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YS110s no response to throttle.

Old 06-12-2014, 01:36 PM
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Default YS110s no response to throttle.

Anyone help with this one please. My 110s had been stored for about 8 months after airframe problems which I recently repaired. Anticipating possible sticky carb or regulator problems I bench ran engine for a tank or so and it appeared to run fine, started, tick'd over, ran up to full throttle without any noticeable issues. I then mounted back in airframe with new tank plumbing from clunk to regulator. Replaced regulator diaphram just in case. Second run 'in flight' engine started to bog down in any mid to high throttle setting but landed OK. Next run engine starts but will not throttle up or it appears to be delayed lightly. Obviously not running cleanly, sounds like its 'breathing' somewhere it should n't, at a guess. A lot of exterior oil/ around engine compartment(?!) Checked all gaskets which appear to be good but found the rear rocker cover screw had very fine metal shavings around the screw. First few threads clearly stripped which allows air to be pushed past gasket at that point, at a guess. Longer screw seems to be the answer and tightens down effectively. ( which probably explains the 'breathing' issues). Now engine will not run past a very 'laboured' tick over, will not respond to any throttle setting, and is now trying to run backwards and will cut after 30 seconds spluttering run.

Good spark plug ok. 20/20 Optifuel YS spec I believe, high needle 1 and 1/4, low needle 3 and 1/4. Regulator at level with barrel perhaps 1/8th turn past. Good tank pressure, and fuel past reg to carb. Good compression, bearings feel ok, and no end 'float'.

Currently. Engine will 'fire' but tries to run backwards, then forwards, or backwards, and no longer than 30 seconds with no response to throttling.

Would appreciate any help. many thanks.

Bob
Old 06-16-2014, 07:09 AM
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Originally Posted by BobV1700
Anyone help with this one please. My 110s had been stored for about 8 months after airframe problems which I recently repaired. Anticipating possible sticky carb or regulator problems I bench ran engine for a tank or so and it appeared to run fine, started, tick'd over, ran up to full throttle without any noticeable issues. I then mounted back in airframe with new tank plumbing from clunk to regulator. Replaced regulator diaphram just in case. Second run 'in flight' engine started to bog down in any mid to high throttle setting but landed OK. Next run engine starts but will not throttle up or it appears to be delayed lightly. Obviously not running cleanly, sounds like its 'breathing' somewhere it should n't, at a guess. A lot of exterior oil/ around engine compartment(?!) Checked all gaskets which appear to be good but found the rear rocker cover screw had very fine metal shavings around the screw. First few threads clearly stripped which allows air to be pushed past gasket at that point, at a guess. Longer screw seems to be the answer and tightens down effectively. ( which probably explains the 'breathing' issues). Now engine will not run past a very 'laboured' tick over, will not respond to any throttle setting, and is now trying to run backwards and will cut after 30 seconds spluttering run.

Good spark plug ok. 20/20 Optifuel YS spec I believe, high needle 1 and 1/4, low needle 3 and 1/4. Regulator at level with barrel perhaps 1/8th turn past. Good tank pressure, and fuel past reg to carb. Good compression, bearings feel ok, and no end 'float'.

Currently. Engine will 'fire' but tries to run backwards, then forwards, or backwards, and no longer than 30 seconds with no response to throttling.

Would appreciate any help. many thanks.

Bob
Did you flush the new fuel line before installing?
I have had huge problems in the past with very small silicone chips and a chalky powder inside new fuel line.
After I started flushing new fuel line before use much of my problems went away.
I did not discover what the problem was until I took apart the fuel filter....it was plugged with debris.
Also....when you push the fuel line on the nipple......the outer circumference of the nipple usually has a sharp edge which will cut into the side of the inner diameter of the silicone wall and carve out a 'flap' which will flutter back and forth causing giant mixture problems and weird running.
Du-Bro fuel line is very soft and especially prone to the chip and 'flap' problem.
Aero-Trend and Prather fuel line was much better in this respect.....too bad both are gone now.

