highside

I have a FZ110S which has had about 1.5 hours of running from new. Half an hour on the bench followed by about 5 flights, during which it ran very nicely across the rpm range. I'm running Model Technics Yamada blend fuel (20% nitro/20% klotz technipate), OS type F plugs, an APC 16x8, hattori header and short muffler.

At this point it went from running lovely to detonating in the upper mid-range and generally running horribly. A quick twiddle didn't resolve so I've done a basic strip down (remove carb, needle assembly, airbox, rocker and clean and check gaskets etc., valve gaps, flush the regulator through, new plug, replace silicon tubing). However, behaviour remains the same. I can chase the settings getting it pretty close over 4 or five stop/starts, then just as I think I'm getting there it'll change drastically and I have to start again, as much as a turn away on the reg.

I've just split the regulator and all seems well inside, no muck or anything.

Questions:

: I notice that the regulator spring sits directly on the silicone valve "poppet", without a washer or cap to protect the silicone. Is this correct or am I missing a piece?

: How is the crankcase pressure feed to the regulator arranged? Does it go down a hole in the crank like the DZ engines? I wonder if there are any small orifices in the crankcase/shaft which might have some muck in them and are varying the pressure to the regulator.

Thanks in advance,

HS

mjfrederick

I don't think the regulator is your problem.

1) Yes, the spring sits directly on top of the silicone plunger.

2) Pressue feeds up from the crankshaft through the fuel fitting, through the tubing, into the bottom of the regulator.

A possibility that I have head of is a mis-aligning of the holes that provide pressure to the regulator (something to do with a brass insert that is pressed into the case slipping). If Xmans is still trolling these boards, he would have more information on that.

highside

OK, thanks muchly. I'm surprised that the little silicon poppet can stand having the spring straight on it!

I should have said, I checked regularly and had tank pressure at all times.

I've reassembled the regulator. Then I removed the carb assembly again and flushed the crankcase from the pressure nipple at the front out through the back; I had to rotate the crank to a position where the disk valve was open and the holes were lined up for passing pressure to the nipple. A couple of little specs of black muck but nothing significant.

I've moved it back to my testbench and will give it another go tomorrow. If I don't have any joy, then you might be right about the aligment of the crankcase "pressure ring" moving around, it'll have to go back under warranty.

:-)

highside

Well, either the reg dissassembly or the back flushing of the crankcase did the trick. Running lovely again, on test bench and in the model.

:-)