Suzuki DT4 Roaring Sound - I'm stumped "help"

[W Cash]

History - bought this motor online seller said he knew nothing about it. Water pump impeller was bad so I installed a new kit corrected problem one. Motor wouldn't rev up or idle so I twice cleaned soaked and blew out and wired all ports. Corrected idle and helped some on the higher rpm's when in gear but still not where it should be. Checked and cleaned all wiring - New Plug- pulled fly wheel cleaned and made sure all was tight underneath. Problem all along off and on I'd get this horrible roar that comes and goes and by feeling of the vibration I thought lower unit bearings wrong there in perfect condition. Tried a very short run even without lower unit on just the engine and didn't have roar but couldn't run long enough to totally rule engine out. Problem "Horriable Roar and will not rev up about 3/4's in gear and sputters. What's next any ideas???

[Solarman]

What's the age of motor?
Has motor been sitting up for a long period of time?
Does sound occur in neutral with lower unit on?
If lower unit is off, you can connect hose to water tube going up, turn water on enough to run motor longer. If exhaust isn't too loud, is sound still there?

Noise might be crankshaft bearing(s), rod, or piston wrist-pin needle bearings. DO NOT run motor if this might be the noise you hear?

If this motor sat-up for several years, or more, humidity may have caused internal bearings to start rusting. higher RPMs may cause these bearings to come apart, and damage this motor.

Good luck.

[W Cash]

Thanks Solarman and yes it does it in neutral with lower unit on but it comes and goes I'll do the other tests today.

[Solarman]

You might be able to use a long screw driver(1.5-2 foot) like a stethoscope, and while motor is idling, place handle on ear and put point in different areas of crankshaft (inline- where it spins) and cylinder (sides where piston travels) on casing, to see if you can tell where sound is closest/ most pronounced.

If you can identify where sound is loudest, you may be able to identify the sound. A growling type chatter sound (roaring?), could easily be needle bearings on rod/piston with flat spots on bearings. If sound closer to crankshaft, may be one of the crankshaft bearings?

It would be better to do these sound tests with foot in large bucket/ container, to keep exhaust noises at minimal to better hear the sound.

Good luck.

[W Cash]

Thanks again here's my progress today so far. I pulled engine and pulled crank case apart and removed crank and piston. All is clean no metal fragments all look great. Heck there's not another bearing I haven't checked. It's worse at high rpm now I'm wondering if it could be the gear shifting rods vibrating in lower unit but hard to believe they could make such a noise. You mentioned flat spots on rod bearing but look great but I didn't pull pins

[W Cash]

I went the route I did because I didn't want to damage anything any further if it was internal.

[W Cash]

One more question should the rubber arms on impeller be bent or curved to fit in the pump housing. The old one was destroyed so had no visual.

[Solarman]

The impeller is a tight fit, and yes the vanes of the impeller have to bend into the cup by turning the drive shaft in its normal operating direction, when you slide the housing cover down over it.

Am glad bearings are all good, was worried motor had set up too long. For your piece of mind the inspection was worth it. When you find out what is causing this motor noise, I do hope you will post us back.

Good luck, post back if you find anything.

[W Cash]

Thanks again Solar u have been a great help I'm in process of getting all back together. I will sooner or later find it and will post.

[W Cash]

As Paul Harvey would say" And the rest of the story" I couldn't and never did find the cause of the roaring noise after tearing the DT4 completely down and I mean completely. I got mad and decided I'd let the dang thing blowup or out so I put in forward gear ran it up to full throttle an roar it did and I walked in the garage. Lol. In about ten minutes the roar quit and I took it to the river and ran it about six miles and it ran great. Your guess is good as mine. "Good Day".