I suggest that you remove the fuel line, clean the filter if you have one....if not, install a filter....then remove the needle valve and it's seat and back flush the entire fuel system with alcohol or fuel.
Use 600 grit sandpaper and smooth off the round edge of the fuel nipples.
Cut new fuel line to length and flush out, then carefully re-install the clunk line with filter to the top nipple on the regulator.

Typically....if a YS wants to run backwards....the pressure line and clunk line are reversed.

Have fun...
Old 06-17-2014, 02:32 AM
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Thanks Dave. The fuel lines, clunk, filter and return valves, regulator set just in from flush, and fuel appears to be flowing properly into carb. Stripped carburettor down last night and found nothing. No build up of goo or crap, nice and clean throughout as far as I can tell. Ive a sneaking suspicion its ' breathing' somewhere it should n't but Ive checked all gaskets and 'faces' and can see nothing obvious. Compression is good, but tank pressure seems 'lower' than Ive previously noted. I get a short 'poof' of pressure when I release the tank stopper whereas before it was more pronounced/ or so it seemed!. But I'm guessing really.

When I first started with this problem a week or so ago, it started up ok and ran fine for a few minutes and then I noticed the throttle began to lag. Not being sure that a servo might be going down I landed. After this run I had more difficulty starting, it was running badly and would not take throttle much above a fast tickover, and now wants to run backwards. There seems to be a lot of unburnt fuel coming out of the air intake which suggests its flooding. New plug same result.

Any other ideas?


Bob V
Old 06-17-2014, 06:57 AM
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Originally Posted by BobV1700
Thanks Dave. The fuel lines, clunk, filter and return valves, regulator set just in from flush, and fuel appears to be flowing properly into carb. Stripped carburettor down last night and found nothing. No build up of goo or crap, nice and clean throughout as far as I can tell. Ive a sneaking suspicion its ' breathing' somewhere it should n't but Ive checked all gaskets and 'faces' and can see nothing obvious. Compression is good, but tank pressure seems 'lower' than Ive previously noted. I get a short 'poof' of pressure when I release the tank stopper whereas before it was more pronounced/ or so it seemed!. But I'm guessing really.

When I first started with this problem a week or so ago, it started up ok and ran fine for a few minutes and then I noticed the throttle began to lag. Not being sure that a servo might be going down I landed. After this run I had more difficulty starting, it was running badly and would not take throttle much above a fast tickover, and now wants to run backwards. There seems to be a lot of unburnt fuel coming out of the air intake which suggests its flooding. New plug same result.

Any other ideas?


Bob V
Hi Bob.....
Considering that the tank does not have much if any pressure.....and that it wants to run backward ....and fuel is coming out of the intake.....I would say check the check valve to ensure that it is really working and installed in the correct direction and on the correct nipple.
If everything is in good condition the tank should hold full pressure for at least a day or two.
You might recheck the diaphragm to be sure that it is still correctly in place and the plunger is in the correct position.

Also you might want to check the adjustment of the rocker arms and make sure the valves operate freely and are not stuck partially open.
In addition....it might be possible to install the valve cover backwards....I had a problem with the earlier 110 with this.

One more thing......the cam could be installed incorrectly....off time...making the valves open at the wrong time....this could cause it to spit fuel and run weird.

When you fix it...be sure to let us know what the problem was.

Dave
Old 06-20-2014, 08:37 AM
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Dave,

Stripped the engine right down to parts except for the valve's and springs/tiny clips, which appear to be fine with little carbon build up, seats look good and same spring compression both sides. The main cylinder body 3mm retaining bolts were suspiciously easy to undue with almost no tension, just finger tight almost, I'm hoping it was something as simple as that. It could account for the low-ish pressure do you think?. The brass bushing in the forward crankcase housing is correctly in place with the hole lining up with the pressure vent, I had a previous problem with this when it rotated thru 90 degrees and blocked the vent. It seems not to be related to current problem. Have you ever had to remove the tiny valve spring retaining clips? First time I had to take them off one flew past my left shoulder at a rapid rate of knots and was never seen again. Do you have a special tool for this or just a lot of patience?

I'll let you know how I get on.

