July 17, 2010

Not such a disaster after all

I bought some new plugs on Ebay earlier in the week, a box of 10 so I’ve got a spare set just in case. I carefully gapped them before leaving for the field and when I fitted them I realised that the leads from each mag are already crossed and are in pairs ready to go straight onto the plugs. Stupidly I didn’t notice that previously and had crossed them again, so I had both leads from each mag on the same cylinders. No wonder it ran rough last time 😯

This time the engine started immediately with plenty of power and ran perfectly. Great 😀

Also all the temp gauges that I’d carefully wired up and checked are in fact working just as they should. I was too impatient last time and they just needed time to come up 😉

But there was still no fuel pressure indicated when the engine was running, although the two Mikuni fuel pumps are producing enough to keep the engine running indefinitely. When you switch the electric fuel pump on with the engine stopped, pressure comes up but falls away again when the pump is switched off, so pressure is being lost somewhere. I haven’t noticed any leaks so I think that one or other of the Mikunis has an internal leak. I even detached and bled the tube running to the pressure gauge by switching on the pump and allowing fuel to run into a container so I don’t think it’s air in the system, which I suspected might be the cause. As a last resort I may have to buy a couple of repair kits for the two Mikunis – not cheap though at nearly £50 each!

But the mags are still not earthing so I will need to find out why that is. As a result I’m still having to shut the engine down by pulling the choke which I don’t like, although I know some two-stroke owners actually prefer to do that all the time because it draws oil into the cylinders when you shut down.

I also did some taxying today. I don’t think my pitch gauge was accurate enough because it isn’t as smooth as I expected, especially when you close the throttle. Having said that with nobody flying because of the wind, I was able to do a couple of aborted take offs. MYRO accelerated beautifully although I think the revs were not quite up to what I want to see at full throttle, so the pitch must be a bit coarse. But the prop seems to whip when you shut the throttle quickly. I don’t know if that’s a feature of the Arplast but I haven’t noticed it before when flying with the wooden GSC two-blade prop, so I’ll have to look into that. I will definitely need to borrow a prop pitch tool, I think.

So my jobs tomorrow are – try the spare Mikuni I have to see if it solves the fuel pressure problem and try to find out why my mag earth connection isn’t connecting. All in all, not as bad as I originally thought, I’m glad to say. I might be flying a bit sooner than I reckoned after last week end 🙂