YS53 midrange
 

Dave,

I have completed the running in of a 53. Top end and idle needles settings are now good, idle is good at 2500 with unhesitating transition to full power. OSF plug and 15% nitro.

However if I set the engine to 5000rpm it soon gets lumpy and stops, or else runs fine for say 20 seconds then just stops. It doesn't speed up. I suspect this may mean the regulator needs adjusting? If so, screw it in or out?

Harry

Update - been out flying this evening after work. The 53 is all over the place. After starting I let it warm up, then disconnect glow plug and slowly go to full power. Get 11200rpm. Go to idle and get 2500rpm, back to full power and now it is just 10200 rpm. I check the main needle setting, it takes 1/4 turn leaner but does not increase the revs, go back out 1/4 turn to where the needle was a moment ago and it runs terribly rich, down to 9k rpm, where a couple of minutes ago it was over 11k rpm, so lean it back 1/4 turn and get at best 10200rpm. Idle, especially fast idle 4 - 5k rpm is hopeless, it either runs fine for about 20 seconds then just stops dead, or starts surging, goes lumpy, loses revs and stops. I have tried the idle needle at every 1/4 turn from fully in to 4 turns out and the only difference it makes is whether the engine cuts after 5 seconds or after 20 seconds.

I will now check the valve gaps again (did this after the initial run in) and replace the plug.

Any other ideas?

Harry

YS53 midrange
 

This engine needs to come into service. It sounds like it needs the gas porting mod for the piston.
You can fight this thing forever and never get it right. Let's fix it.

YS Service
1295 Industrial Court
Gardnerville, NV 89410

Phone 775-782-4562

YS53 midrange
 

Thanks Dave, but there is a slight snag - I am in the UK though the engine was bought in the USA while on holiday.

What is the porting mod and why does YS sell an engine that won't work without a mod?

Harry

YS53 midrange
 

Dave,

I've done a search on mod and found out what you mean. Is this done at the manufacturing stage now, or is it something that you do to all YSs you import before distributing just in the USA? This engine and a 63 were bought in Florida in January 2002, is it likely that they already have the mod? And am I likely to need it, or get better running, with the mod on my 63 and 91?

Harry

YS53 midrange
 

It is done in manufacturing now, but it was never done to 53's until they were sent into us for fixing. Your 63 and 91 likely already have the mod, the 53 probably does not.

YS53 midrange
 

Dave, I see you drill 4 holes in the crown. A friend of mine is a metal machinist for a living and could do it for me.

Are the holes at front, rear, left and right of the crown, or turned at 45 degrees to that?

What is a No.60 drill in millimeters?

Does it really make all that difference?!

Harry

YS53 midrange
 

It doesn't matter how you orient them. Without a drill jig it's difficult to drill into the back side of the ring groove without bending or breaking the drill. YS is now notching the top of the piston in four spots with a 1.5mm end mill. That's easier.

Yes it really works!