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Post by bones on Jan 17, 2021 14:45:53 GMT
Doo640ER...... in my experience the needle jets absolutely can and doo wear. Your symptoms seem rather severe to be just a worn needle jet but possible. Maybe someone cleaned out the one you have with a twist bit in a electric drill at one time ?? If your problem is a worn jet one clip drop of the needle should about fix it. If you found that to be then replacing jet and running stock clip position would be my thought. One of the worst sleds engines I had with the worn needle jet was a 470 (467) MX. I had engine apart and reassembled as it should be. That sled would run OK but just would not perform likely a old 440 fanner would have out performed it. A set of new needle jets and away it went. I would think likely some engines react differently than others from this condition.
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Post by olyman on Jan 17, 2021 18:23:11 GMT
To answer your question about the advance lever causing bogging- for sure it makes it bog. Should move freely and never stick at any position.
Its hard to imagine that carb stuff can wear like that but its true. One less thing to worry about if you replace it.
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Post by Doo640ER on Jan 17, 2021 20:13:34 GMT
Thanks guys for the input. Always helpful! Worst case, I guess I could swap that Mikuni out for a Tilly. LOL, just kidding Bones, I couldnt help myself, 😉✌
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Post by bones on Jan 18, 2021 4:47:33 GMT
Doo640ER sounds like I need to post up the old picture of what happens to silly tilly carbs around my shop ha ha
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Post by Doo640ER on Jan 18, 2021 13:39:14 GMT
That was a classic, Bones. I will admit, having a silly tilly on there with adjustable jets could be pretty helpful in my troubleshooting. After all, I am PETT #119 on another vintage site, LOL. We got about 2 inches of wet snow last night so that has put me back in the mood to get back out there and play with this TNT. I've got today off for MLK day so that's cool. Updates will be shared once I try some things. Might pull the recoil and check the advance lever today. Maybe check the timing while I'm at it with my dial indicator and light.
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Post by bones on Dec 22, 2023 17:27:03 GMT
Doo640ER...Did you ever get this unit up and performing ??
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Post by silverbullet on Dec 23, 2023 21:07:10 GMT
Good to see you checking in on the forum Bones. I was recently musing that I hadn't seen a post from you in a while (admittedly, haven't posted myself but I check in frequently...) Truly appreciate the knowledge that you share.I have a printout of instructions you gave me on the old TNT Board back in January 2020. Almost 24 years ago! yikes.
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Post by Doo640ER on Dec 24, 2023 13:49:41 GMT
Hey Bones, good to hear from you! Well,.....um,......no I never got back to working on this TNT. Over a year ago I did procure new points, condensers and crank seals for it but I never got around to yanking the motor and replacing them. I think the donated 95 Skandic 500 moved into the sled operating room and displaced the TNT which was then relegated to the trailer. I did take the TNT to a couple of vintage sled shows and it ran well enough to drive it back onto the trailer, LOL.
Depending on how much snow we get this season, this might be a good time to get to it. I can bring the engine down to the warm basement and work on it as time permits. I never did do that leak-down test but I'm pretty sure this motor has never been opened-up so those seals should be replaced.
What have you been working on? Anything new in Bone's garage??
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Post by bones on Dec 24, 2023 17:51:41 GMT
Silverbullet....24 years ago huh !! That is a while. Yes I have not been here very much lately, I kinda moved away from the 60/70 sleds, I still think about them often, and also think about all the wonderful memories I have of the countless hours I spent on this board. A truly enjoyable experiance.
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Post by bones on Dec 24, 2023 18:34:07 GMT
Doo640ER... Lately my mind has been kinda wondering to TnT F/As and made me think about this thread. I read through the thread, on Oct-15-2020 Doo640ER made a post. In the post it is mentioned about the idle speed changing as engine warms up, needing to increase the idle speed to keep it running. A couple years back a buddy bought a couple of 97 MZX 440s. One looked fairly good and one looked kinda junky ( there is pics on this board some where). Neither of them sleds ran very well. I spent many hours messing with carbs/fuel delivery etc, some times they would seem to run OK and others not well. He kinda gave up on the better looking one and sold it. He kept the junky looing one LOL. I guess he was attached to it. Well more messing with fuel etc, one thing that seemed to be some what consistent was turning the idle speed screw in as engine warmed up. I would have the screws turned all the way in and engine at 1,000 RPM. Then one time I had it in shop running, reved it up a bit, then shut it down. I heard the spinning wheel after the engine was stopped, "the light finally came on". Tore engine down, as suspected the PTO end crank bearings were shot. Bearings with plastic cages had melted out and you can hear the balls spin after engine stops. Anyway, after engine rebuild, idle speed was consistent as it should be with the speed screws back aways. Recently one of my 503s started doing the same thing, idle speed screws all the way in to get it to stay running. I had done lots of plug chops etc looking for a lean condition, never caught it. Well pulled engine apart. Yep mag end bearing poor. Replaced bearing, new seals etc. Seems to be OK now. It seems like I had small, inconsistent leaks that at idle the engine pulled in too much air and would not pull enough fuel to keep it running. If I remember correctly the 77/78 TnT F/A engines have a poor oiling system to the PTO end outer crank bearing. I am thinking there is a very good chance you have a PTO crank seal leaking What have I been up to for sled wrenching....Well re-did and sold a couple of S chassis sleds. Did a little repairing for others. Dont swear at me now, the latest patient was/is a 1998 Polaris XLT. Tore down and rebuilt. Got it for sale but as most places about no snow so no interest in it ( or maybe no interest cause of the name ha ha).
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Post by Doo640ER on Jan 7, 2024 18:55:39 GMT
Hey Bones, Good to see you checking-in! Excellent input on your experiences and what fixed the problems. The way things are going right now, I won't be getting around to replacing the seals on the 77 TNT until summer. I've brought home more sleds and pulled a third out of storage. I'm suspecting I may have Adult ADD haha. But that is the plan. I will probably do the points and condensers also while I'm in there. That doesn't add much expense and I've got the parts already anyway. I got the points from Goose a while back and they are SP1 brand and not Bosch like I had hoped. Still wondering if I should give them a shot??? I hope the crank bearings are OK since I've never delved into changing those.
Hmmm, S-Chassis Doos. After working on my 95 Skandic I've got a new fondness for S-Chassis sleds. You're a good guy for working on other peoples sleds. I've done the same, sometimes for free and sometimes for money. When I had a guy offer me $200 cash replace the fuel pump on his 03 Legend 700, I couldn't turn that down. And he supplied the new OEM pump. Good luck on that Polaris sale, I bet once the snow falls it will sell. I certainly won't judge anyone for owning or working on a Polaris! I know that if I wasn't a Doo guy I'd be a Poo guy. I just could never get into Cats growing up. I've had a couple Yamahas when I was a kid. Great Enticers, a 78 250 and then a 80 340. Wish I had those now!
Take care for now! Don't be a stranger around here
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