Last effort before splitting the cases rm250. Burning gear oil.

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6/5/2021 7:37 PM
Edited Date/Time: 6/9/2021 5:30 PM

Hey guys,

I’ve been scouring the forums looking for help. However I’m at the point where i am looking at splitting the cases.

rm250 is burning gear oil pretty quickly
- extra smoky exhaust
- the oil I drained is blackened and smells burned

Things I’ve done
- replaced right side crank seal
- leak down tested it and found a leak at countersprocket seal but nothing at the crank seal
- no play in the crank

I’m wondering if the center gasket is shot? That’s the only thing i can think of that is left at this moment. I will if I have to but hoping one of you may have another idea or suggestion
Thanks in advance

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6/5/2021 8:18 PM

Smell is coming from burning your clutch

Whats condition of clutch?

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6/5/2021 8:29 PM

Factor E wrote:

Smell is coming from burning your clutch

Whats condition of clutch?

Clutch is in good shape and works fine. The bike runs good on top end but has a harder time idling than a usual 2 stroke. Last oil change after riding, before I knew there was an issue, there was about 200ml of oil remaining and it was black. If it’s not being sucked in through the crank seal, any other places besides the crankcase center gasket?

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6/5/2021 8:37 PM

Pull pipe and see if oil runs out

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6/5/2021 8:48 PM

Factor E wrote:

Pull pipe and see if oil runs out

Yeah oil runs out of it. There was also gear oil in the power valve front cover. I’m pretty sure it’s gear oil. Same look and smell.

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6/5/2021 8:51 PM

Cases not sealing

Time to rebuild

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6/5/2021 9:32 PM

Factor E wrote:

Cases not sealing

Time to rebuild

If the crank is still good, would you recommend replacing it anyways?

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6/6/2021 9:31 AM

Factor E wrote:

Cases not sealing

Time to rebuild

seanrm250 wrote:

If the crank is still good, would you recommend replacing it anyways?

If it’s the OEM crank, have it rebuilt vs buying an aftermarket. To ensure it’s good, you have to put it on a stand and check runout and other specs. You don’t want to get it back together to have the crank let go 20 hrs down the road.

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If you're not mixing gas, you're not haulin ass.

6/6/2021 11:05 AM

Factor E wrote:

Cases not sealing

Time to rebuild

seanrm250 wrote:

If the crank is still good, would you recommend replacing it anyways?

I see you are in ca. Give Ted a call at boyko racing.. he does very good work and uses pro x rod kits

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6/6/2021 12:43 PM

Factor E wrote:

Cases not sealing

Time to rebuild

seanrm250 wrote:

If the crank is still good, would you recommend replacing it anyways?

TrailDigger wrote:

If it’s the OEM crank, have it rebuilt vs buying an aftermarket. To ensure it’s good, you have to put it on a stand and check ...more

You’re right. Going to go this route, assuming the crank I have is oem. Fingers crossed.

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6/6/2021 1:19 PM

For the clutch side crankshaft seal, do you recall which orientation it was when you installed it?

Most bikes have this seal oriented where the metal portion of the crank seal faces outward. The later RM250s were the opposite. The crank side seal should have the metal side facing in and the black rubber "U" portion facing out.

Another thing to consider, how deep was the crank seal pressed in? If it is pressed in too far, it will make contact with the crank bearing which can cause it to drag, overheat, distort and allow oil to be sucked in. Also depending what size socket you used to press it in, the new seal could be torn or warped.

FYI I've been in the process of restoring a 2007 RM250 and had a hell of a time with this issue. Turns out the clutch side seal was in backwards and really made jetting a pain.

I've also screwed up enough crank seal installs that I always keep a few spares in the tool box.

Also another thing to consider, if it has aftermarket crankshaft bearings, the inner ID might be too big.

When I split the cases on my bike it had a Hot Rods crank and Hot Rods crankshaft bearings. During disassembly the crank bearings would literally fall off the crankshaft. The new OE Suzuki crankshaft and OE Suzuki bearings had a much tighter fit. Loose ID crankshaft bearings and improperly installed or torn crank seals can't be good for this.

Just a few ideas of things to check.

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6/6/2021 1:30 PM

RMguy wrote:

For the clutch side crankshaft seal, do you recall which orientation it was when you installed it?

Most bikes have this seal ...more

Jackpot info! THIS is what makes Vital amazing.

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6/6/2021 1:41 PM

RMguy wrote:

For the clutch side crankshaft seal, do you recall which orientation it was when you installed it?

Most bikes have this seal ...more

Thanks for the response. I installed it with the metal side facing in and have it flush with the case edge. I did the leak down test and sprayed soapy water on it and it was fully sealed.

The guy I bought it from, it was his dads that used to race back in the day. I’m pretty sure it sat for years which makes me think the center gasket is bad and allowing gear oil to seep into the cylinder. I can’t think of anything else at this point.

I’m going to take the motor out today. Ordered oem bearings last night. Will have to see what crank I have and then go from there.

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6/6/2021 1:42 PM

Factor E wrote:

Cases not sealing

Time to rebuild

seanrm250 wrote:

If the crank is still good, would you recommend replacing it anyways?

GoggleFiend904 wrote:

I see you are in ca. Give Ted a call at boyko racing.. he does very good work and uses pro x rod kits

Awesome I will look into this. Thanks

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6/9/2021 5:17 PM

UPDATE:
Split the cases and might have come across my worst nightmare. this part is where one of the transmission bearings sits. Photo

I’m pretty sure I’ll be needing a new crankcase half if I can even find one. Any clue how it could get like this? Man oh man

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6/9/2021 5:55 PM

Every bearing and seal in your motor is shot dude.

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6/9/2021 6:57 PM
Edited Date/Time: 6/9/2021 7:00 PM

Have it welded and re machined

How many hrs on cases?

Was bearing welded to shaft?

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6/9/2021 7:03 PM

Factor E wrote:

Have it welded and re machined

How many hrs on cases?

Was bearing welded to shaft?

Any recommendations on where to possibly get it fixed? Not quite sure about the history of his engine. Bought it last year and rode it 3 times since, finally made some time to dig in to it. The damage is right where the clutch cable/pushrod goes to. Have no idea how this could have happened. The bearing just fell out as soon as I opened the cases.

I did notice a brass dowel pin that fell onto the table which I believe is for the pushrod alignment through the case but didnt see this dowel anywhere in the parts manual. This portion goes into the damaged hole. I don’t want to assume but it looks like it goes here. Photo

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6/9/2021 7:53 PM

After doing a little research, it could have been this brass piece that caused the damage. I saw a video on yt of a tranny rebuild and this brass piece was sitting all the way inside the countershaft, on mine, it’s poking out and I can see the wear line on it which shows it wasnt sitting all the way in. Need to look more into this.

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