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YS 63S won't idle and drips fuel

Old 03-05-2008, 05:38 PM
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Default YS 63S won't idle and drips fuel

I have a buddy that I'm trying to help get his YS 63s running properly. He bought a used Inspire with this YS 63s on it, it ran awesome for several months and then he started having problems with it. We've checked ALL the fuel lines, took apart the fuel regulator and cleaned it, and as far as I know have adjusted the low end properly and I believe he's installed a new glow plug. However, it still won't idle smoothly without dying and drips fuel all the time when at idle. My guess is that the low end still isn't adjusted correctly.

Any help with this matter is greatly appreciated.

Old 03-05-2008, 06:29 PM
Troy Newman
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Default RE: YS 63S won't idle and drips fuel

The regulator is not closing properly....

This is the dripping of fuel.

If it was closing properly it would not be dripping.

So the question is why is it not closing. Dirt or debris is a common soucre. You say you cleaned the regulator out and it is not dirty. Next thing is the it could be not closing because the adjustment screw via the little spring in there is not putting enough pressure on the plunger to close. This regulator adjustment can be too rich and cause this.

The way to properly set the engines mixture.....
With a good glow plug (OS #f or YS) no other plugs are suitable and good fuel with at least 20% oil content. I personally recommend not less than a 20% nitro blend even though the instructions say it will work on 15%. The task at hand gets much much easier at higher nitro from 20 to 30% nitro.

Go to full power using a Tach and slowly peak the engine a click or couple clicks at a time. It will sometimes take a few seconds 5-10 for your adjustment to have full affect so be patient.

Find the Peak RPM and back it off to the rich side aprox 200-300rpm. The 63 should run about 10,500 to 11,000 rpm. If you don't get this high of rpms then you have too much prop or not enough nitro. You need to pick a prop and fuel that gives this rpm. Example the 12-7 to 12-9 APC will give this rpm. Depending of course on the fuel you choose.

Next is to take the tach and throttle the engine to a "high idle" maybe 1/4 power at 4000rpm. Watch the tach. If it surges up and down on the rpms...the regulator is too lean. If the engine starts to load up and slow down when at the 4000rpm number its too rich.

Regulator adjustments are the same as the High Speed needle. IN (CW) is Lean and out (CCW) is richer. Make small adjustments to the regulator. 1/8th turn at a time.

Each time you adjust the regulator you must re-adjust the top end needle the same as before.

Once the top end is set properly and the regualtor is running properly at 4000rpm...its time to adjust the idle mixture.

The test is the exact same same as the regulator bu the rpm you want as a target is 2000rpm. At 2000 rpm if it surges up and down or speeds up its too lean. Richen the Air bleed mixture screw. If the engine idels well then starts to load up and falls off its too rich lean the Idle mixture screw.

This time the idle mixture screw is an air bleed screw and not a needle valve. It controls air flow not fuel flow. Because of this it works backwards from the High Speed needle. Closing it (IN or CW) will richen as it allows less air in. Less air means richer. Opening the Low speed air bleed screw means it leans the mixture or allows more air in. So CCW rotation is leaner on this adjustment screw. This screw only works at 2000rpm...and fine tunes the low idle...if the regulator is not set properly this screw will have little to no affect. In fact anything above about 2300-2400rpm it will have ZERO affect on the mixture. It only works down low at the 2000rpm idle. It only fine tunes the mixture down in the low range.

Once the engine is set per this schedule above it should not drip fuel at idle and will have a good mixture setting through out. If the regulator has been disassembled and not put back together properly it can leak fuel and not close. If dirt or debris is in the regulator it can stick opena dn not close.

Troy Newman
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Old 03-05-2008, 06:35 PM
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Default RE: YS 63S won't idle and drips fuel

Thanks for the detailed tuning instructions! Especially the part about surging and correcting it with the regulator.
Old 04-13-2008, 04:35 AM
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Default RE: YS 63S won't idle and drips fuel

guitardude is a pretty good friend of mine ( bad *** guitarist and flier too LOL) anyway I purchased this engine from our mutual friend who is short on time for tuning/tinkering. I knew I could fix it (and can) so he sold me the engine. . . well for the record. . . it had been (before he owned it) had a lack of lubrication. This led to extreme piston/cylinder scuff and eventually wore away the teflon wristipin retainer on one end of the wristpin. After the piston severely scored the cylinder, the wristpin cut a groove. Needless to say this caused a great deal of blowby which ultimately FILLED the crankcase with fuel. The poor engine was blowing fuel from every orifice possible. Check your engines over, make sure the piston/cylinder look good. The ported piston works so well it msks problems that woudl become apparent before any real damage takes place. I know for a fact the gentleman I purchased my engine from had no knowledge of its state, and has offered to buy it back from me. Instead we agreed on a middle ground. I know he just closed on a house, and I know how $$$ is, so I felt he could use the receiver I gave in trade more than me, and I being a motorhead fell in love with the designe of this amazing little mill.

However, if AAANNNYYYbody has an idea where I could pick up inexpensive parts to get this thing back together I'd be forever grateful. On the cylinder, I'd even be cool with used stuff, as long as it will hold good cylinder pressure with a new ring and piston. Thanks for any help!! =)

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