YS 91 AC Parts List
06-18-2006, 11:14 AM
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YS 91 AC Parts List
Dave,
A friend gave me a YS 91 AC and a 72" Dymond Tiger Moth to put it in. It's my first YS, and though I've made a few mistakes (like getting the plumbing backwards) it runs strong, and I’m sorting it out. I've noticed it needs a few things like a plunger spring and o-ring, and the needle valve has score marks that look like the result of bottoming out. I'm putting together a parts list, things like an o-ring set and gasket set, and wondered if I should get a needle valve assembly, too. I've attached a photo to show you the scores I mentioned – does this look minor, should I remove the scores with 600 grit sandpaper, or should I open up my wallet a bit more?
When reading one of your old posts about sorting out an engine that hadn’t run in a while, I noticed you suggested checking the rear bearings. I did this, and found a few rust stains. The attached photos show them; the largest is at the bottom of the crankcase. Do these warrant bearing replacement? If so, do you replace just the rear or both of them, and how does one do so correctly?
Thanks so much,
Bill
A friend gave me a YS 91 AC and a 72" Dymond Tiger Moth to put it in. It's my first YS, and though I've made a few mistakes (like getting the plumbing backwards) it runs strong, and I’m sorting it out. I've noticed it needs a few things like a plunger spring and o-ring, and the needle valve has score marks that look like the result of bottoming out. I'm putting together a parts list, things like an o-ring set and gasket set, and wondered if I should get a needle valve assembly, too. I've attached a photo to show you the scores I mentioned – does this look minor, should I remove the scores with 600 grit sandpaper, or should I open up my wallet a bit more?
When reading one of your old posts about sorting out an engine that hadn’t run in a while, I noticed you suggested checking the rear bearings. I did this, and found a few rust stains. The attached photos show them; the largest is at the bottom of the crankcase. Do these warrant bearing replacement? If so, do you replace just the rear or both of them, and how does one do so correctly?
Thanks so much,
Bill
06-18-2006, 06:54 PM
#2
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RE: YS 91 AC Parts List
If it runs OK, why are you changing parts?
If it needles OK, why do you want to change the NV assembly?
The rust on the outer race of the rear bearing is minimal. If the balls and retainer were rusted, I would replace. Actually it looks pretty clean inside.
If it needles OK, why do you want to change the NV assembly?
The rust on the outer race of the rear bearing is minimal. If the balls and retainer were rusted, I would replace. Actually it looks pretty clean inside.
06-18-2006, 07:50 PM
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RE: YS 91 AC Parts List
I had put it on a test stand Friday, and first idled it at ~3,500 rpm for five minutes to sort of break it in. After a cool-down, I started it up again to set the high speed needle, but couldn't get it above quarter throttle or it would stumble and die. In fact, it was pretty much unresponsive to the needle valve setting. I went onto this forum and, given the experience of a fellow with a 110FZ and pictures of his installation, now think I had the plumbing wrong - pressure and fuel lines reversed (the drawing in the YS brochure could be a little clearer).
I was planning to put it back on the test stand today, but realized there is supposed to be a spring in the regulator. My guess is not to run it without a plunger spring, that may have been the problem all along. As the spring was missing, I thought it wise to look it over to see if anything else is missing. It does look pretty clean; I'll get a new spring and go from there. Thanks for the advice, I'll let you know how it turns out.
I was planning to put it back on the test stand today, but realized there is supposed to be a spring in the regulator. My guess is not to run it without a plunger spring, that may have been the problem all along. As the spring was missing, I thought it wise to look it over to see if anything else is missing. It does look pretty clean; I'll get a new spring and go from there. Thanks for the advice, I'll let you know how it turns out.
