.

 

[kwiktsi]

To be honest you should only have a small bit of dwell on the rods at TDC and BDC where the stroke switches from push to pull and pull to push but no where else in the rotation, so if your getting that mid stroke I might be concerned. I really want it to be OK for you, you did an awesome job on the install and clean up.

Yeah, it has it anywhere in the stroke as I turn the crank and wiggle it back and forth. That's why I said it sounds like rod bearings - loose, but not completely wiped out to the point that it has a ton of slop. Would be nice if it was a wrist pin bearing- those are simple lol.

I'm going to have my buddy give it a listen tomorrow, he has a lot more experience with PWC's than I and can probably tell me within 5 seconds what it is lol. If it is rod bearings, I may just run it for a bit since it has the one year no fault warranty and I REALLY don't want to take it back apart right now- already had it in and out once this week for another reason and am sick of working on it! If it is wrist a wrist pin bearing, I'll tear the top end off in the ski and fix it, but won't be happy about it!!

Thanks for the compliment, I like how it came out too! Not bad for a rattle can paint job .

 

[CReynoldsMIZ]

Yeah, it has it anywhere in the stroke as I turn the crank and wiggle it back and forth. That's why I said it sounds like rod bearings - loose, but not completely wiped out to the point that it has a ton of slop. Would be nice if it was a wrist pin bearing- those are simple lol.

I'm going to have my buddy give it a listen tomorrow, he has a lot more experience with PWC's than I and can probably tell me within 5 seconds what it is lol. If it is rod bearings, I may just run it for a bit since it has the one year no fault warranty and I REALLY don't want to take it back apart right now- already had it in and out once this week for another reason and am sick of working on it! If it is wrist a wrist pin bearing, I'll tear the top end off in the ski and fix it, but won't be happy about it!!

Thanks for the compliment, I like how it came out too! Not bad for a rattle can paint job .

Im not usually one to do this, because i hate when my ski doesnt work as well. But, a lot of us said to just buy the SBT reman that comes with the full no fault warranty and then this would have been their problem to fix, not yours. Sorry to hear about this tho, its so annoying when they dont work like we hoped. Hope its something easy!

 

[kwiktsi]

I know, I've been second guessing my decision too. I'm just stubborn about doing my own work, I don't let anybody touch my stuff. I don't know, I just like things done my way with my attention to detail.

At least the crank has the same warranty as their motors, so worst case, I'll yank it out and send it back. Even if it was their motor, I'd still have the labor of pulling it out anyway, so the extra work to tear it down isn't a big deal to me, so it would suck just as bad either way.

 

[Spimothy Leary]

I know, I've been second guessing my decision too. I'm just stubborn about doing my own work, I don't let anybody touch my stuff. I don't know, I just like things done my way with my attention to detail.

At least the crank has the same warranty as their motors, so worst case, I'll yank it out and send it back. Even if it was their motor, I'd still have the labor of pulling it out anyway, so the extra work to tear it down isn't a big deal to me, so it would suck just as bad either way.

i wouldn't second guess the decision, you assembled it... thats 90% of the battle, however, its correct to second guess the work if it doesn't pass the eye test, or in this case the ear test, let your buddy listen to it, run it minimally, keep in mind your still vulnerable to top end damage right now, and that's not warranted., you don't want the 10% of the battle to tear up your pretty new engine.

 

[Molotok]

Just thinking out loud here, im not too well versed with these things yet, but ive been reading the shop manual, and this came to mind.

 

[kwiktsi]

i wouldn't second guess the decision, you assembled it... thats 90% of the battle, however, its correct to second guess the work if it doesn't pass the eye test, or in this case the ear test, let your buddy listen to it, run it minimally, keep in mind your still vulnerable to top end damage right now, and that's not warranted., you don't want the 10% of the battle to tear up your pretty new engine.

Good point on the possibility of top end damage. That's all I need is for it to let a bearing loose and chew up the top end..

View attachment 16189

Just thinking out loud here, im not too well versed with these things yet, but ive been reading the shop manual, and this came to mind.

Thanks, but that's good .

 

[Dennis]

How about the possibility of being bored incorrectly and you're hearing piston slap? Does the noise get less when the engine warms up? :cheers:

 

[kwiktsi]

How about the possibility of being bored incorrectly and you're hearing piston slap? Does the noise get less when the engine warms up? :cheers:

Nope, stays the same . Doesn't sound like piston slap either. I checked the bores with a bore gauge before assembling and they were right at spec. The noise wasn't there for the first few runs, but is there now, so it is something "worn" already . Then again, I never let it get too hot yet, so now you got me wondering...

Actually, another thought is I'm gonna check the CB oil- I had it properly filled but had to pull the motor out the other day for something and had the motor laying on it's side on the bench, so I'm wondering if it's possible it escaped through the labyrinth washer? I'm going to just add some to be safe, any extra should get burned out from what I read.

 

[Dennis]

I just noticed that it is a RFI. Hope you didn't do away with the oil injection and go to premix. That would explain the noise.

 

[SabrToothSqrl]

I just noticed that it is a RFI. Hope you didn't do away with the oil injection and go to premix. That would explain the noise.

2 strokes need oil?!:lol:

 

[Dennis]

Also, the RFI crankshaft is different than the carb 787 crank. :cheers:

 

[kwiktsi]

Still has injection, not a fan of premix- not when the pumps are as reliable as they are . Crank is an RFI crank, not carbed.

I had a buddy listen to it today (long time marine mechanic with a wealth of Seadoo experience) and he said it is fine, nothing out of the ordinary :thumbsup:. I figured I was just being too critical, but as I said from the start, I have never heard a bigger two stroke without all sorts of other rattles going on to know how the motor alone is supposed to sound. It's good to go :hurray:.

 

[anthonygrato]

Congrats on a successful build!