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Post by repherence2 on Sept 10, 2021 11:50:52 GMT -5
Have you done a leak down test to check the crank seals?
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Post by wiscootsin on Sept 10, 2021 13:03:44 GMT -5
Just my a small fuel leak wouldn't cause your problem,if you suspect a soft seize has occurred I would strip the top end down and inspect the piston etc. Geoff I was more so thinking maybe what I had thought was a sort of soft-seize was more like a lean condition resulting from carb being completely empty after extended WOT due to a fuel leak. Haven't had time to try it out yet.
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Post by wiscootsin on Sept 10, 2021 13:04:47 GMT -5
Have you done a leak down test to check the crank seals? no
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Post by wiscootsin on Sept 12, 2021 11:21:36 GMT -5
Went on a long ride on Friday night, about 20 miles. It was definitely the best it's every driven. I do have an 85 mainjet in it though the stock one was 82.
The other two times the issue came up were on 90 degree days. This night it was nice thick cool air just below 70.
It did the softseize (or run out of gas thing) at about 13 miles in. I had lots of stretches of WOT for long lengths, but this was probably during the longest one. I was able to keep it going, it didn't totally die, just let off throttle a bit and blipped it a few times, then drove at 25mph a short distance before getting back up to a decent speed.
I may look into shimming the autobystarter further so that that choke needle is more at the precise measurement in the manual. It was 2mm short when I measured and I shimmed it a bit with a custom gasket to get it to around 1.3mm short. I should probably put it back to 82 also to see if that was part of the problem this time.
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Post by repherence2 on Sept 12, 2021 20:40:22 GMT -5
I noticed this scooter was leaking gas very slowly. When I checked the fuel petcock was leaking and there was also a hose line leaking at a connection. I replaced the OEM yamaha vacuum petcock with built in filter with a generic one and fixed the line. The three times I've started it since it has started up immediately. I haven't had a chance to test it yet on a long WOT run, but i'm guessing the issue I've been chasing was just a result of a small fuel leak that was so small it went unnoticed (and i believe it got worse over the last few months). I will update when I fully confirm.
i can see that. i think it's more like the "leak" was allowing air to bleed into the line on long throttle runs. that's why i love clear fuel filters and transparent/translucent (see thru) fuel and oil lines.
you should get a temp gauge for it so you can monitor the heat if you really want to protect that machine.
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Post by wiscootsin on Sept 13, 2021 11:23:12 GMT -5
yeah i actually bought a tto temp gauge but haven't put it on yet. I haven't driven it much for that reason.
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Post by wiscootsin on Apr 10, 2022 21:27:14 GMT -5
i shimmed the auto bystarter and that didn't solve anything.
i can't tell if it's running too lean or running out of gas. The spark plug appears to be the perfect chocolate brown color. It seems like it might be mainly running out of gas.
I did just take the carb completely apart again (which i've done many times). There was some crud in the bowl. maybe a clean will do something.
I took out the air pilot jet, which i am not sure if i have done before. It is very shiny which makes me think it may not be original. The number on it is 96, and if compared to a mainjet with normal number sizing i'd say it's comparable to what a 96 mainjet would be. In the manual it is stated to be a "1.04" so i have no idea how to compare the numbers/units that are used on these things.
The scooter takes a long time to start when cold, which i would guess would especially use the pilot air jet so i'm wondering if maybe my problem is because of this obscure pilot air jet.
I have a different japan/jog carb with an adjustable air screw that i will put on instead of the OEM 1986 one and i'll see how/if that changes things. Maybe there is a reason this is the first jog and only jog without an adjustable air screw.
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Post by Zino on Apr 10, 2022 22:23:23 GMT -5
I will dig around and see if I ave any jets for that carb. Stock pilot is a 42 part #14T-14353-21-00
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Post by wiscootsin on Apr 10, 2022 23:14:47 GMT -5
it's the pilot air jet that i'm unsure about. yamaha part # 680-14347-52-00 If i understand correctly the pilot air jet should only be used when at idle. But i really don't know.
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Post by wiscootsin on May 7, 2022 22:33:15 GMT -5
I think the entire time my problem has actually been the carb running out of gas.
I put on a new carb and it had the same issues (but this carb at least has an air screw). I removed the vacuum petcock and went with a shut-off valve only and I believe that has solved it. I rode it at least 15km today and had no more issues after that.
I'm guessing the vacuum line from the carb wasn't getting enough suction to pull in enough fuel when at WOT. the scooter would run fine if you only wanted to keep it at 25mph.
Now the test will be if it starts well after sitting. I'm hoping it will, and that the slow to start was also related to the vacuum line fuel delivery stuff.
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