RVM

Anyone flying around without a locknut on their 4-stroke? I've got a spinner that will only fit if I don't use a locknut on my Saito 100. I don't think this engine has backfired on me once, and as far as I know that's the only reason a 4-stroke will throw a prop.

Any experience here? I've never flown a 4-stroke without one before.

carrellh

From everything I've heard, you're fine as long as you keep it rich enough to avoid a backfire.

Motorboy

The older 4 stroke engine was without locknut..

Flyboy Dave

My Feedback: (21)

....yep, the early 4 strokes never came with locknuts. The Saito engine is the most
prone to backfire and throw props because they run higher compressions than the
others.

FBD.

liquid_TR

an addition: an over primed starting attempt and running overly rich can also cause a sudden backfire due to the plug filament getting too wet and losing its heat.

aussiesteve

I have 3 or 4 running without the locknuts, never had a problem.
As the others have said - it's only a problem if you have a backfire.

onewasp

RVM

Check the adapter kits from TruTurn. They have a short shaft set up that works extremely well and uses the lock concept.

The spinner mounts easily too. Check for the 8 x 1.25 size for your 100 and right on up the scale too.

Edit addition: TT-0822-A is the adapter kit number.

misterpanda

I've been running an OS 52 four-stroke with a spinner nut (no locknut, of course) for quite a while, and ... never a problem.

Enjoy.

Misterpanda

NM2K

My Feedback: (14)

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One of the reasons that Saito became a favored engine with many was because of their solid thump when idling. This was directly the effect of running higher compression than many other engines.


Ed Cregger

Kweasel

My Feedback: (29)

Locknut or not, you should never stand next to or in front of a fourstroke at any power level above idle. All of them are prone to throwing props.

blw

My Feedback: (3)

I think your impressions of Saito engines comes from a long time ago, and probably with the older model Saito .80s.

Saitos are the mildest running engines around. It is hard to get one to actually backfire, and when they do the ones I've seen only loosen the nuts some. Very forgiving low compression engines.

I would vote any YS 4 stroke as the one to have the nastiest backfires.

XJet

I've even run my TT91FS without a locknut (so I could fit a spinner) and had no problems -- apart from the occasional backfire when starting that merely loosened the prop (didn't throw it).

As for Saitos -- they are perhaps the *sweetest* 4-strokes on the market when it comes to immunity to backfiring.

I don't think any of mine have ever even hinted at backfiring or throwing a prop.

Remember that proper tuning is critical to exactly how balky a 4-stroke is. Don't over-lean them and you'll have no problems.

Flyboy Dave

My Feedback: (21)

Saito engines have always had the highest compression ratios on Planet Earth.
Do you have any proof that they are "the mildest running engines around".
Please post this information.

The fact is....Saito has strived from it's onset to be the most powerful normally aspirated engine
manufacturer around. Their advantage comes from their high compression, and from their straight
cut cam gears. This is not a secret.

They also have the Worlds record for "prop throwing"....

....here are a few examples....right here on RCU.

http://www.rcuniverse.com/forum/m_48...%2Cprop/tm.htm

Post #6, 12, 13, 17, 19, 24, 30.

http://www.rcuniverse.com/forum/m_57...tm.htm#5739033

http://www.rcuniverse.com/forum/m_47...tm.htm#4701392

http://www.rcuniverse.com/forum/m_40...tm.htm#4087709

http://www.rcuniverse.com/forum/m_30...tm.htm#3042670

http://www.rcuniverse.com/forum/m_17...tm.htm#1723235

http://www.rcuniverse.com/forum/m_90.../tm.htm#906956

http://www.rcuniverse.com/forum/m_87.../tm.htm#873634

http://www.rcuniverse.com/forum/m_78.../tm.htm#782025

http://www.rcuniverse.com/forum/m_64.../tm.htm#644886

http://www.rcuniverse.com/forum/m_37.../tm.htm#379911

http://www.rcuniverse.com/forum/m_18.../tm.htm#182154

....thanks,

FBD.

onewasp

They also have the Worlds record for "prop throwing".

