July 23, 2010

Getting set for tomorrow

I’ve had a couple of discussion threads going on the BMAA forum about my fuel pressure problem and also how I should go about changing the tyres on my nose wheel and one of my mains for two spares Rosie gave me when I bought MYRO. She had swapped the wheels and tyres that were on MYRO with those on MZEL and the two I just mentioned are too perished to get through Permit Inspection. However, the replacements she gave me are fine and just need to be swapped over. I would prefer to let a tyre fitting establishment do it but I’ve heard of cases where rims have been damaged because they are much smaller and more fragile than the ones tyre fitters are accustomed to working with. I’m still thinking about it and will decide later, probably after I’ve had a go at doing it manually.

One of the contributors to the fuel pressure thread said that when an electric fuel pump is fitted, the lower Mikuni should be removed and even without the hand primer bulb being fitted, the remaining Mikuni and the fuel pump should be effective together in retaining the system pressure. MZEL still has its lower Mikuni because it has MYRO’s original fuel system fitted, and so also did MYME as MYRO now has its system. I therefore do not see how this can have been the ‘usual’ thing to do if both MYRO and MYME had passed Permit Inspections. I do not want to remove the lower Mikuni which is now in MYRO, mainly because I don’t want to have a ruddy great hole in MYRO’s pod! I’m also concerned that the only Mikuni repair kits I’ve seen being offered by the UK’s official Rotax agent only include gaskets and internal membranes and do not include any parts relating to internal non-return valve repair. I do accept that the Facet electric pump may be worn even though it’s producing enough pressure to prime the system but I’m loathe to chuck it away while it’s doing it’s job ie priming the system before being switched off.

The hand primer bulb incorporates a non-return valve and one option I have is to replace that in the fuel line. That will still allow fuel to flow up to the carbs but should stop it flowing back. But I have to be honest about one thing – I turned out one of the pics that I took when I first got the parts from Mark at Galaxy when the fuel system was more or less complete and that shows the primer in parallel to the electric pump and by-passing it. Such an arrangement would result in any non-return function it had having no effect so if MYME’s system was working properly, it would have needed either or both of the Mikunis or the Facet pump or all three to be functioning as non-return valves. This does rather indicate that the Facet pump at least is worn and should probably be replaced. I’ve found a source (on the Internet of course 😉 ) and the cost is not that high, but I need to get the part number off the existing unit this week-end. In the meantime I have sourced a small non-return valve intended for fuel pipelines that I’ll fit tomorrow just to see if it does work, thereby confirming my diagnosis. It wasn’t expensive (about £4.75 on Ebay) and I prefer that to fitting the primer bulb, many of which have proven somewhat unreliable and liable to block and cause more trouble than they’re worth, the reason why I took MYRO’s out in the first place.

Now onto the starter switch. I checked and found that a replacement two-mag starter switch comes out at about £145 and an Internet search seemed to indicate that there is a Service Bulletin out on the actual switch fitted in MYRO regarding replacement/repair. The latter idea caught my attention and as part of my search, I found a repair kit for the internal switch contacts, which I am sure have failed in MYRO’s switch, on sale in the US for the princely sum of $16.75. A bit different from £145, eh 😡 So I ordered one earlier in the week, together with an outer bezel plate costing a mere $1.75 that will make MYRO’s switch look almost ‘as new’ again. What would we do without the Internet – how did we use to manage 🙂

I’m now just waiting for the small package to be delivered. The supplier kindly advised me that the delivery method I’d asked for was going to cost about twice as much as the items so they switched it to Air Mail. It hasn’t arrived yet and it would be very nice if it dropped onto the doormat tomorrow. If it doesn’t, that’ll be yet another week I’ll be delayed as I can’t see me being able to do the job until next week-end if I can’t do it this 🙄

So there we are – I shall at least try fitting the non-return valve tomorrow and maybe I’ll be able to make a start on the tyres. I’d like it very much if I could do the starter switch as well, though 😉