Growly Saito 115

[..]

Myself and my flying buddy both have new in the box but obtained second hand Saito 115 engines, neither engine had seen any fuel prior to purchase.

My engine is a real beast , I've run it in on the test bed and now its found a home in an airframe.

My friends tho is a different story, its never run properly , is low on power and despite the same (by the book) running in procedure it sounds and performs very badly.

So far he has swapped my carb and my exhaust , this made no difference , he has made & used the "pin" tool to lock and align the cam shaft to ensure the timing is correct , the valves are working and he has even now changed the bearings. All to no avail , here's a short clip on You tube. Anyone got any ideas on what's wrong ??

[Steve Hargreaves - Moderator]

Is it that sort of "popping" sound as you initially open the throttle? It does sound very odd.....almost like the exhaust is exiting into a drainpipe. It sounds more like a "knocking" sound to me....is there any exhaust leak from the head perhaps? Big end OK? Could it be a bit weak & suffering a bit of pre-ignition? What plug is fitted? might it be too "hot" again causing a bit of pre-ignition...

It sounds OK at higher revs....how do peak revs compare with your motor (on a given prop obviously)?

[..]

Steve, no visible leaks , the plug is a OS type f the same as mine. Its an illusion at the top end it just sounds better on here. Mine was not quite peaked out fully as its new was just short of 10000 on a 15/8 his struggles to get 7000.

 

Edited By Justin K. on 03/11/2015 21:32:06

[Area 51]

Is the one that is running okay mounted differently? i.e. not inverted as in this p51... just a thought as I had an 82 in a P51 mounted inverted and it did sound a little like this, fuel also syphoned to the carb due to its position relative to the tank position, my P51 was an ARTF and the tank position was pretty much fixed.. Flew fine but did like to cut out in flight, its demise (for this reason) came when it landed out in another field..

I am guessi but maybe the tank vs carb posn ?

Good luck with , sounds fine as the revs come in.

[..]

No its just a video he shot of it in the airframe, both have been run on my test bed one after the other as we swapped bits to compare. It sounds & runs as bad upright.

[john stones 1 - Moderator]

Might try swapping his fuel for yours and see if that helps.

John

[Steve Hargreaves - Moderator]

Ooo something badly wrong there then, 3000 rpm difference is a lot of lost power.....

Compression OK? No head leaks? It sounds like a very poorly engine one way & another....there must be something very fundamentally wrong.....

Sticky valves? A bent pushrod? Camshaft in the wrong way?.... I think it needs a thorough investigation from top to bottom & remember what a famous detective said...."When you have eliminated the impossible, whatever remains, however improbable, must be the truth"

[..]

Posted by john stones 1 on 03/11/2015 21:35:24:

Might try swapping his fuel for yours and see if that helps.

John

Same test bed same fuel & tank John

[..]

Posted by Steve Hargreaves - Moderator on 03/11/2015 21:37:03:

Ooo something badly wrong there then, 3000 rpm difference is a lot of lost power.....

Compression OK? No head leaks? It sounds like a very poorly engine one way & another....there must be something very fundamentally wrong.....

Sticky valves? A bent pushrod? Camshaft in the wrong way?.... I think it needs a thorough investigation from top to bottom & remember what a famous detective said...."When you have eliminated the impossible, whatever remains, however improbable, must be the truth"

I wonder if it has mix of parts in from the factory ?

[Area 51]

is it the second hand one or one of the new ones?

if its out of warranty, how about sending it off to Just Engines, that'll be as economical as Japan and Saito as I'm guessing if its out of warranty they wont help..

Where is engine doctor, we need his oil hand to give us his input here.. or how about Mr Brian Winch on the other side of the planet...

Good luck with, it'll be some fundemental as you have tried most of our ideas here, good luck with it..

[Braddock, VC]

Check the freedom of the conrod's big end on the crankpin, it has to be absolutely free when cold and spin easily also check that it has gone in the right way round when he did the bearings.

[..]

Posted by Area 51 on 03/11/2015 21:47:10:

is it the second hand one or one of the new ones?

if its out of warranty, how about sending it off to Just Engines, that'll be as economical as Japan and Saito as I'm guessing if its out of warranty they wont help..

Where is engine doctor, we need his oil hand to give us his input here.. or how about Mr Brian Winch on the other side of the planet...

Good luck with, it'll be some fundemental as you have tried most of our ideas here, good luck with it..

Both were as new , yes as you say we have tried most things other than stripping both down & comparing, I'd best keep mine flying so he doesn't get any spanner time on my good one .

[Jon H]

10k on a 15x8? seems a lot for a 115, even with lots of nitro. I would expect about 8500 tops on an apc and 10% nitro as that is exactly what the 115 a friend owned did. What brand of prop are you using?

I do agree however that the engine sounds like its pre igniting and knocking. Most odd.

That said, I have owned two saito 180's in the past. One was new and I ran it in as normal but it was never anywhere near the 2nd hand one I got on ebay. I also ran in a 3rd for a friend and that matched my ebay job leaving my new one behind.

[..]

Graupner g sonic Jon , it could of been a bit less but not a lot. That's not the issue tho? It's advice on the problem I'm after.

[David Ovenden]

Hi had one of these 115s that suffered from a semi- seized big end. I had to replace the conrod and clean and polish up the wrist pin on the crankshaft. The new type conrod has a slot to allow lubrication of the big end rather than a single small hole on the original. Might be worth checking this on the poor running engine?

The 115 seems to have very high compression and mine needed a lot of running in but is now a very powerful for its size.

