RL250 flywheel side main bearing failures

[David Lahey]

I'm rebuilding an RL250 motor. The flywheel side main bearing is very sad. Advice from Suzuki lover Dungar Pilot is that it is a recognised failure mode in those motors. I know that the same or very similar main bearing is found in the highly reliable TM250 and TS250 motors, but both of these come standard with CCI, which provides a good oil supply to that bearing. The RL250 motor comes standard without CCI, and has a similar arrangement to other non-CCI motors that I am familiar with (TY250 and KT250) for providing a whiff of fresh petroil mist through a passage leading from the under-piston area to the space between the crank seal and the main bearing on the flywheel side of the motor. Those other motors run for decades in trials service without LH main bearing failure so I'm wondering what is different with the RL motor that causes the (premature) bearing failures.
From memory the passage in the TY and KT motors is a bit bigger than the RL motor but I am yet to measure them.
I'm expecting that there are people who have successfully converted TM250 motors to premix and that their knowledge will help with understanding the issue with the RL motors.
Thanks
David

[brent j]

I've heard similar things about LHS mains on RL's. I wonder if the extra flywheel weight has something to do with it?

I'd guess if you used a LH TS250 case you could run the oil pump. using a TS case would save the job of drilling the oil ways.
I like the Suzuki system as it feeds oil to the LHS main bearing first then directs it to the big end.

I've just gotten hold of an RL but have yet to strip the motor, it will be interesting to see what the bearings are like

[djr]

I have a Beamish Suzuki which came from new { I believe } with premix. 


I had the opposite problem when I rebuilt my Beamish/RL250 engine, the flywheel side bearing was ok but the other main bearing which runs in gearbox oil was worn out due to low oil level in the gearbox.
hope this is helpful
dave

[pokey]

I remember Doc explaining a few years back that RL were premix engines but i didnt realise the RL Mains were that fragile as Suzuki use damn good bearings. usually enough to run for a year by fools who run premix without removing the slinger. (hence the rumour that you can discconnect the oil pump no problem on a suzuki)

easiest answer would be to run castor. castor leaves a varnish  that also has good lube and good protective properties, Yeah i know it makes a mess but it smells good and does work well. If you feel like splitting the case and giving better access to the  the slippery stuff that has to be better.
Id also be asking over on the Beamish website, Same engine  as the stock RL in the beamish

[brent j]

Something that just occured to me. The fuel/oil hole that feed to behind the LH bearing is only very small.

Perhaps enlarging this could help?

Lozza???

Cheers
Brent

[Doc]

I know of RM's that had left hand main woes due to the bearing spinning up in the case.

I've not done more than 15 hours (trail riding not trials) on my RL but it's the first I've heard of this problem. Can't see why the oil feed hole couldn't be opened up as Brent stated though I don't think it's much smaller than other models that run premix. Not like they get ridden at high RPM (though mine does sometimes )

Extra flywheel weight as Pokey mentioned above could be a factor with lower rpm?? Poor quality replacement bearing maybe??

Not saying the problem is totally unheard of just it's the first I've heard

[Lozza]

Switch to a cylindrical roller bearing with a flanged inner sleeve (NJ series) with a polymide cage, and use castor sythetic oil even with oil pump

[David Lahey]

I know of RM's that had left hand main woes due to the bearing spinning up in the case.

I've not done more than 15 hours (trail riding not trials) on my RL but it's the first I've heard of this problem. Can't see why the oil feed hole couldn't be opened up as Brent stated though I don't think it's much smaller than other models that run premix. Not like they get ridden at high RPM (though mine does sometimes )

Extra flywheel weight as Pokey mentioned above could be a factor with lower rpm?? Poor quality replacement bearing maybe??

Not saying the problem is totally unheard of just it's the first I've heard

Thanks Doc. I  took photos of that oil feed hole on the RL, a TY250 and a KT tonight and the KT and RL holes look the same diameter (about 3mm). TY hole is much bigger. When I pull the crankcases apart (still haven't made a case splitter for the RL yet) I will see if it is the original main bearing there or something inferior, and if the LH main has been spinning in the case or not.
 
I do know the RH main bearing has done a fair bit of spinning on the crankshaft because the nut on the crankshaft gear had been loose for a long time. So long that the gear is a rattle fit on the crankshaft and the drive key is almost chopped in half. I sourced another crankshaft after finding that

[David Lahey]

Something that just occured to me. The fuel/oil hole that feed to behind the LH bearing is only very small.

Perhaps enlarging this could help?

Lozza???

Cheers
Brent

Thanks Brent yes it is pretty small, but no smaller than on a KT250 motor. I'm still trying to decide whether to enlarge it or not

[sleepy]

You should send it back to Suzuki for warranty! Fancy a main bearing not lasting 40 years.

[David Lahey]

You should send it back to Suzuki for warranty! Fancy a main bearing not lasting 40 years.

Well the only Suzuki motorbike I've had since new is now 38 years old and the mains are still perfect, so I assumed they were all meant to be like that

[sleepy]

You should send it back to Suzuki for warranty! Fancy a main bearing not lasting 40 years.

Well the only Suzuki motorbike I've had since new is now 38 years old and the mains are still perfect, so I assumed they were all meant to be like that

That would be a 4 stroke wouldn't it?

[David Lahey]

You should send it back to Suzuki for warranty! Fancy a main bearing not lasting 40 years.

Well the only Suzuki motorbike I've had since new is now 38 years old and the mains are still perfect, so I assumed they were all meant to be like that

That would be a 4 stroke wouldn't it?

[brent j]

To add a little to this thread.
I rebuilt my RL motor with a new Suzuki LHS main bearing with the oil slinger.
The RL cases are drilled and machined for both the oil pump and oil feed to the LHS main bearing. This is done from the factory.
The oil pump has no cable so stays in the idle position and pumps a minimal feed to the bearing. The original oil feed to the inlet is teed back into the feed line from the tank to the pump to prevent the un-used pump feed from building up pressure.
I'm using a Suzuki racing lit oil tank (which lasts about three tanks of fuel) and I run premix at about 50:1. I run MOTUL800 (in all my 2 strokes) and find it burns cleanly while leaving a film on everything.
i was lucky enough to score a TS250A motor from Firko, thanks again, which offered up the oil pump, lines and fittings and also the TM style clutch cover and release mechanism.

[brent j]

And a bit more on RL flywheels and bearings.

My RL has been in regular use for nearly nine months and now I've added a flywheel weight of about 2 pounds.
If anything will test the bearing it will be this