Thanks Bob
Old 06-20-2014, 07:11 PM
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Originally Posted by BobV1700
Dave,

Stripped the engine right down to parts except for the valve's and springs/tiny clips, which appear to be fine with little carbon build up, seats look good and same spring compression both sides. The main cylinder body 3mm retaining bolts were suspiciously easy to undue with almost no tension, just finger tight almost, I'm hoping it was something as simple as that. It could account for the low-ish pressure do you think?. The brass bushing in the forward crankcase housing is correctly in place with the hole lining up with the pressure vent, I had a previous problem with this when it rotated thru 90 degrees and blocked the vent. It seems not to be related to current problem. Have you ever had to remove the tiny valve spring retaining clips? First time I had to take them off one flew past my left shoulder at a rapid rate of knots and was never seen again. Do you have a special tool for this or just a lot of patience?

I'll let you know how I get on.

Thanks Bob
Hi Bob.....some guys put a sandwich bag over the valve stem/spring clips and retainer then put their hands inside the bag in order to capture the flying parts.
so far....you have not responded to the suggestions that I have made...at this point I do not see the need to strip the engine down...after all, you said it was running correctly before you replaced the diaphragm.
I suggest that you put it back together and put it on the test stand and run it to see what it is doing now. then, take corrective action following the symptoms.

Dave
Old 06-20-2014, 11:59 PM
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Dave,

Prior to stripping down I did indeed check the regulator and assembly as you suggested, it appeared to be fine with no blockage, and was fitted correctly. The rocker arms and push rods move freely up and down with only slight carbon build up on the rods as you might expect. I'm hoping that the problem is one of those 'grey' problems that go with the advancing years!

Many thanks Bob
Old 06-23-2014, 01:52 PM
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Dave,

I have now put everything back together again found nothing obvious to report. The bearings are good, the conrod as new with both ends showing no wear on the bushings, the cylinder is likewise with no obvious damage and the piston unmarked except for the usual slight discoloration. The valves move freely and the timing marks as per manual, crank shaft dot at 6 and valve timing gear at 12 just under the valve tube bottoms. Gaskets are good except that the black valve cover bolts have both now part stripped the cylinder head threads, extra long screws have just about sorted the problem and the valve cover gasket is airtight. In short I found nothing obviously wrong or difficult to reassemble. I set the valve gap at .07 mil which is in between the two recommended settings.

Started pretty much first time, but still sounded rich within whole rev range despite tweaking both high and low needles either way. About the third start the engine ran up to almost full throttle on just above tickover throttle setting. Not much more than the ' V knick' in the butterfly being open! I had to pinch off the fuel line quickly as the thing revved away on its own, even going to wide open throttle had the reverse effect and lowered the revs noticeably!. Fuel now coming out thru air intake even when running at full throttle.

It can only be the fuel regulator which I now suspect is stuck full open-ish and allowing fuel to be pushed thru the carb at almost tank pressure quantity (as I had to pull the fuel line off to stop the engine the fuel spurted out 4 to 5 feet up into the air ) No problem with delivery then. I've had the regulator apart three times since starting with this problem and can find nothing wrong, everything is in the correct order according to YS diagram and it feels just like it usually does. But something is obviously wrong somewhere!!. If I vent the tank to normal atmospheric pressure ie when I refill the tank, it runs properly for 10 seconds or so then it speeds up to max revs all on its own. At a guess then its kicked off by the rise in the tank pressure going up to working level. But again, I'm just guessing.

It would be very easy to send it off to Probuild UK and let them fix it in very short order but I would not really have learned anything. So if you have any further suggestions Dave, thanks for reading thru so far.

Bob
Old 06-23-2014, 05:22 PM
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Originally Posted by BobV1700
Dave,

I have now put everything back together again found nothing obvious to report. The bearings are good, the conrod as new with both ends showing no wear on the bushings, the cylinder is likewise with no obvious damage and the piston unmarked except for the usual slight discoloration. The valves move freely and the timing marks as per manual, crank shaft dot at 6 and valve timing gear at 12 just under the valve tube bottoms. Gaskets are good except that the black valve cover bolts have both now part stripped the cylinder head threads, extra long screws have just about sorted the problem and the valve cover gasket is airtight. In short I found nothing obviously wrong or difficult to reassemble. I set the valve gap at .07 mil which is in between the two recommended settings.

