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Post by silverbullet on Mar 3, 2021 0:29:14 GMT
Had some time to get my 68 oly running on the hr7a I cleaned and rebuilt, checked pop off etc. Am very pleased to say if pumped gas immediately and fired right up( I encouraged it with a shot of gas straight in the carb using the EricR mustard bottle).
Started at 3/4 and 1 1/4 on L and H respectively and headed for a spin, grinning all the way. But about 5 minutes along it’s not as crisp or happy, threatening to stall out at idle. Got back to garage and it stopped as soon as I took thumb off gas. Pulled plug and it was black and thick with carbon, telling me it’s rich. So I check the low speed jet and it’s over 2 full turns out! Has anyone heard of jets vibrating out before?
I reset to 3/4 on low and even with the blackened plug it was a crisp idle again and quick to rev on throttle. But was already late for dinner and had to stop for the day. So don’t know if it’s the needle threads, or the spring on the needle, or......? Any suggestions or ideas??
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Post by olyman on Mar 3, 2021 0:49:56 GMT
I wonder if you're missing the rubber o ring that gets compressed behind the little copper washer. The coil spring on the needle is compressed against the shoulder of the needle and that copper washer. With all those pieces the needle should stay in place. Check out the picture. Ignore the cover thing (33). The parts you need are 32, 34, 35 and 36.  |
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Post by silverbullet on Mar 3, 2021 2:36:23 GMT
Thanks for that info. I’ll pull that needle tomorrow and see what’s in there. If that’s what it is it sounds like a straightforward fix......providing I can find a little rubber washer.😊.
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Post by silverbullet on Mar 4, 2021 1:31:10 GMT
I think it’s sorted out. Appears it was the spring on the low jet needle. I believe it was too large, ie wire guage and length. I checked for the copper washer and o ring. I couldn’t pry anything out but I believe they were there ( the washer looked brass, not copper).
Sled would run and drive but kept stalling out when coming to a stop, no idle. Plug would be wet and furry with carbon. I had it down to 1/4 turn on open and it was still fouling. Then counted how many turns from “ seated” I was getting with this spring in place. Then removed spring and found I could get an extra 1.5 turns with the springless needle before it seated. That was the aha moment, I realized that although I thought I was starrting at 3/4 turns open, it was really more than 2 turns open.
Did a visual on my other 299 with same carb and noticed a thinner guage spring. Pulled that needle and found the spring was even a bit shorter. So turns out the spring I started out with was not letting the needle seat before I started counting turns to open. I think it was even letting the needle turn out on its own, though not so certain on that point. Fortunately I was able to rummage up a suitable spring from my bag of used Tilly parts . Put it back together and it idled right off the bat. Throttle was crisp and acceleration gave that lovely tillly snore. So more testing/shake down riding before I declare victory but am much more optimistic.
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olympic
Full Member
Fresh gas first pull got be a DOOO
Posts: 201
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Post by olympic on Mar 4, 2021 3:04:07 GMT
Nice it is always a good feeling when you find something hope that is the culprit.
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Post by olyman on Mar 4, 2021 11:18:16 GMT
Right on silverbullet! And even better that you found the parts in a bag on the shelf.
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olympic
Full Member
Fresh gas first pull got be a DOOO
Posts: 201
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Post by olympic on Mar 4, 2021 12:24:46 GMT
Olyman my wife thinks I'm nuts because I have cans of nuts,washers,little bolts and carb parts. She always says why do you keep things and my answer you never know when you will need something. My theory is the day you throw it out the next day you will need it. |
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Post by olyman on Mar 5, 2021 0:39:22 GMT
Ha! Yes I believe in the same theory - I have boxes and cans of them. Sometimes the hard part is finding that particular saved/salvaged bit when you need it...
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Post by Doo640ER on Mar 7, 2021 11:18:11 GMT
That is such a great catch silverbullet. Glad you got it figured out. Without seeing the carb in person, I can't imagine figuring out what the problem could have been. How doo you think that incorrect spring got installed on there? Previous owner? Or did you install the wrong one somehow?. Just trying to understand how some of these things happen.
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Post by silverbullet on Mar 7, 2021 23:20:51 GMT
Good question. I was asking myself this. The carb was one I picked up at a swap meet. I had it cleaned in an ultrasonic cleaner and reassembled with OEM Tilly parts (diaphragm, welch plug, fulcrum lever, spring) and taught myself how to do a pop off test. So I had every reason to believe all should be good. But the needles and associated springs were the ones that came on it. I'm thinking someone else has obviously had it apart and used one of the offshore springs on it. I say this because in my bag of Tilly parts I had some other springs that looked of gauge/size as the ones that I pulled of this low speed needle. They likely came with a windersosa or similar kit in past. I typically try to reuse the the OEM needles and parts if I have no reason to doubt them. It also helped that I had another Hr7A on a known good runner to compare to. So am pleased to say it all worked out. I've since taken it our for a subsequent test drive and am happy to report I've got his one dialed in. No small feat, in fact a triumph for me, as Tilly's have been hard on me in the past, lol.
Further to what Olympic said, there is value in saving the stuff, ha ha. You never know what will come in handy. Especially the fine threaded stuff ski doo used. It's not run of the mill hard hardware UNC thread stuff. One of the best gifts I've received in this hobby was a fellow who gave me a 48 oz juice tin FULL with nuts, bolts, washers, pins, rubber parts etc from skidoos he'd stripped down over the years. Most often it is rusty but always cleans up well in a wire wheel and has saved the day many times.
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