You MUST be referring to the earlier high compression designs-----the current variety are quite mild to handle and will only loosen the nuts when started too lean only. No, I would not choose to prop one and yes you can do the 'spinner back flip' start though I choose not to.
While the ratio may seem high in numerical expression it currently is lower than earlier models.

Currently I am flying the 82a and 180. I have owned a number of others.

I've yet to see a prop thrown from a Saito (with a locking nut set-up) and I've been around a long time and have flown at many fields over that period.

PS I did not wade through your citations but if there is one you find particularly germane let me know please.

RVM

Thanks for all the replies! I'll see how it goes without one for a bit.

Flyboy Dave

My Feedback: (21)

....here ya' go, onewasp....I'll make it easier for you.... If you do a search here at RCU for
"throw prop" (just in glow engines Forum) you will see that Saito has thrown about 10 times
as many props as the others combined.

post #5
http://www.rcuniverse.com/forum/m_48...tm.htm#4811234

http://www.rcuniverse.com/forum/m_57...tm.htm#5739033

http://www.rcuniverse.com/forum/m_40...tm.htm#4087709

....in Canada....

http://www.rccanada.ca/bb/viewtopic.php?t=34647

This is not new news, it is not a secret.....Saitos throw a lot of props, always have.

FBD.

scratchonly

TIGHTEN the spinner nut properly. If you use wooden props check it regularly.

Flyboy Dave

My Feedback: (21)

Here are a few quick threads you can read. The new Saitos still throw props, and can be dangerous.
If you do a search on RCU for "throw prop" in the Glow Engines Forum you will see that the Saito
engine is the clear winner....always has been, especially the high compression models. The higher
the compression, the more advanced the timing will be. The more advanced the timing, the more
pops, backfires, and thrown props you will have.

Don't get me wrong....other engines throw props too. I had a chart around here somewhere that showed
compression ratios of different engine manufactures. Saito won that category too. They used to have
some really insane compression ratios. I'll see if I can find it.


http://www.rcuniverse.com/forum/m_48...tm.htm#4811234 post #5

http://www.rcuniverse.com/forum/m_57...tm.htm#5739033

http://www.rcuniverse.com/forum/m_40...tm.htm#4087709

http://www.rccanada.ca/bb/viewtopic.php?t=34647

FBD.

broke_n_bummin

Hmmmmm ... now I'm confused (not really an uncommon thing). You talking about an actual nylon locknut or a jam nut? There is a difference. I quit using jam nuts on my 4 strokes and use only a nylon nocknut. If it does backfire, the nut will only loosen instead of throwing a prop.

Hibrass

My Feedback: (1)

Broke,

I think they are referring to a true Jam Nut. Not a nylon lock nut. At least my Saito's have Jam nuts... And trust me they need them if you are miseraly with the fuel.... LOL

Hibrass

blw

My Feedback: (3)

Yes, a jam nut.

RVM

Cannot fit a jam nut so going to just see how it goes without one. I've never had one of my Saitos backfire yet, so we'll see. At least, not that I know of.

w8ye

My Feedback: (16)

I got a lot of Saito's and I've never had one back fire on me. I have some with no lock nuts. They never had a lock nut even when new. The crankshaft is too short to have room for a locknut.

blw

My Feedback: (3)

I've had a new 1.25 backfire. It so mild that I could barely hear it when it happened. It just loosened the two prop nuts some.

I have a .72 that should have backfired dozens of times when I was chasing down an air leak, and a softened/collapsed vent line from the muffler. It would go lean all of a sudden and die on the ground and in the air intermittently. I don't think you can make that engine backfire!

rctrax

The first time I ever tried to start an os 91 without a locknut it backfired and shot the nut and washer 25 ft out in front. never found it. Just try to buy replacements. They're expensive.