Started pretty much first time, but still sounded rich within whole rev range despite tweaking both high and low needles either way. About the third start the engine ran up to almost full throttle on just above tickover throttle setting. Not much more than the ' V knick' in the butterfly being open! I had to pinch off the fuel line quickly as the thing revved away on its own, even going to wide open throttle had the reverse effect and lowered the revs noticeably!. Fuel now coming out thru air intake even when running at full throttle.

It can only be the fuel regulator which I now suspect is stuck full open-ish and allowing fuel to be pushed thru the carb at almost tank pressure quantity (as I had to pull the fuel line off to stop the engine the fuel spurted out 4 to 5 feet up into the air ) No problem with delivery then. I've had the regulator apart three times since starting with this problem and can find nothing wrong, everything is in the correct order according to YS diagram and it feels just like it usually does. But something is obviously wrong somewhere!!. If I vent the tank to normal atmospheric pressure ie when I refill the tank, it runs properly for 10 seconds or so then it speeds up to max revs all on its own. At a guess then its kicked off by the rise in the tank pressure going up to working level. But again, I'm just guessing.

It would be very easy to send it off to Probuild UK and let them fix it in very short order but I would not really have learned anything. So if you have any further suggestions Dave, thanks for reading thru so far.

Bob
Hi Bob......
WOW....you really have a weird problem.
I would think that with increased tank pressure that the engine would go rich instead of speeding up.
I think there is an air leak somewhere....sucking air into the engine causing it to go lean.
Are you sure that the valve gap was set at top dead center?
Usually a excess of fuel coming from the intake means that the compression is leaking into the crankcase blowing out the fuel.
Are you sure the throttle arm is securely bolted to the throttle barrel?
Are all the screws installed and tight?
Did you tighten the head screws evenly?

Alejandro....can you chime in here and help us out?
What do you think??

Bob....hang on and lets see what Al has to say....then if it is still bad....I would send it in.

Dave
Old 06-23-2014, 10:56 PM
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As far as I can tell Dave everything went back together as per normal, there are only a couple of critical items to speak of, the two timing marks which essentially are 6 and 12, and setting them at TDC on the compression stroke. I tightened everything up on the usual 'opposite' diagonal process and apart from the black valve cover screws being down to the last couple of useable threads ( it feels tight enough and makes good all round contact on the gasket, but yes, a possible source of problem) I have no engineering background but understand the basic principles.

regards Bob
Old 07-24-2014, 12:15 PM
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Just to update this thread, I've now managed to get the engine running properly again and am almost certain that the problem all along was caused by the leaky valve cover which was allowing air into the crankcase. By juggling the length of the two cover screws Ive managed to get a good seal and it appears to have done the trick. The seemingly complicated mix of running problems was probably down to the valve cover and screws 'bottoming out' a few thou before the gasket was properly compressed, thus giving the impression of being correctly fitted but not enough to do the job properly. Hopefully I've fixed it in the short term but suspect that the last few threads being engaged wont last long and it will eventually require a new head.

We live and learn.

Bob
Old 07-24-2014, 12:58 PM
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Originally Posted by BobV1700
Just to update this thread, I've now managed to get the engine running properly again and am almost certain that the problem all along was caused by the leaky valve cover which was allowing air into the crankcase. By juggling the length of the two cover screws Ive managed to get a good seal and it appears to have done the trick. The seemingly complicated mix of running problems was probably down to the valve cover and screws 'bottoming out' a few thou before the gasket was properly compressed, thus giving the impression of being correctly fitted but not enough to do the job properly. Hopefully I've fixed it in the short term but suspect that the last few threads being engaged wont last long and it will eventually require a new head.

We live and learn.




Bob
WOW.....interesting situation.
Bob....before going to the expense of a new head I think I would install a couple of steel 'Heli-Coils' in the head and use shorter screws.
That would fix it forever.

Dave

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