Ken6PPC

I don't know if you could get a Saito 82 to fit in the space you have available to you. However, if you could, you would be hard pressed to find more 4C power. It is comparable to the Mag 52 4C in weight (the 82 is slightly heavier), but it is wider than the Magnum.

Look at the specifications table in this link, and you can then measure your Rascal 40 to see if you could make it fit:

[link=http://saito-engines.info/specifications.html]Saito Specifications[/link]

In any case, you can use that table to determine what engine will fit in your cowl. Hope it helps!

Ken6PPC

Yes, I did try setting valve lash to 0.0005" on one of my 1.25's, and I did have trouble getting it to idle well. It didn't start easily either. I opened them back up to just under 0.002", and I was pleased with the performance there.

Just for the sake of knowing, I may try comparing an engine on the test stand at different valve lash settings to see if performance changes. Might be interesting!

w8ye

My Feedback: (16)

Good work

clytle374

What was the effect on top end? Going to .0005" worries me a bit due not allowing oil back between the tappet and cam, but that might not apply in this situation since the area of contact tapers together. Might even force oil into the gap.

Gotta wonder if setting lash that tight with ramps doesn't increase the duration enough to hinder the idle.

@Hobbsy, I didn't feel a burr but that might be it.

Cory

Hobbsy

My Feedback: (102)

My thinking says that the weak top end as Jim describes it would be cause by the overlap period being longer and causing the equivalent of a lean mixture. This would be caused by excessive blow back through the carb. The intake and exhaust valves are both open from about 11:00 o-clock to about 1:00 at the end of the exhaust and the beginning of the intake strokes. Less lash exaggerates the overlap period.

clytle374

Yep, that's what I'm thinking. With rampless profile, setting them tighter will change the duration very very little and effect the overlap twice as much as very very little. But the profile of the ramps greatly spreads out the width of the lobe, so every thousandths of lash you take out quickly increases the duration, and double quickly increases the overlap.

Cory

oldiron410

I too admit I own 2-45s, 2-50s 72, 80GK 90t love em all.

Rudolph Hart

Twenty lashes with an old piece of fuel line for sandbagging

mike early

oldiron410 doesn't post much. Give that man a Saito number!

FNQFLYER

Concerning this business of valve clearences n(and fuel mixes) it appears to me that this "confusion" / discussion could have international inferences.  Take the fuel thing, our instructions are different to the USA and other places, likewise the valve clearence thing.  It was alluded elsewhere that the Saito people (and their reps) take into account the end user when issuing instructions.
Me for general use I always follow the manufacturer except when I am "racing" and finances permitting I usually purchase 2 of the racing engine that I am about to modify / re tune and keep the other stock as a reference point.  Expensive yes but I do have a pristine NIB collection of diesels (Burfords and ED's) and Glo's such as Rossi 40, ST 40 (with pipe) and the OS 40PS and the racing Irvines.
What I am leading up to hear is unless there is need to follow the manufactuers specs it is designed to get the optimum out of the engine and if it breaks back it goes under warrenty.  If you mess with it outside the manufacturers parameters by by warrenty.
Keep up the conversation on this and for my 2 bob's worth (20 cents to the US and 20p to UK)  I run the until the engine is hot and then set the rocker clearence to a tight fit of the factory guage and the adjust the Hs mixture according to what I want the engine to do.  And in duration I use new plugs and a tight gap combined with a "medium" needle valve setting for max rpm for the prop combination.  

FNQFLYER

That last post reads a bit ragged, follow the manufacturers specs for general / sport use vary at you pocket book peril.  Back to the birthday celebrations, Pear cider plus all the local goodies are the go for this newly minted 62 year old

blw

My Feedback: (3)

Excessive blowback thru the carb, and a lean condition isn't a good combination.

jknox

w8ye

My Feedback: (16)

The cylinder is a $125 hit. if you destroyed the rocker arm pivots on one side?

The valve covers are expensive if they are gold plated.

Some of the old parts can be used on the new cylinder head.

mike early

working on saitos is fun. but often expensive to replace parts. Post some photos on here and lots of folks can walk you through it.

hsukaria

Yeah, we like to see other people spend their own money!!!

jknox

OK, here's the post mortem,

Parts List.

w8ye

My Feedback: (16)

Cylinder $116.99
http://www.horizonhobby.com/Products...dID=SAI125A01A

Rocker arms $15.15
http://www.horizonhobby.com/Products...ProdID=SAI5041

Rocker arm adjusting nuts $4.75
http://www.horizonhobby.com/Products...ProdID=SAI5042

Rocker arm pivot pins $3.75
http://www.horizonhobby.com/Products...ProdID=SAI5043

Rocker Covers $15.15
http://www.horizonhobby.com/Products...rodID=SAI5049A

Cylinder screws $2.15
http://www.horizonhobby.com/Products...ProdID=SAI6514

Valve cover gaskets $4.99
http://www.horizonhobby.com/Products...odID=SAI125A32

Push rod tubes $7.99
http://www.horizonhobby.com/Products...odID=SAI90TS40

jknox

Looks Like we match on the parts list. Does the cylinder just sit down on top of the the pushrods/pushrod covers and then you assemble the rocker arm assembly? Anything special to compress the piston ring when lowering the cylinder? And anything I need to know about installing the valves in the head? Never disassembled a Saito before. Thanks for the assist.

w8ye

My Feedback: (16)

The cylinder just sits down on top of everything. You can nudge the ring inside the cylinder with your fingernails.

The hardest part is setting the old head down over a screwdriver handle with the screwdriver shank held in a vice. This is to hold the valves closed while you take the springs off.

You push the valve spring retainer down with a open pair of needle nose pliers and slide the retaining clip off with a small shirt pocket screw driver. This little clip will fly off into parts un known so be careful or do it inside a clear plastic bag to catch the clip?

Then you have to slide the valve out of the head. This is sometimes difficult for the valves will have a lip on them at the top of the keeper grove and at the very tip where the rocker arm taps it. You will have to take this lip off before putting the old valves in a new head.

Then you put the new head down over the screw driver handle with the valves in it and reassemble the springs.

Then you will have to adjust the valves

A guy brought me a 125 that his brother in law had put a new cylinder on. It had absolutely no compression. There is a wax on the valve seats. I had to take the cylinder all apart again and clean the valve seats with a little dot of tooth paste on each valve to get the wax off the valve seats. Sort of like lapping the valves. I spun the valves by putting a pin vice on the stems.

jknox

Valuable advice. Thank you for sharing your knowledge.

Rudolph Hart

Please don't attempt this job till you've had at least two beers mate,it lengthens your pain threshold

Linkan2

This tool makes it easy to change springs
Lars

spaceworm

Or, if you don't otherwise have to remove the cylinder, you could thread some light cord through the plug hole with the piston down and then gently raise the piston allowing the cord to fill the space under the valves and hold them in place while you change the springs or keepers.

Richard

jknox

Update on the crashed 125. Determined bent crank and at least one distorted ball bearing in additon to above. Price to repair now almost 90% of new engine. Sadly it looks like it's finished.