ismen

My Feedback: (1)

I just bought a saito 100 4 stroke engine ,brand new in box just as i was turning itby hand I noticed it has no compression, is this normal on four strokes or maybe engine is defective. can anyone help.

Tony

RS2K

My Feedback: (8)

Do have the glow plug in it? Is the head on tight? You sure you turned it over twice? You only get compression once every two turns.

Ernie Misner

Check the valve clearance before going any further also! You neeeeeeever know what you will find on a new engine.

Ernie

Mighty Mouse-RCU

My Feedback: (145)

If it has a ring, and most do, the compression will get better when the ring comforms to the wall. This will be done when you break the engine in. Check what the guys say above, but I suspect what you are experiencing is normal.

ismen

My Feedback: (1)

head is tight glow plug is on and tight I remember when i first got it it had compression I did not even run this engine yet , as i mounted on the plane i noticed it had no compression I can spin it around one finger with no resistance at all.

PatinIdaho.

My Feedback: (3)

Just a guess. But maybe the engine is dry and a mixture of that and being new it has no compression?

Pat

TimC

I just bought a .91 Saito that I haven't run yet. I has so much compression it can't be turned through tdc on the compression stroke by gripping the drive washer.

dusteater

valves staying open during compression. back out the ??valve adjuster??

ajvpb

My Feedback: (3)

Mine was like that, but it was a magnum .91. Check the valve clearances, make sure everything is in tight, and if all is well, I say go for it. Run it through it's first tank, and then try it with your finger again. It may not be great, but you should notice some improvement. This only gets better with time, and now mine has so much compression I need to back the prop up before I hit it with the starter, otherwise it won't go through.

14thflyer

I am experiencing the same with my brand new Magnum 52. OS plug, 11 x 7 prop. and Cool Cat fuel with 10 % nitro, and castor/symthetic mix. It was mounted on an all metal engine test stand.

Spent the whole of this afternoon trying to start the engine and then finally realized there is no compression, in either stroke, I can hand crank it over with my thumb and forefinger.

Couldn't start the engine and finally gave up. Is this normal, and what should I be doing, just don't want to void the warrenty by fooling around, I was about to pack it and send it to Magnum for warranty claim.

Thanks for your helps, Alex

TimC

ismen and 14thflyer- I'd sure remove the valve covers and make certain the valves are closing completly. Check them with the piston half-way up on the compression stroke. About .003" should do.

outssider

My Feedback: (23)

14thflyer....
these particular engines don't seem to have much compression. I can't start mine by hand...must use an electric starter.....once it starts it seems ok...it won't have as much power for it's size compared to all the other 4 strokes it's size !

proptop

My Feedback: (8)

Maybe you can try squirting a little light oil into the cylinder, and listen for hissing comming from the exh. pipe, or the carb. That'll tell you if the valves are leaking...Just turn it over slowly, and listen...If you hear a bubbling/hissing, then try adj. your valves. My TT.91 had a little bit of a leak @ the ehx. valve, before running, even when adjusted properly, but it went away after a little running-in, and the valves seated...Good luck.

Spaceclam

the fuel will not ignite properly without compression. there is areason that compression exists. the only reasons you will not have compression are
#1 you have no glow plug in it
#2 there is a leak in the cylendar
#3 there is a lot of blow by
#4 the valves are not correctly gapped, or are possibly off timing.
#5 the piston is not attached to the crankshaft

all but #3 and 5 are fixable at home in muinets, unless the leak in the cylendar is caused by bad casting or there is a chunk missing.