OS MAX 15FP Stuck throttle barrel

[Piers Bowlan]

Chaps, I bought this engine second hand some years ago and it was stored well oiled in a dry environment, However the throttle barrel has seized (caster oil lacquer I think) so I thought I better seek advice before messing with it. The throttle arm is plastic and easily removed. What is the next step? Sorry to ask a silly question but apart soaking the carb in glow fuel (or meths?), what should I do next as I don't want to damage it? Any advice is much appreciated. Thanks.

[Martin Harris - Moderator]

Gentle heat normally does the trick.

[Piers Bowlan]

Thanks Martin, would you heat it in situ or remove the carb from the engine or is that a bad idea as it might damage the seal beneath the carb. There a couple of screws holding it in place. Also would it help to remove the spray bar or would that make no difference?

Edited By Piers Bowlan on 22/11/2020 17:31:07

[Martin McIntosh]

Simply put it in a pan of water with some Flash or Tesco hard surface cleaner and simmer for a while. The crankcase may discolour a little.

[Piers Bowlan]

OK, thanks Martin, I'll try that.

[Martin Harris - Moderator]

You could pop the whole thing in the oven at 100 degrees while the missus is snoozing after Sunday dinner - not hot enough to damage anything but should soften the castor.

[Piers Bowlan]

Thanks Martin, I will let you know how that works out.

[ken anderson.]

hello piers,have a go with your heat gun or her indoors hair dryer, after a coupe of mins it will free it....do be gentle with the arm until its happy.....I had an OS 46 in the box,exactly the same...

ken anderson...ne..1....arm dept.

[Piers Bowlan]

Much appreciated Ken. I have removed the carb and currently soaking in glow fuel for several hours before trying gentle persuasion . I have removed the plastic throttle arm and fitted a strip of aluminium instead to try and work the throttle barrel lose - more leverage. I will try a heat gun (when it has dried out ) plus a few choice words, not repeatable on this forum!

[Richard Acland]

I had the same problem with an OS 40 FSR bought on e bay. I didn't want to use heat as the idle control has a rubber "o" ring. I soaked it in a container of glow fuel for 48 hours and it did the trick.

[Robert Welford]

I have found carb barrels on other OS engines seize after quite a short period of none use. Soaking in fuel and lubricating before layup is the answer.

[Piers Bowlan]

Thanks Richard and Robert. I have been marinating my carb in fuel all day, so I will take another look at it tomorrow. This is where an ultrasonic cleaning bath would come in handy. I don't think Santa will bring me one this Christmas.

[Petrol Pete]

hi i did one yesterday on a os 26 four stroke, i replaced the plastic throttle arm, with a nut and bolt and soaked it in wd40 gentle pressure after a bit of soaking and it started to move, cleaned it up and then lubed it with after run oil all good Pete

[Piers Bowlan]

Success!

Thank you all for your suggestions. I must admit that like Richard I was a little wary about applying heat for fear of damaging the rubber (or whatever) seals, although I know many of you heat the engines to good effect.

Thanks too to Jon (of Laser Engines fame) whom I contacted and he also suggested I remove the throttle stop screw. After a good soaking in fuel I was then able to turn the barrel clockwise, past fully closed. Turning it anti-clockwise just undid the temporary ali throttle arm that I had fitted. Now back together and oiled the engine is waiting a test run after umpteen years.