This may not be an ARF question, but I know a lot of the group is equipping ARF's with Saito's. I have a .72 that the intake o-ring keeps backing out of, and leaning the engine out until it doesn't run. Is this a common problem with this engine? It's extremely annoying. The little .30 I have has a flange that keeps it tight to the cylinder, the .72 just has a groove it seems to slip by. Looks like a design issue, any good cures for this one?


Thanks.

neither of my 72's have this problem... I have seen post's on this very problem though. It's the plastic back plate flexing that allows the intake pipe to backout, I guess some flex more than other's? anyway IIRC there is not a metal back plate that fit's the 72, the only solution I remember reading about was placing a zip tie around the head and intake pipe, lock's that intake pipe in place so it can't work it's way out. The other thing you may look for is vibration, it your getting to much vibration I'm sure it's not helping matters.

John

Some very small number have an issue with the fit of the o-ring and the locking flange. Call Horizon hobbies and explain it to the tech dept. They had one of our members return the pair and sent him a replacement in two days under warrantee. In case you don't want to be without the use of the engine, they sell a gasket set and/or a replacement o-rings at a low cost. Do check for vibration from a badly unbalanced prop just for the heck of it and post what you found.

Thanks for the info, I'll try to send it in. The engine was running real smooth without vibration. I thought could've been the heat affecting the o-ring material. They should've made the flange a larger diameter.


Thanks.

I had the same problem on both my .72's... I had the original back plates which broke all the time... I put the newer "redisigned" plates on that seems to have taken care of that... Also if you order a new gasket set you will find a mod in there for the intake manifold where it goes into the head... It simply consists of a small metal washer which keeps a little more pressure on the O ring.... I talked to Horizon and they were going to fix mine under warrenty but it cost more for postage then for the parts... I just ordered the parts (had to pay for them) and did it myself... No big deal... I have always loved Saito's but for what they cost these plastic parts just are not doing it for me ... I just bought a Magnum .70 to try.... Almost 100 dollars less and all metal parts with bushing on the con rods.... We will see...

Horizon product support is sending me a new o-ring kit free. Thanks for the info guys!

Horizon sent me a new carb rebuild kit ( the entire thing), but they say that Saito offers a kit to prevent this problem for $3.50. They'll sell you a kit to fix a design defect? I'll put the new o-ring in, but this is kinda crazy for a high end engine manufacturer, what good is a 3 year warranty if it does'nt cover built-in design problems.

From the price I am guessing the kit they are talking about is the gasket set.. This includes the metal washer to help prevent air leaks... I too was kind of disapointed in there service... They wanted me to send my engine in to replace the defective backplate... The postage cost more then the replacement backplate... Then I had to buy the gasket set to get the fix for the air leak... I have 4 Saito's and thought I was buying a to of the line engine... Like I said above, I just bought a Magnum .70 to try istead of another Saito.. It is all metal with rod bushings... I am still putting the plane together so I haven't fired it up yet... For 100 dollars less we will see...

Freebird - They sent it to you free didn't they? The engines are suposed to come with the proper parts, you just got one without. Don't know what the guy at Horizon meant by saying that they offer a kit to 'prevent' this problem, I would have either just shut up and sent you the free repair part, or apologized for yours not being in accord with the new ones, or even stated that the kit they sent you free was available for $3.50 if you ever wanted to rebuild in the future, but I wouldn't have stated it like you said they did.

Guess that makes Saito poop in your book, but overall they have no more problems than any other good manufacturer. Heck, I even heard that NASA may have some quality problems with their suppliers. Can you believe that?.

quint

Free:

I think your engine just slipped past the inspectors. Every FA-72 I've seen has the metal washer to support the o-ring.

Bill.

William,

Thanks for the photo, I'll try to find a washer that size, mine did'nt have one. quint, overall they're good engines, this model with the plastic back plate was just a bad selection of materials for the application. I'll have to do a little more research before I buy other 4 strokes in the future.

Bill
I purchased two of them that did not have the metal washer on them... They both had the curved exaust pipe and the straight muffler... The backplate where the carb bolts on was very thin and also broke on both of them for no apparent reason. The replacement back plates which I purchased had a lot more meat on them in that area and have so far held up well... I can only asume these must have been early ones.

Does Horizon sell a thgicker back-plate also?, mine hasn't broke yet but I'm sure it will. They should actually re-call all of these engines and fix all of the problems at once.

The replacement ones I got were a little beefier around the part the carburator bolts to.. They added a couple of "ears" to that part... Still not that impressive though... That is all that holds the carb on and the intake manifold pressed into the head... I was kind of disapointed to find Saito doing stuff like this... They were/are great running engines but for the price this part of the design is very disapointing to me...

When you screw the carb onto the plastic backplate, check to see if the carb is pulling the intake manifold inwards too much and causing a bit of a misfit. If so, place washers between the carb and the backplate to keep the manifold on the level.

Ernie