Roller vs Plain Rt side Main Bearing

[smotorboy]

Question for the all knowing motor heads here on the forum:

Which would be the better choice for the Morini Supercharged LSR motor...

I have a spared used, but fixable, crankshaft with the right side main bearing wiped out...

Turn under size for another plain bearing or regrind for the roller conversion ???

I'm keeping the rpm limited to 8500 and the motor will have very short run times with little mileage accumulated...

Robert in California

[mad muller]

hello Robert , a question for you, have you ever ran a standard spec morini engine on the salt, interested to know how it performed, I see you are using a supercharger or blower or whatever to get more fuel and air in, so am I right in saying its in a non standard class? I rebuilt my engine useing parts I borrowed and bought off club members, its a 350 sport , the plain bearing is off another engine so its well used but better than what I had, I set up a road test the other day to check performance , my friend was on his 916 he held 100 mph on a nice stretch the idea was I try and get past him I was flat out and hanging on, the rev counter was way up , showing close on ten grand the engine was screaming and I could smell it burning I nudged past him showing 95 mph on the clock he was smiling at me at this moment, when I stopped, the bike sounded like it was taking its last breath of life but maintained a reasonable idle , it was red hot I could have fried an egg on it , so that's my theory explained, the plain bearing is fine , but it aint on the salts.

[smotorboy]

Great questions for sure....

First,,, Yes I'm in the "modified" class because of the Roots Blower and open megs....My motor is "as received" otherwise...

The most I saw on the bike when it was a box stock 1985 K2 was almost 90 mph on mostly level ground at sea level (using a stopwatch)...that was it without a down-hill or tail wind helping out.

I will take it to Bonneville this August for the first time....

Please Go to the Dart forum as Jarl has set several national records with his stripped down Dart which has the same 350 motor as my K2 and he runs in the Production Stock class.

I think he has gotten the Dart up to 96-97 mph which is very good indeed....

I have run my Supercharged bike al the El Mirage lakebed in California testing and one run in competition...

It was a rocket up to 110 mph , but I had to back off because the engine temperature was going sky high.. More speed is there when and if I get the cooling issues corrected...

I have the motor apart and the right main bearing looks ok from the abuse at this point...the rod bearings have some wear showing , but some of that wear could be just the mileage on the motor...

Robert

[mad muller]

will check out the dart performance figures, its all good stuff and very interesting what you are doing over there I think we all have a romantic idea of riding the Bonneville salt flats, back to my crude and sometimes reckless speed trials my friend on the ducati clocked me at 90mph even though it felt faster to me , his speedo is a bit more honest than mine, I was all out and running out of road so didn't get the magic ton, I think that's about right for a standard sport , on the downside its now developed an oil leak from the base gasket on the front pot lovely! serves me right for being a hooligan biker on a public highway must try it again soon. best of luck muller.

[EVguru]

If I had to grind a crank anyway, I'd probably go for the roller conversion. Unless your engine shop is charging a lot for taking the journal down, then the cost is similar.

For a given power output, supercharging tends to put less load on the crank than conventional tuning, but my guess is that the relative weakness of the plain bearing is why Morini never tuned the 500 engine to even the level of the 350 Strada.

Jarl's engine was all stock parts. I bought the bike with 400 barrels an ported heads and kept those when I sold it, putting on used Kanguro Gilardoni barrels and a pair of repaired stock heads. The airbox was de-restricted and the collector box replaced with a Y piece.

[mad muller]

back with another top end performance question, fith gear was the one to go for when winding it on 80 mph at 8000 rpm, then into top and then revs drop off, to get it spinning again I went back down into fifth and pinned the throttle to 9000rpm then back into top and waited for it to climb it wasn't instant but does get back into the nine grand in top . the feeling I get is like top gear is a bit tall like an overdrive is there another gear ratio that can be used, the disappointment for me is 6th gear can the back wheel sprocket be changed. I think I need to go the pub , ive lost the plot.

[George 350]

I think I need to go the pub , ive lost the plot.

Paul,
If you keep trying to get 9000rpm in top gear you will be losing your licence as well as the plot!

Good to hear it is running well,
George.

[mad muller]

yea your right on that one George, its took me so long to get the engine right I just cant help myself, its now time to reel in a bit , thanks I will take notice. paul.