Martin Arnold 1

No not really, the recomended on ground rpm for this motor is 9,000 - 11,000, only use full power briefly in the climb. Have found that most mid size Siato's make thier best power at over 10,500

just finished setting up my new to me Ripmax Jive, popped a Saito 72 on it just for a bit of fun !! Not short of power the 72 on an APC 13x4W prop at 11,100 rpm, for just over 10lbs of static thrust and the AUW of the model is 4lbs 2oz !! Had to do some moving about of stuff to get the CG right but test flew last Sunday and it's good fun.... Plent of vertical performance !!!

Yep have seen that fault on more than one Sanye (SC, ASP and Magnum etc) four stroke motor, first time was on an ASP 30FS spent ages trying to lap the valves in...... Then realised it was a leak between the bronze valve seat insert and the head casting, not much you can do about that !! On the Wots Wot motor have seen the Saito 91 works very well, bit lighter than an OS70 Surpass and about 35% more power !!

I had the same thought as you on stainless bearings, untill I tried them about 10 years ago and not worn a set out yet and I like to let my 4 strokes rev. Think the rust will kill steel bearings long before the stainless wear out.

Running a four stroke "dry" doesn't really work (unless it's a YS), doing that has no effect on the deposits in the crancase area. Not sure about after run oil either I used to use years ago when 4 strokes first were about, the bearings still rusted, think to have any effect you need to complely flush out the crancase, which is not practical when the motor is in a model.

Most recent Saito single glow motors use a double shielded rear and double sealed front bearing, over the last few years when I,ve done a bearing job on a fourstroke I use stainless steel bearings. Yes the stainless is not so hard but most of our fourstroke bearings fail through rust from the acidic crankase deposits rather than wear, so far my i have not had to replace any SS bearings I have fitted.

Just found this from the add on the rear cover of the June 1996 RCM&E , the 52 Surpass Had a fully sealed rear bearing.

Generally the valve clearances on alloy model four strokes motors increase as the engine warms up, as the alloy barrel expands at a much greater rate than the steel valve gear, which is why the gaps are quite tight cold. I have tried this on various Saitos and OSs check clearance when cold, run it and check directly after running they are larger.

Good point Cuban, been using them for years but will check them pretty easy to remove and back flush..... Have about 15 in service at the moment.

I use a very simple two pipe set up with a Sulivan Crap Trap two stage filter, if the tanks has three holes I just blank off one of them. Fuel by removing the feed pipe from the filter and drain the same way, this also is constantly flushing out the fuel feed, In my opinion I think the Crap Trap is one off the best with no seals to leak.

Have been running my Saito and OS 4 strokes on MT Dynaglo 5% for about the last 20 years, it has 10% total oil 8% synthetic 2% castor (be better without the castor), they run sweet and clean with no trouble at all and I do like to let my Saitos rev !!

Is it the angle of the photo or have you got the crankcese breather attached to the pressure niple of the exhaust ?

Sounds like you have too much oil in the fuel mix, what percentage of oil do you have ? Out of intrest which OS 70 Is it ?

Had a Saito 91 in mine a few years ago at 560gms incl silencer is lighter than both of those.... Went like stink on a 13x7 prop.

Motor had been run on MT Dynaglo 5% for the last 10 years 8% Synthetic 2% castor.