YS 61AR Issue
 

I posted this on RCG, but I know not everyone frequents both sites.

I ran my freshened up YS 61AR today. It has new bearings, new gaskets, new regulator, but not new orings.
First what plug should I be running? I have a OS 8 in there now. The pipe is set at 17.5" to the first disc. It is a Hatori pipe, but not sure which model number. I ran 5% nitro and also 25%, both with 20% oil. The needle is not overly sensitive, and it does not get hot which tells me the pipe is close.
The problem is that the needle is very inconsistent. It will run fine at 9800 on a 13x10 DW prop, then all of a sudden it will go rich. It will quit if I let it. I have to pinch the fuel line to clean it out. If lean the needle, it will clear out, but then be too lean. Back the needle out, then it goes back rich and will not clear.
It idles fairly well, but does load up a bit. I turned the regulator in about 1/2 turn total from flush and that helped, but much more seems excessive. The fuel system is tight and leak free. It will hold pressure for as long as you want it to, and it builds pressure very quickly.
I have run YS 4 strokes for 20 years, but this AR is totally different.
The basic questions are:
what fuel, plug, and prop are the standards?
What should I look for with regards to the wierd needle behavior?

thanks
Jeff

Hello Jeff,
If and only if this happens only after the engine has thoroughly warmed up, then you are probably looking at a worn-out piston/liner.
The first sign of a worn top end is a rich transition and sporadic quitting rich. Why? Combustion blow-by puts way too much pressure into the fuel sstem and this is beyond the range of the regulator to deal with.
Regards,
Dean Pappas

Well crap, lets hope that is not it. The piston and sleeve look almost perfect, but who knows how it was treated heat wise before.
I did blow a plug tonight, so maybe the pipe is too short yet. I have read some guys running a 20" pipe length.

Hello again Jeff.
Silly me ... I thought this was a duplication of a setup that had already run well for you in the past. The pipe probably is short, and the dramatic richening could easily be a result of dropping off the pipe. Lengthen it a full inch, or find a lighter load prop just for test: like a 12-10.
Dean

I have very limited experience but my pipe length is much longer than yours...I'm about 19.7" from the glow plug to the first disk using either Bolly or Hatori 650 pipes...

I'd also get a set of o-rings...They aren't that expensive and not hard to change..

Good luck and keep us posted!!

This is what has worked for me in the past. OS # 8 plug, 20/20 fuel, Hatori 650 pipe,APC 13 x 10 or 12x12 prop.measure 20.3-4 inches from glow plug to first baffle.
After warm up, set high end first ( at least 30secs) to pressurize, then set low end~ 2500rpm. Let the low end stabilize (20-30 secs) after each high rpm run. If it loads up( Rich) turn reg. screw in 1/4 turn at a time. If it is too lean , turn the screw out( counter) again 1/4 turn at a time. After you make any adjustment to the low end make sure you run it up for 20-30secs.

Hope this helps..

B

my pipe is obviously too short, or prop load too light as Dead said. I will lengthen the pipe to the numbers above and run again.

If it is worn out, Bob Oge told me that he can rechrome the sleeve provided that it is not scored.

Thanks everybody, I will keep you posted.

Jeff,

Can you give me the contact information for Bob Oge. Having someone to rechrome would be awesome.

Post here, PM me, or [email protected]

Thanks,

Doug

Here's what I have,

MODEL ENGINE SPECIALTIES
Route 1, Box 611
Hinckley, IL 60520
Custom engine reworking, liners chromed and honed to your specs, racing parts. (Bob Oge)

Thanks Tony. It is for Kevin, not for me. All I care about is electrons!!!

Doug

I spoke with Bob last week. Here is his current contact information:
Bob Oge
15477 Owens Rd
Hinckley, Il.
60520
EMail: f2cline [email protected]
phone: 1-815-286-3969 (daytime is best)

Success. Stretched the pipe out to 19.75"(that was all of the aluminum tube that I had), OS #8 plug, DW 13x10, and 15ish% Nitro. I had to mix some 5% and 25% since it didn't like either alone. The needle now is pretty good, but I will pull the pipe out another 1/2" since I have about 3 clicks either way to be rich or too lean. It will idle at about 2200 and rev nice and clean with the regulator 1/4 turn in from flush.
Thanks for all of the help.

I may have the sleeve chromed anyways just because.