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Saito 150S Always Backfires

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Saito 150S Always Backfires

Old 04-11-2010, 04:27 PM
  #1  
Mustang7
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Default Saito 150S Always Backfires

I have a brand new (NOS) 150S that everytime I crank it will backfire and throw the propnut. I'm running Cool Power 15%, 5 tunrs out on the high side, low side haven't touched. Glow plug is what came from Saito and I checked the valve clearances and they're fine.

Not sure what the try next?[]

Any suggestions??

Thanks in advance for any help.
Old 04-11-2010, 04:37 PM
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Crash Campbell
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Default RE: Saito 150S Always Backfires

Hi,

Follow the run in instructions and make sure the motor is well primed before trying to start it. Is it back firing on kick over or on transition? If it is on transition it is too lean on the low speed adjustment.

Cheers,

Colin
Old 04-11-2010, 04:46 PM
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Mustang7
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Default RE: Saito 150S Always Backfires

Hi Crash Campbell=> It backfires just as it reaches TDC. Never gets a chance to transition since it has yet to run. All settings are per the OEM manual for break-in procedures. I even tried to start it by spinning the prop clockwise (by hand only), to see if this would help. No luck.
Old 04-11-2010, 04:55 PM
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jay2000dakota
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Default RE: Saito 150S Always Backfires

Ive got the same motor, Ive never had a problem with it. I would change the saito plug to an O.S F plug, in my experiance saito builds one hell of a engine but their plugs are junk. My 125 a would kick back if it wasnt primed good enough. Have you put oil down the push rod tubes? could have a sticky lifter. Not to insult you but was the Pistion at Top Dead Center when u checked the valves, and are they set so the feeler gauge has a sight drag pulled out of the gap? If none of that helps, then try cleaning the carb out, I out of ideas. Good luck
Old 04-11-2010, 05:06 PM
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Mustang7
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Default RE: Saito 150S Always Backfires

Jay=> I will try the OS F plug as I should have one in my box. Lifters are working fine. I confirmed this when I checked the valve clearance and yes it was at TDC. I should mention that I have several other Saitos, 91,100, 125, 182, 300, and I have never had this problem with any of them. I will make sure the engine is well primed next time though. Any don't worry, you didn't insult me.

Thanks for the helpful tips. I will try these next and report back.

Regards.
Old 04-11-2010, 06:11 PM
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Kimhoff
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Default RE: Saito 150S Always Backfires

Open ths HS Needle another turn. Are you usung an electric started?
Old 04-11-2010, 06:13 PM
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Mustang7
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Default RE: Saito 150S Always Backfires

Success!!!

Here's what I did, I went ahead and double checked the valve clearance. Adjusted both valves to have a slight drag on the gauge per Jay's suggestion. Went ahead and double nutted the prop to eliminate the prop nut loosening. Went to hand start normally and BANG it kicked back and caught my ring finger...OUCH[:@] Good thing I was wearing a glove. Tried it again and son of a bit#%, it did it again. Now my finger is throbbing So, I tried flipping it backwards and she started up. Ran fine until my igniter died. Tried it again (backwards flip.....finger still throbbing) with a new igniter and she started again.

Thanks for all help guys!!!
Old 04-11-2010, 09:29 PM
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Crash Campbell
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Default RE: Saito 150S Always Backfires


ORIGINAL: Mustang7

Success!!!

Here's what I did, I went ahead and double checked the valve clearance. Adjusted both valves to have a slight drag on the gauge per Jay's suggestion. Went ahead and double nutted the prop to eliminate the prop nut loosening. Went to hand start normally and BANG it kicked back and caught my ring finger...OUCH[:@] Good thing I was wearing a glove. Tried it again and son of a bit#%, it did it again. Now my finger is throbbing So, I tried flipping it backwards and she started up. Ran fine until my igniter died. Tried it again (backwards flip.....finger still throbbing) with a new igniter and she started again.

Thanks for all help guys!!!

The ones you bleed on are the good ones. You will find over time that your Saito will get stronger and stronger as it wears in and it will become more and more fuel efficient. I have two Saito motors a 125A and a 72 both took at least a year before they developed full power and fuel economy, thats with an average of about three to four flights/week.

Cheers,

Colin

Chees,

Colin

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