Another thought. When you swapped carbs did you change the inlet tube as well or just the carb? Is it possible that the O ring seal is missing from the inlet tube causing air leaks?

Final thought. Could one of the cam followers be sticking in the cam housing causing slow or inhibited pushrod movement and affecting valve opening/closing and hence poor running?

Edited By David Ovenden on 03/11/2015 22:57:05

Edited By David Ovenden on 03/11/2015 23:01:33

[Jon H]

Hi Justin, I agree that its not the issue but it is distorting things slightly as those props are really fast, hence my confusion.

In any case for the two engines to be that far apart on the same prop is really weird. Do they feel the same when turned over? it just sounds like the unhappy one is suffering serious pre ignition but why that should be I am not sure.

I assume the valve clearances are all good and there are no strange obstructions in either of the ports?

[Braddock, VC]

Another thing I'd do is check your tachometer, 10k revs is well into saito 180 territory with a 15x8 and good though the engine is, it isn't that good

http://personal.osi.hu/fuzesisz/strc_eng/index.htm this is the web address of a calculator I use to suss prop sizes out.

Upon reflection I'd check that the pushrods are the right way around, tapered end into the valve tappet, check the valve clearances and adjust them to the minimum possible. I'd also check that the valves are sealing correctly when closed. Finally I'd check that neither of the valve springs is broken.

[..]

Posted by David Ovenden on 03/11/2015 22:41:33:

Hi had one of these 115s that suffered from a semi- seized big end. I had to replace the conrod and clean and polish up the wrist pin on the crankshaft. The new type conrod has a slot to allow lubrication of the big end rather than a single small hole on the original. Might be worth checking this on the poor running engine?

The 115 seems to have very high compression and mine needed a lot of running in but is now a very powerful for its size.

Another thought. When you swapped carbs did you change the inlet tube as well or just the carb? Is it possible that the O ring seal is missing from the inlet tube causing air leaks?

Final thought. Could one of the cam followers be sticking in the cam housing causing slow or inhibited pushrod movement and affecting valve opening/closing and hence poor running?

Edited By David Ovenden on 03/11/2015 22:57:05

Edited By David Ovenden on 03/11/2015 23:01:33

Thanks David for some really good input. My engine goes like the clappers, that and the tachometer arnt the issue its the video clip that's the issue for discussion.

[Jon H]

The G sonic prop explains the high rpm of Justin's engine so that is no worry. My initial comment was because i thought that one might be unusually fast and so was giving a false comparison. And if the same tacho is used for both engines then even if it was wrong its wrong on both so it wont matter.

the performance of the engine is identical on the test stand and in the model... so if the prop/plug/fuel are all identical (as in the same ones are used) then my suspicion is something in the cam/valve/intake area. The engine really sounds like its too lean. Are you able to get it to run rich by opening the needle a few more turns?

It would be worth checking the big end to see if david is right because continued running would cause more damage and break the conrod.

Beyond that i am not sure what to suggest. Without seeing the engine first hand its hard to tell. You could send it to JE or MacGregor to be looked at. Or send it to me, i will only charge for post!

 

Edited By Jon Harper on 04/11/2015 08:52:53

[flight1]

have you checked you are not 180` out with the timing gear easily done, also are the valves seated correctly , also have you had the head off and checked the ring, it sounds like you are loosing compression hence it idles and when you try to throttle it's worse.

[Engine Doctor]

Very difficult to diagnose on the video. But it does sound like a saito 100 I sorted for a club mate a few weeks ago that was running like a pig . It would idle OK but didn't like opening up. It sounded very hard like the engine in the video .The timing was one tooth out. I used acam shaft locking pin to reassemble it and it was still very easy to get the timing one tooth out so worth a re check. Make sure that at tdc the valves are on the rock and equal y open . The other thing I did was to make a thicker cylinder base gasket (the same effect as fitting a head shim) from thick paper.If that works then you could easily make one from some litho plate. One final thing to check is the valve springs. It's not unknown for them to break and this will cause low power and very erratic running. Good luck and let us know how you get on.

Edited By Engine Doctor on 04/11/2015 10:25:34

[Braddock, VC]

Nothing to do with the OP but can someone explain the camshaft locking pin. Where is it inserted? on the 5 saios I have there doesn't seem to be provision for inserting anything at all.

Edited By Braddock, VC on 04/11/2015 10:46:43

[..]

Thank you for your input chaps , at work at the moment but we will both look over your comments later.

Braddock this is the te tool **LINK**

[Engine Doctor]

Posted by Braddock, VC on 04/11/2015 10:42:08:

Nothing to do with the OP but can someone explain the camshaft locking pin. Where is it inserted? on the 5 saios I have there doesn't seem to be provision for inserting anything at all.

Edited By Braddock, VC on 04/11/2015 10:46:43

Hello Braddock VC . One other thing to point out is that there are two different sized pins that I know of and each fit differing engine size range. There may be more for the 180 size etc .They are dead simple to turn up although sometimes fiddly to engage in the hole in the rear of the cam lobe.They should be a nice sliding fit into the inlet cam follower guide . One engine I rebuilt the hole in the rear of the lobe was not central making it impossible to use the pin.This I think is  just a one off .

Edited By Engine Doctor on 04/11/2015 15:11:06

[Braddock, VC]

Thanks justin, I'd just had one of my 82s seize on the crankpin and I decided to put new bearings in so this tip was really helpful. In the past I'd done it by eye and checked the valve timing against one of the other 82s I had (I have 3, one unused) but I lost the protractor I had with it marked on so that's a process I'll have to repeat.